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Paul_Mon
02-22-2007, 12:56 PM
What can be done to reduce it? Iíve missed shots and/or position on the most simple shots due to %$#& skid. My regular opponent says that outside english reduces or eliminates skid. I donít think so. I believe that skid is caused by residual chalk on the cueball coming between the contact points of the cueball and object ball. Iíve watched the cueball climb right up an object ball due to this. If that is true then what good will outside English do?

Some other sources of this phenomenon may be scratches on the balls or dirty balls. The hall where this occurs most uses a ball cleaner (with polish) daily and their balls are somewhat worn. Also of note is that skid seems to take place on slow short shots, as in 14.1. This supports the chalk theory, as it is less likely to be removed on these types of shots.

I suppose that I don't really need to chalk up on each and every shot if I'm using center ball. But chalking is a habit I don't want to change.

Paul Mon

dr_dave
02-22-2007, 01:14 PM
<blockquote><font class="small">Quote Paul_Mon:</font><hr> What can be done to reduce it? Iíve missed shots and/or position on the most simple shots due to %$#&amp; skid. My regular opponent says that outside english reduces or eliminates skid. I donít think so.<hr /></blockquote>Your friend is correct. The right amount of outside English (OE) can totally eliminate throw completely, even excessive throw (AKA "clink" or "skid") caused by old, worn, dirty, and/or chalk-covered balls. For illustrations and detailed explanations, see my January '07 instructional article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2007/jan07.pdf). However, if you plan to use OE frequently, you better have good knowledge of and intuition with squirt and swerve compensation.

<blockquote><font class="small">Quote Paul_Mon:</font><hr>I believe that skid is caused by residual chalk on the cueball coming between the contact points of the cueball and object ball. Iíve watched the cueball climb right up an object ball due to this. If that is true then what good will outside English do?

Some other sources of this phenomenon may be scratches on the balls or dirty balls. The hall where this occurs most uses a ball cleaner (with polish) daily and their balls are somewhat worn. Also of note is that skid seems to take place on slow short shots, as in 14.1. This supports the chalk theory, as it is less likely to be removed on these types of shots.

I suppose that I don't really need to chalk up on each and every shot if I'm using center ball. But chalking is a habit I don't want to change.

Paul Mon<hr /></blockquote>

Fran Crimi
02-22-2007, 01:33 PM
Interesting thing about those chalk marks, Paul. I've often encountered the dreaded skid with newly polished balls more often than not. Things really get fun when you add a new cloth in the mix. I suspect that the cb is sliding more and the chalk mark isn't wearing off.

You're right. It's those short easy ones that seem to skid more often. Low outside works best for me, although there's no guarantee for all the time. I've seen many great ones succomb to the dreaded skid over the years. I happen to like low outside anyway, so it's not much of a stretch for me to use it.

Maybe you can get the room owner to ease off on the polish. A spritz of plain water in the ball cleaner does the trick unless they're really dirty.

Fran

cushioncrawler
02-22-2007, 02:23 PM
Hi Paul -- I agree with u n Doc n Fran, i think i go along with what Fran sez about hitting low, but here i will havta re-read my posting (to myself), following, from the thread started by "dutchboy" called "efren wisdom" (dated 6Feb06). Here i call Dr Onoda "Dr G" -- karnt remember why, duz G stand for Gordon or something?? ....

.............." G'day cushioncrawler -- i did a few tests of my own this arvo, relating to Dr G's stuff (skidding -- kicks), and relating to Efren's practice of hitting low with a bit of inside english (to avoid skid-kicks) -- i only did 60 minutes of testing, so i dont expect to get a Nobel Prize for billiards, but here we go.

Rule No 1..... If u hit the qball very high, ie at 11 O'clock, or 12, or 1, u will never get a kick (from a fresh chalk mark), unless u are hitting the object ball full.

Rule No 2..... If u hit the qball leftofcenter (high, or low), u will never get a kick (skid) if u are cutting the objectball to the right, if the qball is rolling when it gets to the objectball.

Rule No 3..... If u hit the qball leftofcenter (low), u will never get a kick (skid) if u are cutting the objectball to the left, if the qball is sliding when it gets to the objectball.

Rule No 4..... Rule No 2 is wrong..... if u hit very low and just leftofcenter and slow, a cut to the right might get a kick.

Rule No 5..... For a fine cut, a kick is impossible (for a rolling qball), unless u use a little inside english, and hit a little low.

So, was Efren correct?? I dont know -- i emptied a bottle of 1998 red -- i will have another think in the morning......"

It looks like Rule 2 supports Fran, but Rule 4 givz an exception. madMac.

cushioncrawler
02-22-2007, 02:37 PM
Its "George Onoda". Dr G's article "Coping With Skid" is on the sfbilliards website, and is the article i was referring to. madMac.

dr_dave
02-22-2007, 02:42 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> Its "George Onoda". Dr G's article "Coping With Skid" is on the sfbilliards website, and is the article i was referring to. madMac. <hr /></blockquote>FYI, several of Dr. Onoda's articles (including this one) can be found here (http://www.sfbilliards.com/onoda_all_txt.pdf). They are excellent!

Regard,
Dave

dr_dave
02-22-2007, 02:55 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> Its "George Onoda". Dr G's article "Coping With Skid" is on the sfbilliards website, and is the article i was referring to. madMac. <hr /></blockquote>
FYI, links to instructional articles from various people (me, Bob, George, and Tom) can be found here (http://www.engr.colostate.edu/~dga/pool/bd_articles/index.html) (see the bottom).

Regards,
Dave

Jal
02-22-2007, 04:05 PM
Here's a diagram of what happens to a chalk mark as the cueball develops roll.

http://ww2.netnitco.net/users/gtech/EquatorialPlane.jpg

The plane in which it sits, and which is perpendicular to the spin axis (ie, equatorial), always rotates upward on the side in which the chalk was initially laid down. This makes hitting with low side a potential problem regardless of whether you're cutting left or right.

Jim

SpiderMan
02-22-2007, 04:27 PM
I'd tend to partially agree with your friend, but instead of just outside I'd expect bottom outside to work best. This should minimize the relative motion of the CB and OB surfaces at contact.

The amount of bottom would depend on distance and speed (so as to effectively decay to slide at contact), while the amount of side would probably be fairly constant.

This may conflict with some theories of minimizing the chance of a just-created chalk mark finding it's way to the contact point, but I don't consider this a bad trade. I'm personally more comfortable with cueing in such a way (low outside) that the effects of such an occurance are minimized, especially since this minimizes the effects of PREVIOUS chalk marks which find their way randomly to the contact point. After all, we can't clean the CB after each shot, so the chalk marks are somewhat cumulative until they wear off.

Of course, position-play considerations often override the desire to minimize throw and skid.

SpiderMan

Cornerman
02-22-2007, 04:39 PM
<blockquote><font class="small">Quote Paul_Mon:</font><hr> Some other sources of this phenomenon may be scratches on the balls or dirty balls. The hall where this occurs most uses a ball cleaner (with polish) daily and their balls are somewhat worn. <hr /></blockquote>

I don't ever remember skidding so prevalent when playing on non-slick cloth. I've thought that the older cloth helped to rub away any excess chalk left on the cueball, while today's worsted cloth doesn't do as a good of a job.

I think it's also an interesting idea that clean, polished, but scratched up balls would skid more. Just like oils on the hands, they might reduce friction, but they also gather up dirt more readily creating more friction. Maybe these nooks and crannies gather chalk more readily as well.



[ QUOTE ]
Also of note is that skid seems to take place on slow short shots, as in 14.1. <hr /></blockquote> The dreaded stun shot unfortunately is going to be your highest occurrence of this.

[ QUOTE ]
I suppose that I don't really need to chalk up on each and every shot if I'm using center ball. But chalking is a habit I don't want to change.<hr /></blockquote>Face it Paul, this game is a curse.

Fred &lt;~~~ onto the White House for some sushi and visit to Mr. Ford....

dr_dave
02-22-2007, 04:46 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr> I'd tend to partially agree with your friend, but instead of just outside I'd expect bottom outside to work best. This should minimize the relative motion of the CB and OB surfaces at contact.

The amount of bottom would depend on distance and speed (so as to effectively decay to slide at contact), while the amount of side would probably be fairly constant.<hr /></blockquote>I disagree (but I'm not saying everybody else is stupid, nor am I being passive aggressive).

In my humble opinion, stun creates the most amount of throw (and "cling" if the contact point between the balls happens to be dirty, chalk-covered, and/or rough). See my October '06 instructional article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2006/oct06.pdf) for justification. Now, if a "gearing" amount of outside English (OE) is used, topspin or bottom spin really won't have an effect on the shot (see my January '07 instructional article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2007/jan07.pdf)). However, if the amount of OE is not exactly the "gearing" amount, there will be some throw (and maybe some "cling"). In those cases, a natural roll shot (or a draw shot) with OE will result in less error than a stun "drag" shot with the same amount of sidespin (see my February '07 instructional article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2007/feb07.pdf)).

What do you think? Did I misinterpret something in your posting. If so, I am terribly sorry.

I hope this disagreement doesn't create a another set of attacks on my character.

Regards,
Dave

PS: Please excuse me for the passive aggressive inside jokes spread throughout my message above. I couldn't resist. These statements were obviously directed at others, not you.

Stretch
02-22-2007, 04:49 PM
<blockquote><font class="small">Quote Jal:</font><hr> Here's a diagram of what happens to a chalk mark as the cueball develops roll.

http://ww2.netnitco.net/users/gtech/EquatorialPlane.jpg

The plane in which it sits, and which is perpendicular to the spin axis (ie, equatorial), always rotates upward on the side in which the chalk was initially laid down. This makes hitting with low side a potential problem regardless of whether you're cutting left or right.

Jim <hr /></blockquote>

I find i never get skid if i've got something on the cue ball whether it's high, low, inside, outside. If i recall my last few bad contacts ( i don't get that many ), they were med. slow speed 3/4 ball angle give or take. the cue ball was just sliding in nicely like a knuckle ball and POP! funny hit. I know snooker players are fanatical about keeping the cueball spotless and have marking devices to routinely clean the ball during play. Pool players on the other hand will accept just about anything as long it rolls without skipping along too much lol. As long as you play with a dirty cueball skid contacts are more common, so either keep it clean or play aggressively with the cue ball and avoid as much as possible those lazy slidy shots. St.

Fran Crimi
02-22-2007, 05:03 PM
[ QUOTE ]
I think it's also an interesting idea that clean, polished, but scratched up balls would skid more. Just like oils on the hands, they might reduce friction, but they also gather up dirt more readily creating more friction. Maybe these nooks and crannies gather chalk more readily as well.
<hr /></blockquote>


Ahhh, but I think we may have to take into account the possible build up of polish in those cracks. Polishing every day is a lot of polish. Heck, all during 14.1 pro tournaments, there were balls skidding. Sure, the cloths were new but the balls were slick. I remember guys like Lassiter and Crane and the Miz and Martin complaining to the TD to ease up on the polish.

Fran

Jal
02-22-2007, 06:37 PM
<blockquote><font class="small">Quote Stretch:</font><hr>...If i recall my last few bad contacts ( i don't get that many ), they were med. slow speed 3/4 ball angle give or take. the cue ball was just sliding in nicely like a knuckle ball and POP! funny hit.<hr /></blockquote>Stretch, if these were cases of abnormally large throw, I wouldn't know how to explain it. Theory has it that when the cueball will end up rolling across the object ball anyway (gearing), an increase in friction shouldn't affect the amount of throw. And a 15 degree cut (or thereabouts) with stun and zero sidespin should be a case where gearing takes place. Being that theory is sacred and inviolate, I would choose to believe that you were lined up for little or no throw, but instead got something like 3 degrees or more, which could happen with a touch of inside english, intentionally or unintentionally applied, and with no abnormal cling effect. However, if you insist that much more than this occurred, under those conditions, and can perhaps offer up an affidavit or two, I'll bow to your observations.

Seriously though, it is puzzling. I just wouldn't want to give up the theory based on informal testimony.

Jim

cushioncrawler
02-22-2007, 06:39 PM
<blockquote><font class="small">Quote Fran Crimi:</font><hr> .....Ahhh, but I think we may have to take into account the possible build up of polish in those cracks. Polishing every day is a lot of polish. Heck, all during 14.1 pro tournaments, there were balls skidding. Sure, the cloths were new but the balls were slick. I remember guys like Lassiter and Crane and the Miz and Martin complaining to the TD to ease up on the polish. Fran <hr /></blockquote>Hi Fran -- Just a few ideas. madMac....

..........I reckon that, if a polished ball is more slippery than a "used" ball, that players using polished balls havta allow for the rezulting "finer" OB angle, and, later in that frame, when the qball has lost polish in parts, an unpolished area in the contact would give more friction, ie a "mini-kick".

.............And, if this bit of the qball happens to find a similar unpolished area on the OB, u will get a "bad-kick". But, this bad-kick is possibly in fact a "normal-kick", ie the sort of kick (and throw) that u expect and allow-for for allmost every shot when uzing nonpolished balls.

...............Polished areas can become unpolished perhaps due to cushion impacts and due to sliding.

...............A balltoball impact-mark on the qball possibly givz a still larger kick. And, for the unhappy event of an old balltoball impact-mark on the qball meeting one on the OB, a still larger kick.

..............Re the earlyr posting that u karnt clean a qball every shot, in English billiards and snooker the player can ask the ref to clean the qball az often az he/she likes, ie when not in-hand. Likewize, an OB. I guess that the ref would soon blow hiz/her top if he/she didnt see any chalk-mark on the ball.

cushioncrawler
02-22-2007, 06:45 PM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote Stretch:</font><hr>...If i recall my last few bad contacts ( i don't get that many ), they were med. slow speed 3/4 ball angle give or take. the cue ball was just sliding in nicely like a knuckle ball and POP! funny hit.<hr /></blockquote>Stretch, if these were cases of abnormally large throw, I wouldn't know how to explain it. Theory has it that when the cueball will end up rolling across the object ball anyway (gearing), an increase in friction shouldn't affect the amount of throw. And a 15 degree cut (or thereabouts) with stun and zero sidespin should be a case where gearing takes place. Being that theory is sacred and inviolate, I would choose to believe that you were lined up for little or no throw, but instead got something like 3 degrees or more, which could happen with a touch of inside english, intentionally or unintentionally applied, and with no abnormal cling effect. However, if you insist that much more than this occurred, under those conditions, and can perhaps offer up an affidavit or two, I'll bow to your observations.

Seriously though, it is puzzling. I just wouldn't want to give up the theory based on informal testimony. Jim <hr /></blockquote>Hi Jim -- U said "....when the cueball will end up rolling across....".

I think u meant to say "....when the cueball starts off rolling across....". madMac.

Jal
02-22-2007, 10:05 PM
Hi Mac,

I've been reading your ideas too, but they're coming at such as fast and furious pace I can't keep up. (I didn't completely believe your assertion that a ball colliding with two balls in line, Newton's Cradle like, would bounce back a little. But after some reading I learned you're right...still not exactly sure why, but you called it true. Nor do I think that grip position/firmness can affect squirt or that it decreases with speed. But give me a couple of years and I'll get back.)

<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>Stretch, if these were cases of abnormally large throw, I wouldn't know how to explain it. Theory has it that when the cueball will end up rolling across the object ball anyway (gearing), an increase in friction shouldn't affect the amount of throw....<hr /></blockquote>Hi Jim -- U said "....when the cueball will end up rolling across....".

I think u meant to say "....when the cueball starts off rolling across....". madMac. <hr /></blockquote>No, actually anytime the cueball reaches roll during impact, eg, start, during, or end. Throw is, or should be according to theory, oblivious to any increase in friction in these cases. It's also independent of a decrease in friction as long as it's not so much that the cueball doesn't reach roll. The form that Dr. Dave's equation takes in this situation does not even include the coefficient of friction.

And it applies to quite a few shots, especially stun (or near stun) at cut angles ranging from zero to 3/4 - 1/2 ball hits. This is probably why people don't notice cling much when using outside english. However, if you use too much or not enough at a particular angle, it can announce itself.

Jim

Jal
02-22-2007, 10:13 PM
<blockquote><font class="small">Quote Jal:</font><hr> Hi Mac,

I've been reading your ideas too, but they're coming at such as fast and furious pace I can't keep up. (I didn't completely believe your assertion that a ball colliding with two balls in line, Newton's Cradle like, would bounce back a little. But after some reading I learned you're right...still not exactly sure why, but you called it true. Nor do I think that grip position/firmness can affect squirt or that it decreases with speed. But give me a couple of years and I'll get back.)

<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>Stretch, if these were cases of abnormally large throw, I wouldn't know how to explain it. Theory has it that when the cueball will end up rolling across the object ball anyway (gearing), an increase in friction shouldn't affect the amount of throw....<hr /></blockquote>Hi Jim -- U said "....when the cueball will end up rolling across....".

I think u meant to say "....when the cueball starts off rolling across....". madMac. <hr /></blockquote>No, actually anytime the cueball reaches roll during impact, eg, start, during, or end. Throw is, or should be according to theory, oblivious to any increase in friction in these cases. It's also independent of a decrease in friction as long as it's not so much that the cueball doesn't reach roll. The form that Dr. Dave's equation takes in this situation does not even include the coefficient of friction.

And it applies to quite a few shots, especially stun (or near stun) at cut angles ranging from zero to 3/4 - 1/2 ball hits. This is probably why people don't notice cling much when using outside english, which tends to bring the spin toward the middle of the range where rolling takes place at some point during the collision. However, if you use too much or not enough at a particular angle, it can announce itself.

Jim

cushioncrawler
02-22-2007, 11:25 PM
<blockquote><font class="small">Quote Jal:</font><hr> .....And it applies to quite a few shots, especially stun (or near stun) at cut angles ranging from zero to 3/4 - 1/2 ball hits. This is probably why people don't notice cling much when using outside english. However, if you use too much or not enough at a particular angle, it can announce itself. Jim <hr /></blockquote> Hi Jim -- Ah yes, i see what u mean now. And, yes, for stun contacts (but not necessaryly excluding non-stun contacts) fuller than say 3/4 ball the balltoball friction value is mostly irrelevent koz gearing kumz into play before impact ends, az u have said.

And, re the inline fullball hit on the 1st of 2 frozen OBs, not only duz (or can) the qball bounce back, but, for the same reason, the 1st ball must bounce throo much more than predicted by a simple "e" calculation, az can be seen in Dr Dave's videos (Video A85 etc i think). madMac.

cushioncrawler
02-22-2007, 11:46 PM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote Stretch:</font><hr>...If i recall my last few bad contacts ( i don't get that many ), they were med. slow speed 3/4 ball angle give or take. the cue ball was just sliding in nicely like a knuckle ball and POP! funny hit.<hr /></blockquote>Stretch, if these were cases of abnormally large throw, I wouldn't know how to explain it. Theory has it that when the cueball will end up rolling across the object ball anyway (gearing), an increase in friction shouldn't affect the amount of throw. And a 15 degree cut (or thereabouts) with stun and zero sidespin should be a case where gearing takes place. Being that theory is sacred and inviolate, I would choose to believe that you were lined up for little or no throw, but instead got something like 3 degrees or more, which could happen with a touch of inside english, intentionally or unintentionally applied, and with no abnormal cling effect. However, if you insist that much more than this occurred, under those conditions, and can perhaps offer up an affidavit or two, I'll bow to your observations. Seriously though, it is puzzling. I just wouldn't want to give up the theory based on informal testimony. Jim <hr /></blockquote> Jim -- I think that it iz difficult to play a soft stun shot unless at very short range. At medium range i would guess that roll had well and truly taken over (for Stretch). Now, for a rolling ball, a kick will put backspin on the OB, hence the throw (mm) might be a certain size, but the throw angle (dg) will appear large, due to the OB's drive being shortened. I know that u will point out that any vertical component of the frictional force robs some (direct) throw, but here i would point out that the vert component creates a large masse effect on the OB (i have seen this kick-masse lots of times, and it iz huge) which adds extra throw angle and offsets the lost bit. madMac.

SpiderMan
02-23-2007, 07:53 AM
Dave,

My comments were based on two assumptions:

1) Zero relative motion between the two surfaces at the contact point would result in zero skid. This would require addressing the CB low outside in most cases. I've assumed here that I can apply superposition to combine the effects of low and outside, and that this really is the situation that will come closest to zero relative motion.

2) Over the years, I seem to detect less mishaps with low outside. Maybe it's a stretch, but it's possible that cause-and-effect has "trained" me toward the situation of #1. Anyway, it's a layman's observation that I assumed to validate my theory.

The two talking points above were as deeply as I had thought into the subject before your response. Can I still rationalize my observations? Here's a stab at it:

I read your treatise on stun/roll/backspin. It wasn't something I had previously considered, but it does make sense. Especially when I imagine the case where side is not applied, or not optimally applied. With non-optimum side, I'll concede roll is arguably better than slide.

However, experience seems to tell me that low outside gives me more consistent results than outside with forward roll.

If this observation is correct, then there still exists an argument that could fit both your theory and my experience. It would imply that I'm generally very successful in getting close enough to the right amount of side. If that is true, then slide would still be better than roll.

Perhaps, since the side decays only slowly during the shot, it may be relatively easy to have the CB arrive with "correct" side at contact because the effects of speed and distance variables are diminished.

SpiderMan
02-23-2007, 08:02 AM
<blockquote><font class="small">Quote Cornerman:</font><hr> I don't ever remember skidding so prevalent when playing on non-slick cloth. I've thought that the older cloth helped to rub away any excess chalk left on the cueball, while today's worsted cloth doesn't do as a good of a job.<hr /></blockquote>

I've always thought that the slick cloth skidded worse because it was slick, and therefore provided less frictional resistance to whatever ball-ball forces were trying to cause skid/throw.

My best reference for this is thinking back to when Spetty first opened up Pettypoint. Her 9' Diamond was brand new and had very slick cloth. Even though the balls were brand-new, spotlessly-clean, and highly polished, everything skidded like crazy on every shot unless you compensated with outside.

My conclusion was that the slick cloth accentuated skids from the "regular" friction forces between CB and OB, without needing a random chalk or dirt mark.

SpiderMan

Fran Crimi
02-23-2007, 08:23 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote Fran Crimi:</font><hr> .....Ahhh, but I think we may have to take into account the possible build up of polish in those cracks. Polishing every day is a lot of polish. Heck, all during 14.1 pro tournaments, there were balls skidding. Sure, the cloths were new but the balls were slick. I remember guys like Lassiter and Crane and the Miz and Martin complaining to the TD to ease up on the polish. Fran <hr /></blockquote>Hi Fran -- Just a few ideas. madMac....

..........I reckon that, if a polished ball is more slippery than a "used" ball, that players using polished balls havta allow for the rezulting "finer" OB angle, and, later in that frame, when the qball has lost polish in parts, an unpolished area in the contact would give more friction, ie a "mini-kick".

.............And, if this bit of the qball happens to find a similar unpolished area on the OB, u will get a "bad-kick". But, this bad-kick is possibly in fact a "normal-kick", ie the sort of kick (and throw) that u expect and allow-for for allmost every shot when uzing nonpolished balls.

...............Polished areas can become unpolished perhaps due to cushion impacts and due to sliding.

...............A balltoball impact-mark on the qball possibly givz a still larger kick. And, for the unhappy event of an old balltoball impact-mark on the qball meeting one on the OB, a still larger kick.

..............Re the earlyr posting that u karnt clean a qball every shot, in English billiards and snooker the player can ask the ref to clean the qball az often az he/she likes, ie when not in-hand. Likewize, an OB. I guess that the ref would soon blow hiz/her top if he/she didnt see any chalk-mark on the ball. <hr /></blockquote>


So, you're basically focusing on the unpolished part. Well, based on what's been learned about dirt and cling, I understand where your coming from. I'm not disputing in any way the effect of dirt on pool balls.

My theory is that there are a couple of reasons why a ball may skid. One is the dirt factor, the other is that the chalk mark has not quite wiped off of the cue ball due to sliding. I think in the case of clean balls if they slide more and the chalk mark doesn't reach the table frequently enough due to lack of normal roll caused by heavy polishing, then it would seem logical to me that the odds of the chalk mark still being on the cue ball at impact with the OB would be higher than normal.

...Which explains to me why we see it so often in tournaments with newly polished balls, particularly on those shorter shots where the CB is still sliding.

I do think that it's possible, however for the porusness (if that's a word) of the ball to act as 'dirt' to create more of a cling factor. ---Creating sort of like a sandpaper effect (but that wouldn't explain the all the brand new ones that skid). I'm just not really not hooked on the dirt buildup theory in this example. I've seen it happen to too many clean balls.

Fran

dr_dave
02-23-2007, 09:31 AM
<blockquote><font class="small">Quote SpiderMan:</font><hr> Dave,

My comments were based on two assumptions:

1) Zero relative motion between the two surfaces at the contact point would result in zero skid.<hr /></blockquote>Agreed.

<blockquote><font class="small">Quote SpiderMan:</font><hr>This would require addressing the CB low outside in most cases.<hr /></blockquote>Agreed.

<blockquote><font class="small">Quote SpiderMan:</font><hr>I've assumed here that I can apply superposition to combine the effects of low and outside, and that this really is the situation that will come closest to zero relative motion.<hr /></blockquote>Superposition applies fine to motion of the ball, but you need to be careful if attempting to extend it to spin-induced and collision-induced throw. Theses effects are not usually additive; in fact, they are sometimes subtractive (see my February '07 instructional article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2007/feb07.pdf)).

<blockquote><font class="small">Quote SpiderMan:</font><hr>2) Over the years, I seem to detect less mishaps with low outside. Maybe it's a stretch, but it's possible that cause-and-effect has "trained" me toward the situation of #1. Anyway, it's a layman's observation that I assumed to validate my theory.<hr /></blockquote>Sounds reasonable to me. If you have gotten very good at judging the amount of OE required for the throw-less "gearing" effect, you will not have trouble with throw compensation or cling (AKA "skid" or "kick"). The potential problem with trying to achieve stun at impact with the low English is that if you are a little off, the error will be much greater than if you had a rolling ball. See the links in my previous message (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=245593&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1) for more information.

<blockquote><font class="small">Quote SpiderMan:</font><hr>The two talking points above were as deeply as I had thought into the subject before your response. Can I still rationalize my observations? Here's a stab at it:

I read your treatise on stun/roll/backspin. It wasn't something I had previously considered, but it does make sense. Especially when I imagine the case where side is not applied, or not optimally applied. With non-optimum side, I'll concede roll is arguably better than slide.<hr /></blockquote>OK so far.

<blockquote><font class="small">Quote SpiderMan:</font><hr>However, experience seems to tell me that low outside gives me more consistent results than outside with forward roll.<hr /></blockquote>Maybe you are personally better at judging the required amount of OE when you use a low hit. Also, because your cue stick will be elevated slightly more with the lower hit, maybe you a slight swerve effect is coming into play providing automatic aim compensation (although, this would vary with shot speed and be a small effect).

<blockquote><font class="small">Quote SpiderMan:</font><hr>If this observation is correct, then there still exists an argument that could fit both your theory and my experience. It would imply that I'm generally very successful in getting close enough to the right amount of side. If that is true, then slide would still be better than roll.<hr /></blockquote>Agreed, per my comment above.

<blockquote><font class="small">Quote SpiderMan:</font><hr>Perhaps, since the side decays only slowly during the shot, it may be relatively easy to have the CB arrive with "correct" side at contact because the effects of speed and distance variables are diminished.<hr /></blockquote>Agreed.

As with most things, an individual needs to use works best for him or her, even if theory suggests a possible improvement with a modified approach. It's all about consistency and confidence.

Thank you for sharing your insight and experience. I look forward to possibly having you and Deeman visit soon. Let's try hard to make this happen.

Regards,
Dave

dr_dave
02-23-2007, 11:47 AM
<blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote Cornerman:</font><hr> I don't ever remember skidding so prevalent when playing on non-slick cloth. I've thought that the older cloth helped to rub away any excess chalk left on the cueball, while today's worsted cloth doesn't do as a good of a job.<hr /></blockquote>

I've always thought that the slick cloth skidded worse because it was slick, and therefore provided less frictional resistance to whatever ball-ball forces were trying to cause skid/throw.<hr /></blockquote>
First, I want to make sure I am clear about your terminology. I use the term "cling" to refer to excessive OB throw caused by dirt, chalk, roughness, or any other source of high friction at the contact point between the CB and OB during contact. It seems like people also refer to this as "skid" or "kick." I assume you guys are talking about what I call "cling." To me, "skid" implies sliding between a ball and the table cloth, for example, with a "drag" shot, where bottom-spin is used to make the CB "skid" across the cloth, making the bottom spin wear off, creating stun at impact (e.g., see the "drag" stop shot in HSV 3.1 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV3-1.htm), where the CB is "skidding" or sliding across the cloth). As far as "kick" goes, this term is too confusing because it can imply a kick shot where the CB hits a rail first before OB contact.

Terminology aside, "cling" (excessive throw) is caused by ball-to-ball friction, and I think it is independent of ball-to-cloth friction. Now there might be another effect at play here. If the cling is strong, and if the CB has any top or bottom spin, a slight amount of bottom or top spin will transfer to the OB. This spin, because of its direction, can create a slight OB masse/swerve effect (see TP A.24 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-24.pdf)). The condition of the cloth will have an impact on this effect ... the swerve motion will appear to be more delayed (and look more wierd) with a slick cloth. However, for a stun shot, only sidespin will transfer to the OB, and there will be no OB swerve, and in this case I think the cloth condition will have absolutely no effect.

What do you guys think?

<blockquote><font class="small">Quote SpiderMan:</font><hr>My best reference for this is thinking back to when Spetty first opened up Pettypoint. Her 9' Diamond was brand new and had very slick cloth. Even though the balls were brand-new, spotlessly-clean, and highly polished, everything skidded like crazy on every shot unless you compensated with outside.

My conclusion was that the slick cloth accentuated skids from the "regular" friction forces between CB and OB, without needing a random chalk or dirt mark.<hr /></blockquote>My conclusion, based on your reported observations, would be that the ball-to-ball friction was somehow larger than you thought it should be, and that the OB swerve effect may have been more evident (delayed) with the slick cloth. What do other people think?

Regards,
Dave

Cornerman
02-23-2007, 01:57 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote Cornerman:</font><hr> I don't ever remember skidding so prevalent when playing on non-slick cloth. I've thought that the older cloth helped to rub away any excess chalk left on the cueball, while today's worsted cloth doesn't do as a good of a job.<hr /></blockquote>

I've always thought that the slick cloth skidded worse because it was slick, and therefore provided less frictional resistance to whatever ball-ball forces were trying to cause skid/throw.

My conclusion was that the slick cloth accentuated skids from the "regular" friction forces between CB and OB, without needing a random chalk or dirt mark.

SpiderMan <hr /></blockquote>If this were the case, then I would expect that normal cut-induced throw on all shots would also be greater by the same reasoning. But that's not been my observation. I see new clean balls on new slick (e.g. worsted Simonis 760) cloth throwing less, but skidding more often.

Fred

SpiderMan
02-23-2007, 02:07 PM
I think all of the observable phenomena we are discussing could be called "throw". I detected that the original poster was using "skid" to refer to excessive, unusual, or unexpected throw.

I don't tend to use the term "cling" very much. Cling (in the common vernacular) is sometimes used in reference to throw or skid, but other times it seems to reference the actual ball-ball interaction that results in throw or skid.

I tend to think of cling as the latter, making it cause rather than effect. Anyway, I don't use the term very much because I'm not sure how it will be taken.

Regarding slick cloth effects, it probably would be useful to set up some experiments using the same set of clean balls on very slick cloth vs something more akin to a putting green. My gut feel is that throw would be more on the slick cloth.

I'm led to this by imagining two limiting cases, a frictionless OB/cloth interface and one so sticky that no OB movement is possible without roll. I would expect the relationship between slickness and throw to be monotonic, so if one of these cases is max and the other is min, then intermediate values of slick/rough should have a similar relationship.

I'm wondering if I can find someplace where two such tables could be found in close proximity.

SpiderMan

cushioncrawler
02-23-2007, 02:44 PM
<blockquote><font class="small">Quote Fran Crimi:</font><hr> .....So, you're basically focusing on the unpolished part. Well, based on what's been learned about dirt and cling, I understand where your coming from. I'm not disputing in any way the effect of dirt on pool balls.

My theory is that there are a couple of reasons why a ball may skid. One is the dirt factor, the other is that the chalk mark has not quite wiped off of the cue ball due to sliding. I think in the case of clean balls if they slide more and the chalk mark doesn't reach the table frequently enough due to lack of normal roll caused by heavy polishing, then it would seem logical to me that the odds of the chalk mark still being on the cue ball at impact with the OB would be higher than normal.

...Which explains to me why we see it so often in tournaments with newly polished balls, particularly on those shorter shots where the CB is still sliding.

I do think that it's possible, however for the porousness (if that's a word) of the ball to act as 'dirt' to create more of a cling factor. ---Creating sort of like a sandpaper effect (but that wouldn't explain all the brand new ones that skid). I'm just not really hooked on the dirt buildup theory in this example. I've seen it happen to too many clean balls. Fran<hr /></blockquote>Fran -- I agree that some cloths wipe the ball clean of chalk better. Which reminds me, that if i praktis draw shots from a fixed spot, pretty soon i will see large build-ups of chalk on the cloth -- An area of chalk where the qtip haz been contacting the cloth, a largish area of spatter, and an area say a halfball distance away forward where the qball wipes its feet (here the qtip chalk marks on the ball were perhaps completely remooved allmost immediately).

Dirt (and allmost anything) would produce cling, perhaps "dirt" is sometimes cigarette ash -- ash produces cling allmost az bad az chalk (my tests show). The dirty black (bridge) hand that u get from playing is i think from burnt cloth -- a sliding ball burns the cloth, hence black residue. Perhaps residue plus sweat (oil) makes a sort of "dirt" that can get on a ball.

But i think that this "dirt-factor" is highly over-rated. And balltoball impact marks are highly under-rated. I think that balltoball impact-marks are to blame for a lot of cling. If i bang 2 balls together, then place them together (touching), then play the qball onto this frozen-combo, i will see "super-throw", ie cling. So, if a new or old impact mark gets into a contact, u get "mini-cling". If this qball mark finds a mate on the OB, u get a fully fledged cling, allmost az large az a "chalk-cling".

On one occasion, we hadta stop a (billiards) match and change the balls, koz we were getting cling perhaps 1 shot in 10. I could see why -- someone had been praktising lots of some sort of short-range hi-paced pot-shot -- and the large impact marks on the redball were plain to see. The white qball would bave had even more marks, but u havta get really close to see these on a white (or yellow) ball. Balltoball impact marks really stand out on a black ball.

Fran, what is the name given to "reverse-cling" ??, ie the reduced throw that u get due to handling a ball with oily hands etc. madMac.

Cydpkt
02-23-2007, 02:52 PM
How would the different types of cue balls (normal, oversized, magnet inside) have an effect on this as well? Two colliding spheres of the same weight will react differently and two of different weights.

cushioncrawler
02-23-2007, 03:04 PM
<blockquote><font class="small">Quote Cydpkt:</font><hr> How would the different types of cue balls (normal, oversized, magnet inside) have an effect on this as well? Two colliding spheres of the same weight will react differently and two of different weights. <hr /></blockquote>I recall that lots of people have done tests with balls of different sizes or diferent wts or one ball sitting up slightly higher etc, and there woz never any especially bad effect found that might affect throw or deflexion etc. Sure, different ball-surfaces and different wts and sizes etc will all lead to different "normal" throw effects etc, but theze "normal" angles etc would be reliable, once u got used to them. No, what we are looking for is something that "iznt reliable", ie something that causes "cling". madMac.

cushioncrawler
02-23-2007, 03:19 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr> I think all of the observable phenomena we are discussing could be called "throw". I detected that the original poster was using "skid" to refer to excessive, unusual, or unexpected throw.

I don't tend to use the term "cling" very much. Cling (in the common vernacular) is sometimes used in reference to throw or skid, but other times it seems to reference the actual ball-ball interaction that results in throw or skid.

I tend to think of cling as the latter, making it cause rather than effect. Anyway, I don't use the term very much because I'm not sure how it will be taken.

Regarding slick cloth effects, it probably would be useful to set up some experiments using the same set of clean balls on very slick cloth vs something more akin to a putting green. My gut feel is that throw would be more on the slick cloth.

I'm led to this by imagining two limiting cases, a frictionless OB/cloth interface and one so sticky that no OB movement is possible without roll. I would expect the relationship between slickness and throw to be monotonic, so if one of these cases is max and the other is min, then intermediate values of slick/rough should have a similar relationship.

I'm wondering if I can find someplace where two such tables could be found in close proximity. SpiderMan <hr /></blockquote>I agree with Fred and Doc that balltocloth friction duznt affect the frequency or size of cling. But, i woz just thinking -- madMac's "Rules for Minimizing the Chances of Getting Cling", particularly Rule-2 and Rule-3, were based on tests done on a fairly old beat-up table. On a very slippery cloth theze "Rules" might need modification, or complete junking.

For instance, Rule-2 sez that its ok to play low outside english (Fran's favorit) for a shot where the qball will have full roll when it gets to the OB. And, i get the impression that most proz favor this sort of shot. But, on a very slick cloth this rule mightnt work. Or, perhaps it duz still work, but, the "rolling" sometimes duznt eventuate, ie the qball haz stun, in which case the player shood have uzed Rule-3 which sez that here (for stun) u shood hit low with inside english (if u want to avoid cling). madMac.

Fran Crimi
02-23-2007, 04:41 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> Fran -- I agree that some cloths wipe the ball clean of chalk better. Which reminds me, that if i praktis draw shots from a fixed spot, pretty soon i will see large build-ups of chalk on the cloth -- An area of chalk where the qtip haz been contacting the cloth, a largish area of spatter, and an area say a halfball distance away forward where the qball wipes its feet (here the qtip chalk marks on the ball were perhaps completely remooved allmost immediately).

Dirt (and allmost anything) would produce cling, perhaps "dirt" is sometimes cigarette ash -- ash produces cling allmost az bad az chalk (my tests show). The dirty black (bridge) hand that u get from playing is i think from burnt cloth -- a sliding ball burns the cloth, hence black residue. Perhaps residue plus sweat (oil) makes a sort of "dirt" that can get on a ball.

But i think that this "dirt-factor" is highly over-rated. And balltoball impact marks are highly under-rated. I think that balltoball impact-marks are to blame for a lot of cling. If i bang 2 balls together, then place them together (touching), then play the qball onto this frozen-combo, i will see "super-throw", ie cling. So, if a new or old impact mark gets into a contact, u get "mini-cling". If this qball mark finds a mate on the OB, u get a fully fledged cling, allmost az large az a "chalk-cling".

On one occasion, we hadta stop a (billiards) match and change the balls, koz we were getting cling perhaps 1 shot in 10. I could see why -- someone had been praktising lots of some sort of short-range hi-paced pot-shot -- and the large impact marks on the redball were plain to see. The white qball would bave had even more marks, but u havta get really close to see these on a white (or yellow) ball. Balltoball impact marks really stand out on a black ball.

Fran, what is the name given to "reverse-cling" ??, ie the reduced throw that u get due to handling a ball with oily hands etc. madMac. <hr /></blockquote>

Hey, you know, speaking of dirt. if it hasn't been done before, maybe it's a good idea to universally define 'dirt'. Even those impact marks you were referring to could be defined as a type of dirt. What's dirt and what's not dirt?

As for another name for 'reverse cling', I don't know if there is one, but I would be comfortable with the word 'slip'.

Fran

dr_dave
02-23-2007, 05:20 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr> I think all of the observable phenomena we are discussing could be called "throw". I detected that the original poster was using "skid" to refer to excessive, unusual, or unexpected throw.

I don't tend to use the term "cling" very much. Cling (in the common vernacular) is sometimes used in reference to throw or skid, but other times it seems to reference the actual ball-ball interaction that results in throw or skid.

I tend to think of cling as the latter, making it cause rather than effect. Anyway, I don't use the term very much because I'm not sure how it will be taken.

Regarding slick cloth effects, it probably would be useful to set up some experiments using the same set of clean balls on very slick cloth vs something more akin to a putting green. My gut feel is that throw would be more on the slick cloth.

I'm led to this by imagining two limiting cases, a frictionless OB/cloth interface and one so sticky that no OB movement is possible without roll. I would expect the relationship between slickness and throw to be monotonic, so if one of these cases is max and the other is min, then intermediate values of slick/rough should have a similar relationship.<hr /></blockquote>I still don't see how throw (ignoring any possible OB swerve for now), could be impacted by cloth friction, but I'm still open to suggestions or experiments to prove otherwise.

<blockquote><font class="small">Quote SpiderMan:</font><hr>I'm wondering if I can find someplace where two such tables could be found in close proximity.

SpiderMan <hr /></blockquote>Put a piece of glass down over a portion of a "sticky" table. That would be good comparison: smooth glass vs. "sticky" cloth, side by side.

If you try it, please let us know what you observe.

Dave

Jal
02-23-2007, 10:14 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>....Terminology aside, "cling" (excessive throw) is caused by ball-to-ball friction, and I think it is independent of ball-to-cloth friction. Now there might be another effect at play here. If the cling is strong, and if the CB has any top or bottom spin, a slight amount of bottom or top spin will transfer to the OB. This spin, because of its direction, can create a slight OB masse/swerve effect (see TP A.24 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-24.pdf)). The condition of the cloth will have an impact on this effect ... the swerve motion will appear to be more delayed (and look more wierd) with a slick cloth. ...What do you guys think?<hr /></blockquote>I agree. If anything, the masse/swerve effect is less on slicker cloth as far as making or breaking a shot since it takes longer for it to play out. But it's such a tiny effect - only a small fraction of throw - that it can't make any practical difference. I don't believe anyone would even notice it in action.

<blockquote><font class="small">Quote dr_dave:</font><hr><blockquote><font class="small">Quote SpiderMan:</font><hr>My best reference for this is thinking back to when Spetty first opened up Pettypoint. Her 9' Diamond was brand new and had very slick cloth. Even though the balls were brand-new, spotlessly-clean, and highly polished, everything skidded like crazy on every shot unless you compensated with outside.

My conclusion was that the slick cloth accentuated skids from the "regular" friction forces between CB and OB, without needing a random chalk or dirt mark.<hr /></blockquote>My conclusion, based on your reported observations, would be that the ball-to-ball friction was somehow larger than you thought it should be, and that the OB swerve effect may have been more evident (delayed) with the slick cloth. What do other people think?<hr /></blockquote>While I think your explanation is correct, I'm beginning to get a little nervous by the number of people who claim that the cloth does make a diference. Still, I can't see how you could be wrong, especially given the tiny vertical movement of the object ball during the brief impact (approx. 0.001" when it is being driven directly down by friction.)

Jim

cushioncrawler
02-23-2007, 10:46 PM
<blockquote><font class="small">Quote Fran Crimi:</font><hr> .....As for another name for 'reverse cling', I don't know if there is one, but I would be comfortable with the word 'slip'. Fran <hr /></blockquote> I remember Bob Byrne in one of hiz books talks of players eating french fries while playing, and the lard getting on the balls and spoiling the angles, and i allwayz thort that he called this slip-effect "cling", but he must have uzed some other term. Slip, slide, skid, reverse-cling, negative-cling, cling-less, where's-the-cling, what-the!! Hmmmmm, "slip" looks as good as any -- pity we karnt think of something better. Could try to inklood -- sweat, oil, fat, soap, moisture, saliva, hair. madMac.

Jal
02-24-2007, 12:09 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> Jim -- I think that it iz difficult to play a soft stun shot unless at very short range. At medium range i would guess that roll had well and truly taken over (for Stretch). Now, for a rolling ball, a kick will put backspin on the OB, hence the throw (mm) might be a certain size, but the throw angle (dg) will appear large, due to the OB's drive being shortened. I know that u will point out that any vertical component of the frictional force robs some (direct) throw, but here i would point out that the vert component creates a large masse effect on the OB (i have seen this kick-masse lots of times, and it iz huge) which adds extra throw angle and offsets the lost bit. madMac. <hr /></blockquote>Mac, I think you've seen this before, but here is a plot of the throw-masse and spin-masse effects compared to throw angle. The throw angle is based on an arbitrary but representative average value for the coefficient of friction during impact of 0.06. Notice that the corresponding throw-masse and spin-masse angles are multiplied by four. I haven't verified that these are the same values generated by Dr. Dave's analysis (TP A.24), but the example he provides also shows a very small effect.

http://ww2.netnitco.net/users/gtech/OB_Masse.jpg

The friction direction (horizontal axis) is the orientation of the friction force in the friction plane. Angles from 0 - 180 degrees represent draw with various amounts of sidespin, while 180 - 360 are for follow.

A larger value of the coefficient increases throw-masse relative to throw. A very large value, say, 0.5, might potentially make it equal to or greater than throw at some orientations of the friction force. But then the balls would proceed to gearing very early during impact, and both throw and massse action would be limited, and this would keep the masse effect relatively small compared to throw. So I think that in any situation, throw will dominate.

Jim

Rod
02-24-2007, 12:23 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote Cornerman:</font><hr> I don't ever remember skidding so prevalent when playing on non-slick cloth. I've thought that the older cloth helped to rub away any excess chalk left on the cueball, while today's worsted cloth doesn't do as a good of a job.<hr /></blockquote>

I've always thought that the slick cloth skidded worse because it was slick, and therefore provided less frictional resistance to whatever ball-ball forces were trying to cause skid/throw.<hr /></blockquote>
First, I want to make sure I am clear about your terminology. I use the term "cling" to refer to excessive OB throw caused by dirt, chalk, roughness, or any other source of high friction at the contact point between the CB and OB during contact. It seems like people also refer to this as "skid" or "kick." I assume you guys are talking about what I call "cling." To me, "skid" implies sliding between a ball and the table cloth, for example, with a "drag" shot, where bottom-spin is used to make the CB "skid" across the cloth, making the bottom spin wear off, creating stun at impact (e.g., see the "drag" stop shot in HSV 3.1 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV3-1.htm), where the CB is "skidding" or sliding across the cloth). As far as "kick" goes, this term is too confusing because it can imply a kick shot where the CB hits a rail first before OB contact.

Terminology aside, "cling" (excessive throw) is caused by ball-to-ball friction, and I think it is independent of ball-to-cloth friction. Now there might be another effect at play here. If the cling is strong, and if the CB has any top or bottom spin, a slight amount of bottom or top spin will transfer to the OB. This spin, because of its direction, can create a slight OB masse/swerve effect (see TP A.24 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-24.pdf)). The condition of the cloth will have an impact on this effect ... the swerve motion will appear to be more delayed (and look more wierd) with a slick cloth. However, for a stun shot, only sidespin will transfer to the OB, and there will be no OB swerve, and in this case I think the cloth condition will have absolutely no effect.

What do you guys think?

<blockquote><font class="small">Quote SpiderMan:</font><hr>My best reference for this is thinking back to when Spetty first opened up Pettypoint. Her 9' Diamond was brand new and had very slick cloth. Even though the balls were brand-new, spotlessly-clean, and highly polished, everything skidded like crazy on every shot unless you compensated with outside.

My conclusion was that the slick cloth accentuated skids from the "regular" friction forces between CB and OB, without needing a random chalk or dirt mark.<hr /></blockquote>My conclusion, based on your reported observations, would be that the ball-to-ball friction was somehow larger than you thought it should be, and that the OB swerve effect may have been more evident (delayed) with the slick cloth. What do other people think?

Regards,
Dave <hr /></blockquote>

Oil from hands + chalk + dirt, throw in some cheeseburger drippings, ketchup and mayo of course all add up to cling/skid. Jeez I'm getting hungry. LOL We all know that can cause skid when two balls collide. One easy way to avoid the problem is of course more speed. However since thats not always possible it jumps up and bites you when least expected. The other way is using a moderate amount of english. Dirty ball to ball contact is the best reason for skid.

Something not considered is worn out balls. With worn balls its possible for the c/b (or any ball for that matter) to contact above the the equator of another ball. This, or with a little added dirt may have some effect. Really its a small point but not out of the realm of possibility.

Cloth, I think its a fact balls skid more on new cloth. However I think it will take a bit more friction than two clean polished balls making contact. It won't take much though especially in the half ball hit range. As the angle increases the prone to skid factor goes down. So yes, look for more skids on new cloth.

Skid can happen on any table at any time. The tables I play on it happens more than I like. The cloth is 860 broke in well but not worn out. They don't keep the tables or balls near as clean as I like. The balls are worn, thats easy to tell even without dial calipers. I play a fair amount of one pocket. That game I think is prone to balls skidding because of more slower speed shots. Add a little dirty condition factor in there and you get the dreaded skid. It really pi%%#$ me off. When I play 9 ball it rarely happens which relates back to more speed.

Over the years I've played in every condition. I've even had the c/b climb up on an object ball and go a different direction, several times. You just have to live with it. If it happens very often, just remember slower speed is prone to cause problems and english helps eliminate the problem.

Rod

Snapshot9
02-24-2007, 04:40 AM
You know everyone always goes on and on about Simonis 860, but if you have played on it about 6 months into it, it skids often and bad.

Fran Crimi
02-24-2007, 07:48 AM
[ QUOTE ]
sweat, oil, fat, soap, moisture, saliva, hair <hr /></blockquote>

<font color="blue"> </font color> Ewwwwwwww. Gross. Sounds like you're chopping up a body. (That's my Italian background talking. LOL)

You may be right...Bob Byrne might have referred to 'cling' as a slip-effect. Maybe that's where the word 'slip' came from in the back of my mind.

Fran

dr_dave
02-24-2007, 08:59 AM
<blockquote><font class="small">Quote Rod:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote Cornerman:</font><hr> I don't ever remember skidding so prevalent when playing on non-slick cloth. I've thought that the older cloth helped to rub away any excess chalk left on the cueball, while today's worsted cloth doesn't do as a good of a job.<hr /></blockquote>

I've always thought that the slick cloth skidded worse because it was slick, and therefore provided less frictional resistance to whatever ball-ball forces were trying to cause skid/throw.<hr /></blockquote>
First, I want to make sure I am clear about your terminology. I use the term "cling" to refer to excessive OB throw caused by dirt, chalk, roughness, or any other source of high friction at the contact point between the CB and OB during contact. It seems like people also refer to this as "skid" or "kick." I assume you guys are talking about what I call "cling." To me, "skid" implies sliding between a ball and the table cloth, for example, with a "drag" shot, where bottom-spin is used to make the CB "skid" across the cloth, making the bottom spin wear off, creating stun at impact (e.g., see the "drag" stop shot in HSV 3.1 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/HSV3-1.htm), where the CB is "skidding" or sliding across the cloth). As far as "kick" goes, this term is too confusing because it can imply a kick shot where the CB hits a rail first before OB contact.

Terminology aside, "cling" (excessive throw) is caused by ball-to-ball friction, and I think it is independent of ball-to-cloth friction. Now there might be another effect at play here. If the cling is strong, and if the CB has any top or bottom spin, a slight amount of bottom or top spin will transfer to the OB. This spin, because of its direction, can create a slight OB masse/swerve effect (see TP A.24 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-24.pdf)). The condition of the cloth will have an impact on this effect ... the swerve motion will appear to be more delayed (and look more wierd) with a slick cloth. However, for a stun shot, only sidespin will transfer to the OB, and there will be no OB swerve, and in this case I think the cloth condition will have absolutely no effect.

What do you guys think?

<blockquote><font class="small">Quote SpiderMan:</font><hr>My best reference for this is thinking back to when Spetty first opened up Pettypoint. Her 9' Diamond was brand new and had very slick cloth. Even though the balls were brand-new, spotlessly-clean, and highly polished, everything skidded like crazy on every shot unless you compensated with outside.

My conclusion was that the slick cloth accentuated skids from the "regular" friction forces between CB and OB, without needing a random chalk or dirt mark.<hr /></blockquote>My conclusion, based on your reported observations, would be that the ball-to-ball friction was somehow larger than you thought it should be, and that the OB swerve effect may have been more evident (delayed) with the slick cloth. What do other people think?

Regards,
Dave <hr /></blockquote>

Oil from hands + chalk + dirt, throw in some cheeseburger drippings, ketchup and mayo of course all add up to cling/skid. Jeez I'm getting hungry. LOL We all know that can cause skid when two balls collide. One easy way to avoid the problem is of course more speed. However since thats not always possible it jumps up and bites you when least expected. The other way is using a moderate amount of english. Dirty ball to ball contact is the best reason for skid.

Something not considered is worn out balls. With worn balls its possible for the c/b (or any ball for that matter) to contact above the the equator of another ball. This, or with a little added dirt may have some effect. Really its a small point but not out of the realm of possibility.

Cloth, I think its a fact balls skid more on new cloth. However I think it will take a bit more friction than two clean polished balls making contact. It won't take much though especially in the half ball hit range. As the angle increases the prone to skid factor goes down. So yes, look for more skids on new cloth.

Skid can happen on any table at any time. The tables I play on it happens more than I like. The cloth is 860 broke in well but not worn out. They don't keep the tables or balls near as clean as I like. The balls are worn, thats easy to tell even without dial calipers. I play a fair amount of one pocket. That game I think is prone to balls skidding because of more slower speed shots. Add a little dirty condition factor in there and you get the dreaded skid. It really pi%%#$ me off. When I play 9 ball it rarely happens which relates back to more speed.

Over the years I've played in every condition. I've even had the c/b climb up on an object ball and go a different direction, several times. You just have to live with it. If it happens very often, just remember slower speed is prone to cause problems and english helps eliminate the problem.<hr /></blockquote>Rod,

I still don't understand why you think the cloth should affect the amount of cling/skid. Do you have any thoughts on this? I totally agree with the effect being largest closest to a half-ball hit (see my Sept '06 article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2006/sept06.pdf)) and the use of outside English to minimize or eliminate the effect (see my Jan '07 article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2007/jan07.pdf)). However, for collision-induced throw, speed doesn't make much difference at small cut angles; although it does at larger cut angles (see my Sept '06 article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2006/sept06.pdf)). Spin-induced throw is a different story (see my Dec '06 article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2006/dec06.pdf)).

Regards,
Dave

dr_dave
02-24-2007, 09:05 AM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr>....Terminology aside, "cling" (excessive throw) is caused by ball-to-ball friction, and I think it is independent of ball-to-cloth friction. Now there might be another effect at play here. If the cling is strong, and if the CB has any top or bottom spin, a slight amount of bottom or top spin will transfer to the OB. This spin, because of its direction, can create a slight OB masse/swerve effect (see TP A.24 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-24.pdf)). The condition of the cloth will have an impact on this effect ... the swerve motion will appear to be more delayed (and look more weird) with a slick cloth. ...What do you guys think?<hr /></blockquote>I agree. If anything, the masse/swerve effect is less on slicker cloth as far as making or breaking a shot since it takes longer for it to play out. But it's such a tiny effect - only a small fraction of throw - that it can't make any practical difference. I don't believe anyone would even notice it in action.<hr /></blockquote>I agree with you completely here. I'm just searching for what people might be noticing about cling and throw when comparing one cloth to another (assuming everything else remains constant). Maybe it has something to do with a correlation between ball conditions and cloth quality. Pool halls with nice cloth might also have newer and cleaner balls. That might explain some of the anecdotes we are reading, but who knows?

<blockquote><font class="small">Quote Jal:</font><hr><blockquote><font class="small">Quote dr_dave:</font><hr><blockquote><font class="small">Quote SpiderMan:</font><hr>My best reference for this is thinking back to when Spetty first opened up Pettypoint. Her 9' Diamond was brand new and had very slick cloth. Even though the balls were brand-new, spotlessly-clean, and highly polished, everything skidded like crazy on every shot unless you compensated with outside.

My conclusion was that the slick cloth accentuated skids from the "regular" friction forces between CB and OB, without needing a random chalk or dirt mark.<hr /></blockquote>My conclusion, based on your reported observations, would be that the ball-to-ball friction was somehow larger than you thought it should be, and that the OB swerve effect may have been more evident (delayed) with the slick cloth. What do other people think?<hr /></blockquote>While I think your explanation is correct, I'm beginning to get a little nervous by the number of people who claim that the cloth does make a difference. Still, I can't see how you could be wrong, especially given the tiny vertical movement of the object ball during the brief impact (approx. 0.001" when it is being driven directly down by friction.)<hr /></blockquote>I feel the same way, but I'm still hoping some people will try to explain the effects they claim they are seeing.

Regards,
Dave

cushioncrawler
02-24-2007, 03:38 PM
<blockquote><font class="small">Quote Jal:</font><hr> .....The friction direction (horizontal axis) is the orientation of the friction force in the friction plane. Angles from 0 - 180 degrees represent draw with various amounts of sidespin, while 180 - 360 are for follow. A larger value of the coefficient increases throw-masse relative to throw. A very large value, say, 0.5, might potentially make it equal to or greater than throw at some orientations of the friction force. But then the balls would proceed to gearing very early during impact, and both throw and massse action would be limited, and this would keep the masse effect relatively small compared to throw. So I think that in any situation, throw will dominate. Jim <hr /></blockquote> Jim -- Duz your graph(s) apply to all cuts to the left, or shood u just draw it (and explain it) for say just a halfball cut??

I reckon that the negative values for masse-throw and spin-throw might be unrealistic. For a rolling qball, for a halfball impact, the spin axis would havtabe more vertical than 45dg (to lazy to work it out exactly), and i am thinking that this might be impossible unless u uzed finger-spin.

I think that if u did a test, where u put some chalk on the OB, and rolled the qball into the OB at say halfball, u would agree that often the OB will show a huge swerve-effect, ie masse. But i guess that "huge" meenz say 3dg at most -- i doubt that this 3dg would depend on the cloth -- i have a napped cloth. Hmmmmm -- 3dg for cling-masse would meen say 1dg for ordinary impact-masse, whereaz your graph (by 4) indicates 0.1dg. 1dg (and 0.1dg) might be "invisible" (like Bob sez), but 3dg aint. See what u can come up with. madMac.

cushioncrawler
02-24-2007, 04:05 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>While I think your explanation is correct, I'm beginning to get a little nervous by the number of people who claim that the cloth does make a difference. Still, I can't see how you could be wrong, especially given the tiny vertical movement of the object ball during the brief impact (approx. 0.001" when it is being driven directly down by friction.)<hr /></blockquote>I feel the same way, but I'm still hoping some people will try to explain the effects they claim they are seeing....Dave<hr /></blockquote>Dr Dave (and Jim) -- I agree with Fred (and i think Fran) that the thicker fuzzyer cloths do a better job of wiping the ball, especially if less-slippery allso.

The English billiardz team told me that their theory was that a newer cloth produced more electrostatic action which picked up (or better held) little bits of chalk dust. Perhaps. Another way that dust could be held is if the cloth was soapy (which i think all woollen cloths are when new), or perhaps if the cloth was oily (dont know if this is possible for a new cloth). If a special "polish" is used to polish balls, duz this (cream??) attract (stick to) chalk powder ??

Sometimes my opponents uze a strange-blue chalk. Straight away i know what will happen -- their balls are allwayz covered with ugly big blue chalk marks -- hence they get lots more cling/kicks (than me). And, i watch their qball like a hawk, and the slightest hint of a qtip chalk-mark etc and i get the ref to clean it (when it is my shot). And, i allways point out to them that they shood throw away their krap-chalk -- but next time, there it iz again. So, stupid players get (and deserve) more cling. I think that their chalk is perhaps too moist. I think that we can get the same sort of moist-chalk if we are in the habit of keeping the chalk in our pocket (due to sweating, due to high temperature, due to adrenalin) -- we are not allowed to rest the chalk-block on the rail -- so, i uze a magnetic chalk-holder on my belt. madMac.

TennesseeJoe
02-24-2007, 04:48 PM
Just my understanding.
If a cue ball is shot at an object ball at 45dg, with natural roll and no side English, the object ball will travel in a direction directly opposite of the contact point, with some influence. This influence is either:
Natural throw---the object ball travels slightly toward the path of the cue ball.
Cling---the object ball travels more toward the cue ball than natural roll.(Dirt on the cue or object ball.)
Slip---the object ball travels less toward the cue ball than with natural roll. (Oil on the cue/object ball.)
Skid---the amount the object ball moves/skids toward the cue ball. This amount may vary based on cloth type, humidity, etc.
My opinion is that the combination of chalk on the contact points and low humidity on Simonis 720 would increase skid amount.

cushioncrawler
02-24-2007, 05:11 PM
<blockquote><font class="small">Quote TennesseeJoe:</font><hr> Just my understanding.
If a cue ball is shot at an object ball at 45dg, with natural roll and no side English, the object ball will travel in a direction directly opposite of the contact point, with some influence. This influence is either:
Natural throw---the object ball travels slightly toward the path of the cue ball.
Cling---the object ball travels more toward the cue ball than natural roll.(Dirt on the cue or object ball.)
Slip---the object ball travels less toward the cue ball than with natural roll. (Oil on the cue/object ball.)
Skid---the amount the object ball moves/skids toward the cue ball. This amount may vary based on cloth type, humidity, etc.
My opinion is that the combination of chalk on the contact points and low humidity on Simonis 720 would increase skid amount. <hr /></blockquote> Joe -- I think that "skid" is just another name for "cling", and, overseas, "kick". Perhaps u meen what i have been calling "cling-masse", this is where the OB heads off on its little'ol cling-throw direction, but then immediately its trajectory describes a small arc, ie swerv, which effectively adds to the initial cling-throw (dg).

In theory, a slick bed-cloth wouldnt change the extra cling-masse angle, koz this iznt affected by cloth-friction, but, a slick bed-cloth would affect the overall cling-throw-masse angle, koz the masse-arc on a slick cloth would be wider (and more vizible), hence this extra "wideness" would add a few mm to the width of the trajectory, and hence would pinch a bit of angle (dg) from the overall cling-throw-masse angle.

I think that this goze against the main thrust of your statement re lower humidity on 720 inkreecing cling. If 720 is woollen, then higher humidity would open up the woollen cellular structure, and inkreec balltocloth friction, and maximize the OB throw angle. But, if 720 iz mainly plastic, then u might be correct i reckon, koz plastic loozes friction when wetter. madMac.

TennesseeJoe
02-24-2007, 06:50 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote TennesseeJoe:</font><hr> Just my understanding.
If a cue ball is shot at an object ball at 45dg, with natural roll and no side English, the object ball will travel in a direction directly opposite of the contact point, with some influence. This influence is either:
Natural throw---the object ball travels slightly toward the path of the cue ball.
Cling---the object ball travels more toward the cue ball than natural roll.(Dirt on the cue or object ball.)
Slip---the object ball travels less toward the cue ball than with natural roll. (Oil on the cue/object ball.)
Skid---the amount the object ball moves/skids toward the cue ball. This amount may vary based on cloth type, humidity, etc.
My opinion is that the combination of chalk on the contact points and low humidity on Simonis 720 would increase skid amount. <hr /></blockquote> Joe -- I think that "skid" is just another name for "cling", and, overseas, "kick". Perhaps u meen what i have been calling "cling-masse", this is where the OB heads off on its little'ol cling-throw direction, but then immediately its trajectory describes a small arc, ie swerv, which effectively adds to the initial cling-throw (dg).

In theory, a slick bed-cloth wouldnt change the extra cling-masse angle, koz this iznt affected by cloth-friction, but, a slick bed-cloth would affect the overall cling-throw-masse angle, koz the masse-arc on a slick cloth would be wider (and more vizible), hence this extra "wideness" would add a few mm to the width of the trajectory, and hence would pinch a bit of angle (dg) from the overall cling-throw-masse angle.

I think that this goze against the main thrust of your statement re lower humidity on 720 inkreecing cling. If 720 is woollen, then higher humidity would open up the woollen cellular structure, and inkreec balltocloth friction, and maximize the OB throw angle. But, if 720 iz mainly plastic, then u might be correct i reckon, koz plastic loozes friction when wetter. madMac. <hr /></blockquote>


The ball to ball contact friction adjusts the object ball direction. When the object ball changes direction it skid/slides on the cloth before it picks up the natural roll. Chalk on the ball may increase this friction. Humidity could increase this friction but since chalk is on the ball, I don't think the added humidity would change the friction much. The low humidity on the cloth would decrease the friction against the cloth and thereby increase the amount of skid across the cloth. Simonis 720 being a slick cloth would allow the object ball to slide even further.

cushioncrawler
02-24-2007, 07:59 PM
<blockquote><font class="small">Quote TennesseeJoe:</font><hr> ....The ball to ball contact friction adjusts the object ball direction. When the object ball changes direction it skid/slides on the cloth before it picks up the natural roll. Chalk on the ball may increase this friction. Humidity could increase this friction but since chalk is on the ball, I don't think the added humidity would change the friction much. The low humidity on the cloth would decrease the friction against the cloth and thereby increase the amount of skid across the cloth. Simonis 720 being a slick cloth would allow the object ball to slide even further. <hr /></blockquote>Yes, now that u explain it, i see that friction allso affects the qball's skid plus roll distance, and that this overall distance can affect the overall angle. But, the friction and overall skid-plus-roll wouldnt affect the throw angle unless there was a sidewayz sort of step in the qball's trajectory in the first place, which i say there is, in which case you are right.

The only thing that no-one haz mentioned (except perhaps Jim, in hiz graph) iz the spin-factor. A sidewayz (off-line) throw of say 0.1 m/s would give the OB a sidespin of 0.25 m/s. Now, can this sidespin affect the final angle ??? Suppozedly, sidespin karnt affect a ball's direction, but i reckon it can. Looking at it az simply az possible, the sideways balltocloth skidding forces due to spin are initially at a max at the leading edge of the balltocloth contact, hence the OB must veer/kurv in that direction, untill the forces at the front and back equalize. Later, while the ball is slowing down, i reckon that the ball will veer back the other way, as these same forces try to equalize "the other way", and, i reckon that the nett effect is close to zero, the ball having done a sort of "S" trajectory overall. Here, the size of the balltocloth friction would i reckon have a small effect on the size of the S, but allmost zero effect on the end rezult (the final angle). madMac.

TennesseeJoe
02-24-2007, 09:44 PM
<blockquote><font class="small">Quote Suppozedly, sidespin karnt affect a ball's direction, but i reckon it can. [/quote:</font><hr>

In my opinion and I think most will agree---side spin on the cue ball will affect the object ball's direction of travel.

Rod
02-24-2007, 11:21 PM
The amount Dave? I didn't know you were looking for specifics. Never really thought about the amount, although itís more in dirty conditions new or used cloth. Just a slight skid is enough to miss a ball, if it skids more you just miss it farther. A miss is a miss, you're done. Are you after a measurement or amount of times?

New cloth as we know is very slick. With less ball to table friction it happens more often. A small skid on new cloth may not happen on used cloth given the same amount of contact friction. A comparison is road conditions. Tires grip better on a dry surface rather that a wet road. A softer tire compound or a special tread also improves traction. Iím not sure what youíre after but to me, as I said, a miss is a miss. I donít care how much or the amount, the c/b pushed the o/b off the target line and it cost me a game.

Rod

cushioncrawler
02-25-2007, 12:35 AM
<blockquote><font class="small">Quote TennesseeJoe:</font><hr> <blockquote><font class="small">Quote Suppozedly, sidespin karnt affect a ball's direction, but i reckon it can. [/quote:</font><hr>In my opinion and I think most will agree---side spin on the cue ball will affect the object ball's direction of travel. <hr /></blockquote>Joe -- I have edited my post to say that it iz the OB that gets 0.25 m/s of sidespin, i had mistakedly said qball, and this would have put u offside, it iz the OB that is doing the "S" stuff. madMac.

dr_dave
02-25-2007, 10:48 AM
<blockquote><font class="small">Quote Rod:</font><hr> The amount Dave? I didn't know you were looking for specifics. Never really thought about the amount, although itís more in dirty conditions new or used cloth. Just a slight skid is enough to miss a ball, if it skids more you just miss it farther. A miss is a miss, you're done. Are you after a measurement or amount of times?

New cloth as we know is very slick. With less ball to table friction it happens more often. A small skid on new cloth may not happen on used cloth given the same amount of contact friction. A comparison is road conditions. Tires grip better on a dry surface rather that a wet road. A softer tire compound or a special tread also improves traction. Iím not sure what youíre after but to me, as I said, a miss is a miss. I donít care how much or the amount, the c/b pushed the o/b off the target line and it cost me a game.<hr /></blockquote>I'm not looking for any numbers. I'm just trying to find a reasonable explanation for why people claim throw and cling are larger on "slick" cloth. I still don't buy it, that's why I was suggesting possible alternative explanations. Now, I can buy that cling might happen more often with a slick cloth if the source for the cling is fresh chalk spots on the CB, since a slick cloth might rub the chalk off more slowly. But people seem to be implying more than this.

Throw and cling result from ball-to-ball friction existing only during the tiny period of time (about one thousandth of a second) during ball contact. The properties of the cloth will have negligible effect (practically speaking, absolutely no effect), during this contact period. That's why I suggested OB swerve or a correlation between ball and cloth conditions as possible explanations. Again, what I am looking for is a reasonable explanation for what people claim they are observing.

Regards,
Dave

SpiderMan
02-25-2007, 11:06 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr> I think all of the observable phenomena we are discussing could be called "throw". I detected that the original poster was using "skid" to refer to excessive, unusual, or unexpected throw.

I don't tend to use the term "cling" very much. Cling (in the common vernacular) is sometimes used in reference to throw or skid, but other times it seems to reference the actual ball-ball interaction that results in throw or skid.

I tend to think of cling as the latter, making it cause rather than effect. Anyway, I don't use the term very much because I'm not sure how it will be taken.

Regarding slick cloth effects, it probably would be useful to set up some experiments using the same set of clean balls on very slick cloth vs something more akin to a putting green. My gut feel is that throw would be more on the slick cloth.

I'm led to this by imagining two limiting cases, a frictionless OB/cloth interface and one so sticky that no OB movement is possible without roll. I would expect the relationship between slickness and throw to be monotonic, so if one of these cases is max and the other is min, then intermediate values of slick/rough should have a similar relationship.<hr /></blockquote>I still don't see how throw (ignoring any possible OB swerve for now), could be impacted by cloth friction, but I'm still open to suggestions or experiments to prove otherwise.

<blockquote><font class="small">Quote SpiderMan:</font><hr>I'm wondering if I can find someplace where two such tables could be found in close proximity.

SpiderMan <hr /></blockquote>Put a piece of glass down over a portion of a "sticky" table. That would be good comparison: smooth glass vs. "sticky" cloth, side by side.

If you try it, please let us know what you observe.

Dave <hr /></blockquote>

Somewhere in the pile, this packrat has some 12" by 18" sheets of 0.005" teflon mat. I also have some large sheets of fine sandpaper. I'll try to locate the stuff this week, and perform a comparison experiment at my next opportunity in a poolroom (I don't own a table).

It will be interesting to see if the throw angle is the same, or if it varies with surface slickness. I'll have several shooters participate without giving them any insight into the experiment, to avoid anyone's preconceived ideas subconsciously influencing the way they shoot.

SpiderMan

Fran Crimi
02-25-2007, 11:42 AM
[ QUOTE ]
The ball to ball contact friction adjusts the object ball direction. When the object ball changes direction it skid/slides on the cloth before it picks up the natural roll. Chalk on the ball may increase this friction. Humidity could increase this friction but since chalk is on the ball, I don't think the added humidity would change the friction much. The low humidity on the cloth would decrease the friction against the cloth and thereby increase the amount of skid across the cloth. Simonis 720 being a slick cloth would allow the object ball to slide even further.

I never had a pretty girl forget my name.
Tennessee Joe
<hr /></blockquote>


Hi Tennessee Joe. Fast Larry here. /ccboard/images/graemlins/grin.gif Interesting thing about Simonis 860: Players have been saying for years that balls slide more on 860 than on any other Simonis cloth. I think Mac is right about the composite of the cloth being what determines it's slide factor moreso than the length of the fibers.

Fran

dr_dave
02-25-2007, 12:55 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr>While I think your explanation is correct, I'm beginning to get a little nervous by the number of people who claim that the cloth does make a difference. Still, I can't see how you could be wrong, especially given the tiny vertical movement of the object ball during the brief impact (approx. 0.001" when it is being driven directly down by friction.)<hr /></blockquote>I feel the same way, but I'm still hoping some people will try to explain the effects they claim they are seeing....Dave<hr /></blockquote>Dr Dave (and Jim) -- I agree with Fred (and i think Fran) that the thicker fuzzyer cloths do a better job of wiping the ball<hr /></blockquote>I also agree with this. So this might affect the frequency of cling for new and/or clean and/or polished balls. However, it seems like people are also claiming that the amount of throw and cling (not just the frequency) will be larger with a slicker cloth. That's where I disagree.

Regards,
Dave

dr_dave
02-25-2007, 01:03 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr> I think all of the observable phenomena we are discussing could be called "throw". I detected that the original poster was using "skid" to refer to excessive, unusual, or unexpected throw.

I don't tend to use the term "cling" very much. Cling (in the common vernacular) is sometimes used in reference to throw or skid, but other times it seems to reference the actual ball-ball interaction that results in throw or skid.

I tend to think of cling as the latter, making it cause rather than effect. Anyway, I don't use the term very much because I'm not sure how it will be taken.

Regarding slick cloth effects, it probably would be useful to set up some experiments using the same set of clean balls on very slick cloth vs something more akin to a putting green. My gut feel is that throw would be more on the slick cloth.

I'm led to this by imagining two limiting cases, a frictionless OB/cloth interface and one so sticky that no OB movement is possible without roll. I would expect the relationship between slickness and throw to be monotonic, so if one of these cases is max and the other is min, then intermediate values of slick/rough should have a similar relationship.<hr /></blockquote>I still don't see how throw (ignoring any possible OB swerve for now), could be impacted by cloth friction, but I'm still open to suggestions or experiments to prove otherwise.

<blockquote><font class="small">Quote SpiderMan:</font><hr>I'm wondering if I can find someplace where two such tables could be found in close proximity.

SpiderMan <hr /></blockquote>Put a piece of glass down over a portion of a "sticky" table. That would be good comparison: smooth glass vs. "sticky" cloth, side by side.

If you try it, please let us know what you observe.

Dave <hr /></blockquote>

Somewhere in the pile, this packrat has some 12" by 18" sheets of 0.005" teflon mat. I also have some large sheets of fine sandpaper. I'll try to locate the stuff this week, and perform a comparison experiment at my next opportunity in a poolroom (I don't own a table).

It will be interesting to see if the throw angle is the same, or if it varies with surface slickness. I'll have several shooters participate without giving them any insight into the experiment, to avoid anyone's preconceived ideas subconsciously influencing the way they shoot.<hr /></blockquote>Sounds good to me, provided you clean the balls periodically to help reduce sporadic "cling" as a factor.

I look forward to hearing your report of the results.

Thanks,
Dave

cushioncrawler
02-25-2007, 01:47 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> ......I also agree with this. So this might affect the frequency of cling for new and/or clean and/or polished balls. However, it seems like people are also claiming that the amount of throw and cling (not just the frequency) will be larger with a slicker cloth. That's where I disagree....<hr /></blockquote> Dr Dave -- Backthereawayz i mentioned that i thort that a slick cloth might give more cling-effect koz the "baseline" would be different, ie koz u might get a finer cut-angle with a slick cloth, koz the "soapyness" might be all over the balls. Likewize perhaps for balls covered in ball-polish. If so, then perhaps the cling-effect (ie the extra throw) might be larger, yet the cling-throw itself might be no larger than what one gets with non-soapy balls. Just a thort. madMac.

TennesseeJoe
02-25-2007, 04:26 PM
<blockquote><font class="small">Quote Fran Crimi:</font><hr> &lt;/font&gt;&lt;blockquote&gt;&lt;font class="small"&gt;Quote:&lt;/font&gt;&lt;hr /&gt;
The ball to ball contact friction adjusts the object ball direction. When the object ball changes direction it skid/slides on the cloth before it picks up the natural roll. Chalk on the ball may increase this friction. Humidity could increase this friction but since chalk is on the ball, I don't think the added humidity would change the friction much. The low humidity on the cloth would decrease the friction against the cloth and thereby increase the amount of skid across the cloth. Simonis 720 being a slick cloth would allow the object ball to slide even further.

I never had a pretty girl forget my name.
Tennessee Joe
<hr /></blockquote>


Hi Tennessee Joe. Fast Larry here. /ccboard/images/graemlins/grin.gif Interesting thing about Simonis 860: Players have been saying for years that balls slide more on 860 than on any other Simonis cloth. I think Mac is right about the composite of the cloth being what determines it's slide factor moreso than the length of the fibers.

Fran <hr /></blockquote>

Well hello Fast Fran er I mean Ms. Fran. (Thanks, humor does go a long way.) Now that I have had 24 hours to sleep on this post I realize I need another 48 hours.

When I stated,"Simonis 720 being a slick cloth would allow the object ball to slide even further", my reference was to other much thicker cloth such as slow bar table rubber backed cloth. This was just an intuitive thought, not really backed by data. It just seems that a ball will skid further on thin/hard cloth than thick/soft cloth.

Rod
02-25-2007, 08:10 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Rod:</font><hr>
Throw and cling result from ball-to-ball friction existing only during the tiny period of time (about one thousandth of a second) during ball contact.

Regards,
Dave <hr /></blockquote>


I think you might need to reevaluate the amount of contact time. When skid occurs I think it lasts a bit longer than with a clean surface. If chalk (or any oil mixed with chalk or dirt substance) caused the skid it absorbs some amount of energy. I think this would increase contact time. Granted were still talking in thousands of a second but its not only possible but probable. When I watch a c/b ride up on an o/b it has to be longer. You can hear and see the c/b come back down on on the bed. Its the same as open wheel car racing. When the front tire of the rear car touches the rear tire of the front car. It rides up and usually both cars loose control.

If I understand your o/b swerve theory I also think that is possible. I think a somewhat variable controlled test could be set up using cameras to capture the moment. It would have to be done on two different tables with new and used cloth and other variables.

Since you don't buy my explanation you can prove me wrong. LOL How about using a 24oz rubber backed thick cloth or a very thin 760 cloth. Are you still saying cloth has no effect? I think you will find cloth does make a difference. You may have to shoot it a hundred times (just a wild guess) to draw a conclusion. I'll add I think a natural slower rolling c/b is the worst culprit for this dreaded disease.

At any rate your not buying because I'm not selling anyway. I just go from years of past experience and what I have observed. I'll still be more attentive on new cloth. You won't have to consider that though since cloth doesn't make a difference. We'll just take different paths until we're proven right or wrong.

In the end increased friction is the cause no matter what cloth is used. It to bad we can't always play on pristine equipment. It would still happen though but not near as often.

Rod

Paul_Mon
02-26-2007, 05:16 AM
Thanks to all who replied and verified the use of low outside-english to reduce the skid. Like Fred says many of these skids occur when a stun shot or slow roll is needed. The hall I frequent does use a polish in their daily cleaning, but the polish is watered down quite a bit. I also believe Bob Jewettís theory that static electricity is a culprit. Most places around here are really dry in the winter using forced air heat without any humidity control.

During yesterdays session at the pool hall there was not one occurrence of skid. While many of my shots required the use of low-outside english only one shot was purposely made using low outside to reduce skid. Is it just coincidence that some days Iíll encounter 4-5 instances and other days none?

dr_dave
02-26-2007, 09:34 AM
<blockquote><font class="small">Quote Rod:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr>Throw and cling result from ball-to-ball friction existing only during the tiny period of time (about one thousandth of a second) during ball contact.<hr /></blockquote>I think you might need to reevaluate the amount of contact time.<hr /></blockquote>Actually, you are right. I should have written: "much less than one thousandth of a second." A was thinking about cue tip contact times when I wrote this. Ball-to-ball contact times are actually much less, even too small to view with the high-speed video equipment I use.

<blockquote><font class="small">Quote Rod:</font><hr>When skid occurs I think it lasts a bit longer than with a clean surface. If chalk (or any oil mixed with chalk or dirt substance) caused the skid it absorbs some amount of energy. I think this would increase contact time.<hr /></blockquote>I don't think this has ever been proven, and I don't accept it (at the moment) conceptually. The next time I shoot some high-speed video, I'll try to look at this; but as I pointed out, the time intervals we are talking about (with or without cling) are tiny.

Regards,
Dave

TennesseeJoe
02-26-2007, 10:11 AM
Rod posts:
"When skid occurs I think it lasts a bit longer than with a clean surface."



In my opinion, cling always occurs when two balls rub against each other. Cling always results in skid. The amount of cling is determined by ball surface, foreign substances on contact points, humidity, speed, some unknowns, i.e. electricity?, etc. The amount of cling is merely one effect determining the amount of skid.

dr_dave
02-26-2007, 11:02 AM
<blockquote><font class="small">Quote Rod:</font><hr>I think you might need to reevaluate the amount of contact time. When skid occurs I think it lasts a bit longer than with a clean surface.<hr /></blockquote>I disagree; but again, I wouldn't be sure until I saw proof (theoretical, experimental, or convincing fact-based arguments). Now, I would agree with you that when cling occurs, it does give the impression visually that the CB is grabbing and hanging on to the OB, but I don't think this is what is actually happening.

<blockquote><font class="small">Quote Rod:</font><hr>If I understand your o/b swerve theory I also think that is possible.<hr /></blockquote>This I am sure about. It is proven in TP A.24 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-24.pdf). However, the effect is tiny compare to the amount of throw.

<blockquote><font class="small">Quote Rod:</font><hr>I think a somewhat variable controlled test could be set up using cameras to capture the moment. It would have to be done on two different tables with new and used cloth and other variables.<hr /></blockquote>Agreed. Although, you will need some might fancy camera equipment ... much better than what I have.

<blockquote><font class="small">Quote Rod:</font><hr>Since you don't buy my explanation you can prove me wrong. LOL How about using a 24oz rubber backed thick cloth or a very thin 760 cloth. Are you still saying cloth has no effect?<hr /></blockquote>If you are asking if I still think cloth properties has no effect on the amount of throw, keeping everything else constant, then my answer is still yes (until I see proof otherwise).

<blockquote><font class="small">Quote Rod:</font><hr>I think you will find cloth does make a difference. You may have to shoot it a hundred times (just a wild guess) to draw a conclusion. I'll add I think a natural slower rolling c/b is the worst culprit for this dreaded disease.<hr /></blockquote>I agree that the cloth will affect the CB's motion dramatically, and it will affect the speed and rate of slowing of both the CB and OB. The cloth will also affect the rate of "OB Swerve." However, as I show in TP A.24 (http://www.engr.colostate.edu/~dga/pool/technical_proofs/new/TP_A-24.pdf), the amount of "OB swerve," as compared to the amount of throw, is tiny. Also, the amount of "OB swerve" does not vary with cloth friction.

<blockquote><font class="small">Quote Rod:</font><hr>At any rate your not buying because I'm not selling anyway. I just go from years of past experience and what I have observed.<hr /></blockquote>If your intuition from past experience is perfect, then more power to you. I still like to understand what is going on. It helps me build my intuition faster and it helps me be more confident (if I know why and when something should or should not happen). I am asking these questions and trying to find answers so we can try to better understand how to explain what people think they are observing. To me, and to many others, I think this is useful. If you don't, nobody is forcing you to participate in the discussion; although, I hope you continue to participate, because you seem to have lots of experience and strong opinions.

Thanks,
Dave

Bob_Jewett
02-26-2007, 12:55 PM
<blockquote><font class="small">Quote Rod:</font><hr> ... I think you might need to reevaluate the amount of contact time. ... <hr /></blockquote>
By a couple of ways of measuring it, ball-to-ball contact time turns out to be around 0.2 thousandths of a second (0.2 milliseconds or 200 microseconds). As I understand the contact, chalk at the contact point could increase the time by effectively making the surface softer, but it should not change it by more than the time it would take the ball to move through the thickness of the chalk layer. I doubt that it could ever more than double the contact time.

dr_dave
02-26-2007, 01:12 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote Rod:</font><hr> ... I think you might need to reevaluate the amount of contact time. ... <hr /></blockquote>
By a couple of ways of measuring it, ball-to-ball contact time turns out to be around 0.2 thousandths of a second (0.2 milliseconds or 200 microseconds). As I understand the contact, chalk at the contact point could increase the time by effectively making the surface softer, but it should not change it by more than the time it would take the ball to move through the thickness of the chalk layer. I doubt that it could ever more than double the contact time. <hr /></blockquote>Thank you Bob. It is good to see you back on the forum. Where have you been?

Dave

Jal
02-26-2007, 01:29 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> Jim -- Duz your graph(s) apply to all cuts to the left, or shood u just draw it (and explain it) for say just a halfball cut?? <hr /></blockquote>Mac, the graph does apply to left cuts generally. There are so many combinations of cut angle, draw/follow, sidespin and speed that I thought it better to just look at the friction direction. But the graphs below are geared to cut angle (no pun intended).

<blockquote><font class="small">Quote cushioncrawler:</font><hr>I reckon that the negative values for masse-throw and spin-throw might be unrealistic. For a rolling qball, for a halfball impact, the spin axis would havtabe more vertical than 45dg (to lazy to work it out exactly), and i am thinking that this might be impossible unless u uzed finger-spin.<hr /></blockquote>The graph uses the convention that positive throw and masse angles are "toward the cueball" after impact (ie, in the typical throw direction). Negative values are away from the cueball (ie, overspin on the cueball).

<blockquote><font class="small">Quote cushioncrawler:</font><hr> I think that if u did a test, where u put some chalk on the OB, and rolled the qball into the OB at say halfball, u would agree that often the OB will show a huge swerve-effect, ie masse. But i guess that "huge" meenz say 3dg at most -- i doubt that this 3dg would depend on the cloth -- i have a napped cloth. Hmmmmm -- 3dg for cling-masse would meen say 1dg for ordinary impact-masse, whereaz your graph (by 4) indicates 0.1dg. 1dg (and 0.1dg) might be "invisible" (like Bob sez), but 3dg aint. See what u can come up with. madMac. <hr /></blockquote>Well, thanks to your urging I looked at this again and plotted maximum throw and subsequent masse action when cling occurs. Both graphs are for a ball at natural roll, one without english and one with max inside english (ie, RWz = 1.75V). The second one should yield the maximum post impact masse angle under any conditions (I think). Draw on cueball produces a little less than follow and the masse opposes the throw.

They assume that the coefficient of friction (mu) is large enough to bring the balls to a gearing state at the end of impact, whether realistic or not. The throw and masse effects are limited by the gearing, no matter how large mu might be. (Technically, the values shown for mu are acutally for (mu)q, where q is the fraction of the total impulse between the balls necessary to bring the balls to gearing. q can be no greater than 1, but can be less. If you assume mu is just large enough for gearing to take place at the end of impact, then q=1.)

http://ww2.netnitco.net/users/gtech/MaxThrowMasse_No_English.jpg

http://ww2.netnitco.net/users/gtech/MaxThrowMasse_Inside_English.jpg

As you can see, they're in the ballpark of the numbers you've been citing. Throw still dwarfs masse, but not by as much as under normal conditions (and may be unrealistic at the larger cut angles). It all depends on how big mu can get.

At any rate, I think you called it right Mac.... Australians 1, Americans 0. (But we get 5 points if squirt increases with speed. If it decreases, I'll purchase a ticket and you can practice your football on me.)

PS. I still haven't verified that the equations I used are in agreement with Dr. Dave's.

Jim

cushioncrawler
02-26-2007, 02:05 PM
<blockquote><font class="small">Quote Rod:</font><hr> ....Oil from hands + chalk + dirt, throw in some cheeseburger drippings, ketchup and mayo of course all add up to cling/skid. Jeez I'm getting hungry. LOL We all know that can cause skid when two balls collide. One easy way to avoid the problem is of course more speed. However since thats not always possible it jumps up and bites you when least expected. The other way is using a moderate amount of english. Dirty ball to ball contact is the best reason for skid. Something not considered is worn out balls. With worn balls its possible for the c/b (or any ball for that matter) to contact above the the equator of another ball. This, or with a little added dirt may have some effect. Really its a small point but not out of the realm of possibility. Cloth, I think its a fact balls skid more on new cloth. However I think it will take a bit more friction than two clean polished balls making contact. It won't take much though especially in the half ball hit range. As the angle increases the prone to skid factor goes down. So yes, look for more skids on new cloth. Skid can happen on any table at any time. The tables I play on it happens more than I like. The cloth is 860 broke in well but not worn out. They don't keep the tables or balls near as clean as I like. The balls are worn, thats easy to tell even without dial calipers. I play a fair amount of one pocket. That game I think is prone to balls skidding because of more slower speed shots. Add a little dirty condition factor in there and you get the dreaded skid. It really pi%%#$ me off. When I play 9 ball it rarely happens which relates back to more speed. Over the years I've played in every condition. I've even had the c/b climb up on an object ball and go a different direction, several times. You just have to live with it. If it happens very often, just remember slower speed is prone to cause problems and english helps eliminate the problem. Rod <hr /></blockquote> Rod -- In English billiards caroms (cannons) and in-offs are the main game. Thusly, us poor billiards players karnt "eliminate the problem" by uzing english. English will (can) reduce "cling-throw" (for the OB), but there is nothing that can be done to avoid cling's widening of the qball's natural deflexion angle (off the OB). Alltho, we can keep the balls clean -- in billiards, when in-hand, all players wipe the qball on shirt or trouser before shooting. And, az madMac pointed out (and Fran and others), we can uze english to help avoid a cling -- and we can not-uze english to help avoid a cling (here i am talking about keeping the fresh qtip chalk-mark out of the equation, u karnt do much about old marks).

Regarding bedcloth friction getting into the act, there might be some sort of bed-reaction i suppoze. But, i karnt follow some of the arguements, i mean, how can a newer slicker cloth inkreec cling when a slicker cloth haz less friction ???? Bob sez that short impact-times dont much allow much bed-reaction. Here the 1st thing to come to my mind iz that the modern impact-time is larger than the oldendayz impact-time, koz, krapamiths are softer than the old ball. In English billiards (and snooker) we nowadayz have what we call a "spot-kick", what u would call "spot-cling". This is a form of cling where the impact is "clean", but the ball iz sitting in a slight cup due to an imperfikt spot. This is a form of bed-reaction. And, spot-kicks have never ever been mentioned in oldish books, ie pre 1973. Why??? -- Koz spot-kicks werent a problem with the old ballz. Its the soft kraps, ie its the longer impact-time. So, bed reaction i reckon can come into play, but it would i think be more of a factor with a thick cloth, and/or a hi-friction cloth, and with a cloth with lots of craters for an OB to sit in, perhaps craters from jump-shots or masses or swerves. madMac.

cushioncrawler
02-26-2007, 02:30 PM
Jim -- Interesting graphs. But, contrary to what i might have said, your graph(s) of masse-angle never gets any bigger than 1/6th or 1/7th the graph of total-throw-angle. Thinking -- i think that this meenz that masse-throw vs non-masse-throw iz about 1:5 or 1:6, but still below my guestimate of 1:3 or something. I wonder if some chalky tests might confirm the dg of cling-masse, but it (dg) might be hard to estimate, u might need an assistant.

One more thort. Did u factor in that backspin on the OB will lessen its "drive", and hence "magnify" the throw(s). If u award this effect to the masse, then this might inkreece the above ratios to say 1:4 or 1:5. Hmmmmm -- getting "better". madMac.

Jal
02-26-2007, 04:14 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> Jim -- Interesting graphs. But, contrary to what i might have said, your graph(s) of masse-angle never gets any bigger than 1/6th or 1/7th the graph of total-throw-angle. Thinking -- i think that this meenz that masse-throw vs non-masse-throw iz about 1:5 or 1:6, but still below my guestimate of 1:3 or something. I wonder if some chalky tests might confirm the dg of cling-masse, but it (dg) might be hard to estimate, u might need an assistant.<hr /></blockquote>Not only an assistant, but someone else to do the whole thing!

<blockquote><font class="small">Quote cushioncrawler:</font><hr>One more thort. Did u factor in that backspin on the OB will lessen its "drive", and hence "magnify" the throw(s). If u award this effect to the masse, then this might inkreece the above ratios to say 1:4 or 1:5. Hmmmmm -- getting "better". madMac. <hr /></blockquote>Yes I did. But you or someone mentioned dampening of the object ball's forward speed by the chalk. If mu is still large enough to produce gearing, this would push the masse angle closer to the throw angle, ie, (mu)q is increased and throw is proportional to (mu)q, but masse is roughly proportional to (mu)q squared.

Jim

cushioncrawler
02-26-2007, 07:27 PM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr> Jim -- Interesting graphs. But, contrary to what i might have said, your graph(s) of masse-angle never gets any bigger than 1/6th or 1/7th the graph of total-throw-angle. Thinking -- i think that this meenz that masse-throw vs non-masse-throw iz about 1:5 or 1:6, but still below my guestimate of 1:3 or something. I wonder if some chalky tests might confirm the dg of cling-masse, but it (dg) might be hard to estimate, u might need an assistant.<hr /></blockquote>Not only an assistant, but someone else to do the whole thing!

<blockquote><font class="small">Quote cushioncrawler:</font><hr>One more thort. Did u factor in that backspin on the OB will lessen its "drive", and hence "magnify" the throw(s). If u award this effect to the masse, then this might inkreece the above ratios to say 1:4 or 1:5. Hmmmmm -- getting "better". madMac. <hr /></blockquote>Yes I did. But you or someone mentioned dampening of the object ball's forward speed by the chalk. If mu is still large enough to produce gearing, this would push the masse angle closer to the throw angle, ie, (mu)q is increased and throw is proportional to (mu)q, but masse is roughly proportional to (mu)q squared. Jim<hr /></blockquote>Jim -- I could do the test(s) if i had a table. The qball is rolled down a (good) ramp, ie a rampball, ie with a fixed speed. The OB is placed at a fixed spot, perhaps marked with a hole-reinforcement-ring, for a say 45dg impact.

.....(N) U do some "normal" impacts, and measure the rampball's direction and the OB's direction.

.....(C) Then u repeat, with chalk on the OB, and measure the cling directions.

.....(NP) &amp; (CP) Then, u repeat both of theze, but with the OB(s) on a pendulum, hanging just lightly touching the bedcloth.

The difference between (C) and (CP) iz the Cling-Masse angle (probably). The (N) test would act az a check of some sort.

The above tests might overvalue the cling-masse effect, koz by placing the OB in a hole or similar (for C) will give the OB a sort of bobble-angle, which wont be there for the (CP) test.

Re the chalk dampening the OB drive, u might remember that we had an arguement about this last year, and i had to do some "e" tests to check, and found that u were more correct (less wrong) than me. I had said that "e" would be drastically reduced (ie that the OB drive would be reduced), but the (pendulum) tests showed that e woz lowered very very little (the figures are back there somewhere). So, the OB drive IZNT reduced much when cling occurs for a STUN impact, but, the OB drive IZ drastically reduced if the qball haz TOPSPIN, koz of backspin on the OB.

Anyhow, the small reduction in OB drive due to a reduced "e" could not be credited to the masse i reckon, neither could it be blamed on Bush.

And, when u say ..."If mu is still large enough to produce gearing"..., dont forget that mu haz allready been defined and/or measured with this dampened drive inklooded, so no "correction" iz needed (mu iz mu). Where are we now ???? madMac.

Rod
02-27-2007, 09:46 AM
<blockquote><font class="small">Quote Rod:</font><hr>At any rate your not buying because I'm not selling anyway. I just go from years of past experience and what I have observed.<hr /></blockquote>If your intuition from past experience is perfect, then more power to you. I still like to understand what is going on. It helps me build my intuition faster and it helps me be more confident (if I know why and when something should or should not happen). I am asking these questions and trying to find answers so we can try to better understand how to explain what people think they are observing. To me, and to many others, I think this is useful. If you don't, nobody is forcing you to participate in the discussion; although, I hope you continue to participate, because you seem to have lots of experience and strong opinions.

Thanks,
Dave <hr /></blockquote>

You're trying to find answers Dave but you're not exactly listening. You say cloth conditions have no value and I say they do. In the original posters question(Paul)he mentions the c/b climbs right up an object ball. Spiderman (Marty) says balls skid like crazy on brand new cloth. No mention of a c/b climbing up an object ball. I seriously doubt it ever happened either. I feel sure the ball just skid or got pushed. He would have to comment on that situation.

Thats what happens on new cloth meaning less ball to table friction. On used cloth and or very dirty, oily, you name it, it will happen. How well do you draw whitey from 7+' away on new cloth? Can you do the same on used cloth? Can you even get it back from there? LOL Cloth condition does make a difference in friction but it seems you don't want to listen.

I'm done with discussing cloth friction but not skid. The original post mentions worn but polished balls. I'm getting this feeling that polish used may be part of the problem. The chemicals used gets on the cloth, ball gutters pocket facings, well everywhere. It seems to me conditions get tacky. Another place I play polishes balls but skid seldom happens. I'm beginning to think the type of polish may have a bearing. However I think who and how they clean the table is just as important.

When I owned a room we rarely polished our balls and skid rarely happened. I just wiped them down and sometimes used alcohol. I had a clean up guy that kept the tables very clean but in large rooms its just a quickie. I honestly don't know the real answer but keeping equipment clean is a big step in the right direction.

Rod

dr_dave
02-27-2007, 11:03 AM
<blockquote><font class="small">Quote Rod:</font><hr>You're trying to find answers Dave but you're not exactly listening.<hr /></blockquote>I disagree.
<blockquote><font class="small">Quote Rod:</font><hr>You say cloth conditions have no value<hr /></blockquote>You are absolutely wrong here.
<blockquote><font class="small">Quote Rod:</font><hr>and I say they do.<hr /></blockquote>We finally agree on something.

Cloth conditions have a huge affect on many shots and effects (e.g., drag shots, draw shots, tangent-line persistence, bank shots, kick shots, jump shots, masse shots, etc., etc., etc. !!!). In fact, my website and book demonstrate, describe, and illustrate many of these effects.

Now, what I still claim is what I keep writing:

The amount of throw (due to either normal or "clingy" ball conditions) should not depend on cloth conditions (e.g., see my previous posting (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=245650&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1)).

Spiderman has proposed an experiment to determine if this claim is true or not. He said he would report his results when he is done. I don't want to talk anecdotes anymore ... I want to see hard data.

As is often the case lately, I think we just have a "failure to communicate" here.

Regards,
Dave

SpiderMan
02-27-2007, 12:09 PM
<blockquote><font class="small">Quote dr_dave:</font><hr>
Spiderman has proposed an experiment to determine if this claim is true or not. He said he would report his results when he is done. I don't want to talk anecdotes anymore ... I want to see hard data.
Regards,
Dave <hr /></blockquote>

That's the fair way to do it. I think I'm capable enough to design an experiment that will limit the impact of extraneous variables, and thick-skinned enough to report the results whether I like 'em or not. Give me the weekend.

SpiderMan

Jal
02-28-2007, 11:25 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>Jim -- I could do the test(s) if i had a table. The qball is rolled down a (good) ramp, ie a rampball, ie with a fixed speed. The OB is placed at a fixed spot, perhaps marked with a hole-reinforcement-ring, for a say 45dg impact.

.....(N) U do some "normal" impacts, and measure the rampball's direction and the OB's direction.

.....(C) Then u repeat, with chalk on the OB, and measure the cling directions.

.....(NP) &amp; (CP) Then, u repeat both of theze, but with the OB(s) on a pendulum, hanging just lightly touching the bedcloth.

The difference between (C) and (CP) iz the Cling-Masse angle (probably). The (N) test would act az a check of some sort.<hr /></blockquote>Hi Mac. I think your proposed test would do the trick. At first it seemed like the thread on which the OB is hanging would cause problems by inhibiting spin (which affects throw), but after further thought, probably not (same argument as for the cloth). But it seems to me that just having it sit on the cloth, sans thread, and hitting it alternately with stun and roll would do it?

I've verified that Dr. Dave's treatment in TP A.24 will produce the same results as shown on the graphs. So to the extent that something hasn't been overlooked (and the huge values for mu are realized), I expect that test results would conform to them. However, something has been overlooked: your "friction squeeze" effect. I would like to incorporate it but it's impossible to do without knowing how mu changes during impact, and still very hard if it's anything but constant (or nearly so).

<blockquote><font class="small">Quote cushioncrawler:</font><hr>Re the chalk dampening the OB drive, u might remember that we had an arguement about this last year, and i had to do some "e" tests to check, and found that u were more correct (less wrong) than me. I had said that "e" would be drastically reduced (ie that the OB drive would be reduced), but the (pendulum) tests showed that e woz lowered very very little (the figures are back there somewhere). So, the OB drive IZNT reduced much when cling occurs for a STUN impact, but, the OB drive IZ drastically reduced if the qball haz TOPSPIN, koz of backspin on the OB...Anyhow, the small reduction in OB drive due to a reduced "e" could not be credited to the masse i reckon, neither could it be blamed on Bush. <hr /></blockquote>I looked at those posts and through the material you sent me last year, but couldn't find anything definitive. Have you done some more testing or did I miss it?

In order to affect the results significantly, the object ball's speed needs to be reduced to something like 0.8 or 0.7 of the idealized value. This corresponds to an "e" of 0.6 or 0.4. From what you're saying, this doesn't happen.

The induced backspin and its effect on the OB's forward speed is taken into account in the graphs, and by Dr. Dave's treatment. We've squeezed out all we can from that. Do you have some results, however informal, that shows that masse is approx. 1/3 of throw?

<blockquote><font class="small">Quote cushioncrawler:</font><hr>And, when u say ..."If mu is still large enough to produce gearing"..., dont forget that mu haz allready been defined and/or measured with this dampened drive inklooded, so no "correction" iz needed (mu iz mu). Where are we now ???? madMac. <hr /></blockquote>For normal values of mu, yes. But for the cling case? If you have these, I would like to see them.

It's not very satisfying to have some of the subtle effects built in to the measured values for mu (in the normal cases); they don't exert the same influence in different situations. They could be separated out, possibly, if Marlow didn't use frozen balls. But given the variations amongst actual balls, it hardly seems worth it (and it isn't that easy to do).

Jim

cushioncrawler
02-28-2007, 03:49 PM
<blockquote><font class="small">Quote Jal:</font><hr> .....Hi Mac. I think your proposed test would do the trick. At first it seemed like the thread on which the OB is hanging would cause problems by inhibiting spin (which affects throw), but after further thought, probably not (same argument as for the cloth). But it seems to me that just having it sit on the cloth, sans thread, and hitting it alternately with stun and roll would do it?<hr /></blockquote> Jim -- I think this would be difficult to set up (align) accurately, ie between the 2 tests. And, it might tell us more about the differences in throw between stun and roll, but wouldnt i think give a better picture of cling-masse.

<blockquote><font class="small">Quote Jal:</font><hr>.....I've verified that Dr. Dave's treatment in TP A.24 will produce the same results as shown on the graphs. So to the extent that something hasn't been overlooked (and the huge values for mu are realized), I expect that test results would conform to them. However, something has been overlooked: your "friction squeeze" effect. I would like to incorporate it but it's impossible to do without knowing how mu changes during impact, and still very hard if it's anything but constant (or nearly so).<hr /></blockquote>Jim -- I wouldnt worry about Friction-Sqeez, it iz smaller than what i might have said last year, ie more like 0.1dg rather than 1.0dg. But FlatSpot-Sqeez iz allways biggish, ie perhaps up to 0.5dg. But, these both occur for all impacts, and, theze are both allready inklooded in mu, so dont need double-counting, if u see what i mean.

<blockquote><font class="small">Quote Jal:</font><hr>.....I looked at those posts and through the material you sent me last year, but couldn't find anything definitive. Have you done some more testing or did I miss it?
In order to affect the results significantly, the object ball's speed needs to be reduced to something like 0.8 or 0.7 of the idealized value. This corresponds to an "e" of 0.6 or 0.4. From what you're saying, this doesn't happen.<hr /></blockquote>Jim -- I found the PM i sent u re this, it was all a part of "efrens wisdom"....

".....I checked my old diaryz, and i couldnt find any meazurements for (e) for a chalky impakt -- so i did a few new tests. I do 2 types of (e) test -- the old-fashioned drop&amp;bounce, off a steel anvil (u meazure h1 &amp; h2) -- and a pendulum test, the swinging ball (on cotton thread) hits a stationary ball (i meazure the distance the swinger swingz throo). The pendulum iz my favorite, and it lendz itself to the chalk test allso. Anyhow, i found that (e) for a 2-1/4" cheap ball, at medium speed, was 0.959. And, with lots of chalk in the contact, 0.952. Bad newz for my silly (skidding) theory. I guess that the thickness of the chalk, and the (wasted) energy needed to flatten it, aint much at all"...

So, this duznt give us an e of 0.8, but, the cling-backspin might rezult in an "effective e" of close to 0.8, if u see what i mean.

<blockquote><font class="small">Quote Jal:</font><hr>.....The induced backspin and its effect on the OB's forward speed is taken into account in the graphs, and by Dr. Dave's treatment. We've squeezed out all we can from that. Do you have some results, however informal, that shows that masse is approx. 1/3 of throw?<hr /></blockquote>No, i saw lots of giant cling-masse swerv in my tests, but never tryd to measure them. If the masse-swerv woz say 3dg, and total throw say 9dg, then this would be 1 in 3, or 1:2, depending on wordage uzed.

<blockquote><font class="small">Quote Jal:</font><hr>.....For normal values of mu, yes. But for the cling case? If you have these, I would like to see them.<hr /></blockquote> Jim -- I will send a PM re my stuff. I think that i have in effect repeated all of Marlowe's balltoball friction tests, not that i have ever seen his work, nor read hiz book.

<blockquote><font class="small">Quote Jal:</font><hr>.....It's not very satisfying to have some of the subtle effects built in to the measured values for mu (in the normal cases); they don't exert the same influence in different situations. They could be separated out, possibly, if Marlow didn't use frozen balls. But given the variations amongst actual balls, it hardly seems worth it (and it isn't that easy to do). Jim <hr /></blockquote>I doubt that the effect of OB-spin, OB-masse, friction-sqeez, flatspot-sqeez etc could all be seperated (measured). madMac.

Bob_Jewett
02-28-2007, 08:55 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> ... Now, what I still claim is what I keep writing:

The amount of throw (due to either normal or "clingy" ball conditions) should not depend on cloth conditions ... ... <hr /></blockquote>
I'm going to slightly disagree with this.

I also feel that at the instant the balls collide, what's happening at the bottom of the balls has at most a tiny, tiny effect on which direction the balls will be going right after the collision. (Think 0.001 degrees.) I think that's your main point. I think that this will be obvious to anyone who has enough grasp of the physics involved to start thinking about the time-evolution of the forces on the balls during the ball-ball collision, but that is a very small percentage of pool players, and so it will be good to have some kind of experimental confirmation. My experience, however, is that even if such experimental confirmation is available, many players will continue to believe the myth because it just seems more reasonable and/or because they do not read about the results of experiments.

My disagreement is in what leads up to the collision. I think the cloth conditions will affect how dirty the contact point is.

Jal
02-28-2007, 11:46 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr> .....Hi Mac. I think your proposed test would do the trick. At first it seemed like the thread on which the OB is hanging would cause problems by inhibiting spin (which affects throw), but after further thought, probably not (same argument as for the cloth). But it seems to me that just having it sit on the cloth, sans thread, and hitting it alternately with stun and roll would do it?<hr /></blockquote> Jim -- I think this would be difficult to set up (align) accurately, ie between the 2 tests. And, it might tell us more about the differences in throw between stun and roll, but wouldnt i think give a better picture of cling-masse.<hr /></blockquote>You're probably be right Mac. I was thinking that if the balls reached gearing during impact, you should see the same amount of throw in both cases, stun and roll. The only difference would be the imparted bacskspin and the subsequent masse in the roll case. But I don't know if mu would be large enough. (You could tell if it is by the amount of throw, but you wouldn't really know this, I guess, unless you used the hanging ball!) So I'll tentatively defer to your judgement.

<blockquote><font class="small">Quote cushioncrawler:</font><hr><blockquote><font class="small">Quote Jal:</font><hr>...... However, something has been overlooked: your "friction squeeze" effect. I would like to incorporate it but it's impossible to do without knowing how mu changes during impact, and still very hard if it's anything but constant (or nearly so).<hr /></blockquote>Jim -- I wouldnt worry about Friction-Sqeez, it iz smaller than what i might have said last year, ie more like 0.1dg rather than 1.0dg. But FlatSpot-Sqeez iz allways biggish, ie perhaps up to 0.5dg. But, these both occur for all impacts, and, theze are both allready inklooded in mu, so dont need double-counting, if u see what i mean.<hr /></blockquote>I think you've talked me into it. Throw, along with the direction of the induced backspin component, will develop according to the average orientation of the impact line. Since this is different than the initial orientation of the impact line, the effective surface speed, for the purpose of determining throw and spin, will be different than the initial conditions would indicate. But this should be a very minor effect in most or maybe all situations. The angle between the throw and spin directions, which is what I've been concerned about since it's a major factor in how much masse occurs, will not change by much since throw itself will not be affected significantly (ie, they're both shifted together with respect to the average impact direction.)

<blockquote><font class="small">Quote cushioncrawler:</font><hr>"....The pendulum iz my favorite, and it lendz itself to the chalk test allso. Anyhow, i found that (e) for a 2-1/4" cheap ball, at medium speed, was 0.959. And, with lots of chalk in the contact, 0.952. Bad newz for my silly (skidding) theory. I guess that the thickness of the chalk, and the (wasted) energy needed to flatten it, aint much at all"...<hr /></blockquote>Thanks Mac. I think I did look at that but somehow missed it. It certainly seems to put that to rest.

<blockquote><font class="small">Quote cushioncrawler:</font><hr><blockquote><font class="small">Quote Jal:</font><hr>.....For normal values of mu, yes. But for the cling case? If you have these, I would like to see them.<hr /></blockquote> Jim -- I will send a PM re my stuff. I think that i have in effect repeated all of Marlowe's balltoball friction tests, not that i have ever seen his work, nor read hiz book.<hr /></blockquote>I would like to see whatever you have.

<blockquote><font class="small">Quote cushioncrawler:</font><hr><blockquote><font class="small">Quote Jal:</font><hr>..... They could be separated out, possibly, if Marlow didn't use frozen balls. ...<hr /></blockquote>I doubt that the effect of OB-spin, OB-masse, friction-sqeez, flatspot-sqeez etc could all be seperated (measured). madMac. <hr /></blockquote>It would help if you knew the contact times to a fair level of precision for the particular balls at hand, and then did exceedingly accurate measurements of the net throw. Given that, the "true" throw could, I think, be teased out; there's a simple formula which relates these things to each other when mu doesn't change much during impact (high surface speeds). Of course, this wouldn't tell you what's going on at low surface speeds. It might be doable there too, without requiring a Phd in math, but I'm not sure. At any rate, it wouldn't be easy.

Jim

cushioncrawler
03-01-2007, 12:35 AM
<blockquote><font class="small">Quote Jal:</font><hr> ......It would help if you knew the contact times to a fair level of precision for the particular balls at hand, and then did exceedingly accurate measurements of the net throw. Given that, the "true" throw could, I think, be teased out; there's a simple formula which relates these things to each other when mu doesn't change much during impact (high surface speeds). Of course, this wouldn't tell you what's going on at low surface speeds. It might be doable there too, without requiring a Phd in math, but I'm not sure. At any rate, it wouldn't be easy. Jim <hr /></blockquote>Nah, this test will be a soda, compared to some of the tests i have done over the last 18 years. Try this, a test for the aerodynamic rezistance (Cd) for a rolling ball -- now, that woz difficult. Anyhow, it will be August before i have my table(s) back, so perhaps someone out there can jump in first. madMac.

Jal
03-01-2007, 12:45 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr>...I also feel that at the instant the balls collide, what's happening at the bottom of the balls has at most a tiny, tiny effect on which direction the balls will be going right after the collision. (Think 0.001 degrees.) I think that's your main point. ...<hr /></blockquote>Just a note of concurrence.

On a 45 degree cut shot with a rolling cueball going at 7 mph, if cling should result in maximum throw (ie, 1/7'th of the initial surface speed is taken up as throw in the diagonal direction), the horizontal throw component should be just slightly more than 8 degrees. This is almost 16X the normal amount of about 0.5 degrees. If the throw velocity should develop instaneously at the beginning of impact (somehow), then even under these conditions the object ball should only travel a distance downward of about .0025" during impact. (Its average distance would be one-half or .0012".) This is hardly enough for any significant ball/cloth force to develop.

If someone should ask "what if the contact time doubles", then we might want to throw out the generous assumption about the throw velocity ramping up instantaneously. But still, .005" isn't much either. And Mac's tests indicate that the contact time likely doesn't change much.

Jim

dr_dave
03-01-2007, 07:53 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> ... Now, what I still claim is what I keep writing:

The amount of throw (due to either normal or "clingy" ball conditions) should not depend on cloth conditions ... ... <hr /></blockquote>
I'm going to slightly disagree with this.

I also feel that at the instant the balls collide, what's happening at the bottom of the balls has at most a tiny, tiny effect on which direction the balls will be going right after the collision. (Think 0.001 degrees.) I think that's your main point. I think that this will be obvious to anyone who has enough grasp of the physics involved to start thinking about the time-evolution of the forces on the balls during the ball-ball collision, but that is a very small percentage of pool players, and so it will be good to have some kind of experimental confirmation. My experience, however, is that even if such experimental confirmation is available, many players will continue to believe the myth because it just seems more reasonable and/or because they do not read about the results of experiments.

My disagreement is in what leads up to the collision. I think the cloth conditions will affect how dirty the contact point is. <hr /></blockquote>No disagreements here. So with brand new and clean balls, where the amount of throw might be smaller than normal with most shots, and with new, slick cloth, where the chalk smudges might not wear off as quickly, occasional cling (excessive throw due to non ideal ball-to-ball contact-point conditions) might be more noticeable.

Thanks,
Dave

cushioncrawler
03-01-2007, 03:47 PM
<blockquote><font class="small">Quote Jal:</font><hr> .....If someone should ask "what if the contact time doubles", then we might want to throw out the generous assumption about the throw velocity ramping up instantaneously. But still, .005" isn't much either. And Mac's tests indicate that the contact time likely doesn't change much. Jim <hr /></blockquote>Jim -- Even tho "e" duznt change much, this duznt necessaryly say much about "t" (impact time). Perhaps if the chalk woz say 0.2mm thick, and impakt flatspot say 0.2mm deep, then this might inkreec t by a goodly %.

And, remember what i said earlyr about "spot-kicks", that theze were unknown before the modern soft krap ball woz foisted on us.

I have measured the load/sqeez figures for cloth, and the sqeez/time (settlement) allso. Which duznt help any of theze arguements. But, it gets me thinking that if a poolcloth is very thin, ie allmost zero nap, the ball sits directly on the "hard" weave, ie allmost zero "give". This might give a "spotkick" on a poolcloth. madMac.

Jal
03-02-2007, 11:59 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote Jal:</font><hr> .....If someone should ask "what if the contact time doubles", then we might want to throw out the generous assumption about the throw velocity ramping up instantaneously. But still, .005" isn't much either. And Mac's tests indicate that the contact time likely doesn't change much. Jim <hr /></blockquote>Jim -- Even tho "e" duznt change much, this duznt necessaryly say much about "t" (impact time)....<hr /></blockquote>You're of course right Mac.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>And, remember what i said earlyr about "spot-kicks", that theze were unknown before the modern soft krap ball woz foisted on us.

I have measured the load/sqeez figures for cloth, and the sqeez/time (settlement) allso. Which duznt help any of theze arguements. But, it gets me thinking that if a poolcloth is very thin, ie allmost zero nap, the ball sits directly on the "hard" weave, ie allmost zero "give". This might give a "spotkick" on a poolcloth. madMac. <hr /></blockquote> What is the mechanism for this and does it increase or decrease net throw? Without having thought about it much, it seems to me that friction operating at the base of the object ball will reduce the apparent throw, normal or otherwise. This is a separate issue from differences in their elevations.

As a side note, it does look as if the object ball curves sometimes at larger cut angles. If this is true, I attribute it to cueball elevation.

Jim

cushioncrawler
03-02-2007, 02:56 PM
<blockquote><font class="small">Quote Jal:</font><hr> ...I have measured the load/sqeez figures for cloth, and the sqeez/time (settlement) allso. Which duznt help any of theze arguements. But, it gets me thinking that if a poolcloth is very thin, ie allmost zero nap, the ball sits directly on the "hard" weave, ie allmost zero "give". This might give a "spotkick" on a poolcloth. madMac. <hr /></blockquote> What is the mechanism for this and does it increase or decrease net throw? Without having thought about it much, it seems to me that friction operating at the base of the object ball will reduce the apparent throw, normal or otherwise. This is a separate issue from differences in their elevations.

As a side note, it does look as if the object ball curves sometimes at larger cut angles. If this is true, I attribute it to cueball elevation. Jim<hr /></blockquote>Jim -- I think a spotkick is due mostly to the spot being a bit sunken, either throo wear, or due to dropping the ball onto the spot, or due to chalk build up under the cloth at the spot (English billiards and snooker). The ball sits in a "dimple". Here u can get a very similar cling sort of effect, even there iz zero chalk in the balltoball contact. The OB suffers more throw, and severe loss of pace. It can only be due to the extra rezistance of the bed inkreecing the contact time (not in itself important to throw), and, this (extra time) rezults in "extra roughing" of the balltoball flatspot. This tends to proov my theory that balltoball friktion is mainly a "war" between "roughing" and "rezidue" (burnt plastic), koz, in spotkicks there need be no difference in the balltoball slippage velocity.

Re the balltobed friktion, this would actually inkreec the throw. A ball trying to shoot out of its own footprint might suffer some bed-friktion, but this would be in a straight line oppozing its travel, so no real effect on the throw angle so far. But, if there is throw, then there is 2.5:1 of sidespin, now, this sidespin will (allwayz) create balltobed friktion (on the side of the dimple) az the ball jumps out of its dimple, this friktion will (allwayz) inkreec the throw. And, if there is any masse-effect (eg koz of a rolling qball), then the dimple wont much affect the masse's effect on throw, it will simply load more of that masse-throw into the OB's first jump, ie it will tend to "hide" some of the masse-swerv, koz this will occur "within the dimple", so to speak.

Re -- object ball curve (sometimes) at larger cut angles -- If this is for a stun-shot, then this kurv must be due to the 2.5:1 sidespin. If for a rolling-shot, then the kurv would allso inklood some masse. If the kurv is due partly to elevation-difference, then this might be due to an additional masse-effect (i reckon) -- and, now that u mention it, elevation difference could be one more factor contributing to spotkicks. madMac.

cushioncrawler
03-03-2007, 03:06 PM
Jim -- The mechanism for balltoball friction works like this. When 2 balls rub, their smooth surfaces become rougher. Rougher meenz more friction. But, there iz a limit to how rough a surface can get due to simple rubbing. Hence a limit to friction.

The roughing is due to loss of plastic, by grinding and melting and burning etc. The lost plastic rezidue is partly thrown out, but there is allways some in the contact zone. This rezidue dekreecez friction. It acts like a mixture of bearings and oil.

So, the harder and more energetic the impact, the more the rezidue, with no upper limit. But (az we have allready said), we karnt say "the more the roughness", koz there iz an upper limit to roughness (without actually cutting gear-teeth into a ball). A microscope shood help to see this (i havent got one). So, rough wins the war at slowish speed impacts, and rezidue winz at hi-speed impacts. There is a bit more i could add to help my arguement, but i have said enuff. madMac.

Cornerman
03-04-2007, 06:15 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> I think the cloth conditions will affect how dirty the contact point is. <hr /></blockquote>I'll toss in a "Me Too" post.

I, also.

Fred

dr_dave
03-16-2007, 11:46 AM
<blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote SpiderMan:</font><hr> I think all of the observable phenomena we are discussing could be called "throw". I detected that the original poster was using "skid" to refer to excessive, unusual, or unexpected throw.

I don't tend to use the term "cling" very much. Cling (in the common vernacular) is sometimes used in reference to throw or skid, but other times it seems to reference the actual ball-ball interaction that results in throw or skid.

I tend to think of cling as the latter, making it cause rather than effect. Anyway, I don't use the term very much because I'm not sure how it will be taken.

Regarding slick cloth effects, it probably would be useful to set up some experiments using the same set of clean balls on very slick cloth vs something more akin to a putting green. My gut feel is that throw would be more on the slick cloth.

I'm led to this by imagining two limiting cases, a frictionless OB/cloth interface and one so sticky that no OB movement is possible without roll. I would expect the relationship between slickness and throw to be monotonic, so if one of these cases is max and the other is min, then intermediate values of slick/rough should have a similar relationship.<hr /></blockquote>I still don't see how throw (ignoring any possible OB swerve for now), could be impacted by cloth friction, but I'm still open to suggestions or experiments to prove otherwise.

<blockquote><font class="small">Quote SpiderMan:</font><hr>I'm wondering if I can find someplace where two such tables could be found in close proximity.

SpiderMan <hr /></blockquote>Put a piece of glass down over a portion of a "sticky" table. That would be good comparison: smooth glass vs. "sticky" cloth, side by side.

If you try it, please let us know what you observe.

Dave <hr /></blockquote>

Somewhere in the pile, this packrat has some 12" by 18" sheets of 0.005" teflon mat. I also have some large sheets of fine sandpaper. I'll try to locate the stuff this week, and perform a comparison experiment at my next opportunity in a poolroom (I don't own a table).

It will be interesting to see if the throw angle is the same, or if it varies with surface slickness. I'll have several shooters participate without giving them any insight into the experiment, to avoid anyone's preconceived ideas subconsciously influencing the way they shoot.<hr /></blockquote>Spiderman,

Did you ever get a chance to try this out?

Dave

SpiderMan
03-16-2007, 01:47 PM
Couldn't get results yet that would pass scientific muster.

I made a crude 1st attempt using the side rail to align the balls, and shooting the CB at about a 45-degree angle to the line of travel. Typical throw was about a diamond at table's length, but the variation was enormous from shot to shot, even with wiped balls. I tried the bare cloth, and with a sheet of paper underneath. I saw no differences that I could separate from shot-to-shot variance. This was a crude 1st try that told me it isn't going to be such an easy experiment to perform and document.

Initial conclusion - with the balls already touching and me forced to shoot down on the CB, I think the sensitivity to technique overshadows the results. <font color="red"> But, for the record, I will state that I was unable to document differences in throw angles attributable to table-surface conditions.</font color>

I'll have to try making an alignment fixture of wood to get the balls out to the middle of the table, and also to allow me to shoot into a repeatable frozen combo to propel the "CB" into the OB with minimized spin.

I also see now that I will need a more precise method of measuring the OB throw angle. I'm thinking of a wooden "target" with a piece of carbon paper on it, so that each ball impact will print a dot.

SpiderMan

cushioncrawler
03-16-2007, 04:34 PM
This reminds me of the 100'z of hours that i have spent on the table doing theze sorts of tests.

Good idea for qball accuracy. I sometimes uze an accurate ball ramp, to give identical repeatable lines of travel, and identical speeds. Fix this ramp in pozzy uzing heavy bricks etc. The first 3 ramps that i made were rubbish.

Allso, u can get a good qball line by setting up 2 balls about 7mm apart. Give the 2 balls a slight tap on the head to give a dimple to accurately locate (and align) the 2 balls. Now, hitting a 3rd ball (placed in line) straight full-ball into the first ball will give the last ball a good repeatable line of travel. I sometimes uze the ball-ramp to roll this 3rd ball, into the "set" balls, to give good speed (albeit a very low speed unless the ramp goze halfway to the ceiling).

The OB is a big problem. How can u locate it time after time without uzing a dimple, or a page-hole-reinforcement-ring, without affecting its travel. The OB will bobble out of its dimple or ring, affecting the rezult. And, worse, a dimple actually moovz along with time, so u havta repeat some sort of baseline initial test to keep a good eye on the dimple, otherwize u will waste hours of tests, like i did. And, a ring will moov i reckon, or at least the whole cloth will (by stretching or something).

I could say much more. I will be watching with interest. Karnt wait to get my tables up and going again. madMac.

cushioncrawler
03-16-2007, 04:41 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr> ......I also see now that I will need a more precise method of measuring the OB throw angle. I'm thinking of a wooden "target" with a piece of carbon paper on it, so that each ball impact will print a dot.... <hr /></blockquote>I allwayz uze a bit of lumber with blue tack along it, and loose toilet paper in front. Carbon paper is too hi-tech for me. madMac.

Bob_Jewett
03-16-2007, 05:27 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr> ... I also see now that I will need a more precise method of measuring the OB throw angle. I'm thinking of a wooden "target" with a piece of carbon paper on it, so that each ball impact will print a dot. ... <hr /></blockquote>
In any case, I think you will have to repeat each condition. Note on the first shot about where the ball lands on the far cushion. Put an object ball there and mark it somehow. Repeat the shot and move the target ball a little until it is in the center of your tries. Record. This can give you accuracy of better than half an inch in six diamonds which is less than half a degree. It is best if you can do this to both sides and one set up the middle without any throw.

dr_dave
03-17-2007, 08:04 AM
<blockquote><font class="small">Quote SpiderMan:</font><hr> Couldn't get results yet that would pass scientific muster.

I made a crude 1st attempt using the side rail to align the balls, and shooting the CB at about a 45-degree angle to the line of travel. Typical throw was about a diamond at table's length, but the variation was enormous from shot to shot, even with wiped balls. I tried the bare cloth, and with a sheet of paper underneath. I saw no differences that I could separate from shot-to-shot variance. This was a crude 1st try that told me it isn't going to be such an easy experiment to perform and document.

Initial conclusion - with the balls already touching and me forced to shoot down on the CB, I think the sensitivity to technique overshadows the results. <font color="red"> But, for the record, I will state that I was unable to document differences in throw angles attributable to table-surface conditions.</font color>

I'll have to try making an alignment fixture of wood to get the balls out to the middle of the table, and also to allow me to shoot into a repeatable frozen combo to propel the "CB" into the OB with minimized spin.<hr /></blockquote>You might consider using a setup similar to Diagram 2 in my September '06 article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2006/sept06.pdf). As described in the article, the setup helps eliminate some of the difficult-to-control variables.

<blockquote><font class="small">Quote SpiderMan:</font><hr>I also see now that I will need a more precise method of measuring the OB throw angle. I'm thinking of a wooden "target" with a piece of carbon paper on it, so that each ball impact will print a dot.<hr /></blockquote>Don't you have a video camera? If so, you might consider using it as described in the article. The cut angle template (http://www.engr.colostate.edu/~dga/pool/resources/cut_angle_template.pdf) and rail and table ruler (http://www.engr.colostate.edu/~dga/pool/resources/rail_ruler.pdf) in the instructor and student resources section of my website (http://www.engr.colostate.edu/~dga/pool/resources/index.html) can be helpful. See the article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2006/sept06.pdf) for more info.

Good luck,
Dave

moglet
05-02-2007, 01:37 PM
This is a lengthy and erudite thread, congratulations. I'm from the UK and am aware of cushioncrawler's work, he is also aware of some of mine! His deductions and experiments are worthy and useful.

But, as cushioncrawler knows but has not bothered to verify, do you guys know that for all the discussion you have had, you have left out one important factor?

If your balls are made of the same stuff that ours are made of, try rolling them on a mirror surface. By all means clean them beforehand, but leave them for half an hour at room temperature and try again. Don't try this with brand new balls they are pretreated to inhibit what the ball will do after some weeks in service. What is the track or snail trail left by the ball on the mirror surface?

Bob_Jewett
05-02-2007, 02:45 PM
<blockquote><font class="small">Quote moglet:</font><hr> ...
If your balls are made of the same stuff that ours are made of, try rolling them on a mirror surface. By all means clean them beforehand, ... <hr /></blockquote>
How do you clean them?

moglet
05-02-2007, 05:11 PM
Cotton cloth, anything to satisfy yourself that there should be nothing foreign on the ball surface.

jamesp
05-03-2007, 08:04 AM
Hi all,

I see that you have worked out that chalk can cause kicks and there are a number of shots you can play in certain circumstances that you can avoid the chalk being there on point of contact and hence avoid a chalk kick.

I help run a cue sports forum in the UK (mainly snooker), I thought after reading this thread here it would be worth sharing information and ideas together as all the balls used in snooker, billiards and pool are all made by the same company Saluc.

So what are these kicks when there is no chalk present?

If you read the 'debate on kicks' section on www.talksnooker.com (http://www.talksnooker.com) which is in the technical section, you will see that there seems to be an oily substance on phenolic resin snooker or pool balls and if this is not present on contact then a kick will occur and the object ball is likely to be caused to square up or forced off the natural line of the shot.

The balls also seem to be able to self lubricate this oily substance after a while, we are talking about molecules of oil and not droplets.

This has been discovered by user 'moglet' (see posts above) and after carrying out a number of experiments under his instruction I support his claims 100%

Anyway, I hope you find the info of interest and together we can help solve this problem.

There is a direct link to this site / thread on the Talk Snooker forum. Here is the direct link to the kick debate on Talk Snooker http://talksnooker.com/showthread.php?t=156

Bob_Jewett
05-03-2007, 11:52 AM
<blockquote><font class="small">Quote jamesp:</font><hr> ...
The balls also seem to be able to self lubricate this oily substance after a while, we are talking about molecules of oil and not droplets. ... <hr /></blockquote>
Well, OK, but for the time being I'll have to file this under the heading of "really strange things the English have come up with like fried tomatoes at breakfast."

If "lubrication" is required between the balls to avoid this special kind of "lack of oil" skids/kicks/cling, then how can I remove the lubrication and demonstrate the kicks at will? Please do not simply suggest acetone, as I have tried acetone without significant results. Throw (in the pool sense, not the UK sense) between two balls cleaned with acetone was not noticeably different from throw between normal balls.

Can you suggest a "kick at will" preparation?

jamesp
05-03-2007, 01:50 PM
Hi Bob,

I suggest you haven't carried out the acetone test correctly, if you wipe both cue ball and object ball correctly, then I gaurantee the balls will kick like a mule and square up on every shot until the balls recover their oil and or wiped with an oil inpregnated cloth.

You have to put some effort into removing the surface oil, while acetone is a very effective cleaner, we are dealing with oil here which most people would agree is difficult to remove.

You can also use Isoprol Alcohol, really any alcohol cleaner that doesnt leave a residue.

The above is really a very crude test and won't happen in the course of normal play.

Using chemicals has also helped to confuse the issue, you can also remove enough oil to induce kicks using a micro fibre cloth, but this will be difficult to remove all the oil, but with a bit of patience it should work.

If you have more patience, without using chalk (to take it out of the equation) just keep playing a centre ball striking shot against the same object ball, a simple sort range full ball shot will do, see how many shots you play before the balls start to kick, what will happen is that every shot played will remove oil and make a dry spot on both balls, as more dry spots are created, then there is more chance of a kick.

If say the cue ball hits the object ball with a dry spot but a fully lubricated part of the object ball, you will only get a subtle kick and it won't square up the angle of the object ball, however when two dry spots come into contact then you get a clonker of a kick and the object ball is very likely to square up.

Have you read the kick thread on Talk Snooker?...if you don't believe there is oil on the balls....then what is the trail the balls leave behind them when doing the mirror test? (details on how to carry out this test are in that thread on Talk Snooker)

If you mannage to strip the balls of their oil which I have done, you will find that then when you do the mirror test, there are no trails left behind them.

jamesp
05-03-2007, 03:21 PM
Just to add, Saluc (Amarith) have the monopoly on ball manufacturing, they make balls for snooker, pool, billiards, carom and even Russian billiards!

I understand they have recently been taken over by and American company, if this is the case, perhaps the Americans can apply more pressure on them than anyone in Europe has managed to achieve so far.

At the moment the market has to accept anything they produce, if anyone here has ever tried to deal with Saluc directly, you will know what I am talking about.

Bob_Jewett
05-03-2007, 03:48 PM
Jamesp commented:

&gt; I suggest you haven't carried out the acetone test correctly,
&gt; if you wipe both cue ball and object ball correctly, then I
&gt; gaurantee the balls will kick like a mule and square up on
&gt; every shot until the balls recover their oil and or wiped
&gt; with an oil inpregnated cloth.

Since I cleaned with acetone in a way I felt was quite thorough, you are going to have to provide more guidance. Kind of acetone, kind of balls, kind of cleaning cloth, would all be helpful . You need to also allow some latitude on my part. "Acetone from the chemist's shop in Leicester Square" would not be appropriate.

"Kick like a mule" in not a helpful phrase. I think we need something more quantitative. Suppose I set up a plant (combination in the US) with two object balls 1mm apart, and the cue ball strikes one of them full from a line 30 degrees from the line joining the two object balls, and at a speed that will drive the far object ball two table lengths. How much will the second object ball be thrown off-line? In typical situations with normal pool balls, that angle is between 3 and 5 degrees.

&gt; You have to put some effort into removing the surface oil,'

I feel that I did put significant effort into doing that.

&gt; while acetone is a very effective cleaner, we are dealing
&gt; with oil here which most people would agree is difficult to remove.

I have the impression from other comments that you do not know what the strange material appearing on the mirror actually is. Why do you call it oil?

&gt; you can also remove enough oil to induce kicks using a micro fibre
&gt; cloth, but this will be difficult to remove all the oil, but with
&gt; a bit of patience it should work.

Have you tried this? I would prefer not to come home without more wild geese.

&gt; If you have more patience, without using chalk (to take it
&gt; out of the equation) just keep playing a centre ball striking
&gt; shot against the same object ball, a simple sort range full ball
&gt; shot will do, see how many shots you play before the balls
&gt; start to kick, what will happen is that every shot played will
&gt; remove oil and make a dry spot on both balls, as more dry
&gt; spots are created, then there is more chance of a kick.

I don't see how you can demonstrate kick on a full-ball shot without any spin on the cue ball. I assume you misspoke. Have you tried the above experiment?

&gt; Have you read the kick thread on Talk Snooker?...if you don't
&gt; believe there is oil on the balls....then what is the trail
&gt; the balls leave behind them when doing the mirror test?

I have read that thread. It might be more interesting if a resin chemist could be found to contribute.

As for what the material is, I think neither one of us knows. Have you done a chemical analysis of the trail?

You may be onto the greatest breakthrough in cue sports since Mingaud invented the leather tip, but I think you need to be far more careful in the experiments you do and the way you present results if you want to convince others.

jamesp
05-03-2007, 04:28 PM
It seems obvivous to me that you are against the idea, perhaps because of a vested interest in an idea of your own perhaps?

If you don't want to share the theroy thats fine by me, I have my own set of Aramith snooker balls and with an occasional wipe with an oil inpreganated cloth the amount of kicks have been reduced dramatically, leaving just chalk kicks as a problem.

Yes I have tried all the experiments I have mentioned so far and more with success, or I wouldn't have wasted everyones time posting them.

For the record the acetone i used is:...manufactured by UniChem, what else can I say?...its acetone.

If you have read the thread on Talk snooker, you will see that chemists have been involved.

Although that is not necesary as the experiments strongly suggest this on its own for any reasonably intelligent person.

If you do an internet search, for other applications for phenolic resin use's, you will see that in most cases an oil is used in the manufacturing process to remove that item from its mould, that also applies in the manufacturing of snooker / pool balls, so we know there is oil there.

Its not, I repeat my theory, but a friend of mine (who uses the name moglet), I now have a set of Amarith balls that kick a lot less than they used to thanks to him and I thought I would share that with you.

Once you have stripped the balls of their oil, with whatever method you use, just set up a half ball pot and watch the object ball square up and and both balls will kick ie the object ball will not take the it normal line, it doesn't have to be complicated as you suggest.

There does not have to be side spin on a full ball contact to get a kick, pool balls are heavier than snooker balls as far as I know (snooker balls are 143 grams + - 3 grams tolerance), so perhaps these kicks are not noticed so much in pool as a result, they definatley exist in snooker I can assure you.

I am not here to convince others, my set play far better as a result, if you dont want to share the theory, then fair enough.

Bob_Jewett
05-03-2007, 05:35 PM
<blockquote><font class="small">Quote jamesp:</font><hr> It seems obvivous to me that you are against the idea, perhaps because of a vested interest in an idea of your own perhaps? ... <hr /></blockquote>
I'm a skeptic. True believers of all stripes make me nervous.

But I asked about specific quantitative values that I could try to confirm in a controlled way. Can you provide an estimate of the specific numeric values you have observed? All of your comments so far have been subjective, and it would be much better to have values to compare against that are a little more solid than "a lot better" or "like a mule" or "reduced dramatically." Or, said better:

"I often say that when you can measure what you are speaking about and express it in numbers you know something about it; but when you cannot express it in numbers your knowledge is a meagre and unsatisfactory kind: it may be the beginning of knowledge but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be."
-- Lord Kelvin (William Thomson) (1824-1907)

jamesp
05-03-2007, 06:30 PM
Hi Bob,

Im pleased you have admitted to being a skeptic, I have no problem with that.

I assume you are a chalk theorist and put all or most kicks down to that?

I agree chalk causes some kicks, I have also done experiments in that respect, if you play a stun shot near a pocket with an object ball (near the pocket so the cloth hasn't the time to clean the chalk of the ball), ie no cue ball involved, just strike a ball in the pocket with stun.

Pick the ball out of the pocket and you should see a chalk mark on the ball, line this object ball up with the chalk mark facing you and play a cue ball into it with a full ball contact straight onto the chalk mark and you will get a kick. (ps no side spin required)

When playing snooker, moglet has worked out that a chalk kick has roughly a 1 in 15 times of occuring when playing a shot with a full ball contact from roughly a foot between cue ball and object ball, they same shot over distance is unlikely to get a chalk kick as the cloth is very efficent at cleaning chalk from the cue ball and so no chalk is likely to be present by the time it has reached the object ball, quite often when playing snooker you will get a kick when playing a roll shot around the black spot area on a dead straight red, you can stop these kicks by not using chalk on these short range shots, ie if just centre ball stricking is required then no chalk is needed, so dont use chalk for these shots and no chalk kicks will occur.

I notice you have used a quote from an Irish man (Kelvin) in an effort for me to supply numbers, what I have done so far and I repeat again under instruction from the person who discovered this has been of a practicle nature, ie as long as it works are the numbers that important?

Lord Kelvin as mentioned was born in Ireland and spent time in Glasgow University and England, ie very close to us English with the mad idea of fried tomatoes!

Bob_Jewett
05-03-2007, 08:47 PM
<blockquote><font class="small">Quote jamesp:</font><hr> ... I notice you have used a quote from an Irish man (Kelvin) in an effort for me to supply numbers, what I have done so far and I repeat again under instruction from the person who discovered this has been of a practice nature, ie as long as it works are the numbers that important? ... <hr /></blockquote>
Yes, because I agree with Kelvin that if you can't put a number on it you know almost nothing about it. All too many people who can't provide numbers simply spout myths and superstitions and subjective confusions. I can provide you with plenty of examples of such people from the world of American pool, so please don't feel I'm picking on the UKer.

cushioncrawler
05-03-2007, 09:17 PM
<blockquote><font class="small">Quote moglet:</font><hr> This is a lengthy and erudite thread, congratulations. I'm from the UK and am aware of cushioncrawler's work, he is also aware of some of mine! His deductions and experiments are worthy and useful. But, as cushioncrawler knows but has not bothered to verify, do you guys know that for all the discussion you have had, you have left out one important factor? If your balls are made of the same stuff that ours are made of, try rolling them on a mirror surface. By all means clean them beforehand, but leave them for half an hour at room temperature and try again. Don't try this with brand new balls they are pretreated to inhibit what the ball will do after some weeks in service. What is the track or snail trail left by the ball on the mirror surface?<hr /></blockquote> Hi Moglet -- Goodta hearfromya again. I will havta roll some balls (ivory, bonzoline, crystalate, BBA, supers, kraps etc, bakelite and polyester etc) on a mirror and compare the (oily) snail-trails. But u know my thorts on the modern soft light hi-gloss kraps that have been foisted on us all.

If we were still uzing the oldenday hard heavy low-gloss balls (bakelite, or cellulose even, and melamine too) then i dont think that we would be now talking muchly about kicks skid cling throw etc. Koz, i reckon that the old balls were superior in that department.

Hmmmm -- What n where n when woz the earlyst written mention of kick or skid or cling in english or american books etc.

I recall that there woz a bit of argueing re whether ivorys or the new-fangled composite balls kicked more (crystalate n bonzoline, made of celluloid etc, in about 1890) -- some said ivorys kicked less, some said ivorys kicked more. But perhaps the argueing actually came up in say 1922, when bakelite balls came on the scene, still named Crystalate n Bonzoline (they denied being bakelite), not to mention Vitalite n Duralite n Monoid n Ivorylene n Compo-ivory n others. And, i am leeving out the best ball ever made (and the hardest), BBA (made of melamine), made in Melbourne in 1973-74.

Oil or not, there woz something about thoze oldendayz balls that gave us fewer chalk kicks, and less-powerfull chalk kicks. Which brings up a thort -- i reckon that ivory duznt have any oil, and that ivory kicks more (than bonzoz), and that this might appear to support the "oil" cartel, but i reckon that this can be explained elsewize.

But i dont care much about chalk kicks. I care about mini-kicks, not related to chalk -- it iz mini-kicks that worry billiards players (not so much worry to snooker and pool players). The kraps have theze mini-kicks inklooded in the box when u buy them. The box shood say "guranteed to kick, or your money back". Why n how is this so?? The answer is somewhere on the same page as the discussion about "why are/were ivory ball impakts, and bonzo etc impakts, so loud n sharp, compared to the kraps soft sickening "thud" impakt. The answer(s) is in there somewhere, and i have (partly) mentioned it in the past. It dont really need "oils" to account for kicks or mini-kicks -- everything can be explained. madMac.

cushioncrawler
05-04-2007, 04:04 AM
I googled bakelite and oil -- this stuff came from the patents office -- might be similar to ball manufacture, despite denials -- lots of mentions of "oils" or "oil-like substances". madMac.

"STATE OF THE ART -- The production of resin-bonded abrasives requires proper coating of the added abrasive grain by the resin and.....Normally, there are used for this purpose pourable phenolic resins which bond well with the filler when various adjuvants are added.

In preparing the mixture, it is customary first to coat the abrasive grain with a liquid phenolic resin, then mixing with the resin powder, possibly adding other abrasive substances or fillers so that a pourable mixture results. To obtain mixtures with constant properties, as needed in particular for pressing operations with pressing machines, they must normally stabilize for some time, as a rule 2 to 12 hours. After this stabilizing time, the mixtures are often agglomerated, so that they must be broken up and screened in an additional costly operation to be ready for use. Also in use are dry mixtures, i.e. without resol addition. Resols can be modified by addition of other substances. As wetting agents, such substances are used also by themselves.

U.S. Pat. No. 1,537,454 describes a manufacture of grinding wheels where furfural as solvent, a plasticizer, and a hardener are added to the phenolic resin. If desired, also a few drops of cresol oil, phenol or cresol may be added. A disadvantage of the addition of furfurol is that thereby not only are the grinding elements coated as desired, but the dry resin particles stick together. For this reason, neutral anthracene oil is used in U.S. Pat. No. 1,803,117 with the abrasive grain being mixed first with the resin powder and the anthracene oil and subsequently with furfurol.

U.S. Pat. No. 2,814,554 deals with the customary use of furfurol in the production of grinding wheels, anthracene oil being used additionally as an anti-dust agent after the mixture of abrasive grains and resin binder has been fully processed. In U.S. Pat. No. 2,825,538, a liquid rubber-like copolymer is mixed with furfurol so that wetting of the abrasive grain and of the phenol resin in the mixture is possible, to which cresol or creosote or guayacol is added in the mixer as an "absorption agent" for the resin particles which have not attached themselves to the abrasive grain particles wetted with furfurol in the liquid rubber. Thereafter, this liquid "absorption agent" is said to prevent the phenomenon known as "bailing."

U.S. Pat. No. 2,943,926 teaches that furfurol together with cresol have been used for a first coating of the resin bond on the abrasive grain in the production of grinding wheels. Lastly, it was possible to mix the resin-coated abrasive grains with creosote oil and liquid resin to form the wheel from the mixture, and then to harden the resin bond. In U.S. Pat. No. 3,784,365, besides furfurol and creosote oil, also fully chlorinated hydrocarbons were added in the production of resin-bonded grinding wheels. Creosote oil is known from the literature as a common anti-dust agent, but to obtain adequate effectiveness, more oil must be introduced than is desirable with respect to the grinding properties. Besides, it is relatively expensive and therefore reduces the profitability of the product. The literature mentions also the addition of xylol, glycol, and the like, but these are too reactive to lead to satisfactory results.

DE-PS 31 49 213 teaches further the addition of hydrocarbon oils of a viscosity of 10 to 2000 mPa.s as wetting agent. Suitable for this purpose are oils which at temperatures&lt;45į C. have little dissolving effect on the phenolic resin. They may be univalent aliphatic alcohols with 6 to 18 carbon atoms or a phenol substituted with alkyl of 6 to 18 carbon atoms or their mixtures, provided the wetting agent is liquid at room temperature. For the manufacture of the grinding elements. the wetting agent may be either mixed with the phenolic resin beforehand, or be added directly during the mixing of all components. A disadvantage here is that unstable compositions are obtained, which also tend to ball when left standing for a short time and are then greatly impaired in their shapability and bonding powder.

THE INVENTION

The homogenous, non-tacky, thermosetting plastic powder mixtures of the invention are formed by mixing component A comprising a solid phenol novolac resin powder and a hardener containing a small amount of an oil-like substance liquid at room temperature with component B comprising a liquid resol, fillers and optionally additives.

It has been found, surprisingly, that pourable, stable thermosetting mixtures for the production of resin-bonded grinding elements or shaping elements can be obtained by mixing a resin powder, namely a phenol novolac together with a hardener containing a small amount of an oil-like substance liquid at room temperature to form component A, and then processing this pourable non-dusting powder with component B consisting of the fillers or respectively the abrasive grain and other additives, previously mixed intensively with a liquid resol so that a homogeneous non-tacky mixture in powder form is formed. Also, the use of other grain wetting agents is possible, as e.g. creosote oil, furfuryl alcohol, etc. as well as the use of its dry mixtures.

Further it has been found, surprisingly, that the thermosetting mixtures produced with the use of the resin powder of the invention practically no longer requires any curing times as they are distinguished by very constant properties. Owing to this, they offer, besides a longer shelf life, the additional advantage of earlier usability; that is, depending on the oil and the quantity used, they can be processed either immediately or after any desired storage time, the normally necessary operation of breaking and screening being eliminated. Therefore storing the mixtures for the purpose of stabilizing is no longer necessary and the direct usability offers advantages in planning for the mixtures. If needed, new, immediately processable mixtures can be produced in a simple manner so that the production of mixtures in excess, as customary at present, is no longer necessary.

For the production of these mixtures, the resin powder to which the hardener, particularly hexamethylenetetramine, had been admixed, can be mixed with the oil-like substance. Alternatively, the hardener is mixed first with the oil-like substance in which the hardener is not soluble so that the hardener particles are coated with a thin oil film, the resin powder being added only thereafter, and this mixture being then homogenized. In both cases, one obtains by means of this premix in the end a thermosetting mixture which is still pourable even after prolonged storage or transportation times, shapes well, and after processing leads to grinding elements of improved grinding output and stability.....

Examples of oil-like substances liquid at room temperature having hydrophobic but non-adhesive properties, but which do not interfere with the hardening reaction, yet act under normal pressure and at room temperature as hydrophobic parting agents. They may be both mineral and animal oils, but also other hydrophobizing substances with polar substituents. Examples of alcohols usable in the invention are hexyl, n-heptyl, lauryl, n-octyl, capryl, n-nonyl, n-decyl, myristyl, cetyl or stearyl alcohol. Preferred are 2-ethylhexanol, decanol, dodecanol, tridecanol, octadecanol and their mixtures. Mixtures are necessary when an alcohol is solid. Generally, this is the case when the carbon chain contains more than 12 carbon atoms......

As hydrocarbon oil suitable for the invention is a liquid product of the plant type or from petroleum having a viscosity ranging between 100 and 2000 mPa.s. Preferred are petroleum-base oils in this viscosity range.

Mineral oils, aromatic concentrates, naphthenic oils, diesel oil, terpenes and limonenes are suitable oils, provided the available commercial products have the respective viscosity and no dissolving action. Examples of natural oils are castor oil or cashew oil. Mixtures of alcohol and oil are usable and desirable, particularly if the alcohol is a solid substance.

If oil-like substances solid at room temperature but melting below 60į C. are used, a good hydropobization of the novolac-hardener mixture can be obtained if the mixing occurs at elevated temperatures. Alternatively, the oil-like substance, molten at low temperature, can be applied to the resin-hardener mixture by atomizing and simultaneous intensive mixing......

The phenol, or the phenolic component, is reacted with formaldehyde or a formaldehyde-eliminating compound to form the desired novolac. The novolacs may be modified by the usual modification substances such as epoxy resins, rubbers, polyvinyl butyral and inorganic additives.

For wetting the fillers or the abrasive grain with a liquid resol, all resols are suitable that are obtained by alkaline condensation of a phenol with formaldehyde or a formaldehyde-eliminating compound. Especially suitable are those resols which are obtained by reaction of a phenol and formaldehyde in the molar ratio of 1:0.7 to 1:4, preferably condensation products with a molar ratio of 1:1....

Fillers or respectively abrasive grains such as aluminum oxide, SiC, FeS2, Na3 [AlF3 ] and/or potassium fluoroborates, finely divided copolymers of vinylidene chloride and vinyl chloride, potassium sulfate, zinc sulfate and barium sulfate can be mixed with the resol.

Component A is produced so that 3 to 16% by weight of hexamethylenetetramine are intensively mixed with 79 to 96.5% by weight of a novolac and thereafter with 0.5 to 5% by weight of an oil-like substance. The mixing may be done by joint grinding, by stirring, or in a suitable commercial mixer. If oil-like substances are used which melt at temperatures only a little above the mixing temperature, it is possible to melt them beforehand and to atomize them in a suitable mixer.

Component B is produced so that 1.5 to 8% by weight, preferably about 5%, are mixed with the abrasive grain or fillers whereby the individual grains or particles are coated entirely with a thin resol film. During the mixing, additives such as silanes, furfuryl aldehyde, etc. can be added in generally customary amounts."

jamesp
05-04-2007, 05:19 AM
Thanks for that, maybe this will convince Bob Jewett that there is oil on the balls.

moglet
05-04-2007, 09:02 AM
Hi again to you crawler, how's that bible - no don't answer that /ccboard/images/graemlins/wink.gif

All this fuss, it is only another variable that I've tried to add. From your point of view it could be seen as another nail in the coffin, amongst all the other aberrations this is just another to consider.

You never said, did you then get any traces on a mirror?

dr_dave
05-04-2007, 09:12 AM
<blockquote><font class="small">Quote jamesp:</font><hr> Thanks for that, maybe this will convince Bob Jewett that there is oil on the balls. <hr /></blockquote>I think Bob and others (e.g., me) would be happy to hear your theories and conjectures if they are backed up by controlled experiments. For example, see the experiment and results in my September '06 instructional article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2006/sept06.pdf). Bob has also done this experiment. First perform the experiment with a new (or old, but clean) set of balls. Then repeat the experiment after cleaning the "oil" off the balls with a solvent as you have suggested. It would be interesting to see how the results change with different types of cleaning and polishing.

I hope your experiments help discover new knowledge. I'm sure Bob and others would be excited if your experiments can conclusively change conventional wisdom on this topic. I would certainly be curious.

Thanks,
Dave

moglet
05-04-2007, 10:39 AM
Hi Dave, before we get too excited by all this I wonder if the use of solvent to remove whatever may be on the ball is valid. My understanding of your tournament conditions forbids the use of any slippery treatment of the ball, so much so that it is suggested in the "rules" that diluted alcohol should be used to prepare any suspicious ball or balls, is this correct and can you tell me which alcohol and the dilution, presumably in water?

Bob_Jewett
05-04-2007, 11:40 AM
<blockquote><font class="small">Quote moglet:</font><hr>... it is suggested in the "rules" that diluted alcohol should be used to prepare any suspicious ball or balls, is this correct and can you tell me which alcohol and the dilution, presumably in water? <hr /></blockquote>
So far as I know, this has never been done in any tournament in the US. The standard at the US carom championships was to clean the balls with Aramith polish after each match.

An interesting excitement happened at those championships this year. One player was losing an important match badly, and when the match was more than half over he started to complain that his opponent had applied silicone lubricant to one of the cue balls with his glove. It was determined by the tournament official that there was no silicone on the glove. A desperate psychological move?

Bob_Jewett
05-04-2007, 12:24 PM
<blockquote><font class="small">Quote jamesp:</font><hr> Thanks for that, maybe this will convince Bob Jewett that there is oil on the balls. <hr /></blockquote>
CC posts a rather dense, not clearly applicable, ten-page-long item about how to put abrasives into resin grinding wheels that happens to mention oil and oil-like substances, and your conclusion is that Aramith mixes oils into their cast phenolic resin balls. Remarkable. The posting clearly shows that is it possible to put oils into grinding wheels that are made from phenolic resin, but it proves nothing about what may or may not be left on your mirror.

Yes, I am absolutely convinced that oils are used in various manufacturing processes, but I have believed that for quite some time. I'm also certain that some manufacturing processes avoid oil and oil-like substances at all costs.

So, let me state your hypothesis as I understand it:

<font color="blue"> Aramith cast phenolic balls depend on a slightly oily surface to react properly during collisions. This condition is achieved by mixing oil into the phenolic resin during manufacturing. As the oil wears off the surface of the ball, more oil from inside the ball seeps out to again coat the surface. When the surface coating is intentionally cleaned off of two balls and one strikes the other with relative surface motion, friction between the two balls much larger than the typical friction is observed. </font color>

Is that what you are saying?

Cornerman
05-04-2007, 01:48 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> I googled bakelite and oil -- this stuff came from the patents office -- might be similar to ball manufacture, despite denials -- lots of mentions of "oils" or "oil-like substances". madMac.<hr /></blockquote>Bakelite has not been used for pool balls for decades.

The phenolic resin used in pool ball manufacturing is related, but not the same as the process used to make true Bakelite.

And this patent information discusses "the ability to add oil," and not the necessity to add oil. In the thermoplastics industry, we do the same thing. That is, there are certain products that we must add fillers, strengtheners, and lubricants. But just because we do it one product doesn't mean every product get any of these fillers.

Fred &lt;~~~ FWIW

Deeman3
05-04-2007, 02:26 PM
Let me further question this! If I begin to understand these finer points of the migration of certain oils to the surface of balls, will I then miss shots I am now making?

Further, how will this impact my games as we move from worsted cloth to a mirror playing surface?

How much oil does a ball hold/require and how do you change it? Midas? Quickie Lube? If a wood chuck could?

Will oiling my balls help the age spots go away? Will my wife notice?

Is there some defining point that will improve my game or get me that coveted GED I've been considering?/ccboard/images/graemlins/smirk.gif

Paul_Mon
05-04-2007, 02:43 PM
Now that this thread has been resurrected I can say with confidence that the largest contributor to skid at the pool hall I play at is undersized object balls. They routinely (every 2 years or so) replace the cue ball but the object balls are still in use from 8-12 years ago. Upon close inspection the object balls are loaded with dings and scratches. These balls are polished daily. This is the second factor that contributes to skid, the chalk clings to the polish. I bring my matched set of Centennials there for polishing and they skid more after being polished.
Once again, this skid happens most on short, soft shots with follow.

Paul Mon

dr_dave
05-04-2007, 02:53 PM
<blockquote><font class="small">Quote moglet:</font><hr> Hi Dave, before we get too excited by all this I wonder if the use of solvent to remove whatever may be on the ball is valid. My understanding of your tournament conditions forbids the use of any slippery treatment of the ball, so much so that it is suggested in the "rules" that diluted alcohol should be used to prepare any suspicious ball or balls, is this correct and can you tell me which alcohol and the dilution, presumably in water? <hr /></blockquote>I don't know what is done to clean or polish balls at different tournaments, but I think it would still be interesting to try a range of treatments to see what difference they make.

Regards,
Dave

dr_dave
05-04-2007, 03:05 PM
<blockquote><font class="small">Quote Deeman3:</font><hr>Is there some defining point that will improve my game or get me that coveted GED I've been considering?/ccboard/images/graemlins/smirk.gif<hr /></blockquote>I hereby bestow on you an honorary GED from Dr. Dave. Feel free to list it on your resume along with a reference from me. I think you're as smart as any PhD I've ever met.

Regards,
Dave

jamesp
05-04-2007, 03:58 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote jamesp:</font><hr> Thanks for that, maybe this will convince Bob Jewett that there is oil on the balls. <hr /></blockquote>
CC posts a rather dense, not clearly applicable, ten-page-long item about how to put abrasives into resin grinding wheels that happens to mention oil and oil-like substances, and your conclusion is that Aramith mixes oils into their cast phenolic resin balls. Remarkable. The posting clearly shows that is it possible to put oils into grinding wheels that are made from phenolic resin, but it proves nothing about what may or may not be left on your mirror.

Yes, I am absolutely convinced that oils are used in various manufacturing processes, but I have believed that for quite some time. I'm also certain that some manufacturing processes avoid oil and oil-like substances at all costs.

So, let me state your hypothesis as I understand it:

<font color="blue"> Aramith cast phenolic balls depend on a slightly oily surface to react properly during collisions. This condition is achieved by mixing oil into the phenolic resin during manufacturing. As the oil wears off the surface of the ball, more oil from inside the ball seeps out to again coat the surface. When the surface coating is intentionally cleaned off of two balls and one strikes the other with relative surface motion, friction between the two balls much larger than the typical friction is observed. </font color>

Is that what you are saying? <hr /></blockquote>

Yes, that is what I am saying.

cushioncrawler
05-04-2007, 06:15 PM
<blockquote><font class="small">Quote moglet:</font><hr> Hi again to you crawler, how's that bible - no don't answer that /ccboard/images/graemlins/wink.gif All this fuss, it is only another variable that I've tried to add. From your point of view it could be seen as another nail in the coffin, amongst all the other aberrations this is just another to consider. You never said, did you then get any traces on a mirror? <hr /></blockquote>I will havta print another say 50 copyz of the bible later this year, after i shift into my new house in the bush. So, i probably wont do any of yor standard "snail trail" mirror tests untill after i shift, in November.

But, oil karnt flow out of a ball unless something (air) flows in. And, if a ball were left in storage for a very long time, surely any oils would tend to be seen below the equator -- our snail trail would be weak-strong-weak-strong etc. I think that u would point out here that a new ball wouldnt leak koz of the coating, but an oldish ball might, if not too-old (ie dry, ie empty).

But i go along with Cornerman, making balls would be one application where they would avoid or mimimize uzing oils.

And, one thing caught my eye in that patents office stuff, they sometimes can uze alcohol instead of oil. Now, balls and alcohol do mix very well.

Further to the sorts of things that Bob haz mentioned, re Lord Kelvin, what billiards is missing is a good test to measure ball-to-ball friktion, i mean a calibrated graduated authorized apparatus of some sort, sitting in a laboratory. But, rolling or sliding one ball on another mightent tell u a lot, it would still need a collision happening. I karnt think of anything except slo-mo to help meazure the OB's rate of rotation, and something near the wall to meazure the qball's direction (qball hangs on a string, ie pendulum) to allow a good approximation of the fullness of the contact. I will work on it one day. madMac.

cushioncrawler
05-04-2007, 06:39 PM
<blockquote><font class="small">Quote jamesp:</font><hr> Thanks for that, maybe this will convince Bob Jewett that there is oil on the balls. <hr /></blockquote>James -- Nice to meet u. I am a skeptik re this oil bizness. But, if the KKK and the BrotherHood can share the same bed over some issues, then u and me can join forces against soft lite hi-gloss kraps. The first rule iz -- they are to be called "kraps", to avoid confuzion with real proper balls. If enuff players callem kraps for long enuff, the chinese might come to our aide and make some proper balls. I dont care if they cost double, and i dont care if they only "last" half az long, give me bonzoz.

I have allwayz sed that mini-kicks dont much affekt pool, but are terrible for snooker, and poizon for billiards. And, i have allwayz sed that pool n snooker players can minimize the occurrence of chalk-Kicks, and minimize the severity of both chalk-Kicks and mini-kicks, but that the poor old billiard player, who is concerned by the trajektory of the qball mostly, karnt.

But, it occurred to me, that billiards players might have a small advantage over pool players in one respect. We allready know that the coefficient of restitution (e) for a balltoball collision for kraps drops from say 0.96 to say 0.95 when there is a chalk-kick -- a surprizingly small drop. But, i think that the drop in (e) for our oldenday (hard n heavy) balls might be from say 0.82 to say 0.79 -- here the drop in e would narrow the qball's angle, which would partly offset the wider qball angle arizing from the higher (kick) friktion -- ie extra stun-throo (due to chalk-kick) enjoyed by the qball would partly offset the loss of topspin suffered by the qball -- which iz in effekt what one oldtimer told me once (ie that bonzoz dont kick az hard az the kraps kick). madMac.

ras314
05-04-2007, 06:42 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> I karnt think of anything except slo-mo to help meazure the OB's rate of rotation <hr /></blockquote>

Strobe light? Would be much cheaper equipment but probaly take many trials at various strob rates to get good info.

cushioncrawler
05-04-2007, 07:07 PM
<blockquote><font class="small">Quote ras314:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr> I karnt think of anything except slo-mo to help meazure the OB's rate of rotation <hr /></blockquote>Strobe light? Would be much cheaper equipment but probaly take many trials at various strob rates to get good info. <hr /></blockquote>A standard video plus strobe v's a hi-speed slo-mo -- sounds ok. But i must admit that up to now (20 years of testing and meazuring and writing) the only real dough that i have spent on equipment etc woz about $20 for a big lump of steel to uze az an anvil for ball-bounce tests. Since then i have bort a small electronic set of scales ($104) to weigh balls (i keep the scales in my cue-case and weigh balls before play). So i might havta fork out for a video camera.

Just thinking some more, if i meazure the trajektoryz (angles) of both balls, then that is probably all i really need. The qball would be on a string (pendulum), and would leev an impression on bluetack where it hits the wall. The OB would be sitting on the edge of the kitchen table, and would make a mark where it hits the lino. The ht of qball drop givz u the qball speed. Hmmmmm -- could work. Then kums the mandatory fudging and flumming of rezults to get the right answers. madMac.

Jal
05-05-2007, 12:59 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> <blockquote><font class="small">Quote ras314:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr> I karnt think of anything except slo-mo to help meazure the OB's rate of rotation <hr /></blockquote>Strobe light? Would be much cheaper equipment but probaly take many trials at various strob rates to get good info. <hr /></blockquote>A standard video plus strobe v's a hi-speed slo-mo -- sounds ok. But i must admit that up to now (20 years of testing and meazuring and writing) the only real dough that i have spent on equipment etc woz about $20 for a big lump of steel to uze az an anvil for ball-bounce tests. Since then i have bort a small electronic set of scales ($104) to weigh balls (i keep the scales in my cue-case and weigh balls before play). So i might havta fork out for a video camera.

Just thinking some more, if i meazure the trajektoryz (angles) of both balls, then that is probably all i really need. The qball would be on a string (pendulum), and would leev an impression on bluetack where it hits the wall. The OB would be sitting on the edge of the kitchen table, and would make a mark where it hits the lino. The ht of qball drop givz u the qball speed. Hmmmmm -- could work. Then kums the mandatory fudging and flumming of rezults to get the right answers. madMac. <hr /></blockquote>Mac, I think something else needs to be isolated from surface speed in any throw tests, namely, the normal (line-of-centers) velocity. Ideally mu is independent of this, but here are some results which suggest that this is not the case.

I measured throw from Dr. Dave's HSV A.84, which consists of full ball hits with lots of english (large tip offsets). (It can be obtained reasonably accurately from the acquired spin/speed ratio of the object ball.) Below is a comparison of the predicted values versus the measured ones for the three shots in the video. Since you can't measure the cueball's pre-impact spin/speed ratio in this video, at least not easily, the comparisons are done against assumed values of 1 and .7. The cueball's pre-impact velocity is taken to be the object ball's post-impact velocity, which is close enough.

speed: 2.6 mph, measured: 3.0 deg, predicted: 2.3 deg (RW/V=1), 3.1 deg (RW/V =.7)

sp: 6.1 mph, meas: 2.7 deg, pred: .9, 1.3 deg

sp: 9.8 mph, meas: 1.5 deg, pred: .6, .8 deg

The predicted and measured values match up pretty well at the slow speed, but are off by about a factor of two (or worse) at the higher ones. The predictions are based on Marlow's data, gathered from shots at 45 deg cut angles, and Dr. Dave's equation, which estimates mu on the basis of surface speed alone.

So I think you need to vary surface speed while holding the normal velocity constant, and/or vice versa to sort this stuff out. Unfortuntely, neither is easy and would probably require more elaborate equipment than has been employed thus far. Why don't you add that laboratory to your new home? I'm sure Dr. Dave and Bob Jewett would be more than happy to outfit it with whatever you need. Maybe Qtec could contribute too.

Jim

moglet
05-05-2007, 01:40 PM
Hi Paul_Mon, I'm sorry to be a nuisance, your update post again raises some of the issues that concern me. Reduction in ball size is well known over here in the UK. We do not generally and certainly not in the professional game use the Aramith polishing product. In my experience it serves only to make matters worse, some tests suggest that use of this product increases the risk of what we call kicks.

What you describe in both your posts is the much the same problem we have, usually this can be put down to chalk or plain mechanical misalignment, but not always. It is the other cause we are trying to find, our cuesport community has a phobia about science and such, this may be an advantage - all that they require is an answer in the form of a solution not some lengthy thesis full of equations and obscure theory (worthy as that may be). I tender an alternative way of thinking which does have some basis in science, however if no-one is prepared to take the first step to a possibly greater understanding I may just as well not bother, the requirement is not for me to conform to your cuesport community's experiments and theory, though I am happy to do that, it is more of a matter of keeping an open mind and a willingness to find an answer.

Question to your boffins: if all other conditions can be made constant why does the ball's surface coefficient of friction vary so much within the conditions it is expected to perform?

dr_dave
05-05-2007, 03:43 PM
<blockquote><font class="small">Quote Jal:</font><hr>I measured throw from Dr. Dave's HSV A.84, which consists of full ball hits with lots of english (large tip offsets). (It can be obtained reasonably accurately from the acquired spin/speed ratio of the object ball.) Below is a comparison of the predicted values versus the measured ones for the three shots in the video. Since you can't measure the cueball's pre-impact spin/speed ratio in this video, at least not easily, the comparisons are done against assumed values of 1 and .7. The cueball's pre-impact velocity is taken to be the object ball's post-impact velocity, which is close enough.

speed: 2.6 mph, measured: 3.0 deg, predicted: 2.3 deg (RW/V=1), 3.1 deg (RW/V =.7)

sp: 6.1 mph, meas: 2.7 deg, pred: .9, 1.3 deg

sp: 9.8 mph, meas: 1.5 deg, pred: .6, .8 deg

The predicted and measured values match up pretty well at the slow speed, but are off by about a factor of two (or worse) at the higher ones. The predictions are based on Marlow's data, gathered from shots at 45 deg cut angles, and Dr. Dave's equation, which estimates mu on the basis of surface speed alone.<hr /></blockquote>Jim,

I don't think it is worthwhile trying to compare data from some of my high-speed tests with numbers predicted by Marlow's data. Friction properties and how they vary with speed, cut angle, English, and spin will vary from one set of balls and conditions to another. I think the trends are useful to look at and compare, but I don't think it is appropriate to compare values between totally different sets of conditions. As I have pointed out before, my equations and Marlow's data do predict many of the trends that have been verified with experiments. To me, that is the value of the models ... they predict and help us understand the trends. Exact values and ranges will vary with ball conditions, so a player needs to be able to do some calibration (e.g., to know the maximum amount of throw possible under given conditions).

<blockquote><font class="small">Quote Jal:</font><hr>Why don't you add that laboratory to your new home? I'm sure Dr. Dave and Bob Jewett would be more than happy to outfit it with whatever you need. Maybe Qtec could contribute too.<hr /></blockquote>Jim, I'm not sure what you are implying here, but I will assume your intentions were honorable.

Regards,
Dave

Jal
05-05-2007, 05:38 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> ...I don't think it is worthwhile trying to compare data from some of my high-speed tests with numbers predicted by Marlow's data. Friction properties and how they vary with speed, cut angle, English, and spin will vary from one set of balls and conditions to another. I think the trends are useful to look at and compare, but I don't think it is appropriate to compare values between totally different sets of conditions. As I have pointed out before, my equations and Marlow's data do predict many of the trends that have been verified with experiments. To me, that is the value of the models ... they predict and help us understand the trends. Exact values and ranges will vary with ball conditions, so a player needs to be able to do some calibration (e.g., to know the maximum amount of throw possible under given conditions).<hr /></blockquote>Dr. Dave, I beg to differ although I do appreciate your overall point. I think that if mu varies with normal velocity to the extent that predictions based soley on surface speed are off by a factor of two (perhaps more), that is a trend itself worth quantifying. The above measured values, based on three shots with different balls than Marlow's used, don't prove anything of course. But since there is fair agreement at the lowest speed, there is a suggestion there that the differences at higher speeds might not be so much the result of differences between the balls, but due to the full hit.

This can be important, for instance, in helping to explain the discrepancies between the measured pivot points of various cues. Prior to this, I thought that throw could not be much more than a fraction of a degree for "normal" balls under these conditions (full hit, lots of english, brisk speed).

<blockquote><font class="small">Quote dr_dave:</font><hr><blockquote><font class="small">Quote Jal:</font><hr>Why don't you add that laboratory to your new home? I'm sure Dr. Dave and Bob Jewett would be more than happy to outfit it with whatever you need. Maybe Qtec could contribute too.<hr /></blockquote>Jim, I'm not sure what you are implying here, but I will assume your intentions were honorable.<hr /></blockquote>Sorry, just trying to lighten it up a bit (although I would like to see Mac tackle the problem).

Jim

cushioncrawler
05-05-2007, 08:56 PM
Hi Jim -- Dont forget that Marlow's "effective" mu under-estimates "pure" mu, due to significant flatspot-sqeez at the higher speeds. Dr Dave's full-ball impacts wouldnt suffer flatspot-sqeez (only friction-sqeez). All the same, i am thinking that mu might vary as OB speed inkreeces (i think mu drops), besides dropping as balltoball slippage speed inkreeces (which we all know).

But i have been thinking a bit more about that last bit. I think that Dr Dave fitted a sort of exponential curve of best fit to Marlow's 3 data points. But perhaps Dr Dave's curve rightly estimated that mu haz a max of say 0.20 or something at near zero slippage. Even so, i reckon that a plot of more (new) test data would show that mu inkreeces with slippage, before it drops, ie Dr Dave's smoothish curve will have a peak mu at perhaps 0.2m/s.

Re some charitable outfitting of equipment for my new lab -- i am ok for cotton, bluetack, rulers, magnifying glasses, pins, chalk, sticky tape, bricks, ball-ramp, lumber, scissors, ladder, diary, kitchen scale, bathroom scale, and computer. But badly need a microscope, slo-mo video camera, strobe light, universal testing machine, and an assistant. madMac.

moglet
05-06-2007, 05:37 AM
I have to agree with cushioncrawler, I have done many tests and experiments at these lower velocities and have found the same peak at something a little under 0.2m/s. I am not certain whether this is entirely due to Ķ or elasticity or a combination of both. The outer, resin only, shell of the ball is about 1.25 mm thick, the inner core is a bulked mixture of resin and mineral filler, during these low speed impacts only the shell material may play a part in the result of the impact, at higher speeds the characteristics of the core material would play a much more significant role.

It is not clear to me what reference data has been used to assign a value to Ķ, if it is based on the ball surface after being polished with Aramith cleaner, this value will not be the same after the balls have been in use for a short while and it will certainly not be constant. Even the residue from a fingerprint on the ball will change the ball condition, not to mention any other contaminants. I would assume from the posts here that the value of Ķ has been derived theoretically. There is nothing wrong in this, but it cannot account for aberration or anomaly.

Jal
05-06-2007, 12:47 PM
<blockquote><font class="small">Quote moglet:</font><hr> ...Question to your boffins: if all other conditions can be made constant why does the ball's surface coefficient of friction vary so much within the conditions it is expected to perform? <hr /></blockquote>Since nobody has answered, I'll offer some uneducated opinions, but I'm not sure what the sense of your question is:

If you're asking why the manufacture(s) haven't bothered to make it such that mu doesn't vary, the answer probably is that it is a non-issue. A lot of folks aren't aware of throw to begin with, and even if mu were constant, throw would still vary with the particulars of a shot: spin, cut angle and whether or not the balls end up rolling across each other during impact (gearing). Other priorities likely far outweigh considerations of friction and maybe it would be nearly impossible (or expensive) to achieve.

If you're asking what the physical cause of mu's variance with, say, surface speed, here are some candidates:

1) Friction pushes the surfaces apart, ie, there is a normal component. With increasing speed, the little mountains on the surface (asperities) collide at higher "elevations", where, in general, they are less steeply sloped. The collision forces are thus more normal as the equilibrium separation is reached.

2) A greater percentage of the collisions result in shearing of the asperities.

3) The surfaces are lubricated more at higher speeds through melting or generation of surface residues ("bearings"). At first blush this seems like a contradiction, but after some thought you may find it plausible.

4) In the case of amorphous polymers especially, the surfaces might become more mobile and pliant with heating (although the balls are made from thermal setting resins, so maybe not?).

Well, if nothing else, the above are free. Mac (Cushioncrawler) has definite ideas about this, especially #3, and maybe you know more about it than I do.

Jim

Jal
05-06-2007, 01:45 PM
<blockquote><font class="small">Quote moglet:</font><hr>...I would assume from the posts here that the value of Ķ has been derived theoretically. There is nothing wrong in this, but it cannot account for aberration or anomaly. <hr /></blockquote>Dr. Dave derives it here (see TP A.14):

http://www.engr.colostate.edu/~dga/pool/technical_proofs/index.html

It's a very thorough treatment which incorporates the notion of gearing to explain various test results. One of the interesting consequences (of gearing), is that the amount of throw is independent of any abnormal increase in mu for a variety of shots, and quasi-independent of a decrease.

If Marlow (see the article) used frozen balls in perforiming the tests, mu may be overestimated as a result. At the highest speed though (10 m/s), the shift in the tangent line due to compression, which is not accounted for, should result in an underestimation, as Mac mentioned. Maybe these two things happen to mutually cancel, more or less?

As you may have gotten the impression, few are interested in getting it "right" to the n'th decimal place, since real life conditions vary. It would be nice to know though, just how much variance there is amongst different balls in different states of wear and cleanliness.

Jim

cushioncrawler
05-06-2007, 03:06 PM
<blockquote><font class="small">Quote moglet:</font><hr> I have to agree with cushioncrawler, I have done many tests and experiments at these lower velocities and have found the same peak at something a little under 0.2m/s. I am not certain whether this is entirely due to Ķ or elasticity or a combination of both. The outer, resin only, shell of the ball is about 1.25 mm thick, the inner core is a bulked mixture of resin and mineral filler, during these low speed impacts only the shell material may play a part in the result of the impact, at higher speeds the characteristics of the core material would play a much more significant role..... <hr /></blockquote>I formed this opinion when doing my frozen-throw tests, ie for a set-shot (which some call a plant). I found that frozen-throw woz definitely less at very hi speed, and, strangely, less at very low speed. Tribology seems to deal mainly with metal to metal -- but here themz too say that metal-to-metal mu is less at very low speeds.

Az Jim sez, i reckon that mu iz a war between rough n rezidue (for plastik-to-plastik). Rough has an upper limit, Rezidue dont have an upper limit. Thusly too little energy, and u get little rough. Too much, and u get lots of rezidue, burnt plastic, acting like oil n bearings.

Yes, Mr Aramith told me that there aint nothing in their kraps xcept "pure" 100% phenolic rezin -- lie -- they must uze clay filler, like everyone allwayz did. Anyhow, what about coloring agents -- aint pure rezin a sort of brown ?? madMac.

moglet
05-06-2007, 05:13 PM
My interest in this thread was focussed on the original poster who highlighted a problem that we notice here. Whilst chalk and vertical misalignment can account for some anomalous impact results, though he cites the slow paced follow shot where this mechanical effect is unlikely, leaving chalk as the most likely culprit - yet we know also that this can be mitigated if you have some knowledge of how it occurs, you guys are obviously aware of this and have found ways of avoiding the trap.

He also comments that (in his update post) he has discovered that the object balls are undersize and that a regularly renewed cue ball accounts for the size difference, yet if this was the case the effect would be noticed on every shot - or if one or more balls were significantly smaller they would be identified by familiarity. Yet he still comments after some reference to polishing techniques and ball condition that his set suffers more after polishing from the effect he describes. "Once again, this skid happens most on short, soft shots with follow", is his finishing sentence.

I see no offer of a reason for this, it is great that the thread goes of into a fugue of technical counterpoint - fascinating, but it does not answer the first question.

Crawler, surely we know that the craps we use have a mineral filler to bulk up the weight of the ball, take one to bits and it is quite clear that the core is not just pure resin (on this aspect I do not see why we cannot have a heavier ball). Pure resin in its initial curing is amber/brown in colour, I believe they are doing a post cure through to glass transition in a controlled atmosphere that "clears" this discolouration allowing for a thicker outside shell that does not taint the dyestuff in the core material as much. It is interesting to note that the white ball, which is a none too reliable light creamy colour on the outside is flat white in the interior. All this suggests to me that there is a great deal we do not know about the ball's chemistry. In the absence of any deeper understanding in this area we are left with speculation and experiment.

All the theory expounded here is of the greatest interest, could we not bring it all to bear on the original question?

moglet
05-06-2007, 05:31 PM
Jal, I omitted to thank you for your two replies, thank you and duly noted.

cushioncrawler
05-06-2007, 05:41 PM
<blockquote><font class="small">Quote moglet:</font><hr> My interest in this thread was focussed on the original poster who highlighted a problem that we notice here. Whilst chalk and vertical misalignment can account for some anomalous impact results, though he cites the slow paced follow shot where this mechanical effect is unlikely, leaving chalk as the most likely culprit - yet we know also that this can be mitigated if you have some knowledge of how it occurs, you guys are obviously aware of this and have found ways of avoiding the trap.

He also comments that (in his update post) he has discovered that the object balls are undersize and that a regularly renewed cue ball accounts for the size difference, yet if this was the case the effect would be noticed on every shot - or if one or more balls were significantly smaller they would be identified by familiarity. Yet he still comments after some reference to polishing techniques and ball condition that his set suffers more after polishing from the effect he describes. "Once again, this skid happens most on short, soft shots with follow", is his finishing sentence.

I see no offer of a reason for this, it is great that the thread goes of into a fugue of technical counterpoint - fascinating, but it does not answer the first question.

Crawler, surely we know that the craps we use have a mineral filler to bulk up the weight of the ball, take one to bits and it is quite clear that the core is not just pure resin (on this aspect I do not see why we cannot have a heavier ball). Pure resin in its initial curing is amber/brown in colour, I believe they are doing a post cure through to glass transition in a controlled atmosphere that "clears" this discolouration allowing for a thicker outside shell that does not taint the dyestuff in the core material as much. It is interesting to note that the white ball, which is a none too reliable light creamy colour on the outside is flat white in the interior. All this suggests to me that there is a great deal we do not know about the ball's chemistry. In the absence of any deeper understanding in this area we are left with speculation and experiment.

All the theory expounded here is of the greatest interest, could we not bring it all to bear on the original question?<hr /></blockquote>Moglet -- Yes, in fact all of the original questions have now been answered, except one. It has been mentioned that there are chalk-Kicks and mini-kicks, that there are certain ways of playing the shot to avoid chalk-Kicks, that there are certain ways of playing to minimize or eliminate the OB throw for both chalk-Kicks and mini-kicks, and that qball size isnt a big deal. If i can answer the last question (or inference) about old marks and scratches on the OBs -- theze do not affect chalk-Kicks nor mini-kicks. My test show that fresh scratches etc do indeed cause large mini-kicks, but this problem dissapears very quickly as the ball polishes itself naturally over time, even if the scratches continue to look awfull.

Yes, bakelite haz a SG of about 1.24 to 1.32, so obviously they add a heavy filler. Ivory has a SG of about 1.83 to 1.92, and kraps are about 1.7 for the 2-1/16" ball, less for the 2-1/4", Bonzoz were about 1.875.

Mr Aramith sez that the outer layer is "vitreous", so perhaps it aint bakelite at all. madMac.

Qtec
05-07-2007, 04:18 AM
I remeber a docu about an experiment that kept being contaminated and it turned out that the test tubes were leaking oil. So I suppose balls might do the same.
Any club player will tell you that they don't get as many kicks as the pro's . Maybe the refs shouldn't wear gloves?
Gabber........new balls always feel sticky to me.

moglet
05-07-2007, 04:21 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>

Yes, bakelite haz a SG of about 1.24 to 1.32, so obviously they add a heavy filler. Ivory has a SG of about 1.83 to 1.92, and kraps are about 1.7 for the 2-1/16" ball, less for the 2-1/4", Bonzoz were about 1.875.

&gt;&gt;&gt;&gt;

Odd, my playing set measures 1.873 for SG

moglet
05-07-2007, 04:38 AM
<blockquote><font class="small">Quote Qtec:</font><hr> I remeber a docu about an experiment that kept being contaminated and it turned out that the test tubes were leaking oil. So I suppose balls might do the same.
Any club player will tell you that they don't get as many kicks as the pro's . Maybe the refs shouldn't wear gloves?
Gabber........new balls always feel sticky to me. <hr /></blockquote>


The referee's gloves are certainly a problem here, not to use them would be anathema. Ironically our cloth is also a problem, for the same reason. So handling the balls may help, but still the problem will exist.

Thanks for that.

dr_dave
05-07-2007, 10:37 AM
<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> ...I don't think it is worthwhile trying to compare data from some of my high-speed tests with numbers predicted by Marlow's data. Friction properties and how they vary with speed, cut angle, English, and spin will vary from one set of balls and conditions to another. I think the trends are useful to look at and compare, but I don't think it is appropriate to compare values between totally different sets of conditions. As I have pointed out before, my equations and Marlow's data do predict many of the trends that have been verified with experiments. To me, that is the value of the models ... they predict and help us understand the trends. Exact values and ranges will vary with ball conditions, so a player needs to be able to do some calibration (e.g., to know the maximum amount of throw possible under given conditions).<hr /></blockquote>Dr. Dave, I beg to differ although I do appreciate your overall point. I think that if mu varies with normal velocity to the extent that predictions based soley on surface speed are off by a factor of two (perhaps more), that is a trend itself worth quantifying.<hr /></blockquote>Good point. It would be nice to have experimental data, and a model, that account for how the ball-to-ball COR and COF vary with all variables (normal speed, relative surface speed, cut angle, and ball condition). This is on my list; but it is so far down, I doubt I'll ever get to it.

<blockquote><font class="small">Quote Jal:</font><hr>The above measured values, based on three shots with different balls than Marlow's used, don't prove anything of course.<hr /></blockquote>Agreed.

<blockquote><font class="small">Quote Jal:</font><hr>But since there is fair agreement at the lowest speed, there is a suggestion there that the differences at higher speeds might not be so much the result of differences between the balls, but due to the full hit.<hr /></blockquote>That sounds reasonable, but I would want more data for all variables before making such a conclusion.

Regards,
Dave

cushioncrawler
05-07-2007, 03:46 PM
<blockquote><font class="small">Quote moglet:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr> Yes, bakelite haz a SG of about 1.24 to 1.32, so obviously they add a heavy filler. Ivory has a SG of about 1.83 to 1.92, and kraps are about 1.7 for the 2-1/16" ball, less for the 2-1/4", Bonzoz were about 1.875. &gt;&gt;&gt;&gt; Odd, my playing set measures 1.873 for SG <hr /></blockquote>I cheated -- i got some of this from a 1975 article. They said that polyester woz 1.875, and that kraps were "approx 1.7" (probably iz 1.7 for 2-1/4" pool balls). madMac.

KellyStick
05-08-2007, 11:38 AM
I shoot a fair bit of pool but I'm no pro. I like to study the game but after attempting to read all of this I really got lost. Is this really that big of a deal. Seems to me the ball will throw under various playing conditions, your stroke and cp proximity to the ob and some other issues I guess. On occasion the OB does something very baffling. My gut feel is this is just not that big of a deal. But on the other hand this is a huge post. What am I missing? Maybe I would not know skid if it hit me in the face. Can you give me a couple lines to introduce me to the definition of skid? I think I understand but maybe I'm missing it.

Bob_Jewett
05-08-2007, 12:05 PM
<blockquote><font class="small">Quote KellyStick:</font><hr> ... Maybe I would not know skid if it hit me in the face. Can you give me a couple lines to introduce me to the definition of skid? I think I understand but maybe I'm missing it. <hr /></blockquote>
First, what to call it:

The words "skid" "kick" and "cling" are all used to apply to the same phenomenon. The word "kick" is used in the UK and other snooker-playing regions. It is also referred to as "bad contact" and in French, "butage." ("Kick" means something entirely different in the US. Skid is very different from "slide" but sometimes the two are confused.)

What it is:

Sometimes when the cue ball contacts the object ball, the balls do something really strange. This appears to be due to a very large increase in friction between the balls. This is most disastrous on soft cut shots where the angle of the cut is changed by perhaps 10-15 degrees. It can also occur on plain follow shots where the cue ball will jump into the air and not follow very well and the object ball will also go more slowly than expected.

The cause:

Chalk on the cue ball (and maybe the object ball) seems to be the largest cause of skids. Most of this thread deals with a very strange hypothesis that the balls ooze oil and that keeps their surfaces lubricated and if the oil is missing you will get skids.

Deeman3
05-08-2007, 12:25 PM
It is not a big deal until it happens to you in an important game. However, these guys are getting pretty deep into the applied science of the effect when you just need to know that it exists, what makes it occur and how to best avoid it, when possible. It's like one pocket, there aint no cure, just hazard avoidance in particular cases. Otherwise you will just be spending so much time looking into the physics of the game, you won't be able to get out there and play. /ccboard/images/graemlins/smirk.gif

moglet
05-08-2007, 12:52 PM
Most interesting, I did preface my first post with "if your balls are made of the same stuff that ours are made of...."

I think we agree the definition.

Can you, the scientific posters here, categorically state that there is never any discrete lubricating substance on your balls unless it has been either deliberately or accidentally introduced?

I am fast drawing the conclusion that there are some significant differences between the balls we use and yours.

Bob_Jewett
05-08-2007, 01:29 PM
<blockquote><font class="small">Quote moglet:</font><hr> ... Can you, the scientific posters here, categorically state that there is never any discrete lubricating substance on your balls unless it has been either deliberately or accidentally introduced? ... <hr /></blockquote>
Proper scientists never, ever make categorical statements.

But this case is tempting. Is there any case other than deliberate and accidental? I can't think of one. Would divine intervention be something else? Does God act with deliberation? Einstein assures us He does not act by accident. Hmm.....

moglet
05-08-2007, 02:36 PM
Bob, it matters not but this site is difficult to use if you want to select a quote to reply to.

Your recent post raises issues that I find offensive, reference to the almighty is OK with me but what do you mean by it? Any sane person reading the post would and should question your motives. I prefaced my original post with a perfect "get out", you choose to question an alternative way of thinking that was not aspersive but questioning. Fair do's but to invoke the Almighty does betray the foundation of your thinking. If you have no real scientific contribution to make, I suggest it would be better not to do so.

moglet
05-08-2007, 03:07 PM
Post Script, I would have edited my post but have little confidence in the software.

Bob, differences aside - whether religious or otherwise, my interest here is to try to identify another factor, it may not be relevant to your game or to the balls you use, but it is to us. Our games depend on greater accuracy and freedom of cue ball control, if we are to be reduced to playing only certain shots because of the balls, a relatively recent problem, we are lost. Our game(s) becomes a farce for us if this random event is to become an accepted playing condition.

Deeman3
05-08-2007, 03:22 PM
Moglet,

I believe you are correct. The differences don't impact our game as much here or at least we are not aware that it does as much as it seems to effect the games you play.

I am, honestly, only aware of added substances in relation to our balls, such as oils from people's hands, handling food while playing (I know but this is a different society) and some cases of silicon being used by persons to "doctor" a cue ball. IN addition, some people wax the balls. While I have not tried your mirror test, I am fairly confident that we are not leaking enough substances where that would show up. As someone mentioned, many of us have balls that have been stored for many years and we don't seem to see any residue when we do examine them.

Your response was to my post but, in reference to Bob, I don't believe he ment any il will by his statement about God.

I would be interested to know if you guys do come up with a resolution that might even tell us something about our game we were not aware of. i still think it has very minor implications in pool, overall.

moglet
05-08-2007, 03:43 PM
Hells bells Deeman3, I may not be correct for all balls and all cases, my study has been with the balls we use here in the UK. If there are differences between the balls in different countries we should be aware of it and not accuse each other of making undue claims based on the product we use in our own country, and, in good faith. There is something odd occurring here and because of the nature of our games it is significant, if it don't figure in the States then so be it. If it is of interest to you In the States, I would be happy to keep you abreast of developments here as and when (long pause!) they happen.

Bob_Jewett
05-08-2007, 04:19 PM
<blockquote><font class="small">Quote moglet:</font><hr> ... Any sane person reading the post would and should question your motives. ... <hr /></blockquote>
I would have thought that any sane person reading my post would have thought it humorous, but I have been mistaken on this point before.

dr_dave
05-08-2007, 04:36 PM
<blockquote><font class="small">Quote KellyStick:</font><hr> I shoot a fair bit of pool but I'm no pro. I like to study the game but after attempting to read all of this I really got lost. Is this really that big of a deal. Seems to me the ball will throw under various playing conditions, your stroke and cp proximity to the ob and some other issues I guess. On occasion the OB does something very baffling. My gut feel is this is just not that big of a deal. But on the other hand this is a huge post. What am I missing? Maybe I would not know skid if it hit me in the face. Can you give me a couple lines to introduce me to the definition of skid? I think I understand but maybe I'm missing it.<hr /></blockquote>Throw (and squirt and swerve) can be a big deal if it makes you miss shots, or if you don't know how to use it to make shots you might not make otherwise. For information, illustrations, and examples, please refer to my recent series of instructional articles dealing with throw (http://www.engr.colostate.edu/~dga/pool/bd_articles/index.html). If you don't feel like reading all of them, at least read the May '07 article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2007/may07.pdf). It does a pretty good job of presenting the "big picture."

Happy reading,
Dave

PS: If you just want definitions (e.g., of throw, CIT, SIT, cling, kick, skid, etc.), refer to my online glossary (http://www.engr.colostate.edu/~dga/pool/resources/glossary.pdf).

KellyStick
05-08-2007, 04:45 PM
Perhaps this string should contact guiness (not the beer, the book). I have shot a lot of pool in a lot of dirty places but never had the cb try to climb the ob on a follow shot. I trust it happens though. I'll watch for that.

However, there are some bars I grab the brush and start making a huge dust cloud while I brush the table (often for the first time it seems). Don't tell anyone but last week I was a bad boy. I took the big powder block and pitched in the the trash. Those things should be illegal. Our APA home bar has always had nice well maintained tables. New management doesn't know what a vacuumm cleaner is and on top of that they put these huge powder blocks out. For somereason people think they need like four pounds of powder on themselves and even more all over the table! When I am ruler of the universe I will out law these powder blocks along with flat head screws. MOre than once the cb has gotten a bath as well at various bars. Some call me picky but maybe I'm preventing the cb from humping the ob. That is a good thing. hopefully no one takes offense to my change in terms there. It just seems appropriate and also a bit crude which unfortunately feels confortable for me.

ras314
05-08-2007, 05:50 PM
<blockquote><font class="small">Quote KellyStick:</font><hr> Perhaps this string should contact guiness (not the beer, the book). I have shot a lot of pool in a lot of dirty places but never had the cb try to climb the ob on a follow shot. I trust it happens though. I'll watch for that.

However, there are some bars I grab the brush and start making a huge dust cloud while I brush the table (often for the first time it seems). Don't tell anyone but last week I was a bad boy. I took the big powder block and pitched in the the trash. Those things should be illegal. Our APA home bar has always had nice well maintained tables. New management doesn't know what a vacuumm cleaner is and on top of that they put these huge powder blocks out. For somereason people think they need like four pounds of powder on themselves and even more all over the table! When I am ruler of the universe I will out law these powder blocks along with flat head screws. MOre than once the cb has gotten a bath as well at various bars. Some call me picky but maybe I'm preventing the cb from humping the ob. That is a good thing. hopefully no one takes offense to my change in terms there. It just seems appropriate and also a bit crude which unfortunately feels confortable for me. <hr /></blockquote>
Man, I'm with you. Lets ban those powder cones! Damn stuff is not allowed in the same room as my table. In fact I'm adding on a wash room so people can wash and dry their hands as needed.

As far as climbing the ob, it is not clear to me if the cb is a bit off the cloth on contack, but I have seen it hop on the hit. Hard for me to believe it is possible to produce enough top spin and friction to actually climb the ob. Watch some videos of a hard break, often the cb will hop up. Sometimes you can see a shadow under the cb just before the hit indicating it was in the air.

moglet
05-08-2007, 06:04 PM
Hi ras314, the original poster talks about the slow shot with follow. I think we are all aware of the misalignment problem, very common here, but not a likely culprit for the slow shot. In fact you don't need top spin for this particular anomaly to make the ball climb, the high friction contact is sufficient with a rolling ball, just like it would with chalk. I add the caveat that your balls may be different from ours.

KellyStick
05-08-2007, 06:25 PM
I have a very small container of powder hidden by my table. IF someone asks for powder i challenge them to just dry off a bit. If they still "need" powder I get it out and apply the powder myself. Then put it back in it's hiding place. Sorry, I'm picky about the table.

cushioncrawler
05-08-2007, 06:27 PM
<blockquote><font class="small">Quote moglet:</font><hr> Bob, it matters not but this site is difficult to use if you want to select a quote to reply to. Your recent post raises issues that I find offensive, reference to the almighty is OK with me but what do you mean by it? Any sane person reading the post would and should question your motives. I prefaced my original post with a perfect "get out", you choose to question an alternative way of thinking that was not aspersive but questioning. Fair do's but to invoke the Almighty does betray the foundation of your thinking. If you have no real scientific contribution to make, I suggest it would be better not to do so.<hr /></blockquote>Moglet -- I havta go along with Bob here. Things must be either (1) deliberate, (2) accidental, or (3) divine. I could add -- (4) illusory. madMac.

Bob_Jewett
05-08-2007, 06:32 PM
<blockquote><font class="small">Quote ras314:</font><hr> ... As far as climbing the ob, it is not clear to me if the cb is a bit off the cloth on contack, but I have seen it hop on the hit. Hard for me to believe it is possible to produce enough top spin and friction to actually climb the ob. ... <hr /></blockquote>
No, I'm talking about a relatively soft shot. For example a ball two diamonds from a pocket and you are trying to follow straight forward about two diamonds to leave the cue ball near that same pocket. There is a sort of "clunk" and the cue ball jumps a little into the air -- just a few millimeters -- and it doesn't follow properly. If you have an ear for it, you can tell immediately from the sound of the ball-to-ball contact that there was a "vertical skid" when it happens.

The thing that makes vertical skid more likely is that the chalk mark that the cue tip transfers to the cue ball has a good chance to be at the contact point assuming you do the "right" thing and don't put any side spin on the ball. If the cue ball makes exactly 0.45 revolutions forward on its way to the object all (or 1.45 or 2.45 full revolutions)then the spot will be at the contact point. Also, since the ball is likely rolling smoothly on the cloth, there is not much friction with the cloth to rub off the chalk spot.

cushioncrawler
05-08-2007, 06:51 PM
<blockquote><font class="small">Quote Paul_Mon:</font><hr> Now that this thread has been resurrected I can say with confidence that the largest contributor to skid at the pool hall I play at is undersized object balls. They routinely (every 2 years or so) replace the cue ball but the object balls are still in use from 8-12 years ago. Upon close inspection the object balls are loaded with dings and scratches. These balls are polished daily. This is the second factor that contributes to skid, the chalk clings to the polish. I bring my matched set of Centennials there for polishing and they skid more after being polished. Once again, this skid happens most on short, soft shots with follow. <hr /></blockquote>Paul -- Further to what others have said re undersize OBs -- Vertical misalignment iznt an obvious candidate for skid (az Jim and others have pointed out in the past). But, az i have pointed out more than once....
1.... In the modern era, the impact time for soft kraps (large temporary flatspots) is much longer than for the oldendays hard balls (small flatspots).
2.... We all know that impakt time is much greater for very slow impakts.
3.... I reckon that, for a modern ball sitting on an old bare hard bedcloth, for a slow impakt, the OB's bed-reaction can produce skid (kick), ie sort of "bed-kick", due to the extra long impakt time.

Here, i reckon, the (balltoball) impakt time is so long that the (OB) bed forces feed back to the qball, ie during the balltoball impakt. We get this all the time now in english billiards, when the OB (red krap ball) is sitting on "The Spot" -- twer never so in the old dayz (bonzoz), spot-kicks were never heard of.

Pool players shood certainly be afraid of a spot-kick sort of effect when the OB is sitting in a "hole". If u see an OB ball "fall" into a hole or something, as it slows and stops, then beware of a spot-kick, especially for a slowish shot, especially if the OB is undersize. madMac.

Qtec
05-08-2007, 06:59 PM
Did you watch the World Champs in Sheffield?.They are using a new slo-mo cam called the Tornado. It seems that the balls are bouncing on almost every shot- Qball and OB!

Qtec

ras314
05-08-2007, 07:09 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr>
No, I'm talking about a relatively soft shot. For example a ball two diamonds from a pocket and you are trying to follow straight forward about two diamonds to leave the cue ball near that same pocket. There is a sort of "clunk" and the cue ball jumps a little into the air -- just a few millimeters -- and it doesn't follow properly. If you have an ear for it, you can tell immediately from the sound of the ball-to-ball contact that there was a "vertical skid" when it happens.

<hr /></blockquote>

I like the term "vertical skid", seems quite descriptive. Have you calculated the friction (mu?)this would require? Not a fair question I admit, since it seems the whole effect may be very difficult to quantify. Possibly just reducing the force of the cue ball on the cloth would cause the odd sound and strange resulting position? I have seen some screwy paths followed by seemingly good shots.

Moglet, I am probably way out of my depth here, but does not most every place in the world use at least some sets of balls made by Saulk (sp)? At any rate the effect you describe sounds like the same as Mr Jewett's description.

problems with internet here...OK, different ob and cb diameters seems a culprit, however this should be easily quantified? I am unfortunately somewhat used to using a larger heavier cb (wish everybody would steal the abominations on sight) which renders any opinion of mine suspect.

Roy

Jal
05-09-2007, 12:40 AM
<blockquote><font class="small">Quote ras314:</font><hr>...I like the term "vertical skid", seems quite descriptive. Have you calculated the friction (mu?)this would require? Not a fair question I admit, since it seems the whole effect may be very difficult to quantify.<hr /></blockquote>If the maximum amount of throw (vertically or horizontally) you could ever hope to see is x degrees, the corresponding mu would be tan(x). So if 15 degrees is about max, mu for this would be tan(15), or 0.27. Typically it's about 0.05 but varies considerably with speed.

<blockquote><font class="small">Quote ras314:</font><hr>problems with internet here...<hr /></blockquote>I wonder if you have the same problems I sometimes have in connecting to this forum?

<blockquote><font class="small">Quote ras314:</font><hr>OK, different ob and cb diameters seems a culprit, however this should be easily quantified?<hr /></blockquote>I really don't think it causes much of a problem with regard to normal or abnormal throw. Take a cueball whose center is 1/8" higher than the object ball's center. That makes the cueball 2.5" in diameter - a pretty gross mismatch. On any type of shot, straight or cut, the OB will be thusly driven down at an angle of 3.0 degrees. Any horizontal throw will put a spin on the OB which will cause it to masse since its spin axis is inclined from the vertical by 3.0 degrees. But it isn't much. For every degree of throw, only an extra 5% (percent) will added by the masse action, approximately. So if you're the victim of a 10 degree kick, I don't think you would be too distraught over the additional half-degree.

I can't see it having much effect on vertical kicks either.

The only reservation I have about the above is Mac's spot kick stuff, which I'm not sure what to make of?

Jim

ras314
05-09-2007, 06:51 AM
I was in a tournament once that had three tables with a different size cb on each. One normal size but heavy, one large and heavy (typical bar cb), and one bigger than I've ever seen before or since. I didn't see anything like the slow rolling vertical skid being described but I was mostly trying to figure out where the cb was going to head after contact. With the giant cb I basically just slow rolled every shot and hoped.

In Bryne's New Standard Book of Pool and Billiards there is a short discussion of "cling". The list of culprits includes fingerprints,sweat,hair oil, and chalk. He also mentions the opposite effect where there is less than normal throw when there is reduced friction. His example is a trick shot that uses spit to reduce the coefficient of friction.

On rare occasions it seems the forum's site is down, more often I simply can't access the internet. Only trouble I've had with the forum itself is generally due to my ignorance. /ccboard/images/graemlins/blush.gif

Deeman3
05-09-2007, 07:37 AM
<blockquote><font class="small">Quote moglet:</font><hr> Hells bells Deeman3, I may not be correct for all balls and all cases, my study has been with the balls we use here in the UK. If there are differences between the balls in different countries we should be aware of it and not accuse each other of making undue claims based on the product we use in our own country, and, in good faith. There is something odd occurring here and because of the nature of our games it is significant, if it don't figure in the States then so be it. If it is of interest to you In the States, I would be happy to keep you abreast of developments here as and when (long pause!) they happen. <hr /></blockquote>

<font color="blue"> Just with a little time on my hands last night, I put a 18" x 48" mirror on my table (4&amp;1/2' x 9'). I rolled a centential on it after wiping it off (the mirror) with a lint free cloth and saw nothing but a bit of chalk residue from the ball (these were the balls in the pocket at present.) I took a set of 3 cushion Ivory balls out of a leather sack (they have been there since about 1980 or so) and rolled one of them and saw nothing. In fairness, the leather bag could absorb any liquid from these balls. I got them in 1969 and have never hit them on a table. I think they are about from 1925 or so. I rolled a brand new, out of the box, Aramith SuperPro that I got about a year ago and saw nothing. I cleaned the mirror and took out some circa 1950 faded, chipped phenolic resin balls and rolled a couple on the mirror. I saw nothing but a little collected lint.

I have two sets of snooker balls one I got in UK and one set in Belgium but could not find either as I rumaged through junk last night.

The only three things I learned was my table is not level enough to play on a mirror, my Ivory balls are as much a .021" out of round and my cue ball on my centenial set is .0003" under my one ball size.

I did learn one more thing, don't every ask your wife if she has seen your other balls! /ccboard/images/graemlins/blush.gif

</font color>

moglet
05-09-2007, 08:52 AM
<blockquote><font class="small">Quote Deeman3:</font><hr> <blockquote><font class="small">Quote moglet:</font><hr> Hells bells Deeman3, I may not be correct for all balls and all cases, my study has been with the balls we use here in the UK. If there are differences between the balls in different countries we should be aware of it and not accuse each other of making undue claims based on the product we use in our own country, and, in good faith. There is something odd occurring here and because of the nature of our games it is significant, if it don't figure in the States then so be it. If it is of interest to you In the States, I would be happy to keep you abreast of developments here as and when (long pause!) they happen. <hr /></blockquote>

<font color="blue"> Just with a little time on my hands last night, I put a 18" x 48" mirror on my table (4&amp;1/2' x 9'). I rolled a centential on it after wiping it off (the mirror) with a lint free cloth and saw nothing but a bit of chalk residue from the ball (these were the balls in the pocket at present.) I took a set of 3 cushion Ivory balls out of a leather sack (they have been there since about 1980 or so) and rolled one of them and saw nothing. In fairness, the leather bag could absorb any liquid from these balls. I got them in 1969 and have never hit them on a table. I think they are about from 1925 or so. I rolled a brand new, out of the box, Aramith SuperPro that I got about a year ago and saw nothing. I cleaned the mirror and took out some circa 1950 faded, chipped phenolic resin balls and rolled a couple on the mirror. I saw nothing but a little collected lint.

I have two sets of snooker balls one I got in UK and one set in Belgium but could not find either as I rumaged through junk last night.

The only three things I learned was my table is not level enough to play on a mirror, my Ivory balls are as much a .021" out of round and my cue ball on my centenial set is .0003" under my one ball size.

I did learn one more thing, don't every ask your wife if she has seen your other balls! /ccboard/images/graemlins/blush.gif

</font color> <hr /></blockquote>

Deeman3,

Thanks for making the effort, I would not expect any oily trace to be left by a ball made before 1972/3. I have a set of British made super crystalates from that time, initially I got no result on a mirror - I should add that the Ķ value for them was abnormally high and "vertical skid" was noticeable and frequent, only after some applied warmth did they exhibit some trace on the mirror, and, only then did the incidence of high friction contacts subside.

I have noticed with Tournament Champion balls (our Aramith top of the range ball) that use of the Aramith Polishing cream inhibits whatever is happening to our balls and that the frequency of high friction contacts is greater than when not using it - needless to say I do not use it now.

The trace left, if there is one, can be quite hard to see, however the ball can still have an "oily" surface albeit extremely thin and not leave any visible trace. You will also have to be careful not to handle the ball directly, you will add far more of your skin's fatty substance than could already exist on the ball.

The, our, balls do not weep, it seems that as soon as the surface has acquired a molecular (?) layer no more is produced. If you use isopropanol to swab the surface, no matter how many times you do this the layer always returns - if you try to play with our balls after swabbing them you are certain to get high friction contacts and in any real sense they would be unplayable. I am no resin chemist and am concerned that some solvents could affect the resin substrate, nevertheless similar results can be demonstrated with these new microfibre cloths and napped cotton cloth. Again here, using more powerful solvents can cause seize between the balls.

SPetty
05-09-2007, 02:42 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote moglet:</font><hr>... Any sane person reading the post would and should question your motives. ...<hr /></blockquote>I would have thought that any sane person reading my post would have thought it humorous, but I have been mistaken on this point before.<hr /></blockquote>Huh... I haven't been accused of being sane in awhile...

/ccboard/images/graemlins/smile.gif

I thought it was humorous.

moglet
05-09-2007, 02:52 PM
<blockquote><font class="small">Quote SPetty:</font><hr> <blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote moglet:</font><hr>... Any sane person reading the post would and should question your motives. ...<hr /></blockquote>I would have thought that any sane person reading my post would have thought it humorous, but I have been mistaken on this point before.<hr /></blockquote>Huh... I haven't been accused of being sane in awhile...

/ccboard/images/graemlins/smile.gif

I thought it was humorous. <hr /></blockquote>

I guess your right, I should lighten up and get out more /ccboard/images/graemlins/smirk.gif

moglet
05-09-2007, 04:59 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote jamesp:</font><hr> Thanks for that, maybe this will convince Bob Jewett that there is oil on the balls. <hr /></blockquote>
CC posts a rather dense, not clearly applicable, ten-page-long item about how to put abrasives into resin grinding wheels that happens to mention oil and oil-like substances, and your conclusion is that Aramith mixes oils into their cast phenolic resin balls. Remarkable. The posting clearly shows that is it possible to put oils into grinding wheels that are made from phenolic resin, but it proves nothing about what may or may not be left on your mirror.

Yes, I am absolutely convinced that oils are used in various manufacturing processes, but I have believed that for quite some time. I'm also certain that some manufacturing processes avoid oil and oil-like substances at all costs.

So, let me state your hypothesis as I understand it:

<font color="blue"> Aramith cast phenolic balls depend on a slightly oily surface to react properly during collisions. This condition is achieved by mixing oil into the phenolic resin during manufacturing. As the oil wears off the surface of the ball, more oil from inside the ball seeps out to again coat the surface. When the surface coating is intentionally cleaned off of two balls and one strikes the other with relative surface motion, friction between the two balls much larger than the typical friction is observed. </font color>

Is that what you are saying? <hr /></blockquote>


For clarity I feel this needs restating more accurately:

Aramith Tournament Champion snooker and billiard balls supplied to the British market rely on a discrete but extremely thin oily surface to achieve a low level of friction between contacting balls. However, during play the thickness of the oily layer is reduced by the interaction between the ball or balls and the bed and cushion cloths, this interaction is both abrasive and absorptive. Generation of this oily substance is generally not fast enough to replace the loss during normal play, this results in random areas of the ball's surface being inadequately lubricated. Abnormally high friction occurs between two or more balls when depleted areas coincide at the contact points.
This hypothesis does not deny or exclude other causes that may have a similar effect and at this time how the ball surface and internal chemistry generates this surface film is uncertain.
<font color="blue"> </font color>

Bob_Jewett
05-10-2007, 03:15 PM
<blockquote><font class="small">Quote moglet:</font><hr> ...
For clarity I feel this needs restating more accurately:

<font color="blue"> Aramith Tournament Champion snooker and billiard balls supplied to the British market rely on a discrete but extremely thin oily surface to achieve a low level of friction between contacting balls. However, during play the thickness of the oily layer is reduced by the interaction between the ball or balls and the bed and cushion cloths, this interaction is both abrasive and absorptive. Generation of this oily substance is generally not fast enough to replace the loss during normal play, this results in random areas of the ball's surface being inadequately lubricated. Abnormally high friction occurs between two or more balls when depleted areas coincide at the contact points.
This hypothesis does not deny or exclude other causes that may have a similar effect and at this time how the ball surface and internal chemistry generates this surface film is uncertain.
</font color> <hr /></blockquote>
I just got the following response from a representative at Aramith/Saluc:

<font color="red"> We don't use or mix or add any oil or oily substance in our Aramith balls. </font color>

I would describe that as unequivocal.

Qtec
05-11-2007, 06:23 AM
Bouncing balls.
web page (http://www.youtube.com/watch?v=Qnc64VJoQd4)
Q

moglet
05-11-2007, 07:28 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote moglet:</font><hr> ...
For clarity I feel this needs restating more accurately:

<font color="blue"> Aramith Tournament Champion snooker and billiard balls supplied to the British market rely on a discrete but extremely thin oily surface to achieve a low level of friction between contacting balls. However, during play the thickness of the oily layer is reduced by the interaction between the ball or balls and the bed and cushion cloths, this interaction is both abrasive and absorptive. Generation of this oily substance is generally not fast enough to replace the loss during normal play, this results in random areas of the ball's surface being inadequately lubricated. Abnormally high friction occurs between two or more balls when depleted areas coincide at the contact points.
This hypothesis does not deny or exclude other causes that may have a similar effect and at this time how the ball surface and internal chemistry generates this surface film is uncertain.
</font color> <hr /></blockquote>
I just got the following response from a representative at Aramith/Saluc:

<font color="red"> We don't use or mix or add any oil or oily substance in our Aramith balls. </font color>

I would describe that as unequivocal.
<hr /></blockquote>


If we are to take Saluc's statement as unequivocal and I entirely accept the possibility, the English snooker and billiards community is faced with an even more serious problem.

To use our balls in their raw state, undamaged, no Aramith polish and swabbed with alcohol or wiped with a microfibre cloth, renders our games unplayable unless you use plain stun. If the introduction of a surface lubricant makes the ball more playable and reliable we have to assume that the introduction is by simply handling the ball and transferring human fatty secretions to the balls - that this coating will come off due to the interaction between the balls and the table cloths leaves us in an embarrassing predicament. Do we deliberately lubricate our balls to make them playable?

Tournament conditions here are near "sterile" and it is in these conditions that the problem seems worst.

DickLeonard
05-11-2007, 08:07 AM
moglet as a tournament player[past tense] I have never had a ball skid that wasn't caused by a tenative stroke. This is my first reply to this long post because I have nothing to add because it had little effect on my pool life. I had seen many shids I just didn't cause any.

Why would I want to arm the enemy.####

My favorite seen skid was Steve Mizerak shooting off the rail in the Salt City Open against my mentor Joe Canton. You saw the tenative stroke You heard the ball skid it missed the shot but the skid flipped the object ball right into the pocket and he continued running out. ####

DickLeonard
05-11-2007, 08:12 AM
Bob Jewett I have only watched to Billiard matches on tape and played it off and on. Are skids related to Billiards or does the heavier balls protect themselves?

Bob_Jewett
05-11-2007, 11:34 AM
<blockquote><font class="small">Quote DickLeonard:</font><hr> Bob Jewett I have only watched to Billiard matches on tape and played it off and on. Are skids related to Billiards or does the heavier balls protect themselves? <hr /></blockquote>
No, lots of skids occur at carom billiards. Recently the World One-Cushion Championships were on the net, and the players were commenting in their interviews that lots of skids were happening the first rounds. They seemed to feel that skids, which they called "butages" or bad contacts, were fewer in the later rounds.

cushioncrawler
05-11-2007, 05:53 PM
<blockquote><font class="small">Quote Qtec:</font><hr> Bouncing balls.
web page (http://www.youtube.com/watch?v=Qnc64VJoQd4) Q <hr /></blockquote>Q -- The qball is bouncing on the way to the OB mostly koz this screw-shot needs a steep angle koz of the proximity of the cushion. Are there any slo-mo close-ups showing a qball bouncing up or down off an OB, ie due to vertical throw??? madMac.

dr_dave
05-13-2007, 08:48 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>Are there any slo-mo close-ups showing a qball bouncing up or down off an OB, ie due to vertical throw???<hr /></blockquote> HSV A.123 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-123.htm) shows the cue ball reaction during a break shot. This is probably the most dramatic example of the effect; although, when the cue ball really hops, it is because it is airborne at impact due to skipping caused by downward squirt due to an above-center hit on the cue ball (see the "hop on break" links under "cue ball" here (http://www.engr.colostate.edu/~dga/pool/threads.html) for more info).

Regards,
Dave

cushioncrawler
05-13-2007, 04:35 PM
Dr Dave -- Thanks for the links and footage. The qball jump here is of course a bit bigger (than for a single OB) koz the qball here feels the wt of at least 3 OB's (i think Bob J estimates the actual effektiv wt on his site somewhere). And, i notice that u can see the tranzmitted side on the one-ball very well, but possibly a bit magnyfyd allso (due to the wt of the other balls), but mightbe not. madMac.