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wayne crimi
10-12-2006, 07:07 AM
I play with a Predator 314 I bought when they first came out. It's over ten years old. I haven't played much in recent years, but I shot a few times this week and it seems to be different than I recall when I was playing regularly.

Is is possible that it deflects more now than it did originally?

The second question is related to how much the cue ball will deflect depending on where you hit it. I seem to be getting almost wild deflection when I hit the cue ball at either approximately 4:30 or 7:30 1 1/2 tips below center with a slow to medium stroke. The deflection amount is much smaller when I'm to the left or right of center or above center. This is also a new experience for me. Either I used to adjust to it properly in the past and didn't know it, or something else is going on.

Is there an "physics" reason why this would be the case or am I just doing something in my stroke I can't see?

Note: I'm certain my cue is level so swerve and other factors are not the main issue.

MrLucky
10-12-2006, 07:30 AM
This sounds like a Dr Dave question, but let me ask this, could it be that you are more knowledgable and experienced now and therefore more sensitive to the "deflection" value? /ccboard/images/graemlins/confused.gif

wayne crimi
10-12-2006, 07:35 AM
<blockquote><font class="small">Quote MrLucky:</font><hr> This sounds like a Dr Dave question, but let me ask this, could it be that you are more knowledgable and experienced now and therefore more sensitive to the "deflection" value? /ccboard/images/graemlins/confused.gif <hr /></blockquote>

Not likely. I've been playing on and off for 30 years and have been aware of these issues for a long time. I actually play worse now than I did 10 years ago because I rarely get to play anymore.

dr_dave
10-12-2006, 08:05 AM
<blockquote><font class="small">Quote wayne crimi:</font><hr>The second question is related to how much the cue ball will deflect depending on where you hit it. I seem to be getting almost wild deflection when I hit the cue ball at either approximately 4:30 or 7:30 1 1/2 tips below center with a slow to medium stroke. The deflection amount is much smaller when I'm to the left or right of center or above center. This is also a new experience for me. Either I used to adjust to it properly in the past and didn't know it, or something else is going on.

Is there an "physics" reason why this would be the case or am I just doing something in my stroke I can't see?<hr /></blockquote>

Physically speaking, squirt (cue ball deflection) should be larger for a larger horizontal cue tip offset (the number of tips left or right of center). There also seems to be a slight correlation with speed ... more squirt at higher speed. You should be able to observe the largest squirt at 3 and 9 o'clock. Now, when you hit below center, there is slightly more cue stick elevation, which should produce more cue ball swerve (masse action) at slower speeds, so one might expect less apparent squirt at 4:30 and 7:30 (since swerve is in the opposite direction from squirt). Also, as you go further below (or above) center, you cannot create as much horizontal cue tip offset without miscuing.

That's the long answers. The short answer is that I have no physical explanation for what you think you are observing.

Sorry,
Dave

wayne crimi
10-12-2006, 08:18 AM
That's exactly my understanding and prior experience. Yet my experience yesterday was pretty close to the opposite of what should be happening.

That's why when I missed a few shots by a couple of inches (shots that I should be about 98% on) I did a double take and started questioning the cue stick. I was actually able to duplicate the experience several times. Without a video, I can't exactly see or think of what else could be going on. Perhaps some action in my stoke, but I can't think of anything.

<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote wayne crimi:</font><hr>The second question is related to how much the cue ball will deflect depending on where you hit it. I seem to be getting almost wild deflection when I hit the cue ball at either approximately 4:30 or 7:30 1 1/2 tips below center with a slow to medium stroke. The deflection amount is much smaller when I'm to the left or right of center or above center. This is also a new experience for me. Either I used to adjust to it properly in the past and didn't know it, or something else is going on.

Is there an "physics" reason why this would be the case or am I just doing something in my stroke I can't see?<hr /></blockquote>

Physically speaking, squirt (cue ball deflection) should be larger for a larger horizontal cue tip offset (the number of tips left or right of center). There also seems to be a slight correlation with speed ... more squirt at higher speed. You should be able to observe the largest squirt at 3 and 9 o'clock. Now, when you hit below center, there is slightly more cue stick elevation, which should produce more cue ball swerve (masse action) at slower speeds, so one might expect less apparent squirt at 4:30 and 7:30 (since swerve is in the opposite direction from squirt). Also, as you go further below (or above) center, you cannot create as much horizontal cue tip offset without miscuing.

That's the long answers. The short answer is that I have no physical explanation for what you think you are observing.

Sorry,
Dave <hr /></blockquote>

dr_dave
10-12-2006, 08:32 AM
Wayne,

When I experience dilemmas like this, I try to do a controlled experiment. For example, set up the cue ball on the head spot and shoot to the foot spot with various types and amounts of English and speeds. Try each shot multiple times for an average. You can use the "rail ruler" under "templates" here (http://www.engr.colostate.edu/~dga/pool/resources/index.html) to help you (or a camera or a helper) measure the amount of squirt at a certain distance (e.g., at mid table and/or at the foot rail). You should recruit a friend or two to participate. Let us know if you come up with any additional insight.

Dave

<blockquote><font class="small">Quote wayne crimi:</font><hr> That's exactly my understanding and prior experience. Yet my experience yesterday was pretty close to the opposite of what should be happening.

That's why when I missed a few shots by a couple of inches (shots that I should be about 98% on) I did a double take and started questioning the cue stick. I was actually able to duplicate the experience several times. Without a video, I can't exactly see or think of what else could be going on. Perhaps some action in my stoke, but I can't think of anything.

<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote wayne crimi:</font><hr>The second question is related to how much the cue ball will deflect depending on where you hit it. I seem to be getting almost wild deflection when I hit the cue ball at either approximately 4:30 or 7:30 1 1/2 tips below center with a slow to medium stroke. The deflection amount is much smaller when I'm to the left or right of center or above center. This is also a new experience for me. Either I used to adjust to it properly in the past and didn't know it, or something else is going on.

Is there an "physics" reason why this would be the case or am I just doing something in my stroke I can't see?<hr /></blockquote>

Physically speaking, squirt (cue ball deflection) should be larger for a larger horizontal cue tip offset (the number of tips left or right of center). There also seems to be a slight correlation with speed ... more squirt at higher speed. You should be able to observe the largest squirt at 3 and 9 o'clock. Now, when you hit below center, there is slightly more cue stick elevation, which should produce more cue ball swerve (masse action) at slower speeds, so one might expect less apparent squirt at 4:30 and 7:30 (since swerve is in the opposite direction from squirt). Also, as you go further below (or above) center, you cannot create as much horizontal cue tip offset without miscuing.

That's the long answers. The short answer is that I have no physical explanation for what you think you are observing.

Sorry,
Dave<hr /></blockquote><hr /></blockquote>

Jal
10-12-2006, 11:44 AM
<blockquote><font class="small">Quote wayne crimi:</font><hr>...Is there an "physics" reason why this would be the case or am I just doing something in my stroke I can't see? <hr /></blockquote>You described the amount of squirt as "almost wild", which suggests that you may be partially miscuing (miscuing late during the contact period). The ball will have rotated some, and this may be taking the offset past the miscue limit. If so, you may be dipping the tip down more than you're aware, and/or it may still be in motion (moving downward) as it contacts the ball, which might exacerbate things. Have you tried moving your grip hand back or shortening your bridge length?

Another poster on this or another forum thought that their Predator was squirting more with age. It doesn't seem likely.

Jim

Fran Crimi
10-12-2006, 12:13 PM
Hi Wayne,

Maybe I can help. I can meet you with my digital camera and can zoom-in on your stroke and play it back in slo-mo. Send me a PM where and when and I'll be there. I'm curious myself, because I have an old Predator shaft, too.

Fran

Cornerman
10-12-2006, 01:53 PM
<blockquote><font class="small">Quote wayne crimi:</font><hr> I seem to be getting almost wild deflection when I hit the cue ball at either approximately 4:30 or 7:30 1 1/2 tips below center with a slow to medium stroke.

Note: I'm certain my cue is level so swerve and other factors are not the main issue. <hr /></blockquote> I don't know, Wayne. I gave up on the low squirt shafts because the slow to medium low english (4:00 and 7:00) shots' swerve/squirt combination was never ingrained into my tiny brain.

That is, it never took much for swerve to overtake squirt by a lot. Hitting low, you're naturally angled. And again, it doesn't take much angle for swerve to be noticeable on a low squirt shaft. Especially if you're coming back to it anew, without the ingrained compensation.

That was my problem, but it sounds like you're actually getting more overall squirt, not less.

On the first problem, I recall several people reporting that their Predator squirted more after several years. And these are people that we (you and I) know for sure understand how to test squirt.

Have you weighed your cueball? Is there some schmutz sticking to your tip?

Fred

wayne crimi
10-12-2006, 03:47 PM
Hi Fran,

I've been playing at the old Bayside Billiard Club, but I could easily go to La Cue also. Tuesday afternoon is usually best for me, but I never know what my schedule looks like until a day or so before. I could probably also make it on another day. I'll let you know.

My mechanics are so screwed up right now, it could really be anything. /ccboard/images/graemlins/confused.gif

cushioncrawler
10-12-2006, 09:25 PM
Is it the original tip ?? -- i suspect that u put a new tip on, and that it is softer than what u are/were used to -- soft tips squirt more. Which reminds me of when i found my old original cue (bought it in 1965) in about 1996 -- i hadnt used it since 1967 -- in 1996 i found that the original old-fashioned leather tip had gone so hard that the cue wasnt use-able (and i love hard tips).

And/Or -- the bed-cloth is more slippery than what u were used to -- hence more squirt. I know that u said that u hold the cue nearnuff horizontally -- if so then the slipperyness of the cloth shouldnt make a difference -- but.

And/Or -- in the oldendayz u used to play all of your shots with the butt jacked-up a bit -- hence u will now get more squirt if dont jack up as much. madMac.

pooltchr
10-13-2006, 05:12 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> Physically speaking, squirt (cue ball deflection) should be larger for a larger horizontal cue tip offset (the number of tips left or right of center). There also seems to be a slight correlation with speed ... more squirt at higher speed. You should be able to observe the largest squirt at 3 and 9 o'clock. Now, when you hit below center, there is slightly more cue stick elevation, which should produce more cue ball swerve (masse action) at slower speeds, so one might expect less apparent squirt at 4:30 and 7:30 (since swerve is in the opposite direction from squirt). Also, as you go further below (or above) center, you cannot create as much horizontal cue tip offset without miscuing.
Dave <hr /></blockquote>


Dave,
This would be a good subject for some of your video testing. I think you might find that squirt is actually greater when side spin is applied below the horizontal center than you would have with the same amount of side spin applied above horizontal center.
Steve

dr_dave
10-13-2006, 06:44 AM
<blockquote><font class="small">Quote pooltchr:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> Physically speaking, squirt (cue ball deflection) should be larger for a larger horizontal cue tip offset (the number of tips left or right of center). There also seems to be a slight correlation with speed ... more squirt at higher speed. You should be able to observe the largest squirt at 3 and 9 o'clock. Now, when you hit below center, there is slightly more cue stick elevation, which should produce more cue ball swerve (masse action) at slower speeds, so one might expect less apparent squirt at 4:30 and 7:30 (since swerve is in the opposite direction from squirt). Also, as you go further below (or above) center, you cannot create as much horizontal cue tip offset without miscuing.
Dave <hr /></blockquote>


Dave,
This would be a good subject for some of your video testing. I think you might find that squirt is actually greater when side spin is applied below the horizontal center than you would have with the same amount of side spin applied above horizontal center.
Steve <hr /></blockquote>
Sounds reasonable to me since an above center hit drives the cue ball into the table a little (although my intuition tells me this should be a very small effect). I'll add the experiment to my things-to-do list.

Regards,
Dave

pooltchr
10-13-2006, 08:00 AM
I think it's more the effect of hitting below center with side spin causes the bottom of the ball to "kick out" so to speak. The cue ball tracks along the line where the ball actually contacts the table, so the effect is to push the whole ball off track. Anyway, I will be interested to see what you come up with on that one.
Steve

dr_dave
10-13-2006, 08:32 AM
<blockquote><font class="small">Quote pooltchr:</font><hr> I think it's more the effect of hitting below center with side spin causes the bottom of the ball to "kick out" so to speak. The cue ball tracks along the line where the ball actually contacts the table, so the effect is to push the whole ball off track. Anyway, I will be interested to see what you come up with on that one.
Steve <hr /></blockquote>
I think we're basically saying the same thing. I look forward to seeing how big of an effect it realy is.

Regards,
Dave

Jal
10-13-2006, 11:17 AM
<blockquote><font class="small">Quote Cornerman:</font><hr>...On the first problem, I recall several people reporting that their Predator squirted more after several years. And these are people that we (you and I) know for sure understand how to test squirt.<hr /></blockquote>It may be that the shafts do squirt more with age. But I wonder who really knows how to test for it. For the fresher shafts, the figures reported by some technically knowledgeable people and the test results from Predator and Platinum Billiards disagree by a factor of 3-4.

Jim

wayne crimi
10-13-2006, 03:53 PM
<blockquote><font class="small">Quote pooltchr:</font><hr> I think it's more the effect of hitting below center with side spin causes the bottom of the ball to "kick out" so to speak. The cue ball tracks along the line where the ball actually contacts the table, so the effect is to push the whole ball off track. Anyway, I will be interested to see what you come up with on that one.
Steve <hr /></blockquote>

That sounds like what I'm experiencing.

The other thing I can add is that I'm definitely "out of stoke". My mechanics are poor because I haven't been playing much. My stroke is punchier and tighter than it used to be when I was playing regularly. I'm not following through with a smooth and relaxed stroke the way I'd like.

I'm not sure how that would change the CB action.

Alfie
10-13-2006, 07:01 PM
<blockquote><font class="small">Quote Fran Crimi:</font><hr> I can meet you with my digital camera and can zoom-in on your stroke and play it back in slo-mo. <hr /></blockquote>Hey Fran, what make and model camera? Are you happy with it?

Fran Crimi
10-14-2006, 05:24 AM
<blockquote><font class="small">Quote Alfie:</font><hr> <blockquote><font class="small">Quote Fran Crimi:</font><hr> I can meet you with my digital camera and can zoom-in on your stroke and play it back in slo-mo. <hr /></blockquote>Hey Fran, what make and model camera? Are you happy with it? <hr /></blockquote>

It's a Cannon Powershot SD450. Yes, I'm happy with it for taking quick clips. It's compact, reasonably priced and it's got a decent zoom. The playback is very smooth as opposed to some I've seen, where the playback is jerky. Plus, I can play back the clip in slow motion or frame by frame. One setback is that you do need a little bit of light when filming. Pool table light is fine, but the surrounding area light sometimes falls short, so you have to keep it on or near the table.

Fran

jingle
10-16-2006, 11:41 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr> Is it the original tip ?? -- i suspect that u put a new tip on, and that it is softer than what u are/were used to -- soft tips squirt more.
<hr /></blockquote>

Is this generally accepted as true? (soft tips produce more squirt than harder tips) It seems to me to be the case, just curious if it has actually been tested before?

pooltchr
10-16-2006, 01:24 PM
<blockquote><font class="small">Quote wayne crimi:</font><hr> <blockquote><font class="small">Quote pooltchr:</font><hr> I think it's more the effect of hitting below center with side spin causes the bottom of the ball to "kick out" so to speak. The cue ball tracks along the line where the ball actually contacts the table, so the effect is to push the whole ball off track. Anyway, I will be interested to see what you come up with on that one.
Steve <hr /></blockquote>

That sounds like what I'm experiencing.

The other thing I can add is that I'm definitely "out of stoke". My mechanics are poor because I haven't been playing much. My stroke is punchier and tighter than it used to be when I was playing regularly. I'm not following through with a smooth and relaxed stroke the way I'd like.

I'm not sure how that would change the CB action. <hr /></blockquote>

If your stroke is off, it doesn't matter what cue you are using. Get the stroke fixed, and you may find that your cue isn't causing any problem at all.
Steve

dr_dave
10-16-2006, 01:34 PM
<blockquote><font class="small">Quote jingle:</font><hr> <blockquote><font class="small">Quote cushioncrawler:</font><hr> Is it the original tip ?? -- i suspect that u put a new tip on, and that it is softer than what u are/were used to -- soft tips squirt more.<hr /></blockquote>
Is this generally accepted as true? (soft tips produce more squirt than harder tips) It seems to me to be the case, just curious if it has actually been tested before?<hr /></blockquote>
I did some limited tests with different shafts and tip hardnesses (see here (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=201674&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1)). Unfortunately, I didn't look at squirt vs. tip hardness as carefully as I would have liked. Softer tips do create a longer contact time between the cue tip and cue ball (my tests did back this up), but I'm not sure this causes more squirt.

Regards,
Dave

cushioncrawler
10-16-2006, 02:46 PM
<blockquote><font class="small">Quote jingle:</font><hr> ...Is this generally accepted as true? (soft tips produce more squirt than harder tips) It seems to me to be the case, just curious if it has actually been tested before? <hr /></blockquote>
In english-billiards (12' table) the acid-test of squirt is the long-jenny -- i used to uze very hard (brown) leather tips, made extra hard by hammering or viceing -- when i tried to wean myself onto ordinary elk tips (softish) , i found that i had to stroke towards the door of the lady's toilets to get the same contact on the object ball -- it is as Dr Dave suspects, the extra tip-ball contact time brings more of the wt of the cue into the equation, hence extra squirt.

But i disagree with Dr Dave (and Bob??) re the effect of speed -- my tests (uzing a qball on a pendulum) show that pure-squirt is less the harder u hit the qball -- but Dr Dave is usually talking about impure-squirt (ie real squirt on a real table), this is less (or can be less) depending on how much u (naturally) jack-up. madMac.

dr_dave
10-16-2006, 02:59 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>But i disagree with Dr Dave (and Bob??) re the effect of speed -- my tests (uzing a qball on a pendulum) show that pure-squirt is less the harder u hit the qball -- but Dr Dave is usually talking about impure-squirt (ie real squirt on a real table), this is less (or can be less) depending on how much u (naturally) jack-up. madMac.<hr /></blockquote>
Mac,

I'll have to try that pendulum thing one day. That's a good idea.

When I did my squirt measurements from the high-speed-videos, I was measuring the squirt amount fairly close to the original cue ball location, so I doubt swerve was corrupting my results very much. Maybe something else is going on. Hopefully, some of the people with repeatable robots and decent measuring tools can do better experiments for us in the future.

Still unsure about squirt's dependence on speed (and its physical explanation),
Dave

cushioncrawler
10-16-2006, 03:32 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> ....Still unsure about squirt's dependence on speed (and its physical explanation)...<hr /></blockquote>
Hi Dr Dave -- this just reminded me -- i remember Bob's tests where a wt was gradually shifted along the cue, ie further from the tip, and when the wt was 8" from the tip the wt made zero difference to the squirt. But, i couldnt help thinking that had Bob mooved the wt to 9" then 10" etc, eventually he might have found that the wt entered the picture again -- in other words, 8" represented a node or center of percussion or something. Koz, i know that i can affect the squirt by how i hold the butt of the cue -- ie a gentle little one-finger-and-thumb grip gives the minimum squirt (especially if your cue is a stiffy).

Regarding the action of swerve -- i found something new (new to me) the other day. I aligned a qball and objectball so that a direct centerball hit on the objectball would result in the objectball jawing out of the (corner) pocket -- by uzing a bit of swerve (and sidespin) i could pot the ball, and bring the qball back to sit on the same line -- looks impossible -- but perhaps this sort of (trick) shot has been mentioned before. madMac.

Cornerman
10-16-2006, 05:23 PM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>
i remember Bob's tests where a wt was gradually shifted along the cue, ie further from the tip, and when the wt was 8" from the tip the wt made zero difference to the squirt. But, i couldnt help thinking that had Bob mooved the wt to 9" then 10" etc, eventually he might have found that the wt entered the picture again -- in other words, 8" represented a node or center of percussion or something. <hr /></blockquote>There are two "waves" if you want to look at it like that. One is due to the speed of sound through the cue. That wave is extremely quick, and easily goes the entire length of the cue during the short cueball/cuestick contact time.

The other is the lateral wave (due to hitting the cuestick on the side). IMO, that's the one to consider when looking at squirt. The lateral wave seems to go approximately 3" per msec (as measured in one of the slo-mo videos). Since the measurements saw the contact time between the tip and cueball at something less than 2msec at the most extreme, then that lateral wave would travel ~6" while the contact was taking place. In other word, that's how much of the stick the cueball feels from the lateral (side) force: approximately 6" or so. So, past 6" or 7", the theory says won't affect squirt since the cueball won't see that weight from the lateral direction.

I believe several of these "add weight" tests have been performed, including adding the weight past 8", added to the joint, and added elsewhere.

Fred &lt;~~~ IMO, of course

dr_dave
10-17-2006, 06:53 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>i know that i can affect the squirt by how i hold the butt of the cue -- ie a gentle little one-finger-and-thumb grip gives the minimum squirt (especially if your cue is a stiffy).<hr /></blockquote>
I find this very hard to believe. Again, maybe the robot people can simulate different grips for us to put this issue to rest.

<blockquote><font class="small">Quote cushioncrawler:</font><hr>Regarding the action of swerve -- i found something new (new to me) the other day. I aligned a qball and objectball so that a direct centerball hit on the objectball would result in the objectball jawing out of the (corner) pocket -- by uzing a bit of swerve (and sidespin) i could pot the ball, and bring the qball back to sit on the same line -- looks impossible -- but perhaps this sort of (trick) shot has been mentioned before. madMac.<hr /></blockquote>
Masse'/throw shots are cool (although, not always so easy to control). Several have been mentioned/diagrammed here, and I think one of Buddy Hall's YouTube clips shows a good example.

Regards,
Dave

Cornerman
10-17-2006, 07:16 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> I find this very hard to believe. Again, maybe the robot people can simulate different grips for us to put this issue to rest.<hr /></blockquote>Well... they did put it to rest. A robot grip can affect squirt. But, that's only because the robot's grip was so tight that the cueball/cue tip contact time increased beyond what the testers (Jewett and others) believed was/is possible for a human.

I think a viable test would make a grip molded with that special effects gel that the Myth Busters use to make Buster. That way, the grip can only be as tight as the gel can get, which supposedly is pretty close to the properties of human flesh.

One of these days, I might actually get around to doing this.

Fred

dr_dave
10-17-2006, 07:38 AM
<blockquote><font class="small">Quote Cornerman:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> I find this very hard to believe. Again, maybe the robot people can simulate different grips for us to put this issue to rest.<hr /></blockquote>Well... they did put it to rest. A robot grip can affect squirt. But, that's only because the robot's grip was so tight that the cueball/cue tip contact time increased beyond what the testers (Jewett and others) believed was/is possible for a human.

I think a viable test would make a grip molded with that special effects gel that the Myth Busters use to make Buster. That way, the grip can only be as tight as the gel can get, which supposedly is pretty close to the properties of human flesh.

One of these days, I might actually get around to doing this.

Fred<hr /></blockquote>
It would be interesting to see how much a realistic range of possible human grips would affect squirt. Please share your results here if you do some tests. The only test I've ever done with grip was described in a previous thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=176991&amp;Foru m=ccb&amp;Words=HSV%20A.34&amp;Match=Entire%20Phrase&amp;Searc hpage=0&amp;Limit=25&amp;Old=allposts&amp;Main=176991&amp;Search=t rue#Post176991). Unfortunately, I only looked at a light grip and firm shot.

Several questions:
- How much did the artificially tight robot grip affect squirt?
- How can this be explained in light of the lateral vibration theory, which predicts that only the last 8" or so are involved?

Thanks,
Dave

Cornerman
10-17-2006, 08:43 AM
<blockquote><font class="small">Quote dr_dave:</font><hr>
Several questions:
- How much did the artificially tight robot grip affect squirt?
- How can this be explained in light of the lateral vibration theory, which predicts that only the last 8" or so are involved?

Thanks,
Dave <hr /></blockquote>I don't know if the Jacksonville group took measurements, but the squirt would be effected if the robot and its grip could increase the contact time.

Since the robot grip was tighter than a humans, the robot could theoretically still accelerate during the tip/cueball collision creating a longer contact time. That is, where a cue held by a human undergoes rapid deceleration upon contact, a robot held gripped cue does not. A robot can continue to add force to the collision.

If the contact time increased to, say, .003 seconds (up from .002 seconds of lotsa english), then the amount of mass the cueball sees from the lateral wave would be approximately:

3msec (approx. contact time) X 3 inches/msec (approx. lateral/transverse wave speed down the cue) = 9 inches.

If the robot could accelerate such that the contact time goes to .004 msec, then the mass "seen" could be 12" or so.

And so on. Each increase in time adds more mass to the lateral collision, which is what seems to make up the majority of the squirt angle.



So, my questions would be,

"can a human grip sufficiently tight enough such that they can reduce the rapid deceleration of the cue upon contact with the cueball and increase the contact time."

and

"what parameters affect the speed of the tranverse wave down the cue"? Materials? Taper?

These ideas also help to explain why the Predator doesn't do so well on the Meucci Myth Destroyer robot.

Fred

dr_dave
10-17-2006, 08:55 AM
Fred,

Great post!

Thanks,
Dave

<blockquote><font class="small">Quote Cornerman:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr>
Several questions:
- How much did the artificially tight robot grip affect squirt?
- How can this be explained in light of the lateral vibration theory, which predicts that only the last 8" or so are involved?

Thanks,
Dave <hr /></blockquote>I don't know if the Jacksonville group took measurements, but the squirt would be effected if the robot and its grip could increase the contact time.

Since the robot grip was tighter than a humans, the robot could theoretically still accelerate during the tip/cueball collision creating a longer contact time. That is, where a cue held by a human undergoes rapid deceleration upon contact, a robot held gripped cue does not. A robot can continue to add force to the collision.

If the contact time increased to, say, .003 seconds (up from .002 seconds of lotsa english), then the amount of mass the cueball sees from the lateral wave would be approximately:

3msec (approx. contact time) X 3 inches/msec (approx. lateral/transverse wave speed down the cue) = 9 inches.

If the robot could accelerate such that the contact time goes to .004 msec, then the mass "seen" could be 12" or so.

And so on. Each increase in time adds more mass to the lateral collision, which is what seems to make up the majority of the squirt angle.



So, my questions would be,

"can a human grip sufficiently tight enough such that they can reduce the rapid deceleration of the cue upon contact with the cueball and increase the contact time."

and

"what parameters affect the speed of the tranverse wave down the cue"? Materials? Taper?

These ideas also help to explain why the Predator doesn't do so well on the Meucci Myth Destroyer robot.

Fred <hr /></blockquote>

Bob_Jewett
10-17-2006, 08:55 AM
<blockquote><font class="small">Quote Cornerman:</font><hr> ... I don't know if the Jacksonville group took measurements, but the squirt would be effected if the robot and its grip could increase the contact time.
... <hr /></blockquote>
I'll try to address that point more later. We did do some experiments with bubble-wrap between the cue's butt and Iron Willie's "grip hand" and that was a lot more like a real hand. The problem with IW's normal grip is that it effectively make the cue stick several pounds in weight.

Another problem with IW is that the "bridge" hand is also much harder than human fingers. I think both of these problems have been addresses in Predator's current robot.

A heavier cue stick is expected to have a shorter contact time, but not by much.

Cornerman
10-17-2006, 09:07 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> Another problem with IW is that the "bridge" hand is also much harder than human fingers. I think both of these problems have been addresses in Predator's current robot.<hr /></blockquote>This is one of the problems I believe the Myth Destroyer has as well. There's a V-block at the bridge, and I think they also used the hard rubber clamp. So, if the transverse wave gets to the V-block, squirt multiplies.

<blockquote><font class="small">Quote Bob Jewett:</font><hr>A heavier cue stick is expected to have a shorter contact time, but not by much<hr /></blockquote> I assume this is in the hands of a human. I've also been under the assumption that robot was able to just blast through (not literally) the cueball.

Fred

Jal
10-17-2006, 10:27 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> ...Hopefully, some of the people with repeatable robots and decent measuring tools can do better experiments for us in the future.

Still unsure about squirt's dependence on speed (and its physical explanation)<hr /></blockquote>Steve of Platinum Billiards found an increase in squirt of .2% - .3% per mph over a range of speeds from 9 mph to 21 mph. See his post here, about three-quarters of the way down the page under "Platinum Billiards":

http://tinyurl.com/tfboh

A rough calculation based on the increased average tip offset predicts an increase of about 1% per mph.

Jim

wolfdancer
10-17-2006, 10:56 AM
do you think the Meucci robot could beat Patrick in VP?

dr_dave
10-17-2006, 11:46 AM
<blockquote><font class="small">Quote wolfdancer:</font><hr> do you think the Meucci robot could beat Patrick in VP?<hr /></blockquote>
Definitely not. That VP performance was "legendary."

Dave

dr_dave
10-17-2006, 11:59 AM
Jim,

Thanks for the link. There's some good discussion there.

Dave

<blockquote><font class="small">Quote Jal:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> ...Hopefully, some of the people with repeatable robots and decent measuring tools can do better experiments for us in the future.

Still unsure about squirt's dependence on speed (and its physical explanation)<hr /></blockquote>Steve of Platinum Billiards found an increase in squirt of .2% - .3% per mph over a range of speeds from 9 mph to 21 mph. See his post here, about three-quarters of the way down the page under "Platinum Billiards":

http://tinyurl.com/tfboh

A rough calculation based on the increased average tip offset predicts an increase of about 1% per mph.

Jim <hr /></blockquote>

dr_dave
10-17-2006, 12:06 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote Cornerman:</font><hr> ... I don't know if the Jacksonville group took measurements, but the squirt would be effected if the robot and its grip could increase the contact time. ...<hr /></blockquote>
I'll try to address that point more later. We did do some experiments with bubble-wrap between the cue's butt and Iron Willie's "grip hand" and that was a lot more like a real hand. The problem with IW's normal grip is that it effectively make the cue stick several pounds in weight.

Another problem with IW is that the "bridge" hand is also much harder than human fingers. I think both of these problems have been addresses in Predator's current robot.

A heavier cue stick is expected to have a shorter contact time, but not by much.<hr /></blockquote>
Bob,

If a tighter grip increases the effective "weight" of the cue stick (for longitudinal momentum calculations), and if a heavier stick exhibits shorter contact time (although, maybe you don't know this for a fact ... did you measure this? ... I haven't), wouldn't you expect less squirt, assuming the shaft and bridge are not changed?

Regards,
Dave

Bob_Jewett
10-17-2006, 02:27 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> ... wouldn't you expect less squirt, assuming the shaft and bridge are not changed?... <hr /></blockquote>
I would expect very slightly less squirt. This is the sort of thing that should be measured, but it's hard to do in a sufficiently controlled way.

cushioncrawler
10-17-2006, 03:32 PM
<blockquote><font class="small">Quote Cornerman:</font><hr> <hr /></blockquote> ...There are two "waves" if you want to look at it like that. One is due to the speed of sound through the cue. That wave is extremely quick, and easily goes the entire length of the cue during the short cueball/cuestick contact time. The other is the lateral wave (due to hitting the cuestick on the side). IMO, that's the one to consider when looking at squirt. The lateral wave seems to go approximately 3" per msec (as measured in one of the slo-mo videos). Since the measurements saw the contact time between the tip and cueball at something less than 2msec at the most extreme, then that lateral wave would travel ~6" while the contact was taking place. In other word, that's how much of the stick the cueball feels from the lateral (side) force: approximately 6" or so. So, past 6" or 7", the theory says won't affect squirt since the cueball won't see that weight from the lateral direction. I believe several of these "add weight" tests have been performed, including adding the weight past 8", added to the joint, and added elsewhere.... <hr /></blockquote>
A few months ago i found on a website photos of dry spaghetti breaking into very short pieces when hit end-wise (i think this was for a phd thesis, cookery probably) -- and a allso for a column of teflon (standing vertically and hit down on the end axially by a projectile of some sort) -- the teflon had a wave in it, but, what got my attention, was that the top (free) end mooved a mile sideways, ie like a qtip would do during a miss-cue. But, admittedly some of the sideways moovment would have been after contact had ended. madMac.

cushioncrawler
10-17-2006, 04:01 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> ....When I did my squirt measurements from the high-speed-videos, I was measuring the squirt amount fairly close to the original cue ball location, so I doubt swerve was corrupting my results very much. Maybe something else is going on. Hopefully, some of the people with repeatable robots and decent measuring tools can do better experiments for us in the future. Still unsure about squirt's dependence on speed (and its physical explanation)... <hr /></blockquote>
Not counting the original bed-reaction, i think that the distance (and speed) to where the measure was made would affect whether the qball bounced once or twice or thrice -- the ball changing direction with each bounce, and perhaps a bit more when not bouncing allso.

cushioncrawler
10-17-2006, 04:14 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> ...A heavier cue stick is expected to have a shorter contact time, but not by much.... <hr /></blockquote>
Hi Bob -- I have difficulty believing the short qtip contact times -- if a central tip-qball contact gave say 3 millisec, then wouldnt an extreme off-center contact give say 6 msec -- hmmm, or perhaps 5 msec -- nah, perhaps 4 and a bit -- hmmm, disregard this posting. madMac.

dr_dave
10-17-2006, 05:55 PM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> ... wouldn't you expect less squirt, assuming the shaft and bridge are not changed?... <hr /></blockquote>
I would expect very slightly less squirt. This is the sort of thing that should be measured, but it's hard to do in a sufficiently controlled way.<hr /></blockquote>
Well, if it is so difficult to measure and if the effect is so slight, it probably isn't that important of a question in the first place.

Regards,
Dave

SPetty
10-18-2006, 11:09 AM
<blockquote><font class="small">Quote cushioncrawler:</font><hr>A few months ago i found on a website photos of dry spaghetti breaking into very short pieces when hit end-wise (i think this was for a phd thesis, cookery probably) -- and a allso for a column of teflon (standing vertically and hit down on the end axially by a projectile of some sort) -- the teflon had a wave in it, but, what got my attention, was that the top (free) end moved a mile sideways, ie like a cue tip would do during a miscue. But, admittedly some of the sideways movement would have been after contact had ended. <hr /></blockquote>
http://www.sciencenews.org/articles/20051112/a6709_1127.jpg
High-speed video reveals that (left to right) a stick of dry spaghetti whacked at the end by a metal slug (top) buckles in waves before shattering.

http://biophysics.physics.brown.edu/BPJC/JC%20pdf%20paper%20files/BPJC%202005%20Yifeng/Dynamic%20Buckling%20and%20Fragmentation%20in%20Br ittle%20Rods.pdf

cushioncrawler
10-19-2006, 06:28 PM
Dang -- i spent hours making a cue of dry spaghetti taped up nicely, and it broke into a million pieces when i hit the end a little too hard with the chalk -- dang. madMac.

colincolenso
10-25-2006, 08:22 AM
On firm draw shots with english using Back Hand English to align and compare I've also found that squirt is larger than for the same shots played with center level english.

I think the main reason for this is speed. That when we use draw, we are actually hitting the CB harder than we tend to think. Rarely will be hit the CB so hard when playing english on a stun or follow shot.

Also, with the CB moving quite fast and with considerable spin, throw is decreased, which can, on certain shots, add to the effect.

Colin

dr_dave
10-25-2006, 08:49 AM
<blockquote><font class="small">Quote colincolenso:</font><hr>On firm draw shots with english using Back Hand English to align and compare I've also found that squirt is larger than for the same shots played with center level english.

I think the main reason for this is speed. That when we use draw, we are actually hitting the CB harder than we tend to think. Rarely will be hit the CB so hard when playing english on a stun or follow shot.<hr /></blockquote>
I tend to agree there is a relationship between the amount of squirt and speed (even if only slight). Although, there are many people that disagree. The claim is backed up anecdotally (although, with some swerve effects) in NV A.17 (http://www.engr.colostate.edu/~dga/pool/normal_videos/new/NVA-17.htm). High-speed video results (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=201674&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1) also back up the claim.

<blockquote><font class="small">Quote colincolenso:</font><hr>Also, with the CB moving quite fast and with considerable spin, throw is decreased, which can, on certain shots, add to the effect.<hr /></blockquote>
Agreed. This is backed up quite thoroughly by my October '06 instructional article (http://www.engr.colostate.edu/~dga/pool/bd_articles/2006/oct06.pdf).

Regards,
Dave

colincolenso
10-25-2006, 09:22 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> I tend to agree there is a relationship between the amount of squirt and speed (even if only slight). Although, there are many people that disagree. The claim is backed up anecdotally (although, with some swerve effects) in NV A.17 (http://www.engr.colostate.edu/~dga/pool/normal_videos/new/NVA-17.htm). High-speed video results (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=201674&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1) also back up the claim.

Regards,
Dave <hr /></blockquote>
Thanks for the links Dave!

I used to think that squirt varied more with speed than I currently do, though I still believe speed does add to squirt. Clearly some accurate experiments are still needed to prove and quantify this.

Some of my testing has revealed that swerve is much more significant than I had earlier thought, and even throw variations due to dirty v clean balls and humid v dry conditions have significant affects on adjustment for aiming with english.

Using BHE (inside english) at medium/firm speed for a 3/4 ball pot, 2 feet of separation, on my own table which is affected by humidity considerably, I need to play this shot with a bridge length of 15".

In the super dry condtions in Reno, I had to change my bridge length to around 9" to make the same shot.

This indicated to me that my CB had been swerving much more than I had imagined it could at this speed over this distance, even with follow.

Colin

dr_dave
10-25-2006, 10:28 AM
Colin,

I hope we've been able to recruit you as a more permanent fixture on the BD CCB. Your insight and experience is very much appreciated.

Regards,
Dave
<blockquote><font class="small">Quote colincolenso:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> I tend to agree there is a relationship between the amount of squirt and speed (even if only slight). Although, there are many people that disagree. The claim is backed up anecdotally (although, with some swerve effects) in NV A.17 (http://www.engr.colostate.edu/~dga/pool/normal_videos/new/NVA-17.htm). High-speed video results (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=201674&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;vc=1) also back up the claim.

Regards,
Dave <hr /></blockquote>
Thanks for the links Dave!

I used to think that squirt varied more with speed than I currently do, though I still believe speed does add to squirt. Clearly some accurate experiments are still needed to prove and quantify this.

Some of my testing has revealed that swerve is much more significant than I had earlier thought, and even throw variations due to dirty v clean balls and humid v dry conditions have significant affects on adjustment for aiming with english.

Using BHE (inside english) at medium/firm speed for a 3/4 ball pot, 2 feet of separation, on my own table which is affected by humidity considerably, I need to play this shot with a bridge length of 15".

In the super dry condtions in Reno, I had to change my bridge length to around 9" to make the same shot.

This indicated to me that my CB had been swerving much more than I had imagined it could at this speed over this distance, even with follow.

Colin <hr /></blockquote>

colincolenso
10-25-2006, 04:09 PM
Thanks Dave,
I will try to post here a bit more often. There is a good collection of wisdom and experience here.

I have learned quite a bit from perusing threads here in the past.

Cheers,
Colin


<blockquote><font class="small">Quote dr_dave:</font><hr> Colin,

I hope we've been able to recruit you as a more permanent fixture on the BD CCB. Your insight and experience is very much appreciated.

Regards,
Dave
<hr /></blockquote>

dr_dave
10-26-2006, 06:56 AM
<blockquote><font class="small">Quote colincolenso:</font><hr> Thanks Dave,
I will try to post here a bit more often. There is a good collection of wisdom and experience here.

I have learned quite a bit from perusing threads here in the past.<hr /></blockquote>
I feel the same way about this forum. That's why I chose it over others when deciding where to dedicate my time. I also write for BD magazine, so it also made sense for that reason.

FYI, I maintain a website with links to important highlights from past threads (http://www.engr.colostate.edu/~dga/pool/threads.html). I find the site useful when wanting to refer back to useful posts in various topical areas. It's also useful if you want to read up on topics of interest you may have missed.

I look forward to seeing your name more around here.

Cheers,
Dave