Squirt. End Mass and Cue Flexibility.

LAMas said:

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.

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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

dr_dave said:

...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

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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

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.

dr_dave said:

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

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Patrick Johnson said:

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.

Click to expand...

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

Corwyn_8 said:

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.

Click to expand...

Corwyn, that's not precession, but a demonstration of the independent evolution of the horizontal component.

Jim

Jal said:

Corwyn, that's not precession, but a demonstration of the independent evolution of the horizontal component.

Click to expand...

Sure it is.
Precession: the slow movement of the axis of a spinning body around another axis due to a torque.

Friction of the ball with the table is producing a torque, which is changing the axis of the spinning ball. Precession.

Which part do you disagree with?

Thank you kindly.

p.s. For anyone wondering what we are talking about:
https://www.youtube.com/watch?v=ty9QSiVC2g0

Jal said:

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

Click to expand...

I don't know a way to retain them within a single post that you're responding to, but you can click the "multi-quote" button (see pic below) at the bottom right of each separate post you want to quote and then the "Post Reply" button at the bottom of the page to collect those multiple quotes (separately, not nested) into your reply.

Another way is to highlight the entire post with the nested quotes you want to retain and paste it into your reply - but then you'll have to monkey with the "

" tags to make it look right.

pj
chgo

View attachment 52475

Click to expand...

ENGLISH! said:

...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

Click to expand...

The 1.5% that Dave mentioned is not a measure of consistency or variation.

Yet another thing you don't understand and don't know enough to shut up about.

AzB's resident anti-educational thread killer.

pj
chgo

ENGLISH! said:

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

Click to expand...

^^^^^^^^^^^

Corwyn_8 said:

Sure it is.
Precession: the slow movement of the axis of a spinning body around another axis due to a torque.

Friction of the ball with the table is producing a torque, which is changing the axis of the spinning ball.

Which part do you disagree with?

Click to expand...

I don't disagree with either of the above, but the second statement, which is true, is not an example of the first, which is, of course, also true. As it develops, the horizontal spin component does not cause the combined (net) spin axis to rotate about another axis. Also, precession is associated with a fixed spin rate, whereas the spin rate of the cueball increases as the horizontal component is added in.

Jim

When a ball is rolling straight around the horizontal axis into a rail on an angle the rail 'grabs' one side of the ball & torques it & it comes out of the contact with the rail NOT rolling straight around the horizontal axis.

It picks up a sideways rotation that can 'open the angle' if hit slowly enough for that rotation to take the effect.

Please note the single quotes. Another way of saying it is that the ball will have swerve on it as it exists the rail.

This is a Billiard Forum & not a physics forum. What good does it do to make posts of which a high number of readers probably do not & can not have any understanding?

Patrick Johnson said:

I don't know a way to retain them within a single post that you're responding to, but you can click the "multi-quote" button (see pic below) at the bottom right of each separate post you want to quote and then the "Post Reply" button at the bottom of the page to collect those multiple quotes (separately, not nested) into your reply.

Another way is to highlight the entire post with the nested quotes you want to retain and paste it into your reply - but then you'll have to monkey with the quote tags to make it look right.

Click to expand...

Thanks Patrick. For some reason I'm missing the multi-quote button. I guess I'll have to raise a stink about that.

Jim

ENGLISH! said:

When a ball is rolling straight around the horizontal axis into a rail on an angle the rail 'grabs' one side of the ball & torques it & it comes out of the contact with the rail NOT rolling straight around the horizontal axis.

It picks up a sideways rotation that can 'open the angle' if hit slowly enough for that rotation to take the effect.

Click to expand...

This is wrong (surprise!). The angle is "opened" by the rolling (vertical) rotation of the ball - this would happen whether or not the ball picks up sideways rotation from contact with the rail.

What good does it do to make posts of which a high number of readers probably do not & can not have any understanding

Click to expand...

How about constantly making posts that are simply wrong because you're ignorant, pigheaded and self-absorbed?

pj
chgo

Jal said:

Thanks Patrick. For some reason I'm missing the multi-quote button. I guess I'll have to raise a stink about that.

Jim

Click to expand...

Might only come with certain "skins"...?

pj
chgo

Patrick Johnson said:

This is wrong (surprise!). The angle is "opened" by the rolling (vertical) rotation of the ball - this would happen whether or not the ball picks up sideways rotation from contact with the rail.


How about constantly making posts that are simply wrong because you're ignorant, pigheaded and self-absorbed?

pj
chgo

Click to expand...

Again.

Apples to Oranges & out of context.

The discussion was not about a sliding or a backward spinning ball compared to a rolling ball & I did not say it was the ONLY reason that an angle can be opened when compared to other parameters.

My post can certainly give some knowledge to those that are missing some slowly hit banks or kicks long & explains in a simple manner & language the change in the rotation of the ball.

That's the point or should be, IMO, which is to possibly help others to play better & not trying to show one's self off as you seem to want to almost always want to do & then add in the personal 'attacks'.

Patrick Johnson said:

Might only come with certain "skins"...?

Click to expand...

Yes, I see. Thanks again.

Jim

Jal said:

I don't disagree with either of the above, but the second statement, which is true, is not an example of the first, which is, of course, also true. As it develops, the horizontal spin component does not cause the combined (net) spin axis to rotate about another axis. Also, precession is associated with a fixed spin rate, whereas the spin rate of the cueball increases as the horizontal component is added in.

Click to expand...

How could it not? If the combined spin axis is a combination of two components, how could changing one of those components NOT affect the combination?

Precession is NOT associated only with fixed spin rate. See the definition. The Earth precesses, its spin rate is not fixed. A top precesses, its spin rate is not fixed. Check out the video I linked. The spin of the bicycle wheel is slowing due to friction, and the torque from hanging from only one side is causing precession.

Thank you kindly.

ENGLISH! said:

I did not say it was the ONLY reason that an angle can be opened

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Side spin picked up from the ball's contact with a rail is not any of the reasons its rebound angle can be opened - in fact, the ball/rail friction that causes the side spin actually shortens the rebound angle.

You're simply wrong, as usual, and unwilling/unable to admit it, as usual. Go away and stop dis-educating readers with your aggressive ignorance.

pj
chgo

Sorry I've not been able to reply and be involved in the discussion. I was actually playing pool all morning ... imagine that ... somebody on AZB actually spending time at the table instead of sitting at a keyboard. :grin-square:

I'll read through everything now and post replies as I go.

I'm glad to see interesting discussion without too much mud slinging for a change. I hope that continues.

Regards,
Dave