Does your BACKHAND GRIP affect the action of the CB?

[jsp]

Does it matter how firmly or loosely you grip the cue? If it does, how exactly does it affect the shot? I've been pondering this for a while. There are lots of mixed information regarding this subject out there, either from my own experience or from posts/papers that I've read.

My own experience says that a lighter and looser grip causes me to draw the CB further back. This implies the lighter you grip the cue, the more bottom spin can be achieved. Dr. Dave even has high speed videos of draw shots with varying grips (HSVA.35 - HSVA.59), and his data shows that he can draw the CB back further with a lighter grip (all other things being equal).

So my common sense says that if you can get more bottom spin with a lighter grip, why can't you also achieve more sidespin with a lighter grip? I've read a few posts on this forum that Efren and some of the other Filipino players attribute the great amount of spin they put on the CB to their ultra-loose grips. However, I've also read on this forum and in Shepard's technical papers that your grip should NOT affect the amount of squirt on the CB. But aren't sidespin and squirt related? If your grip doesn't affect the amount of squirt, then it shouldn't affect the amount of sidespin, no?

Okay, forget about spin...what about forward velocity of the CB. To me, it makes sense that the harder you grip the cue, the more effective mass you attach on the cue, and thus you would have a greater resulting forward CB velocity for the same cue/arm speed at contact. However, Ron Shepard's papers describe a "loose skin" approximation that basically drops the mass of your arm/hand entirely out of the equation. His explanation is that the contact time between CB and cue is too short, that "the soft skin and flesh in the hand do not have time to tighten sufficiently in order to apply any additional forces to the stick that may be transmitted to the ball." My opinion is that he uses this approximation as a way to greatly simplify his derivations and calculations, and that it isn't a very accurate approximation. In Point #8 of Bustamante's breaking article, Django even says, "You have to hold [the butt of the cue] tight - very tight."

Again, lots of conflicting information out there. My opinion is that your grip on the butt of the cue affects everything. What is your take?

 

[Andrew Manning]

My take on it is this: a loose grip helps you achieve higher cue speed without a lot of extraneous muscle effort.

Higher cue speed increases forward velocity, spin (on any axis), and squirt. I don't know if there's a strict correlation between side spin and squirt, but I believe an increase in cue speed will increase all the things you mentioned. And I believe the best way to increase cue speed in a controlled manner is with a relaxed grip, efficient stroking motion, and smooth acceleration.

-Andrew

 

[Cornerman]

My take on it is this: a loose grip helps you achieve higher cue speed without a lot of extraneous muscle effort.

Me too.

This is one of the examples when I try to discuss a need for a study of biomechanics. There are definitely times when "moving less parts" is absolutely harder than moving more parts for the average person.

It's simply easier for most people to get to that high speed with the loose grip.

Fred

 

[jsp]

I understand the points Andrew and Fred are trying to make...that a looser grip will help you accelerate your cue with less effort. I agree with what you two are saying.

However, I'm not really asking how your grip affects your stroke. I'm asking how the grip affects CB action, given the same cue/arm speed, tip offset, etc. The only factor that changes is how loosely or tightly you grip the cue...everything else remains constant. I guess I should have mentioned that in my initial post.

 

[Island Drive]

I understand the points Andrew and Fred are trying to make...that a looser grip will help you accelerate your cue with less effort. I agree with what you two are saying.

However, I'm not really asking how your grip affects your stroke. I'm asking how the grip affects CB action, given the same cue/arm speed, tip offset, etc. The only factor that changes is how loosely or tightly you grip the cue...everything else remains constant. I guess I should have mentioned that in my initial post.

Which type of grip are you talking about?

 

[Andrew Manning]

I understand the points Andrew and Fred are trying to make...that a looser grip will help you accelerate your cue with less effort. I agree with what you two are saying.

However, I'm not really asking how your grip affects your stroke. I'm asking how the grip affects CB action, given the same cue/arm speed, tip offset, etc. The only factor that changes is how loosely or tightly you grip the cue...everything else remains constant. I guess I should have mentioned that in my initial post.

If you put in that "given the same cue/arm speed" caveat, then I change my vote to "grip has negligible affect on speed, spin, or squirt". If you can manage to stroke the cue the same with a tight grip and a loose grip, I think any affect grip has on the outcome will be negligible.

-Andrew

 

[Tennesseejoe]

I would guess that grip has little to do with cue ball action---but a guess is just that---absolutely nothing. I always thought that accelerating through the cue ball created more spin and contact time but that was before the Jacksonville experiement. I am still not sold on the idea that a little flick of the wrist doesn't significantly increase spin without a major increase in speed. I think there are some unknowns here.

I have appreciated the studies and comments from the technical members of this forum and look forward to their comments.

 

[CaptainHook]

I tried and failed at using the Loose grip back in the late 80's. I started missing ball's like crazy. I went back to my 3 finger & thumb grip.

 

[Cornerman]

I understand the points Andrew and Fred are trying to make...that a looser grip will help you accelerate your cue with less effort. I agree with what you two are saying.

However, I'm not really asking how your grip affects your stroke. I'm asking how the grip affects CB action, given the same cue/arm speed, tip offset, etc. The only factor that changes is how loosely or tightly you grip the cue...everything else remains constant. I guess I should have mentioned that in my initial post.

I wanted to hijack the thread, but apparently you won't let me.

If the tip is moving the same speed and hits the same spot, then, IMO, the grip changes nothing provided that you don't have a steel hand.

OTOH, if you do have a steel hand, then I believe the tight grip can potentially increase the contact time significantly, which could possibly increase squirt.

Fred

 

[Da Poet]

Closed vs Open Bridge a factor?

I play with an open bridge and I recently discovered that when I was going for a hard draw, requiring a tighter grip, I was also tensing up on my bridge hand keeping the cue a little more elevated on contact than I thought. I conciously made the effort to relax my bridge hand during firmer shots and the ball started drawing nicely again.

Conciously relaxing the bridge hand and conciously tightening the grip was a little like rubbing your stomach and patting your head to me. Just try making a fist over and over a few times while keeping your other hand face down on the table in front of you totally relaxed, and maybe you'll know what I'm talking about.

I suspect having a closed bridge might avoid this issue, but it's only a theory. Any thoughts from any experts? 'cause I sure ain't one!


Edit : Sorry, didn't catch an earlier post specifically asking what effect grip had without other considerations. My bad. I would say backhand grip strength has no effect on the activity of the tip on contact when it comes to spin. I personally think the poll may be reflecting opinions based on overall execution of a shot, rather than the physical effect question.

 

[Da Poet]

On second thought...

Okay, maybe I'm jumping the gun here a little, but after re-reading all the posts, I don't think you can discount the direct effect of having a tighter backhand grip without considering the indirect effect on the bridge hand. A tighter back hand grip usually means a tighter bridge hand whether open or closed. I think it's quite possible that a tighter, firmer bridge hand may deaden the effect of the shaft near impact, especially when trying to draw the ball. I think, when it comes to grip strength and spin, we may be focusing on the wrong end of the cue.

If I'm wrong shoot me.

 

[Jal]

...My own experience says that a lighter and looser grip causes me to draw the CB further back. This implies the lighter you grip the cue, the more bottom spin can be achieved.

General speaking, I've found this to be true as well. However, I use an open bridge and with a tighter grip I tend to lift the shaft up off of my bridge and thus get less draw (or maybe I'm doing what Da Poet is describing above?) When I've taken some care to hit really low despite the tight grip, I haven't found any significant difference in the maximum distance the cueball draws back. Very anecdotal, but there it is.

...However, I've also read on this forum and in Shepard's technical papers that your grip should NOT affect the amount of squirt on the CB. But aren't sidespin and squirt related? If your grip doesn't affect the amount of squirt, then it shouldn't affect the amount of sidespin, no?

Let's say, as you conjecture below, that a tight grip adds effective mass to your cue by bringing your arm into the picture. This will, as you say, increase the speed of the cueball. It will also increase its spin, proportionally, so its spin/speed ratio should remain the same.

What does this mean for squirt? I don't know exactly because I'm not up on Ron's equations at the moment. But it suggests to me that you won't see any change in it.

More obvious is that the magnitude of the cue's endmass won't be affected by your grip.

Okay, forget about spin...what about forward velocity of the CB. To me, it makes sense that the harder you grip the cue, the more effective mass you attach on the cue, and thus you would have a greater resulting forward CB velocity for the same cue/arm speed at contact. However, Ron Shepard's papers describe a "loose skin" approximation that basically drops the mass of your arm/hand entirely out of the equation. His explanation is that the contact time between CB and cue is too short, that "the soft skin and flesh in the hand do not have time to tighten sufficiently in order to apply any additional forces to the stick that may be transmitted to the ball." My opinion is that he uses this approximation as a way to greatly simplify his derivations and calculations, and that it isn't a very accurate approximation. In Point #8 of Bustamante's breaking article, Django even says, "You have to hold [the butt of the cue] tight - very tight."

You might want to have a look at the last page (9) of this document:

http://www.sfbilliards.com/jax_bd150.pdf

Note that he leaves open the possibility that a very tight grip might alter things.

Jim

 

[Jal]

Although Bob Jewett's article shows that the hand/arm mass is negligibe when normal grip pressure is used, there still is some question (in my mind anyway) as to whether a very tight grip might change this. I think the following gives a pretty clear answer.

During impact the cue slows down and is pushed back in the grip hand by a certain amount. We need to figure out how much this is (at least an upper limit), and whether this is enough to generate sufficient force between the hand and the cue. (The extra mass of the hand/arm will be subject to a proportional amount of the reaction force from the cueball.) I'll ignore energy losses for simplicity.

For a centerball hit the cueball's speed is given by:

Vb = 2Vs/(1 + Mb/Ms)

where Vs is the speed of the cue and the M's are the corresponding masses (or weights)of the ball and stick/hand/arm. Using 18 oz for the nominal cue weight, a 10% increase in its apparent mass will produce a 2% increase in cueball speed:

Vb'/Vb = (1+ 6/18)/(1 + 6/(18 + 1.8)) = 1.333/1.303 = 1.02

This is hardly noticeable so lets try for a 33% increase in the apparent mass (+6 oz). This yields:

(1 + 6/18)/(1 + 6/(18 + 6)) = 1.333/1.25 = 1.067

or almost a 7% increase in ball speed. Small but it can make a difference.

Suppose that at the cue's nominal weight of 18 oz, a cueball is propelled at 20 mph. With the added mass it will now take off at 21.3 mph. The stick's speed in both cases is:

Vs = (1+Mb/Ms)Vb/2 = 1.33333(20mph)/2 = 13.33 mph = 19.55 ft/sec = 235 inch/sec

The average force on the cueball during impact is:

Fav = (Mb)(Vb)/T = (.0117 slugs)(21.3 mph)(1.467 ft/sec/mph)/.001 sec = 365 lbs

This is also the reaction force on the stick/hand/arm. Since the hand and arm now comprise a fourth of the combined mass, the average force between the hand and cue during impact will have to be 365/4 or 91 lbs, albeit briefly.

To find the maximum amount of cue movement in the grip hand, let's look at the loose grip case where there is essentially no coupling between the hand and cue. Immediately after impact the cue's speed is:

Vs' = Vs(1 - Mb/Ms)/(1 + Mb/Ms) = Vs(2/3)/(4/3) = (1/2)235 inch/sec = 117 inch/sec

Because the force buildup and decay is symmetric (approximately), the average relative speed between the cue and the hand is half of this, or 59 inch/sec. So its total movement relative to the hand is:

X = (59 in/sec)(.001 sec) = .059 inch

This is another discussion but it can be shown that for a time symmetric force its average movement during the impact period is about .27 of this (it's somewhere between .25 and .30 so .27 is not a bad guess). We have:

Xav = (.27)(.059 inch) = .016 inch or about 1/63 inch

This is for the uncoupled case. With a tight grip this number must be even smaller if we want that extra 6 oz to be present throughout most of the impact, but we'll go with it.

Is it possible to generate this much force (90 lbs) between the hand and cue from this amount of movement (1/63 inch)?

I tried pressing my cue down on a bath scale while watching the movement of the edge of my grip hand. With the tightest grip I could muster (my hand cramped and is now permanently afixed to the cue) it moved about 3/32 to 1/8 inch when the scale registered only 30 lbs. So it seems highly unlikely to me that you could add to the cue's mass in any significant way. You might question the contact time time I used above, which should change with the added mass, but I don't think this can come anywhere close to making up for the large disparity.

Jim

 

[Island Drive]

Although Bob Jewett's article shows that the hand/arm mass is negligibe when normal grip pressure is used, there still is some question (in my mind anyway) as to whether a very tight grip might change this. I think the following gives a pretty clear answer.

During impact the cue slows down and is pushed back in the grip hand by a certain amount. We need to figure out how much this is (at least an upper limit), and whether this is enough to generate sufficient force between the hand and the cue. (The extra mass of the hand/arm will be subject to a proportional amount of the reaction force from the cueball.) I'll ignore energy losses for simplicity.

For a centerball hit the cueball's speed is given by:

Vb = 2Vs/(1 + Mb/Ms)



where Vs is the speed of the cue and the M's are the corresponding masses (or weights)of the ball and stick/hand/arm. Using 18 oz for the nominal cue weight, a 10% increase in its apparent mass will produce a 2% increase in cueball speed:

Vb'/Vb = (1+ 6/18)/(1 + 6/(18 + 1.8)) = 1.333/1.303 = 1.02

This is hardly noticeable so lets try for a 33% increase in the apparent mass (+6 oz). This yields:

(1 + 6/18)/(1 + 6/(18 + 6)) = 1.333/1.25 = 1.067

or almost a 7% increase in ball speed. Small but it can make a difference.

Suppose that at the cue's nominal weight of 18 oz, a cueball is propelled at 20 mph. With the added mass it will now take off at 21.3 mph. The stick's speed in both cases is:

Vs = (1+Mb/Ms)Vb/2 = 1.33333(20mph)/2 = 13.33 mph = 19.55 ft/sec = 235 inch/sec

The average force on the cueball during impact is:

Fav = (Mb)(Vb)/T = (.0117 slugs)(21.3 mph)(1.467 ft/sec/mph)/.001 sec = 365 lbs

This is also the reaction force on the stick/hand/arm. Since the hand and arm now comprise a fourth of the combined mass, the average force between the hand and cue during impact will have to be 365/4 or 91 lbs, albeit briefly.

To find the maximum amount of cue movement in the grip hand, let's look at the loose grip case where there is essentially no coupling between the hand and cue. Immediately after impact the cue's speed is:

Vs' = Vs(1 - Mb/Ms)/(1 + Mb/Ms) = Vs(2/3)/(4/3) = (1/2)235 inch/sec = 117 inch/sec

Because the force buildup and decay is symmetric (approximately), the average relative speed between the cue and the hand is half of this, or 59 inch/sec. So its total movement relative to the hand is:

X = (59 in/sec)(.001 sec) = .059 inch

This is another discussion but it can be shown that for a time symmetric force its average movement during the impact period is about .27 of this (it's somewhere between .25 and .30 so .27 is not a bad guess). We have:

Xav = (.27)(.059 inch) = .016 inch or about 1/63 inch

This is for the uncoupled case. With a tight grip this number must be even smaller if we want that extra 6 oz to be present throughout most of the impact, but we'll go with it.

Is it possible to generate this much force (90 lbs) between the hand and cue from this amount of movement (1/63 inch)?

I tried pressing my cue down on a bath scale while watching the movement of the edge of my grip hand. With the tightest grip I could muster (my hand cramped and is now permanently afixed to the cue) it moved about 3/32 to 1/8 inch when the scale registered only 30 lbs. So it seems highly unlikely to me that you could add to the cue's mass in any significant way. You might question the contact time time I used above, which should change with the added mass, but I don't think this can come anywhere close to making up for the large disparity.

Jim

Well JSP you have got allot more now to think about before you pull the trigger You just had to ask ))

 

[cheesemouse]

Now that cracks me up.....

 

[tedkaufman]

All things being equal, it makes no difference how tightly or loosely you grip the cue. HOWEVER, acceleration of the cue and speed through the cueball definitely does affect cueball action. So the "all things being equal" stipulation is very significant. It is much more difficult to accelerate the cue with a tighter grip than a looser grip; and for maximum acceleration, wrist snap adds considerable speed. It's very difficult to grip tightly and maintain fluidity in the wrist.

So, theoretically, tight and loose grips are equal provided the cue is delivered at the same speed. However, in practical terms, a loose grip will deliver more speed for most players, thus more cueball action.

One final note, I find deflection (squirt) is minimize by a smooth and fluid stroke. Accordingly, because a relaxed grip is more conducive to smooth acceleration, it is easier to deliver a fluid stroke, thereby reducing squirt.