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View Full Version : new high-speed video of hand grip during impact



dr_dave
01-26-2005, 04:39 PM
FYI,
I just posted a new high-speed video (see HSV A.34 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-34.htm)) showing the hand grip during a firm stroke, striking the cue ball at the bottom of the pendulum swing. It's kind of difficult to draw conclusions from the video, but I like to think that it supports the following statement:

With a light grip, the hand has very little effect on the cue stick during impact with the cue ball.

This statement certainly makes sense physically, because the cue tip is in contact with the cue ball for such a short period of time (~ 0.001 sec) and because the hand flesh is so flexible.

Maybe these statements are obvious to most of you. I hope you don't take offense if they are. I hope you find the video interesting anyway.

SpiderMan
01-26-2005, 04:56 PM
Dave,

Can you give me a reference (maybe to the running timer) to indicate exactly when the impact is occuring? I couldn't seem to see it, at least not with my expectation of the cue suddenly moving with respect to the hand.

If this is furnished in accompanying audio I apologize, I don't have sound at the moment.

SpiderMan

yegon
01-26-2005, 05:11 PM
as I understand it the impact is at the bottom of the pendulum, when the hand stops going down and starts going up

now if this is a hard stroke I am very surprised that the impact on the cue ball is virtually unnoticable

Bob_Jewett
01-26-2005, 06:42 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> ...
With a light grip, the hand has very little effect on the cue stick during impact with the cue ball.
... <hr /></blockquote>
For a detailed stick speed versus time plot squeezed from the Jacksonville tape, see the June 1999 issue of Billiards Digest. The stick speed drops to 50% in the
millisecond it's on the ball, and then speeds back up to 80% of peak speed as the hand follows through. It is possible to determine from the rate at which the stick is re-accelerated after the tip leaves the ball that the hand is about 100 times softer than the tip. This is the reason that the grip has essentially no effect on the shot.

kyle
01-26-2005, 09:15 PM
DrDave, IMO the reason for a loose grip is it acts as a better hinge your cue can remain level longer whereas with a firmer grip your stroke could become more rocky and less effiecent.

GeraldG
01-26-2005, 09:59 PM
The idea is to let the cue do the work. If you have a "death grip" on the cue, your whole stroke will be tense and stiff and you will end up trying to overpower the cueball and "steer" the cue, plus you will lose some of the natural "hit" of the cue because you deaden the cue's action by gripping it too tightly. Keeping your arm and grip relaxed allows a smooth,natural stroke.

JohnnyP
01-26-2005, 10:29 PM
Dr. Dave:

I can't get that one to play, but I can watch the other videos just fine.

Thanks for posting here.

dr_dave
01-27-2005, 09:00 AM
<blockquote><font class="small">Quote SpiderMan:</font><hr>Can you give me a reference (maybe to the running timer) to indicate exactly when the impact is occuring? I couldn't seem to see it, at least not with my expectation of the cue suddenly moving with respect to the hand.<hr /></blockquote>
It is more difficult to see exactly what's going on in the posted compressed video. The image quality was much better on the high-speed camera monitor. Impact occurs at about frame 1275. The impact is easiest to see at the FWD30 speed. The video was shot at 1000 frames/sec. "FWD30" means forward playback at 30 frames/sec, so one second of viewing time corresponds 30/1000 of a second (0.03 second).

<blockquote><font class="small">Quote SpiderMan:</font><hr>If this is furnished in accompanying audio I apologize, I don't have sound at the moment.<hr /></blockquote>
There is no audio with the HSVs.

dr_dave
01-27-2005, 09:03 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> ...
With a light grip, the hand has very little effect on the cue stick during impact with the cue ball.
... <hr /></blockquote>
For a detailed stick speed versus time plot squeezed from the Jacksonville tape, see the June 1999 issue of Billiards Digest. The stick speed drops to 50% in the
millisecond it's on the ball, and then speeds back up to 80% of peak speed as the hand follows through. It is possible to determine from the rate at which the stick is re-accelerated after the tip leaves the ball that the hand is about 100 times softer than the tip. This is the reason that the grip has essentially no effect on the shot. <hr /></blockquote>
Bob, is that article available online? I'm sure many people would want like to see it. If you send me a PDF file or an original hard-copy, I would be happy to post it on my website for you.

dr_dave
01-27-2005, 09:10 AM
<blockquote><font class="small">Quote kyle:</font><hr> DrDave, IMO the reason for a loose grip is it acts as a better hinge your cue can remain level longer whereas with a firmer grip your stroke could become more rocky and less effiecent.<hr /></blockquote>
Good point. I agree with you.

Also, IMHO, a firm grip can help increase the effective mass of the cue stick. This can change the dynamics of certain shots (e.g., a masse shot). I will be posting several large collections of high-speed-video clips over the next two weeks that will show some interesting results for various types of draw, follow, and masse shots.

dr_dave
01-27-2005, 09:15 AM
<blockquote><font class="small">Quote JohnnyP:</font><hr>I can't get that one to play, but I can watch the other videos just fine.<hr /></blockquote>
Other people have also reported this problem. I'm using a new version of the Pinnacle software, but the video works fine on every computer I have tested. Have you tried upgrading to the latest Windows Media Player? I have the upgrade link on my website. Has anyone that has had this problem found a solution? If so, please respond here to share your information.

Fred Agnir
01-27-2005, 09:50 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> FYI,
I just posted a new high-speed video (see HSV A.34 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-34.htm)) showing the hand grip during a firm stroke, striking the cue ball at the bottom of the pendulum swing. It's kind of difficult to draw conclusions from the video, but I like to think that it supports the following statement:

With a light grip, the hand has very little effect on the cue stick during impact with the cue ball.
<hr /></blockquote>It's tough to tell, but I think I see the web between the thumb and index finger collapsing as the stick decelerates (presumably at contact), while the rest of the hand moves at a near constant speed. Is that what you see?

Fred

SpiderMan
01-27-2005, 09:51 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr>
For a detailed stick speed versus time plot squeezed from the Jacksonville tape, see the June 1999 issue of Billiards Digest. The stick speed drops to 50% in the
millisecond it's on the ball, and then speeds back up to 80% of peak speed as the hand follows through. It is possible to determine from the rate at which the stick is re-accelerated after the tip leaves the ball that the hand is about 100 times softer than the tip. This is the reason that the grip has essentially no effect on the shot. <hr /></blockquote>

That's what I was trying to pick up visually from the tape, but I wasn't able to detect it by watching the relative stick/hand motion.

SpiderMan

Fred Agnir
01-27-2005, 09:54 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> Also, IMHO, a firm grip can help increase the effective mass of the cue stick. This can change the dynamics of certain shots (e.g., a masse shot). <hr /></blockquote>That would be interesting if you could prove this. I've been going under the premise that no matter how firm a human could grip, it makes little to no difference as far as the collision was concerned since the skin is so much more compliant than the tip itself.

Increasing the effective stick mass would definitely change the dynamics if the grip hand was rigid and non-compliant.

Fred

dr_dave
01-27-2005, 09:59 AM
<blockquote><font class="small">Quote Fred Agnir:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> Also, IMHO, a firm grip can help increase the effective mass of the cue stick. This can change the dynamics of certain shots (e.g., a masse shot). <hr /></blockquote>That would be interesting if you could prove this. I've been going under the premise that no matter how firm a human could grip, it makes little to no difference as far as the collision was concerned since the skin is so much more compliant than the tip itself.

Increasing the effective stick mass would definitely change the dynamics if the grip hand was rigid and non-compliant.<hr /></blockquote>
We can discuss this more after I post my large collection of most recently filmed videos. I also want to spend more time thinking about the physics and watching the new videos. I'm not saying you are wrong yet (and maybe I won't).

JohnnyP
01-27-2005, 10:30 AM
Dr. Dave:

The latest version of WMP didn't help. I'm running OS 9.2 on an older iMac.

Your video showing cue stick deflection is interesting. With my thin shafted lightweight cue, using an open bridge and a light grip, I can see the stick visibly deflect (or roll off) the cueball. I thought I was seeing things. Maybe it rotates about the center of mass? When I shoot that way, the squirt is much less than when I am ham fisted.

dr_dave
01-27-2005, 10:42 AM
<blockquote><font class="small">Quote JohnnyP:</font><hr>The latest version of WMP didn't help. I'm running OS 9.2 on an older iMac.<hr /></blockquote>
Hopefully, there's a knowledgable MAC person out there who can help.

<blockquote><font class="small">Quote JohnnyP:</font><hr>Your video showing cue stick deflection is interesting. With my thin shafted lightweight cue, using an open bridge and a light grip, I can see the stick visibly deflect (or roll off) the cueball. I thought I was seeing things. Maybe it rotates about the center of mass? When I shoot that way, the squirt is much less than when I am ham fisted.<hr /></blockquote>
I haven't studied the effect of the hand bridge on squirt. Maybe Bob Hewett has and he can share his thoughts. Although, it would make sense that a firm hand bridge close to the cue tip could change the effective end-mass of the cue stick, thereby increasing the amount of squirt.

Fred Agnir
01-27-2005, 11:00 AM
<blockquote><font class="small">Quote dr_dave:</font><hr> Although, it would make sense that a firm hand bridge close to the cue tip could change the effective end-mass of the cue stick, thereby increasing the amount of squirt. <hr /></blockquote>I think the bridge hand can only effect end-mass if the bridge was within the shaft lenghth traveled by the sideways wave during the tip/ball contact time. I believe this was measured at about 6", shorter than most, but not beyond the realm of possibility. If the skin compression time is less than a millisecond, then I think the bridge in the setup could affect end-mass.

These issues are precisely why Bob Meucci's robot gives what I consider misleading information. The grip of his robot is less compliant than a human hand (increasing contact time), and the v-block bridge is less compressive than a human hand. So, in his setup, the ball "sees" much more mass than compared to a normal human being's shot resulting in more squirt for most cues except the cues specifically designed to defeat his Myth Destroyer.

Mr. Jewett?

Fred

Rod
01-27-2005, 11:23 AM
Impact happens around that 1270 area, I can really see the cue slow down over the next 10 or so frames.

Rod

JohnnyP
01-27-2005, 12:03 PM
Dr. Dave: What do you think of my theory that a firm back hand grip increases squirt, since it limits the rotation of the stick, as it rolls off the cue ball?

dr_dave
01-27-2005, 12:17 PM
<blockquote><font class="small">Quote JohnnyP:</font><hr> Dr. Dave: What do you think of my theory that a firm back hand grip increases squirt, since it limits the rotation of the stick, as it rolls off the cue ball?<hr /></blockquote>
Honestly, I don't think it is a very accurate theory. Sorry. /ccboard/images/graemlins/frown.gif All of the cue stick action contributing to squirt appears (from high-speed video) to be a result of extremely fast sideways deflection of the cue stick at the cue tip end of the shaft (see HSV A.13 through A.20 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/index.html)). That's why the only truly important variable is the effective end-mass of the cue shaft. IMHO, the hand grip could not possibly have an effect of the cue ball during ball impact.

JohnnyP
01-27-2005, 02:33 PM
Isn't it possible that the grip changes the effective end mass?

Imagine that the cue is supported on a cushion of air, and aimed at the cue ball to impart side spin.

Now launch the cue toward the cue ball. At impact, the cue ball will deflect the tip of the cue as before, but since the "grip" is exceedingly light (the air cushion), the sideways force at the tip will rotate the cue about its center of mass, and the tip will deflect farther than if the grip is firm, possibly resulting in less squirt.

You must agree with me or I will flame you. /ccboard/images/graemlins/laugh.gif

DavidMorris
01-27-2005, 02:59 PM
<blockquote><font class="small">Quote JohnnyP:</font><hr> Isn't it possible that the grip changes the effective end mass?

Imagine that the cue is supported on a cushion of air, and aimed at the cue ball to impart side spin.

Now launch the cue toward the cue ball. At impact, the cue ball will deflect the tip of the cue as before, but since the "grip" is exceedingly light (the air cushion), the sideways force at the tip will rotate the cue about its center of mass, and the tip will deflect farther than if the grip is firm, possibly resulting in less squirt.

You must agree with me or I will flame you. /ccboard/images/graemlins/laugh.gif <hr /></blockquote>

Well, I'm not the physicist here, but in my mind the grip hand being 50+ inches away from the tip, as well as being pliable as Fred said, would do little to add any effective mass to the end of the cue. If you consider the grip a fulcrum, the leverage factor at the end of the cue as the tip is deflected to the side would have to be pretty high. So I just can't correlate in my mind a soft/firm grip with tip-end-mass.

Fred? Bob? /ccboard/images/graemlins/smile.gif

dr_dave
01-27-2005, 03:47 PM
<blockquote><font class="small">Quote JohnnyP:</font><hr> Isn't it possible that the grip changes the effective end mass?<hr /></blockquote>
Anything is possible. I just don't think it is very likely because the cue tip is in contact with the cue ball for only a very short period of time (0.001 to 0.002 seconds). Also, the end of the shaft deflects regardless of how tightly or loosely the grip is held.

<blockquote><font class="small">Quote JohnnyP:</font><hr>Imagine that the cue is supported on a cushion of air, and aimed at the cue ball to impart side spin.

Now launch the cue toward the cue ball. At impact, the cue ball will deflect the tip of the cue as before, but since the "grip" is exceedingly light (the air cushion), the sideways force at the tip will rotate the cue about its center of mass, and the tip will deflect farther than if the grip is firm, possibly resulting in less squirt.<hr /></blockquote>
The grip end of the cue stick does not move sideways very much during the short tip contact time. Now, the motion and vibration of the cue stick, well after impact, could be very different depending on how (or if) the grip end were held. But that has no effect on squirt. I know others (e.g., Bob) can shed more light on this. I honestly have not studied squirt effects that much.

<blockquote><font class="small">Quote JohnnyP:</font><hr>You must agree with me or I will flame you. /ccboard/images/graemlins/laugh.gif <hr /></blockquote>
Please don't flame me. My fire extinguisher is quite empty by now. /ccboard/images/graemlins/grin.gif

Bob_Jewett
01-28-2005, 12:38 PM
<blockquote><font class="small">Quote JohnnyP:</font><hr> Isn't it possible that the grip changes the effective end mass?
... <hr /></blockquote>
Very unlikely. Squirt is caused by side-to-side motion of the cue stick. That kind of motion is transmitted very slowly down the length of the stick. This is why only the first six inches or so of the shaft contribute to effective end mass. During the tip-to-ball contact time the side-to-side vibration in the stick (like a violin string) only gets that far.

And, as pointed out before, the hand is very, very soft compared to the tip and stick, so it cannot usefully participate in the action during contact. It can get the stick up to speed, but what happens while the tip is on the ball is essentially unaffected by the hand.

Leviathan
01-28-2005, 12:52 PM
Bob: Any ideas about effects of tight (closed) and loose (vee) bridges on tip deflection? Thanks--AS

Bob_Jewett
01-28-2005, 01:04 PM
<blockquote><font class="small">Quote Leviathan:</font><hr> Bob: Any ideas about effects of tight (closed) and loose (vee) bridges on tip deflection? Thanks--AS <hr /></blockquote>
I think there has been no direct test, but if the bridge is eight inches long, it is very unlikely to have an effect. Also, it's important to remember that even with a closed bridge, the stick is against very, very soft material -- the flesh of your fingers. If you wanted to try to observe more squirt -- deflection, while commonly used by some, is the wrong name -- you could get a heavy bridge head and hold it in your hand and use a very short bridge.

dingle
01-28-2005, 03:29 PM
Dr. Dave,

In looking at your stroke on these videos, I'd say overall you have a poor stroke. You're using quite a stiff wrist. Not only should your grip be relaxed, your wrist should be relaxed as well. Also, your stance is terrible (NV2-5) and your practice strokes are way too fast and you don't seem to be pinpointing the target on the cue ball.

I'd be interested in your pool PLAYING accomplishments and experience?

Anyone else agree?

-Dingle

Leviathan
01-28-2005, 05:24 PM
Bob: I think you may have misinterpreted my question. I didn't ask about effects of bridge type on squirt; I asked about effects of bridge type on tip deflection. By tip deflection I mean deflection of the tip from the line of stroke as a result of the tip's contact with the cb. I wondered whether it has been shown that type of bridge (closed or vee) has no significant effect on the distance or timing of tip deflection. Thanks--AS

Bob_Jewett
01-28-2005, 07:52 PM
<blockquote><font class="small">Quote Leviathan:</font><hr> ... I wondered whether it has been shown that type of bridge (closed or vee) has no significant effect on the distance or timing of tip deflection. Thanks--AS
<hr /></blockquote>
But the current theory says that squirt is equal and opposite to the mass that of the cue that is pushed in the other direction.

Is there any practical reason to consider the speed with which the tip is pushed to the side separately from the squirt it causes?

Leviathan
01-29-2005, 06:38 AM
Not that I know of, Bob. But JohnnyP says that he's observed decreased squirt with a vee bridge, and Fred says he thinks that Meucci's apparatus gives false results partly because it has a loose bridge. Evidently, then, some people see or suspect a connection between bridge type and squirt. I'm not suggesting that the tip-end mass explanation is wrong; I'm only asking whether anyone has shown by experiment that bridge type has no effects, or only minute effects, on deflection of the tip. If this were shown it would tend to support the tip-end mass explanation--and that would be okay with me. AS

Fred Agnir
01-29-2005, 03:50 PM
<blockquote><font class="small">Quote Leviathan:</font><hr> Not that I know of, Bob. But JohnnyP says that he's observed decreased squirt with a vee bridge, and Fred says he thinks that Meucci's apparatus gives false results partly because it has a loose bridge.
<hr /></blockquote>Sorry if I mislead you. I think Meucci's apparatus is faulty because of the rigid material for the grip and the v-block. I don't think there is any bridge "looseness" in his Myth Destroyer.

Fred

Leviathan
01-30-2005, 05:22 AM
Sorry, Fred. I see that I had your post all wrong--very careless of me. AS

dr_dave
02-23-2005, 05:03 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> <blockquote><font class="small">Quote Fred Agnir:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> Also, IMHO, a firm grip can help increase the effective mass of the cue stick. This can change the dynamics of certain shots (e.g., a masse shot). <hr /></blockquote>That would be interesting if you could prove this. I've been going under the premise that no matter how firm a human could grip, it makes little to no difference as far as the collision was concerned since the skin is so much more compliant than the tip itself.

Increasing the effective stick mass would definitely change the dynamics if the grip hand was rigid and non-compliant.<hr /></blockquote>
We can discuss this more after I post my large collection of most recently filmed videos. I also want to spend more time thinking about the physics and watching the new videos. I'm not saying you are wrong yet (and maybe I won't).<hr /></blockquote>
Fred,

I finally found time to post all of my new clips. See my recently posted thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&amp;Board=ccb&amp;Number=181518&amp;page =0&amp;view=collapsed&amp;sb=5&amp;o=&amp;fpart=1). With a light grip, the cue stick does tend to loose more speed during impact (because there is less effective mass). HSV A.52 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-52.htm) vs. HSV A.48 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-48.htm) shows a good example. With the firm grip, an imperceptible [in real time] (and arguably illegal???) multiple hit occurs and the amount of follow is reduced slightly by the secondary collisions. With a firm grip, the effective mass of the cue stick is larger and the cue stick maintains more speed after impact. I also found that a firm grip allowed me to achieve better masse action (e.g., with HSV A.60 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-60.htm)).

Enjoy,
Dave

Bob_Jewett
02-23-2005, 05:24 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> ...I finally found time to post all of my new clips. ... <hr /></blockquote>
A brief heads-up. The format used in your recent videos is different from the format you used in your earlier clips, and it is viewable on fewer systems. If you turned on some kind of special features that are not really necessary, it might help to turn them off. It is unfortunate that people keep screwing with the video clip "standards."

Bob_Jewett
02-23-2005, 05:29 PM
<blockquote><font class="small">Quote dr_dave:</font><hr> ... With a light grip, the cue stick does tend to loose more speed during impact (because there is less effective mass). ... <hr /></blockquote>
Is it possible to make a plot of the velocity of the stick versus time for the two cases? This will require a time resolution of about 0.2 milliseconds for good results and a corresponding stick position resolution.

wolfdancer
02-23-2005, 05:47 PM
Bob, without getting into a loose Vs firm grip debate...and I seem to remember from Byrne's that it makes no difference???
what do you prefer for a long, or "hard" draw shot?
I've seen both recommended
AND.. I seem to get better draw using an open bridge...but can't figure out why????
AND....(not being an engineer myself, not even sure I'm spelling it right) I'm confused on how a firm grip adds to the effective mass????....but if E = MC(2) ??? the mass increase wouldn't add that much to the force???
AND....does it change the effective mass if you grip nearer the butt end as opposed to gripping near...or ahead of the balance point???
Thanks if you can bother to answer any of these,jjd

Bob_Jewett
02-23-2005, 06:25 PM
<blockquote><font class="small">Quote wolfdancer:</font><hr>... what do you prefer for a long, or "hard" draw shot?

AND....(not being an engineer myself, not even sure I'm spelling it right) I'm confused on how a firm grip adds to the effective mass????... <hr /></blockquote>
I try not to think about the grip. I prefer a wrap (or lack of wrap) that permits a relatively loose grip without slipping.

As for the effective mass, imagine a grip like a huge pair of vise-grips that is as solid as the stick itself. In such a case, the effective mass of the stick would include the mass of the vise-grips.

The problem with trying to translate this to a human grip is that the flesh of the hand is very much softer than steel or wood. Even what we think of as a tight grip is pitifully weak and springy compared to normal solid mechanical connections.

When the tip hits the ball, the stick slows down and the hand continues forward. The grip sort of "winds up" and puts additional force on the stick and if the ball has not left the tip yet, that force will be partly transmitted to the ball. The question becomes how much force the hand adds during the tip-ball contact time. In theory, this can be answered by making a static measurement of force versus stick displacement in the hand:

Hold the stick with the grip tightness you want to test with your wrist firmly clamped in place. Have someone pull on the stick with 10 pounds of force. See how far the stick moves relative to your wrist or hand. That gives the effective spring constant for that tightness of grip. With a little calculation, you can find how much force there will be between your hand and the stick during the tip-ball contact. That contact takes place over only about 1-3mm, depending on the speed of the shot. That force has to be compared to the tip-ball force during contact for the same speed of shot.

For example, if the peak tip-ball force were 50 pounds, the distance of contact 1mm, and the spring constant of the tightest grip 5mm for ten pounds of force, my conclusion would be that grip has negligible effect on the shot.

Of course in a precise analysis, you need to worry about dynamic effects and the fact that I might have used PI=3 in the above discussion, and the fact that the tip-ball contact is governed by Hertz' law and not Hooke's.

dr_dave
02-24-2005, 09:13 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr>A brief heads-up. The format used in your recent videos is different from the format you used in your earlier clips, and it is viewable on fewer systems. If you turned on some kind of special features that are not really necessary, it might help to turn them off. It is unfortunate that people keep screwing with the video clip "standards."<hr /></blockquote>
Sorry about that. I am using a newer version of Pinnacle Studio (the digital video editing software), but I am using all of the most basic settings. I hope this is not an issue for a large number of people. The clips have worked on every computer I have tested.

dr_dave
02-24-2005, 09:25 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr> <blockquote><font class="small">Quote dr_dave:</font><hr> ... With a light grip, the cue stick does tend to loose more speed during impact (because there is less effective mass). ... <hr /></blockquote>
Is it possible to make a plot of the velocity of the stick versus time for the two cases? This will require a time resolution of about 0.2 milliseconds for good results and a corresponding stick position resolution. <hr /></blockquote>
Most of the clips were shots at 3000 FPS (time resolution = 0.33 milliseconds). I have not created plots; but if you feel like counting pixels, the data is there.

HSV A.52 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-52.htm) vs. HSV A.48 (http://www.engr.colostate.edu/~dga/pool/high_speed_videos/new/HSVA-48.htm) shows a good qualitative example. With the firm grip, an imperceptible [in real time] (and arguably illegal???) multiple hit occurs. With a firm grip, the cue stick seems to maintain (or regain) more speed after impact. Maybe I will try to make some plots from the videos one day. Thanks for the suggestion.

Dave

wolfdancer
02-24-2005, 11:04 AM
Bob, thanks for the detailed input. In layman's ( that's me ) terms....seems like it doesn't add or subtract too much to the equation, using either grip.
I had to look up both Hert's Law, and Hooke's law.
Turns out that Fred Hertz is an Atty in Oakland, practicing family law...Hooke it seems does not.
But reading further, I did find the laws you used for an analysis.
Just a couple of final Q's :
is the effective mass constant for different grip locations?
and does the loose grip itself become a "slip grip", or was that a horse of another color? Never did see anyone use this, but urban legend has it that all the old-timers....of which I am now a member....employed that as part of their shtick????