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(#32)
Corwyn_8
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01-23-2016, 11:23 AM

Quote:
 Originally Posted by 336Robin Im not qualified to talk about such but what about off center hits, high or low? Do they not spin sideways while rotating end over end to some degree?
Not really (or at least, that is a confusing way to think of it). Imagine, if you will, a cue ball with only side spin, the axis of rotation is vertical (up for right spin); it is perpendicular to the line between the contact point and the line parallel to the cue direction, passing through the center of the ball; it is also perpendicular to the direction of the hit. On the other hand imagine hitting with just draw, the axis is pointing directly to the right (relative to cue direction). Hitting with low right, therefore gives you an axis in between those two, namely an axis canted to the right, in the plane perpendicular to the direction of the cue.

Now as the draw wears off, it is easy to visualize the axis swinging from that slanted axis to one straight up, followed by one slanted to the left, as forward roll is acquired. If you practice this with a striped ball you can sometimes get it to show in an obvious way. Try it with the stripe angled at your intended start axis.

This in a excellent demonstration of precession, should you want further thought on the matter.

Thank You kindly.

Last edited by Corwyn_8; 01-23-2016 at 11:31 AM.

(#33)
Patrick Johnson
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01-23-2016, 11:40 AM

Quote:
 Originally Posted by 336Robin ...what about off center hits, high or low? Do they not spin sideways while rotating end over end to some degree?
Quote:
 Originally Posted by Corwyn_8 Not really (or at least, that is a confusing way to think of it).
For understanding the effects of rotating balls in pool, I think that's the clearest way to think of it. For instance, a rolling ball with sidespin curves a little - that's easiest to understand when we realize that a component of its total spin is some rotation about the horizontal axis parallel with its direction of travel ("masse spin").

And when the same rolling ball with side spin hits a rail, it's easiest to understand the angle change that occurs when we realize that another component of its total spin is some rotation about the vertical axis.

pj
chgo

(#34)
dr_dave
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01-23-2016, 02:54 PM

Quote:
 Originally Posted by dr_dave I haven't calculated and/or measured this before, but I'll add it to my list. I would suspect that the direct stiffness effect would be a tiny fraction (maybe less than 1%) of the effective endmass effect. I'll reply to this post if and when I'm able to do the calculations.
FYI, to those interested, I did some measurement and calculations. The analysis is here:

TP B.19 - Comparison of cue ball deflection (squirt) "endmass" and stiffness effects

For the example numbers I used, the direct stiffness effect is only about 1.5% of the total cue ball deflection (squirt) effect. That is indeed very small.

Regards,
Dave

(#35)
Patrick Johnson
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01-23-2016, 07:54 PM

Quote:
 Originally Posted by dr_dave FYI, to those interested, I did some measurement and calculations. The analysis is here: TP B.19 - Comparison of cue ball deflection (squirt) "endmass" and stiffness effects For the example numbers I used, the direct stiffness effect is only about 1.5% of the total cue ball deflection (squirt) effect. That is indeed very small. Regards, Dave
Wow - quick turnaround, Dave!

The effect of stiffness on squirt appears to be even smaller than I thought - inconsequential at the level you suggest.

Thanks for keeping us as real as possible under the circumstances.

pj
chgo

P.S. Does 1.5% include the increase of involved end mass attributable to stiffness?

Last edited by Patrick Johnson; 01-23-2016 at 07:57 PM.

(#36)
Corwyn_8
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01-23-2016, 07:57 PM

Quote:
 Originally Posted by Patrick Johnson For understanding the effects of rotating balls in pool, I think that's the clearest way to think of it.
Opinions clearly differ, but whatever works for you.

For me, I never understood ball spin until I got that there is only one axis (and the torque acted at right angles to applied force). What really did it for me was trying figure out what a natural rolling left english ball would do after hitting cushion. Now 'top' isn't top any longer. What is it? Can you quickly intuit what the new direction of travel will do to the current spin? It is pretty easy if you consider the existing spin axis and the new force applying torque perpendicular to the new (friction) force. For me anyway.

Thank you kindly.

 I understand
(#37)
336Robin
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I understand - 01-23-2016, 08:23 PM

Quote:
 Originally Posted by Corwyn_8 Not really (or at least, that is a confusing way to think of it). Imagine, if you will, a cue ball with only side spin, the axis of rotation is vertical (up for right spin); it is perpendicular to the line between the contact point and the line parallel to the cue direction, passing through the center of the ball; it is also perpendicular to the direction of the hit. On the other hand imagine hitting with just draw, the axis is pointing directly to the right (relative to cue direction). Hitting with low right, therefore gives you an axis in between those two, namely an axis canted to the right, in the plane perpendicular to the direction of the cue. Now as the draw wears off, it is easy to visualize the axis swinging from that slanted axis to one straight up, followed by one slanted to the left, as forward roll is acquired. If you practice this with a striped ball you can sometimes get it to show in an obvious way. Try it with the stripe angled at your intended start axis. This in a excellent demonstration of precession, should you want further thought on the matter. Thank You kindly.
Quote:
 Originally Posted by Patrick Johnson For understanding the effects of rotating balls in pool, I think that's the clearest way to think of it. For instance, a rolling ball with sidespin curves a little - that's easiest to understand when we realize that a component of its total spin is some rotation about the horizontal axis parallel with its direction of travel ("masse spin"). And when the same rolling ball with side spin hits a rail, it's easiest to understand the angle change that occurs when we realize that another component of its total spin is some rotation about the vertical axis. pj chgo
I understand the both of you. I get it very much and thank you both.

"Let your "Stick" do the talking!"

336Robin
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(#38)
LAMas
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01-23-2016, 10:57 PM

Quote:
 Originally Posted by dr_dave FYI, to those interested, I did some measurement and calculations. The analysis is here: TP B.19 - Comparison of cue ball deflection (squirt) "endmass" and stiffness effects For the example numbers I used, the direct stiffness effect is only about 1.5% of the total cue ball deflection (squirt) effect. That is indeed very small. Regards, Dave
Thanks Dave,
I hope that I get a 1.5% raise next month...it will mean a lot to my wife...rather than getting cut.

Rod Cross, Physics Department, University of Sydney invested a lot of time resources and science to conclude that a thinner shaft reduces squirt. I hope that he is informed that his study was not for naught and contributes 1.5% according to your calculation. Even scientist can be punked.

dumluk

Last edited by LAMas; 01-24-2016 at 12:18 AM.

(#39)
LAMas
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01-23-2016, 11:27 PM

Quote:
 Originally Posted by 336Robin Im not qualified to talk about such but what about off center hits, high or low? Do they not spin sideways while rotating end over end to some degree?
Hi,
From the OP by Rod Cross:

III. EXPERIMENTAL METHODS
When a ball is struck with side spin on a billiard table, the amount of sidespin is difficult to measure experimentally because the ball initially slides and then rolls forward. The ball therefore rotates about two different axes simultaneously.

Be well

dumluk

(#40)
SilverCue
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01-24-2016, 05:48 AM

Quote:
 Originally Posted by dr_dave FYI, to those interested, I did some measurement and calculations. The analysis is here: TP B.19 - Comparison of cue ball deflection (squirt) "endmass" and stiffness effects For the example numbers I used, the direct stiffness effect is only about 1.5% of the total cue ball deflection (squirt) effect. That is indeed very small. Regards, Dave
Dr Dave
Wouldn't it depend on the end mass vs flexibility?
What if you had a 14 mm tip with brass ferrule and the last
10 inches shaped like an hour glass with the mid point 9 mm?
Verses same 14 mm shaft with pro taper?

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Last edited by SilverCue; 01-24-2016 at 09:22 AM.

(#41)
ENGLISH!
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01-24-2016, 06:38 AM

Quote:
 Originally Posted by LAMas Thanks Dave, I hope that I get a 1.5% raise next month...it will mean a lot to my wife...rather than getting cut. Rod Cross, Physics Department, University of Sydney invested a lot of time resources and science to conclude that a thinner shaft reduces squirt. I hope that he is informed that his study was not for naught and contributes 1.5% according to your calculation. Even scientist can be punked.
Big E,

I doubt in about 5 hours or less that Dr. Dave could compared every type of shaft taper & all of the various degrees of flex to all of the various amounts of front end masses to arrive at his definitive figure of which PJ then determines to be "inconsequential". I would also surmise that his research was not done with robotic testing.... so as to take out any human subconscious interpretations & variances out of the the picture for all of the results.

But what I'm left with is that if I'm playing using the TOI method that relies on the use of squirt, what flex shaft would be best for me so that the amount of squirt that I get will be the most consistent, because a 1.5% variation can mean the difference between a make or a miss, the win or loss of a game, who wins the match, & who gets the money, trophy, or bragging rights.

It seems that if I want the most AND the most consistent amount of squirt that I should go with the stiffest shaft that I can find...

& if I want to reduce the squirt & maybe bring other components into play that would make the squirt more variable like what loads are put on it, then I should go with a very flexible shaft.

What do you think? Is my thinking correct or is it in ANY way in error? I know that I used the 1.5% thing not technically correct but I think you get the idea.

I'm fairly sure that CJ Wiley varied the diameter of shaft for the size of table that he would be playing on for a given tournament. I think he went bigger & more stiff (& a bit more natural front end mass) for smaller tables & thinner (& a bit less natural front end mass) with more flex for the larger tables.

Be & Stay Well,
Rick

Last edited by ENGLISH!; 01-24-2016 at 08:27 AM.

(#42)
Jal
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01-24-2016, 08:14 AM

Quote:
 Originally Posted by dr_dave ...For the example numbers I used, the direct stiffness effect is only about 1.5% of the total cue ball deflection (squirt) effect. That is indeed very small
Dr. Dave, in view of the conservation of momentum (transverse), I don't understand the dichotomy between stiffness and endmass. In other words, I humbly suggest that all of the lateral force on the ball has to be attributed to accelerating mass. (The endmass itself, though, is a function of stiffness and mass.)

Jim

 The 1.5% differences
(#43)
336Robin
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The 1.5% differences - 01-24-2016, 08:38 AM

I read but did not understand the physics of the paper but here are some observations that I have noted during the work I am completing now on Side Spin.

Squirt is not irrelevant as more can be increasingly difficult to deal with however if you understand the squirt values of your current cue shaft in a measurable sort of way you can calculate and apply them accurately over distance by using the stroke that you planned the shot with.

So any formulas for squirt allowance would be subject to stroke speed as the cue ball travels in an arc towards the object ball.

For what I have seen this 1.5% is negligible in the sense that shaft stiffness, end mass such as the use of an Ivory ferrule is so small that when you use a cue over time that you easily adapt to if you understand the values of your stroke over distance and the allowance amount for your cue.

Quote:
 Originally Posted by dr_dave FYI, to those interested, I did some measurement and calculations. The analysis is here: TP B.19 - Comparison of cue ball deflection (squirt) "endmass" and stiffness effects For the example numbers I used, the direct stiffness effect is only about 1.5% of the total cue ball deflection (squirt) effect. That is indeed very small. Regards, Dave

"Let your "Stick" do the talking!"

336Robin
"Improve your shot making forever for \$5.99!"

The Target Ball Concept-Aiming,
The Flight of the Cue Ball-Aiming Adjusted for Side Spin,
Robbing the Bank Shot!-Pass Over Banking
Change your game for a couple of Bucks! and
Comes with a lesson!

website:http://aimisthegameinpool.com

(#44)
Jal
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01-24-2016, 08:39 AM

Quote:
 Originally Posted by Patrick Johnson For understanding the effects of rotating balls in pool, I think that's the clearest way to think of it. For instance, a rolling ball with sidespin curves a little - that's easiest to understand when we realize that a component of its total spin is some rotation about the horizontal axis parallel with its direction of travel ("masse spin"). And when the same rolling ball with side spin hits a rail, it's easiest to understand the angle change that occurs when we realize that another component of its total spin is some rotation about the vertical axis.
Couldn't agree more with your posts on this. I think some people incorrectly believe the components are just a convenient mathematical (or logical) fiction.

Is there an easy way to retain multiple and/or nested quotes?

Jim

(#45)
Jal
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01-24-2016, 08:48 AM

Quote:
 Originally Posted by Corwyn_8 Not really (or at least, that is a confusing way to think of it). Imagine, if you will, a cue ball with only side spin, the axis of rotation is vertical (up for right spin); it is perpendicular to the line between the contact point and the line parallel to the cue direction, passing through the center of the ball; it is also perpendicular to the direction of the hit. On the other hand imagine hitting with just draw, the axis is pointing directly to the right (relative to cue direction). Hitting with low right, therefore gives you an axis in between those two, namely an axis canted to the right, in the plane perpendicular to the direction of the cue. Now as the draw wears off, it is easy to visualize the axis swinging from that slanted axis to one straight up, followed by one slanted to the left, as forward roll is acquired. If you practice this with a striped ball you can sometimes get it to show in an obvious way. Try it with the stripe angled at your intended start axis. This in a excellent demonstration of precession, should you want further thought on the matter.
Corwyn, that's not precession, but a demonstration of the independent evolution of the horizontal component.

Jim

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