More elbow dropping nonsense

[dr_dave]

http://billiards.colostate.edu/high_speed_videos/new/HSVB-40.htm
(turn on the sound if you have it off)

Bob Jewett and Dr Dave did have equipment hooked up to both of them shooting a pendulum stroke and someone else shooting with both elbow drop and wrist action.

Reviewing the video and pausing over and over it appears that both Dr Dave and Bob Jewett are at perpendicular or just before perpendicular in the "Set" position. Looking at the graphs it is very easy to see that they are no longer accelerating the stick as they hit the cue ball and there is some indication that speed is actually decreasing right before contact if you look at the graphs closely on these two shots. The audio acknowledges that they aren't accelerating into the cue ball too.

A key feature of a pendulum stroke is no acceleration (i.e., the cue has reached maximum speed and is coasting) at CB impact. This makes the shot speed less sensitive to stroke timing. That is one important point of the video. If the elbow drops after CB contact (e.g., with a "J" stroke), the motion into the ball can still be the same as with a complete pendulum stroke, so many elbow-drop strokes might have a similar plot into the ball.

Dr Dave could probably provide some insight as to what happened on other shots as they surely shot mapped more than these few.

We didn't analyze very many shots, because it took a lot of time. However, all of the results looked similar to the ones included in the video.

One thing worth noting perhaps: when we accelerate into the cue ball the effective mass of the cue stick seems to be greater. Note the lesser deceleration of the cue stick when Dave G hits the cue ball.

Not true. With all three shots, the cue speed decreases by about 40% when it hits the CB. The grip can do nothing significant to the cue during the 0.001 second of cue tip contact. The speed of the cue (and not the acceleration) is all that really matters at impact.

Regards,
Dave

 

[JoeW]

FYI, I had done a physics-based study a while back. Here's a quote from my results:

With typical pendulum (p) strokes, the speed is more constant (i.e., leveled-off) at CB impact, possibly making it easier to control shot speed, because the speed is less sensitive to variations in bridge and stroke length.

With typical "accelerate into the ball" (a) strokes, the force increases and levels off during the stroke, and force is being applied all of the way up to (and through?) ball impact. Is this conclusion based on an analysis of data or on a theoretical analysis?

With a classic pendulum stroke, it is natural to coast into the ball with no force at impact. (other than that which is derived by momemtum?)

The peak force is typically lower with an "accelerate into the ball" stroke than with a pendulum stroke (for the same shot speed) because force is applied over a larger distance (for the P stroke?). Is this conclusion based on data or theory?I can conceptualize adding power to the natural momentum of the P stroke and a J stroke would seem to have more force -- would it not?

Therefore, for some people, this type of stroke (P stroke?) might seem to require less effort for a given speed, and higher speeds might be possible (how is this possible for a fixed pure P stroke?).

A typical "accelerate into the ball" stroke usually involves more of a "piston-like" stroke, with shoulder motion and elbow drop, allowing some people to generate force more easily throughout the stroke. One disadvantage of a piston stroke is that tip-contact-point accuracy might be more difficult to control.​

For more info, see:

http://billiards.colostate.edu/threads/stroke.html#acceleration​

Regards,
Dave

This reads like a theoretical analysis.

Seems to me that if a pure "P" stroke is used there is only one speed (assuming the cue is always drawn back to the same point). Momentum is the source of the power obtained in a P stroke, is it not? The J stroke adds power to the momentum derived -- does it not? and therefore allows for more power during and through the stroke. Perhaps your data lead to different conclusions?

 

[JoeW]

The cue tip acceleration study does not state which type of stroke was used but it does state, "This (change in curve) corresponds to a big increase in forward speed in the final stroke." How is this acceleration in momentum obtained?

1. Inthe preliminary strokes he was using a truncated pendulum that was not completed and was checked prior to contact?

2. He was using an additional source of power to obtain this acceleration? the J stroke?

 

[Celtic]

Celt-man,
Damnit, you made me post again in this stupid thread.

Muahahaha! 1 point 4 me!

 

[Neil]

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[Neil]

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[ShootingArts]

Thanks

Dave,

Thanks for taking time to answer my questions clearly, that is a big help.

A key feature of a pendulum stroke is no acceleration (i.e., the cue has reached maximum speed and is coasting) at CB impact. This makes the shot speed less sensitive to stroke timing. That is one important point of the video. If the elbow drops after CB contact (e.g., with a "J" stroke), the motion into the ball can still be the same as with a complete pendulum stroke, so many elbow-drop strokes might have a similar plot into the ball.

There is a very fine line between coasting and deceleration. I don't know if there is actually a line or only a point. However this clarifies some things and points out one place we are in conflict. Based on my reading over the years and of course my own individual experience I feel we have more control and our stroke is more accurate when the muscles are lightly loaded. I most particularly try to dodge the key part of the action being at a transition. Your findings or beliefs are just the opposite, that it is best to hit the cue ball with the muscles unloaded, or so I understand. A basic conflict in our goals here and I think we can both support our beliefs with a little digging.

I'm also not in agreement that coasting significantly increases speed control. Generally we shorten the stroke and accelerate into the cue ball for a soft shot. I have absolutely lousy speed control if I try to maintain the same speed over a long stroke. Any way we go about it we are still accelerating to a certain speed. Our pause at a set position at the cue ball somewhere in our preshot routine has told our unconscious exactly where we want to be at the right speed. I think that any controlled stroke is equally able to deliver the tip at that speed at the cue ball. Here again I'm not trying to declare one of us right and the other wrong, pointing out basic differences in our beliefs as to what we are trying to achieve in a stroke. I am seeking acceleration into the cue ball.

We didn't analyze very many shots, because it took a lot of time. However, all of the results looked similar to the ones included in the video.

Thanks a bunch, that was a key question, how similar other shots were. I do understand what you are saying about the time taken and being unable to work with many shots. I'd like to set up equipment somewhere like the DCC and then spend weeks or months closely studying the data gathered. I think a careful look at Dave G's stroke and the graph might reveal where shoulder, elbow, and wrist each came into play as one example. It would be great to have data from a wide variety of strokes. Nice to daydream anyway!


Not true. With all three shots, the cue speed decreases by about 40% when it hits the CB. The grip can do nothing significant to the cue during the 0.001 second of cue tip contact. The speed of the cue (and not the acceleration) is all that really matters at impact.

I was looking at the time over which it decreased. I seem to remember that Dave G's stick speed decreased more gradually while in contact or after contact with the cue ball when I had studied this or similar video awhile back. Looking now it is debatable if there is anything significant between the deceleration time of his shot and yours. Of course I am guessing that speed and distance can be translated into time to begin with. Is there more video of Dave G's stroke with it graphed or was I just working from faulty memory?


Regards,
Dave

Dave,

Thanks again. Civil discussion allows us to dig deeply enough to increase understanding. Some goals you and I are seeking from a stroke are different even though we are ultimately trying to achieve the same result. It may be partially the terminology used but I'm not happy with the idea of the stick coasting into the cue ball while that is what you are trying to achieve if I understand correctly. Easy to see that you and I wouldn't be equally satisfied if we used exactly the same stroke due to different expectations.

If I had your test equipment I would have been trying to develop a different graph curve for my stroke than seen with you and Bob J's. All I really need is way to measure acceleration so maybe I will get around to testing to get hard numbers someday. Of course there are dozens of other things I want to do someday too so it may never happen.

Hu

 

[JoeW]

I'm seeing a difference here between a robot doing the stroke, and me doing the stroke. The robot just drops, that gives one set of data. I only just drop on a very soft shot. The rest of the time, my bicep is what is moving my cue. I can contract it plenty fast enough to obtain what speed I need. And, I feel (think) that my cue is accelerating until contact, when it will of course slow down, just as any other stroke will upon contact.

I am not trying to get picky here, I am trying to pursue the discussion to its conclusion.

In the pendulum swing the elbow is fixed and becomes a hinge for the stroke. I think that this will remove the bicep from the stroke. Try it sitting at your desk and I think you will find that if the elbow is fixed you have to use the forearm for additional power.

None-the-less, if one is using the forearm and the bicep for anything other than pulling the stick back in a pendulum swing then the player is using muscle to power the stroke.

In all of the sports that come to mind when using muscle to power a stroke, shot, etc. The usual recommendation is to follow through past and substantially beyond the point of contact. I am thinking here about baseball, tennis, golf, etc. The follow through is on the same line as the trajectory of the ball. In pool the pendulum theory stops the use of the bicep and the natural follow through when the arc of the pendulum is reached. This seems contrary to most other sports.

If I sit at my desk with the arm hanging down, as in a pendulum swing, I cannot use my bicep to thrust the arm without moving the elbow.

 

[JoeW]

Neil I have an experiment for you and anyone else who might be interested. It is somewhat subjective but could be used in a study of players with a sufficient number of players.

Place an OB three diamonds off the corner pocket. Place the cue ball at the other end of the table so the shot is reasonably lined up to the pocket.

The idea is to shoot the OB into the pocket with just enough force to pocket the OB. This is a soft shot.

Play the shot three times using a pendulum stroke that does not allow the elbow to drop.
Notice how many times you split the pocket.

Now play the shot allowing (not forcing) your elbow to drop as you direct the cue ball and the cue stick down the line of aim.

Go back and repeat this six shot sequence a few times. I just did it at my table. I need to preface my comments by stating that I have thought of myself as basically a pendulum player for a few years. I don’t know what I used before that.

What I found is that I am more likely to split the pocket with something like a J stroke. More importantly, I felt like I was in better control of the shot making and that I had better control of the cue ball.

This is of course a subjective feeling but it interesting to note that I had thought of myself as a pendulum player until this whole discussion. Now I find that the more I use a J stroke the more I like it and that I am more likely to split the pocket with this type of stroke.

For those who don’t know what it means to split the pocket this means that the ball goes directly to the back of the pocket without touching any cushion before it drops.

I am coming around to the idea that the J stroke actually feels more like natural than the pendulum stroke which may be easier to teach.

 

[Neil]

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[Neil]

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[JoeyA]

The J Stroke

Neil I have an experiment for you and anyone else who might be interested. It is somewhat subjective but could be used in a study of players with a sufficient number of players.

Place an OB three diamonds off the corner pocket. Place the cue ball at the other end of the table so the shot is reasonably lined up to the pocket.

The idea is to shoot the OB into the pocket with just enough force to pocket the OB. This is a soft shot.

Play the shot three times using a pendulum stroke that does not allow the elbow to drop.
Notice how many times you split the pocket.

Now play the shot allowing (not forcing) your elbow to drop as you direct the cue ball and the cue stick down the line of aim.

Go back and repeat this six shot sequence a few times. I just did it at my table. I need to preface my comments by stating that I have thought of myself as basically a pendulum player for a few years. I don’t know what I used before that.

What I found is that I am more likely to split the pocket with something like a J stroke. More importantly, I felt like I was in better control of the shot making and that I had better control of the cue ball.

This is of course a subjective feeling but it interesting to note that I had thought of myself as a pendulum player until this whole discussion. Now I find that the more I use a J stroke the more I like it and that I am more likely to split the pocket with this type of stroke.

For those who don’t know what it means to split the pocket this means that the ball goes directly to the back of the pocket without touching any cushion before it drops.

I am coming around to the idea that the J stroke actually feels more like natural than the pendulum stroke which may be easier to teach.

Joe is this the shot you are talking about?

CueTable Help

If not, modify it or tell me where you want the cue ball so all of us are shooting the same shot. I'm game.

Just so I am not mistaken, please confirm the following: The J stroke is nothing more than a pendulum stroke which also includes an elbow drop after cue ball contact is made. The reason why I ask you to confirm this, is I have seen Johnny Archer and Earl Strickland both use an extreme follow through and twist their wrists clockwise, so that the bottom of their fingers are facing the sky when finished stroking.

Also I don't want to refer to the "pendulum" stroke as the P stroke because we also have a "piston" stroke.

JoeyA

 

[pooltchr]

All this talk about being able to generate more power with this stroke or that stroke has me wondering. Just how much power do you need to make a pool shot? The table is only 9 feet long.
I've been playing this game for almost 50 years, and can't recall very many times over those years where I couldn't generate enough power to make the shot.
I tend to be one of those who is more inclined to consider accuracy over power (speed) of stroke.
What percentage of shots require the shooter to put that much energy into moving the cue ball?

Steve

 

[JoeyA]

All this talk about being able to generate more power with this stroke or that stroke has me wondering. Just how much power do you need to make a pool shot? The table is only 9 feet long.
I've been playing this game for almost 50 years, and can't recall very many times over those years where I couldn't generate enough power to make the shot.
I tend to be one of those who is more inclined to consider accuracy over power (speed) of stroke.
What percentage of shots require the shooter to put that much energy into moving the cue ball?

Steve

Steve,
As JoeW discusses, perhaps there are multiple benefits to the elbow drop and maybe increased accuracy is one of them. Hope you and some of the other instructors participate in this "test" as well as some of the posters discussing and reading this thread. It isn't a long, difficult test and should be able to be accomplished in just a few short minutes.

Joe really has my curiosity up with this but I promise to put my best effort on both styles of stroking.

I think I may shoot the series of shots going first with the pendulum shot then the elbow drop and then reversing the sequence, just so that I don't get "dialed in" on the shot while shooting the shot one particular way.

I'll wait until JoeW confirms that the cuetable diagram is what he had in mind.


JoeyA

 

[Neil]

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[JoeW]

Joe is this the shot you are talking about?

CueTable Help

If not, modify it or tell me where you want the cue ball so all of us are shooting the same shot. I'm game.

Just so I am not mistaken, please confirm the following: The J stroke is nothing more than a pendulum stroke which also includes an elbow drop after cue ball contact is made. The reason why I ask you to confirm this, is I have seen Johnny Archer and Earl Strickland both use an extreme follow through and twist their wrists clockwise, so that the bottom of their fingers are facing the sky when finished stroking.

Also I don't want to refer to the "pendulum" stroke as the P stroke because we also have a "piston" stroke.

JoeyA

Sorry, we have been having dinner and playing pool with friends.

This is th shot I referred to except that I have the cB closer to the foot rail. Incidently my friend and I played an 8-ball race to seven and he usually wins by two - three games. Tonight he had me 6 - 2 and I cam back and won using only my new J stroke. One 8 on the break helped !

The type of stroke I am using is a natural elbow fall with added power from the bicep that is needed to keep the stick on line. I do not twist the wrist as I don't think that it is needed. There is a bend inthe wrist like you see on pros during the break shot as can be seen in this series of stills.

http://www.sunburstselect.com/PBReview/ShootLikePros.htm

Have to run as friends are still here but friends on AZB are also important :grin:

Sorry to hear it did not work for Neil. Lets see what others find.

 

[KMRUNOUT]

I'm seeing a difference here between a robot doing the stroke, and me doing the stroke. The robot just drops, that gives one set of data. I only just drop on a very soft shot. The rest of the time, my bicep is what is moving my cue. I can contract it plenty fast enough to obtain what speed I need. And, I feel (think) that my cue is accelerating until contact, when it will of course slow down, just as any other stroke will upon contact.

Well said.

 

[KMRUNOUT]

i am not trying to get picky here, i am trying to pursue the discussion to its conclusion.

In the pendulum swing the elbow is fixed and becomes a hinge for the stroke. I think that this will remove the bicep from the stroke. Try it sitting at your desk and i think you will find that if the elbow is fixed you have to use the forearm for additional power. i don't think so. Given the forces required on the vast majority of pool shots (*possibly* excluding the most powerful breaks) the bicep provides all the power you would need. In fact, if we are looking at a pure pendulum stroke, it is hard to picture how anything *but* the bicep would produce the power. It would appear that you either let the forearm and cue fall forward, which would produce peak speak at cueball impact, and not too much power, or else contract the bicep as forcefully as required. This may or may not result in peak speed at impact, but certainly could. I would say the bicep is really the only muscle used in a pure pendulum stroke (not including forearm muscles, which while possible to use are not necessary to use.

none-the-less, if one is using the forearm and the bicep for anything other than pulling the stick back in a pendulum swing then the player is using muscle to power the stroke.

In all of the sports that come to mind when using muscle to power a stroke, shot, etc. The usual recommendation is to follow through past and substantially beyond the point of contact. I am thinking here about baseball, tennis, golf, etc. The follow through is on the same line as the trajectory of the ball. In pool the pendulum theory stops the use of the bicep and the natural follow through when the arc of the pendulum is reached. This seems contrary to most other sports. don't forget that a cue stick weighs less than a bat, and the forces used in a tennis swing or a golf swing are way more than in any pool shot. The reason that a tennis player swings the racket 3 feet through the ball is because the racket is probably travelling, i don't know, 60 mph or more?i'm pretty sure golf clubs are going well over 100 mph on a drive, probably more. A cuestick is travelling maybe 5 mph on a fairly firm stroke. Given these large differences of scale, it could be argued that a 4" follow through *is* following substantially past the point of contact, relatively speaking.

if i sit at my desk with the arm hanging down, as in a pendulum swing, i cannot use my bicep to thrust the arm without moving the elbow. this just means that you are not effectively isolating your bicep. I am able to sit at my desk with the upper arm parallel to the floor, and forcefully punch myself in the chest without moving my elbow at all. I don't think this is any different than a pool stroke.

fwiw

kmrunout

 

[KMRUNOUT]

Neil I have an experiment for you and anyone else who might be interested. It is somewhat subjective but could be used in a study of players with a sufficient number of players.

Place an OB three diamonds off the corner pocket. Place the cue ball at the other end of the table so the shot is reasonably lined up to the pocket.

The idea is to shoot the OB into the pocket with just enough force to pocket the OB. This is a soft shot.

Play the shot three times using a pendulum stroke that does not allow the elbow to drop.
Notice how many times you split the pocket.

Now play the shot allowing (not forcing) your elbow to drop as you direct the cue ball and the cue stick down the line of aim.

Go back and repeat this six shot sequence a few times. I just did it at my table. I need to preface my comments by stating that I have thought of myself as basically a pendulum player for a few years. I don’t know what I used before that.

What I found is that I am more likely to split the pocket with something like a J stroke. More importantly, I felt like I was in better control of the shot making and that I had better control of the cue ball.

This is of course a subjective feeling but it interesting to note that I had thought of myself as a pendulum player until this whole discussion. Now I find that the more I use a J stroke the more I like it and that I am more likely to split the pocket with this type of stroke.

For those who don’t know what it means to split the pocket this means that the ball goes directly to the back of the pocket without touching any cushion before it drops.

I am coming around to the idea that the J stroke actually feels more like natural than the pendulum stroke which may be easier to teach.

I think all that you say about how you felt is very worthwhile, and represents the specific value of one stroke or the other for you. I personally drop my elbow, and prefer many things about that type of stroke, primarily the feel. However, I do not think there is a difference in accuracy between either stroke. If anything, I might be more likely to favor the pinned elbow stroke for pure accuracy. Of course, shotmaking isn't all there is to it, hence my preference for the elbow drop stroke.

KMRUNOUT

 

[KMRUNOUT]

..........

I think Neil made some excellent points here. In particular, I meant to say in my last post that if you are experiencing a difference in accuracy *only* between the two strokes, chances are you have other alignment problems.

KMRUNOUT