If the tip and cue ball only touch so briefly, why the difference in power?

[JoeW]

Given the preceding technical discussions what happens when one increases the cue stick weight and decreases the cue tip hardness? Does this lead to better control of the CB at the same or higher speeds?

Would a softer tip allow for more contact points between tip and cb?

A heavier cue stick (say from 18 to 22 oz) could be accelerated to similar speeds by a reasonably good player.

Does it not follow that more power and possibly more control is obtained with a relatively heavier stick and a soft tip?

 

[Patrick Johnson]

Given the preceding technical discussions what happens when one increases the cue stick weight and decreases the cue tip hardness? Does this lead to better control of the CB at the same or higher speeds?

Would a softer tip allow for more contact points between tip and cb?

A heavier cue stick (say from 18 to 22 oz) could be accelerated to similar speeds by a reasonably good player.

Does it not follow that more power and possibly more control is obtained with a relatively heavier stick and a soft tip?

Do you have any particular reason to think more weight + softer tip might increase control? Maybe because of the longer contact time for softer tips? But then why would longer contact time increase control? And what would weight have to do with it? And how does more weight + softer tip = more power? Wouldn't they tend to cancel each other out for that?

There are several unexplained assumptions there.

pj
chgo

 

[Jal]

....A heavier cue stick (say from 18 to 22 oz) could be accelerated to similar speeds by a reasonably good player.

Does it not follow that more power [....] is obtained with a relatively heavier stick [....]?

For a particular player that might be the case, but it doesn't follow, in general. Since you have to accelerate your arm plus the cue, for any particular player there is some optimal cue weight that produces the most cueball spin/speed at some particular tip offset.

If the mass of a player's arm was zero, the optimal cue weight for a center ball hit would be the mass of the cueball (6 oz). Hitting at an offset of (2/5)R (ie, near maximum offset), the optimal weight would be this divided by 1.4, or 4.3 oz.

If the mass of a player's arm was equivalent to the mass of their cue, the optimal weight for a center ball hit would be 3X the weight of the cueball (18 oz). At an offset of (2/5)R, it would be this divided by 1.4, or 12.9 oz.

The moral is that a heavier cue, up to a point, is better suited to a heavier arm. If you like to spin the ball a lot, a lighter cue might be called for.

(I should note that the above calculations were done ignoring the rotational aspect of a pendulum stroke, by simply treating the arm's inertia as some equivalent mass added to the cue's mass.)

Jim

 

[JoeW]

PJ said, "Do you have any particular reason to think more weight + softer tip might increase control? Maybe because of the longer contact time for softer tips? But then why would longer contact time increase control? And what would weight have to do with it? And how does more weight + softer tip = more power? Wouldn't they tend to cancel each other out for that?

There are several unexplained assumptions there."



If force is a product of mass and acceleration then it seems that increasing the mass (weight) of a cue stick would increase the force applied to the CB -- right? I am assuming that one could accelerate two cue sticks that same amount with only a 4 ounce difference between sticks.

I think that someone said that softer tips remain in contact for longer periods of time than harder tips. If this is true, then a soft tip with more force (based on a heavier cue) could lead to more control of the CB. By control I mean the ability to make the CB spin and go where one wants it to go.

I don't understand JAL's answer in that a four ounce difference should not make that much difference to an adult male with regard to accelerating a cue stick over the stroke distance.

These are questions, not comments. I have no idea what the best answers are and hence have asked for answers from people with training in physics.

 

[Patrick Johnson]

Joe:
...a soft tip with more force (based on a heavier cue) could lead to more control of the CB. By control I mean the ability to make the CB spin and go where one wants it to go.

Let's say you're right that a heavier stick + soft tip means more force and more spin (although I'm not convinced of either). You're assuming that means more control. Why? It isn't obvious to me.

pj
chgo

 

[Jal]

I'm not sure anyone can answer with a general statement on control since we're dealing with the human element. I tried to address the issue of what cue weight yields the greatest cueball speed/spin, or equivalently, what cue weight requires the least amount of force applied during the stroke to produce a particular speed/spin. Less force generally means more control I think, although a player may have the best control at some intermediate speed. And as the numbers indicate, the optimal cue weight varies with tip offset.

I should have mentioned a hidden assumption that the same average force is applied regardless of cue weight during the stroke. This would not be true when considering the maximum force that coud be applied, for instance, as this will be less for a lighter cue. So the numbers just indicate a trend and aren't to be taken literally, even if you somehow know the equivalent mass of your arm.

...If force is a product of mass and acceleration then it seems that increasing the mass (weight) of a cue stick would increase the force applied to the CB -- right? I am assuming that one could accelerate two cue sticks that same amount with only a 4 ounce difference between sticks.

Yes, but it requires more force for the heavier cue, and therefore, perhaps, some fine control is lost.

When a moving object collides with another object head on (centerball hit), the second object gains the most speed if their masses are equal. If some offset is involved resulting in rotation, the first object "sees" the second object object as having less mass than it actually does, so the optimal mass for the first is something less than the second's. For pool though, we have to consider the mass of the stick as well as the player's arm in the acceleration process (getting the first object up to speed). So a balance has to be struck between the acceleration process and the collision process, and these yield the numbers indicated earlier (under the somewhat naive assumption that the same maximum force can be applied to any cue, regardless of its weight.)

I think that someone said that softer tips remain in contact for longer periods of time than harder tips. If this is true, then a soft tip with more force (based on a heavier cue) could lead to more control of the CB. By control I mean the ability to make the CB spin and go where one wants it to go.

It's just not clear, as Patrick indicated, why this would lead to more control. A soft tip does stay in contact longer, but the average force during the collision is at least proportionally less. In fact, there is probably more energy loss with a soft tip, and if so, you end up losing some speed/spin.

This is a difficult subject and I don't mean to be preachy. Just taking my best stab at an answer.

Jim

Edit: Hmmm, let me revise this statement:

"When a moving object collides with another object head on (centerball hit), the second object gains the most speed if their masses are equal."

to:

When a moving object collides with another object head on (centerball hit), the second object gains the greatest fraction (100%) of the first object's speed when their masses are equal.

Sorry about that. The erroneous first statement wasn't integral to the rest of the logic.

 

[Patrick Johnson]

Jim:
I tried to address the issue of what cue weight yields the greatest cueball speed/spin, or equivalently, what cue weight requires the least amount of force applied during the stroke to produce a particular speed/spin.

[...]

there is probably more energy loss with a soft tip, and if so, you end up losing some speed/spin.

Doesn't the pre-collision speed/spin ratio depend solely on the tip offset? I would think the amount of force would only affect the after-collision ratio (more change with fuller hits).

pj
chgo

["collision" = CB/OB collision]

 

[JoeW]

Thanks guys, I am trying to understand and think that I have a better handle on it now.

JAL said, "When a moving object collides with another object head on (centerball hit), the second object gains the most speed if their masses are equal. If some offset is involved resulting in rotation, the first object "sees" the second object object as having less mass than it actually does, so the optimal mass for the first is something less than the second's."

So that tends to explain my misunderstanding. I thought that more force would allow one to exert more control though the specifically directed impact. Something like using one's fingers to throw a curve ball exactly as desired through the use of simultaneous thrust and twist as needed. If there is reserve force then it can be used as needed via the offset and force of stroke. Apparently this is not true. So I will take that bolt out of my cue that makes it a 22.5 ounce monster.

 

[Bob Jewett]

... When a moving object collides with another object head on (centerball hit), the second object gains the most speed if their masses are equal. ...

Perhaps I missed the context of this, but it appears to be wrong. Equal masses is the condition you want for complete energy transfer. The condition you want for maximum speed on the struck object is that it should be much lighter than the striking object. In the limit of a very light struck object, it will be going at twice the speed of the striking object. In the case of pool cues and balls, the cue ball ends up going about 130% of the initial speed of the cue stick (from an old measurement that needs to be redone).

 

[Jal]

Doesn't the pre-collision speed/spin ratio depend solely on the tip offset? I would think the amount of force would only affect the after-collision ratio (more change with fuller hits).

pj
chgo

["collision" = CB/OB collision]

I'm not sure what you mean by pre-collision speed/spin ratio, but I agree with what you're saying about the post-impact ratio depending solely on tip offset (except for a slight increase in ratio with an increase in cue speed because of a slight increase in effective offset during impact).

By spin/speed, I meant spin and speed, not the ratio. Poor syntax on my part.

Jim

 

[Patrick Johnson]

I'm not sure what you mean by pre-collision speed/spin ratio

I mean CB/OB collision. Greater force only produces greater spin/speed ratio when speed is reduced by another factor such as CB/OB collision or drag draw.

pj
chgo

 

[elvicash]

When I spoke about the jerk earlier I did not mean it was for only a moment in time I suggest the jerk happens over a period of time. This would also mean the motor of the stroke would need the strength to accelerate all items involved in the collision. The following story illustrates the difference in stroke using two famous payers. I am not sure which book this is from but anyway.

In a book I read it talked about a tourney some where and Minnesota Fats was putting on a display and tried to do some masse shots and had no luck due to the tough conditions. Fats said the humidity is too high in here and you cannot do masse shots right now.

Harold Worst heard that and was on a table and immediatly began executing some extreme power masse shots. He retorted to the fat man that the conditions did not seem that bad to him.

My point of this old story is probably Harold Worst had a stronger stroke than Fats. I think not only was he stronger but he stroked the ball better.

If the camera experiments are correct and it all comes down to velocity at impact then Fats should have just shot faster. He knew how to shoot masse shots when conditions were softer (at least I guess he did I never saw him shoot live). However Harold Worst just powered on through resulting in an extreme masse.

 

[Jal]

...JAL said, "When a moving object collides with another object head on (centerball hit), the second object gains the most speed if their masses are equal. If some offset is involved resulting in rotation, the first object "sees" the second object object as having less mass than it actually does, so the optimal mass for the first is something less than the second's."

Joe, please see my edit to the post at the end of that post. As Bob Jewett points out, this is baloney. I was also considering in that statement the force needed to propel the first object (get it going) in the case where the propelling entity (say, one's arm) has no mass itself.

... So I will take that bolt out of my cue that makes it a 22.5 ounce monster.

Well, 22.5 could be the best for you. Unfortunately, you can't just plop your arm on a scale and plug that into a formula. Although there is a formula, determining the equivalent mass of your arm isn't so easy. Trial and error is the simplest way I would think. It depends on how integral spin is to your game too, and what exactly you mean by control. But there should be some best weight (for a given tip offset), which doesn't mean more and more weight.

Jim

 

[JoeW]

Thanks Jim. Guess I will just have to work with it. I do use a lot of spin and I am able to draw the ball long distances as compared to some of my friends. I thought that it was the extra weight that lead to the ease with which I can control the amount of force and spin. Now I am not so sure.

I do find that I can draw just as well, maybe even further, with the weight bolt removed. I have played with a heavy cue for many years and recently find that extremely soft hits seem to be more difficult for me than for some others. This could be expected based on the cue weight.

Without the cue weight, the arm swing does not seem to be as consistent. So I need some trade offs and I will just have to keep searching. There are some good ideas from the physics described but I suppose that some of the issues are not in the physical relm.

 

[crosseyedjoe]

When I spoke about the jerk earlier I did not mean it was for only a moment in time I suggest the jerk happens over a period of time. This would also mean the motor of the stroke would need the strength to accelerate all items involved in the collision. The following story illustrates the difference in stroke using two famous payers. I am not sure which book this is from but anyway.

In a book I read it talked about a tourney some where and Minnesota Fats was putting on a display and tried to do some masse shots and had no luck due to the tough conditions. Fats said the humidity is too high in here and you cannot do masse shots right now.

Harold Worst heard that and was on a table and immediatly began executing some extreme power masse shots. He retorted to the fat man that the conditions did not seem that bad to him.

My point of this old story is probably Harold Worst had a stronger stroke than Fats. I think not only was he stronger but he stroked the ball better.

If the camera experiments are correct and it all comes down to velocity at impact then Fats should have just shot faster. He knew how to shoot masse shots when conditions were softer (at least I guess he did I never saw him shoot live). However Harold Worst just powered on through resulting in an extreme masse.

Given the same pool cue level, contact point, distance and acceleration contact of "a", the effect is the same for a stroke that took 1sec and a stroke that took 1day from start of the back swing to contact.

"Jerk" or jolt has no effect on the force.

Jerk however will be considered by the physician for those players who like to "punch" stroke the cue ball after examining you for wrist injuries.

 

[Jal]

When I spoke about the jerk earlier I did not mean it was for only a moment in time I suggest the jerk happens over a period of time. This would also mean the motor of the stroke would need the strength to accelerate all items involved in the collision. The following story illustrates the difference in stroke using two famous payers. I am not sure which book this is from but anyway.

In a book I read it talked about a tourney some where and Minnesota Fats was putting on a display and tried to do some masse shots and had no luck due to the tough conditions. Fats said the humidity is too high in here and you cannot do masse shots right now.

Harold Worst heard that and was on a table and immediatly began executing some extreme power masse shots. He retorted to the fat man that the conditions did not seem that bad to him.

My point of this old story is probably Harold Worst had a stronger stroke than Fats. I think not only was he stronger but he stroked the ball better.

If the camera experiments are correct and it all comes down to velocity at impact then Fats should have just shot faster. He knew how to shoot masse shots when conditions were softer (at least I guess he did I never saw him shoot live). However Harold Worst just powered on through resulting in an extreme masse.

Elvicash,

Masse shots are a little bit of a different animal: contact time is significantly longer. But it's still possible that the major difference between Worst and Fats was pre-impact cue speed. I don't see that this example disprooves that.

But I will grant that with the intrinsically greater contact time, things become a bit more murky as far as force applied during impact goes. I still suspect that it wouldn't make much of a difference because the collision force (sans any extra applied force) also is increased significantly on a masse shot. You would have to apply an even greater force during the collision to add noticeably to that force.

Jim

 

[Jal]

Thanks Jim. Guess I will just have to work with it. I do use a lot of spin and I am able to draw the ball long distances as compared to some of my friends. I thought that it was the extra weight that lead to the ease with which I can control the amount of force and spin. Now I am not so sure.

I do find that I can draw just as well, maybe even further, with the weight bolt removed. I have played with a heavy cue for many years and recently find that extremely soft hits seem to be more difficult for me than for some others. This could be expected based on the cue weight.

Without the cue weight, the arm swing does not seem to be as consistent. So I need some trade offs and I will just have to keep searching. There are some good ideas from the physics described but I suppose that some of the issues are not in the physical relm.

Joe,

Thanks for bringing the issue up in the first place. Although the problem has likely been worked a million times before (can't remember off-hand if Ron Shepard dealt with it), it spurred me on to see what the math says about it. It is interesting that the most efficient cue weight can potentially be so different from a center-ball hit to one with large offset (with the already stated caveat that the max average force that can be applied during a stroke also changes somewhat with weight, so the real numbers are likely not as different as the simple treatment suggests).

It'll be interesting to see what happens in the pool room when I get a chance to see how draw is affected by different house cues. If you do some more testing in this area, please report the results, however informal they may be, if you will.

Jim