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UTAddb
07-20-2005, 07:14 PM
I can see and hear when it happens and I know a touch of outside english cures it, but I still don't know why it happens or what is going on exactly. Rempe mentions it in 'How to run a 100 balls' but doesn't go into the physics.... Dr. Dave...

Rod
07-20-2005, 07:48 PM
When two balls stick to each other at the contact point. Caused by chalk, soda, cheesburger drippings, mayo, ketsup or mustard. LOL When this happens they don't take a natural roll and skid. It's very obvious on the o/b. On new cloth excess friction between two balls make them skid easier on the slick cloth. Oh, I left out french fries. /ccboard/images/graemlins/grin.gif

Rod

Leviathan
07-21-2005, 04:15 AM
"Skid" is another name for collision-induced throw. Collision-induced throw, and techniques for reducing or compensating for it, are discussed in the thread "Using outside English to canel [sic] or reduce throw."

JimS
07-21-2005, 04:35 AM
I think another word for the cause of skid is cling. The cb and ob cling to each other for a moment and cause the ob to skid or deviate from the path that it should have taken.

pooltchr
07-21-2005, 05:09 AM
I don't want to start another "terminology" debate here, but quite simply, skid is when a ball is moving along the cloth without any forward roll or spin. The easiest way to observe skid is to take a striped ball, place it on the table and shoot it with bottom spin down the table. You can see the back spin decrease as it travels down the table until it reaches a point where there is no back spin, but forward roll has not yet taken over. The ball is just sliding across the cloth. It happens in many different places and there are many causes. But it is simply a point when the ball is simply sliding along on the cloth.
Steve

Bob_Jewett
07-21-2005, 09:33 AM
<blockquote><font class="small">Quote Leviathan:</font><hr> "Skid" is another name for collision-induced throw. Collision-induced throw, and techniques for reducing or compensating for it, are discussed in the thread "Using outside English to canel [sic] or reduce throw." <hr /></blockquote>
That's certainly not the way I've heard most people use the term. I think it is much better to refer to a sliding ball as sliding.

Skid is synonymous with "cling" and in the UK, "kick." It is what happens when there is a bad contact between the cue ball and the object ball, probably due to chalk at the contact point. It in not a normal part of shots.

Collision-induced throw, on the other hand, occurs on all cut shots that are played without side spin. It is a normal part of the game.

Bob_Jewett
07-21-2005, 09:35 AM
<blockquote><font class="small">Quote pooltchr:</font><hr> I don't want to start another "terminology" debate here, but quite simply, skid is when a ball is moving along the cloth without any forward roll or spin. ... <hr /></blockquote>
This is not the way many, many players use the term. If you want to be unambiguous, it's better to call a sliding ball, "sliding."

Leviathan
07-21-2005, 09:52 AM
Thanks, Bob--You're right; I see the distinction now.--AS

SpiderMan
07-21-2005, 09:57 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote Leviathan:</font><hr> "Skid" is another name for collision-induced throw. Collision-induced throw, and techniques for reducing or compensating for it, are discussed in the thread "Using outside English to canel [sic] or reduce throw." <hr /></blockquote>
That's certainly not the way I've heard most people use the term. I think it is much better to refer to a sliding ball as sliding.

Skid is synonymous with "cling" and in the UK, "kick." It is what happens when there is a bad contact between the cue ball and the object ball, probably due to chalk at the contact point. It in not a normal part of shots.

Collision-induced throw, on the other hand, occurs on all cut shots that are played without side spin. It is a normal part of the game. <hr /></blockquote>

To clarify then, "Skid" is normally used to describe an extreme case of Collision-Induced Throw, as exacerbated by unusually-high ball-ball friction.

I also suggest, though the degree is certainly open to debate, that CIT would also be exacerbated by unusually-low ball-cloth friction.

SpiderMan

Fran Crimi
07-21-2005, 10:00 AM
Bob, I had heard a long time ago that there were ways of striking the cb that could lower the probability that the chalk mark would arrive at the point of contact with the ob, particularly on closer shots where the chalk hasn't had time to wear off.

Is this an old wives tale or is there something to it?

Fran

Bob_Jewett
07-21-2005, 10:10 AM
<blockquote><font class="small">Quote SpiderMan:</font><hr>...
To clarify then, "Skid" is normally used to describe an extreme case of Collision-Induced Throw, as exacerbated by unusually-high ball-ball friction.
... <hr /></blockquote>
No, actually, you see the worst cases of cling (skid, kick, bad contact) when using inside english. It is also seen on shots when you are shooting full at a near-by ball and use follow without english. In that case, cling causes the cue ball to jump into the air and not follow as well as it should.

"Collision-induced throw" is the normal throw that occurs on all cut shots without english and is due to the sideways movement of the cue ball relative to the object ball. While it is also due to friction, I think it is very bad to confuse it with cling.

Bob_Jewett
07-21-2005, 10:16 AM
<blockquote><font class="small">Quote Fran Crimi:</font><hr> Bob, I had heard a long time ago that there were ways of striking the cb that could lower the probability that the chalk mark would arrive at the point of contact with the ob, particularly on closer shots where the chalk hasn't had time to wear off.

Is this an old wives tale or is there something to it?

Fran <hr /></blockquote>

Well, if it's a cut shot, you can simply avoid any side spin, and then the transferred chalk can't arrive at the contact point. This is yet another reason to avoid side spin. You can also figure out the path of the chalk spot when using side spin -- maybe by using a red-dot and cueing at the dot and noticing where the dot goes -- but I think that's pretty complicated. There could be a simple rule, but as the cue ball picks up follow, the "orbit" of the chalk spot around the cue ball's surface will change in a way that seems pretty complicated to me.

Come to think about it, if you want to try the "orbit tracking" experiment, maybe an Elephant object ball -- half red and half black -- woould be the ball to use. Just be sure to cue the ball with the tip landing in the middle of the red. That will be easier to see than a single spot on the cue ball.

SpiderMan
07-21-2005, 10:51 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> No, actually, you see the worst cases of cling (skid, kick, bad contact) when using inside english. It is also seen on shots when you are shooting full at a near-by ball and use follow without english. In that case, cling causes the cue ball to jump into the air and not follow as well as it should.

"Collision-induced throw" is the normal throw that occurs on all cut shots without english and is due to the sideways movement of the cue ball relative to the object ball. While it is also due to friction, I think it is very bad to confuse it with cling. <hr /></blockquote>

Bob,

Gotta disagree some there.

Calling it "CIT" when no english is used, and then switching the term to "cling/skid" upon application of a little bit of inside, seems like unneccesary complication since the underlying cause is identical.

I like to consider "sideways movement of the cue ball relative to the object ball" to produce it's "throw" effect independently of the origin of that motion.

In other words - collision-induced-throw happens due to the relative motion of these surfaces, inside english increases the relative motion, outside english decreases it, and the continuous range of possible object-ball reactions merely reflect what was happening at contact.

SpiderMan

SpiderMan
07-21-2005, 11:04 AM
<blockquote><font class="small">Quote Fran Crimi:</font><hr> Bob, I had heard a long time ago that there were ways of striking the cb that could lower the probability that the chalk mark would arrive at the point of contact with the ob, particularly on closer shots where the chalk hasn't had time to wear off.

Is this an old wives tale or is there something to it?

Fran <hr /></blockquote>

Fran,

The only way I could imagine guaranteeing that would be for the chalk mark to remain on the vertical axis.

On the other hand, it wouldn't matter if the chalk mark coincided with the contact point if the "perfect" amount of outside spin was also present. This would avoid the throw effect, independent of large variations in surface friction.

So I guess that's one more consideration - use centerball to minimize opportunity for a frictional variation vs trying to blend outside spin to achieve negation of the consequences.

I still feel that you must make these choices by evaluating position-play needs, on a shot-by-shot basis.

SpiderMan

Fran Crimi
07-21-2005, 12:07 PM
It sounds like it would be difficult to track, even with the elephant ball.

Now that I think about it, I do have a vague recollection of a discussion about striking the cb with a kill-type stroke, just enough to encourage 1/2 revolution of back spin to force the chalk mark to the bottom. The cb would then go into a slide, with the chalk mark wearing off before contact with the ob. Would that make sense?

Fran

BoroNut
07-21-2005, 02:08 PM
<blockquote><font class="small">Quote UTAddb:</font><hr>What exactly is skid?<hr /></blockquote>

When gentlemen players are faced with a dolly pot to win a large sum of money, there is often a high risk of skid occuring. As well as the characteristic sound, these unfortunate marks often prove to be indelible, and may prevent the gentleman's under trolleys ever being hung out to dry in public again.

Boro Nut

SpiderMan
07-27-2005, 06:13 AM
HaHaHa! I almost missed this reply /ccboard/images/graemlins/wink.gif

SpiderMan

Alfie
07-27-2005, 03:20 PM
<blockquote><font class="small">Quote SpiderMan:</font><hr> <blockquote><font class="small">Quote Bob_Jewett:</font><hr> "Collision-induced throw" is the normal throw that occurs on all cut shots without english and is due to the sideways movement of the cue ball relative to the object ball. While it is also due to friction, I think it is very bad to confuse it with cling.<hr /></blockquote>Gotta disagree some there.

Calling it "CIT" when no english is used, and then switching the term to "cling/skid" upon application of a little bit of inside, seems like unneccesary complication since the underlying cause is identical.

I like to consider "sideways movement of the cue ball relative to the object ball" to produce it's "throw" effect independently of the origin of that motion.

In other words - collision-induced-throw happens due to the relative motion of these surfaces, inside english increases the relative motion, outside english decreases it, and the continuous range of possible object-ball reactions merely reflect what was happening at contact.<hr /></blockquote>Cling is a special case of both CIT and/or SIT. I'm not sure but I think each has a different range of throw. So, though all three are caused by friction, for practical purposes it's often better to treat CIT and SIT separately and always better to treat cling separately (exaggerated throw, occurring seemingly randomly) when discussing the cause and effect of throw with pool players. IMO.

Bob_Jewett
07-27-2005, 03:44 PM
<blockquote><font class="small">Quote Alfie:</font><hr>... So, though all three are caused by friction, for practical purposes it's often better to treat CIT and SIT separately and always better to treat cling separately (exaggerated throw, occurring seemingly randomly) when discussing the cause and effect of throw with pool players. IMO. <hr /></blockquote>
I think the main thing is that throw can be (and must be) planned for and happens on most shots. Skid (cling/kick/bad contact) cannot be planned for and generally results in a botched shot.

Well, skid can be planned for in two senses. You can ask the referee to clean the cue ball frequently. You see this all the time at snooker and carom matches.

The other way to plan for it is to use perfect outside english on a shot, but that's more prevention than planning, and its use usually is not compatible with other parts of the shot.

Fred Agnir
07-28-2005, 05:33 AM
<blockquote><font class="small">Quote Alfie:</font><hr> ]
Cling is a special case of both CIT and/or SIT. <hr /></blockquote>I've always considered Cling a special case of chalk orientation.

Fred

dr_dave
07-28-2005, 07:45 AM
FYI, the following postings are relevant and provide info on the various topics being discussed here:

- various conclusions about throw effects (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=200743&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;fpart=1)

- "skid," "cling," "drag," and "push" (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=200545&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1)

- using outside English to cancel or reduce throw (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=200869&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1)

- English transfer and throw at various speeds (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=201668&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1)

Additional info can be found under "throw" in the threads summary area of my website (http://www.engr.colostate.edu/~dga/pool/threads.html).

Regards,
Dave

dr_dave
07-28-2005, 07:58 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr>I think the main thing is that throw can be (and must be) planned for and happens on most shots. Skid (cling/kick/bad contact) cannot be planned for and generally results in a botched shot.

Well, skid can be planned for in two senses. You can ask the referee to clean the cue ball frequently. You see this all the time at snooker and carom matches.

The other way to plan for it is to use perfect outside english on a shot, but that's more prevention than planning, and its use usually is not compatible with other parts of the shot.<hr /></blockquote>
Excellent summary, Bob!

I personally like the term "cling" better than "skid" because people sometimes confuse "skid" with a "drag" shot, where a draw stroke is used to create "stun" at OB impact on a long or slow shot. "Drag" and "skid" can conjure the image of the CB sliding along the cloth before rolling develops. "Cling" implies "sticking" due to excessive friction (from dirt or chalk).

Regards,
Dave