Squirt. End Mass and Cue Flexibility.

[Jaden]

This is exactly why I stayed out of this thread as long as I did...

Not necessarily. When struck at 2/5'ths of its radius off-center, its surface speed from spin is equal to its forward speed. At 1/2 radius (the miscue limit), its surface speed can be slightly greater than its forward speed.

Anytime it's struck off-center, spin is created simultaneously with forward motion. This happens from the very first moment the tip comes into contact with the cueball. Every ounce of forward force generates not only translational velocity, but a concomitant amount of spin, depending on the tip offset. Spin is not a delayed reaction. Jaden, this is very, very basic physics.

Take these words by Dr. Dave to heart, if you would:

"Also, the grabbing force of the tip is not separate from the primary force ... it is necessary to help create the primary force pushing the CB forward."

Jim

I don't play the appeal to authority or paradigms game...

I will always trust my own experimentation and visualization before I will trust the paradigms or "authority" on understanding reality.

That's not to say I won't listen to what the paradigms are and give them a fair shake, provided they don't conflict with my experimentation and understanding from real world trial and experience.

Many times it ends up being a misunderstanding and we are often describing the same understanding of reality but in different ways. Sometimes there is a fundamental difference in understanding of what is really going on.

Be that as it may, you want to SHOW me the experimentation that metes out the claims, I'll be happy to look at it. You want to try and explain your understanding of what is going on and I'll listen to it.

You want to play bullshit appeal to authority games with me and you can go pound sand.

Jaden

p.s. nothing in my description of what was going on required that the GRIPPING force be separate from the primary force moving the ball forward, it was only the cause of the opposing to the force being exerted on the shaft side action of the shaft and therefore the cause of the action that causes the sidespin that my description changes.

 

[LAMas]

I don't play the appeal to authority or paradigms game...

I will always trust my own experimentation and visualization before I will trust the paradigms or "authority" on understanding reality.

That's not to say I won't listen to what the paradigms are and give them a fair shake, provided they don't conflict with my experimentation and understanding from real world trial and experience.

Many times it ends up being a misunderstanding and we are often describing the same understanding of reality but in different ways. Sometimes there is a fundamental difference in understanding of what is really going on.

Be that as it may, you want to SHOW me the experimentation that metes out the claims, I'll be happy to look at it. You want to try and explain your understanding of what is going on and I'll listen to it.

You want to play bullshit appeal to authority games with me and you can go pound sand.

Jaden

p.s. nothing in my description of what was going on required that the GRIPPING force be separate from the primary force moving the ball forward, it was only the cause of the opposing to the force being exerted on the shaft side action of the shaft and therefore the cause of the action that causes the sidespin that my description changes.

Jaden,
Hi.
I saw this high speed photo with grid and time lines that showed graphic evidence that - to me:



- The tip compresses before the CB moves.
- The compressed tip becomes distorted like being extruded by the accumulating
force of the shaft.
- The CB starts to move or roll forward and rotates CCW while in contact with the compressed tip.
- The front of the shaft follows the tip down - bending from the bridge hand and grip.

Be well

 

[Jaden]

what you;re failing to see..

Jaden,
Hi.
I saw this high speed photo with grid and time lines that showed graphic evidence that - to me:

View attachment 411121

- The tip compresses before the CB moves.
- The compressed tip becomes distorted like being extruded by the accumulating
force of the shaft.
- The CB starts to move or roll forward and rotates CCW while in contact with the compressed tip.
- The front of the shaft follows the tip down - bending from the bridge hand and grip.

Be well

The force has already been exerted on the ball as soon as the tip begins to decompress... the release of the stress and the pressure against the shaft by the mass of the ball is what allows the shaft to react to the flexion and move in the opposite direction which is what then imparts the spin on the ball...

you be well as well sir...

Jaden

 

[askalf]

...... The tip compresses before the CB moves.....

http://i.imgur.com/fhvu4Zs.jpg

 

[Bob Jewett]

...
- The tip compresses before the CB moves.
...

I'm puzzled by this statement. I hope you realize that if there has been force to compress the tip that same force has started cue ball movement. They must occur at the same time.

This is very, very basic physics.

My conclusion is that since the cue ball is just beginning its acceleration, the distance moved is small and the photography is not good enough to capture the small movement that has taken place.

 

[LAMas]

I'm puzzled by this statement. I hope you realize that if there has been force to compress the tip that same force has started cue ball movement. They must occur at the same time.

This is very, very basic physics.

My conclusion is that since the cue ball is just beginning its acceleration, the distance moved is small and the photography is not good enough to capture the small movement that has taken place.

Bob,
Thanks

The tip has to overcome the inertia of the CB.
You may still be right but in is infinitesimal in regards to the effective front end mass.

Fom the link askalf posted up.



Be well

 

[dr_dave]

The force has already been exerted on the ball as soon as the tip begins to decompress

This isn't true. The force builds up gradually as the tip compresses (reaching a peak at maximum compression) and then decreases as the tip springs back. But force is acting over the entire tip contact period, starting a zero, reaching a peak near the middle, and returning to zero. And both CB speed and CB spin increase proportionally over this entire period as a result of this force and the moment it creates about the CB's center.

Regards,
Dave

 

[dr_dave]

I hope you realize that if there has been force to compress the tip that same force has started cue ball movement. They must occur at the same time.

This is very, very basic physics.

Agreed.

My conclusion is that since the cue ball is just beginning its acceleration, the distance moved is small and the photography is not good enough to capture the small movement that has taken place.

Agreed.

Good post,
Dave

 

[Corwyn_8]

(as the tip bends to point closer to CB center)

What force is bending the tip toward the cue ball? Is this just the swing of the tip (i.e. first away then back due to springiness)?

Thank you kindly.

 

[dr_dave]

It seems that some people think the tip has a lot to do with the amount of CB deflection a shaft creates. The tip is certainly critical in that it must grip the CB. If it doesn't, a miscue results. And if a tip could be made much lighter and harder than existing tips, it could results in less CB deflection (by reducing contact time and effective endmass). However, careful tests comparing a wide range of tip types and hardnesses currently available show very little variation (i.e., insignificant differences, in practical terms). For those interested, here's a video summary of the experiment and results:

NV D.15 - Cue and Tip Testing for Cue Ball Deflection (Squirt)

And much more info is available here:

cue tip hardness effects

Enjoy,
Dave

 

[dr_dave]

What force is bending the tip toward the cue ball?

For the cue to deliver its forward force to the CB, a significant amount of gripping force develops between the tip and CB. This gripping force (acting equal and opposite on both the CB and tip) causes the tip to deform sideways, and it also bends the end of the shaft as a larger portion of the shaft is pushed away from the CB due to the spin that develops.

Regards,
Dave

 

[john coloccia]

If nothing else, you need to overcome static friction first. It may not be significant, but everything (including the cue ball) deforms at least a little bit before anything can move. If I had to guess, I would guess that different cloths/condition might yield measurably different results.

edit:
And again, I don't think it really matters. The research I've read through is good. It would just be interesting, that's all.

 

[Jaden]

I don't agree...

For the cue to deliver its forward force to the CB, a significant amount of gripping force develops between the tip and CB. This gripping force (acting equal and opposite on both the CB and tip) causes the tip to deform sideways, and it also bends the end of the shaft as a larger portion of the shaft is pushed away from the CB due to the spin that develops.

Regards,
Dave

I don't agree with your perception that the cb is PUSHING the shaft outwards...

The CB's mass was pushing the shaft backwards and putting tension on the inside (relative to the center mass of the ball) portion of the shaft, as the ball starts to move away from the tip, that tension is released and the shaft reacts by moving in the opposite direction of the built up tension.

The fact that the ball is moving AWAY from the tip and shaft precludes it being able to PUSH the shaft anywhere.

Jaden

 

[askalf]

.......the distance moved is small and the photography is not good enough to capture the small movement that has taken place.

http://i.imgur.com/f1d6O1s.jpg

Russian billiard
30.000 frames per second
T=0ms Beginning of contact between tip and cue ball
T=0.35-0.4ms Maximum deformation tip, movement of cue ball <0.02mm, angle of cue ball rotation <0.01deg
T=1.4-1.5ms Completion of contact between tip and cue ball
sorry my bad English

 

[Jal]

I don't play the appeal to authority or paradigms game...

I will always trust my own experimentation and visualization before I will trust the paradigms or "authority" on understanding reality.

Given the BS we've been handed by authorities over the ages, I have considerable empathy with your skepticism. Science, however, tends to be different. If you believe you've done an experiment that defies what engineers and physicists have "known" for a long, long time, don't you think you should examine that experiment very carefully? Do you have an example?

Many times it ends up being a misunderstanding and we are often describing the same understanding of reality but in different ways. Sometimes there is a fundamental difference in understanding of what is really going on.

Nope. It's always one or the other. Trust me, I happen to be an authority on that.

Be that as it may, you want to SHOW me the experimentation that metes out the claims, I'll be happy to look at it. You want to try and explain your understanding of what is going on and I'll listen to it.

Since you snapped at me, I don't wanna. But I will suggest you look into things like force, torque, mass, moment-of-inertia and center of mass.

You want to play bullshit appeal to authority games with me and you can go pound sand.

Well, I could do some math, but before you could follow it, I think you'd have to do what I just suggested....but then you probably wouldn't need the math.

p.s. nothing in my description of what was going on required that the GRIPPING force be separate from the primary force moving the ball forward, it was only the cause of the opposing to the force being exerted on the shaft side action of the shaft and therefore the cause of the action that causes the sidespin that my description changes.

The forward force can be analyzed into two component forces: one directed at the center of the cueball and one tangential to its surface. As long as the tip is not slipping and the forward force is thus pointing forward, both components are at play. The tangential one is, of course, friction. It both causes the end of the shaft to bend inward a bit (for a time), and at the same time, the cueball to start spinning (equal and opposite forces). In the meantime, the force that's directed toward the center of the cueball, is also pushing back and outward on the shaft (equal and opposite again). It eventually "wins" and the entire front end of the shaft is propelled outward. But during all of this, the friction force has been doing its thing.

Like I said, questioning authoritative pronouncements when there's a real possibility of either examining their logic or subjecting them to tests, is in fact to be admired. But you're going up against what has been the product of just such a process. You might want to familiarize yourself its results before becoming too headstrong.

Jim

 

[Jaden]

I wasn't the one that said that it was the outward moevement of the tip and shaft....

Given the BS we've been handed by authorities over the ages, I have considerable empathy with your skepticism. Science, however, tends to be different. If you believe you've done an experiment that defies what engineers and physicists have "known" for a long, long time, don't you think you should examine that experiment very carefully? Do you have an example?

Nope. It's always one or the other. Trust me, I happen to be an authority on that.

Since you snapped at me, I don't wanna. But I will suggest you look into things like force, torque, mass, moment-of-inertia and center of mass.

Well, I could do some math, but before you could follow it, I think you'd have to do what I just suggested....but then you probably wouldn't need the math.

The forward force can be analyzed into two component forces: one directed at the center of the cueball and one tangential to its surface. As long as the tip is not slipping and the forward force is thus pointing forward, both components are at play. The tangential one is, of course, friction. It both causes the end of the shaft to bend inward a bit (for a time), and at the same time, the cueball to start spinning (equal and opposite forces). In the meantime, the force that's directed toward the center of the cueball, is also pushing back and outward on the shaft (equal and opposite again). It eventually "wins" and the entire front end of the shaft is propelled outward. But during all of this, the friction force has been doing its thing.

Like I said, questioning authoritative pronouncements when there's a real possibility of either examining their logic or subjecting them to tests, is in fact to be admired. But you're going up against what has been the product of just such a process. You might want to familiarize yourself it before becoming too headstrong.

Jim

BTW, I WASN'T the one that said the outward movement of the shaft and tip is what causes the spin. Dave said that. I was simply stating that IF that was the case, it wouldn't be the ball pushing the shaft outward, it would be the tension in the shaft causing it to move outward after the ball starts to move away from the tip.

There you go again stating that you know maths and I don't (lol) and therefore your perception is better than mine. Fallacy at it's best.

You're doing nothing but bloviating about what SCIENCE knows without illustrating it AT ALL...

Please, illustrate what you are stating. I'm all ears. Just because you say that physics agrees with you, doesn't mean jack shit. Your perception of what physics states can be completely wrong..

Oh, and yes sometimes you can be saying the same thing in a different way, me and Colin have done so several times regarding BHE and determined we were saying the same things in different ways.

I'm not saying we are here...just saying it is sometimes the case.

Jaden

 

[Corwyn_8]

For the cue to deliver its forward force to the CB, a significant amount of gripping force develops between the tip and CB. This gripping force (acting equal and opposite on both the CB and tip) causes the tip to deform sideways, and it also bends the end of the shaft as a larger portion of the shaft is pushed away from the CB due to the spin that develops.

Sorry, I am still not getting it. Can you draw those forces on your diagram?

As I see it, the tip HAS to be moving away from the initial contact point (perpendicular(ish) to the forward motion of the cue). That action, and that action ALONE has to be what is moving the rest of the cue stick in that same direction as the collision continues. How is it accomplishing that while at the same time being pulled back towards the cue ball by the gripping force? In other words the section of the cue 2" back from the tip moves further than the tip itself (in your diagram). How?

Thank you kindly.

 

[dr_dave]

I don't agree with your perception that the cb is PUSHING the shaft outwards...

This is not a perception. It is a necessary fact. Again, this is fully explained, illustrated, proven with analyses, and verified with experiments from reputable pool-physics experts via the info and links here:

what causes squirt

squirt endmass and stiffness effects

If you still haven't studied these resources in detail, please do so. They might help change your perceptions.

The physics of endmass momentum balancing out the sideways momentum the CB develops (causing squirt or CB deflection) is very straightforward and clearly proven on the resource pages. In simple terms, the reason why the CB gets pushed sideways (causing CB deflection or squirt) is because the CB pushes the endmass sideways (and the endmass pushes back).

Again, if you have any alternative theories to explain squirt, the burden of proof is on you to convince us your theories have any merit. I personally won't be convinced unless you can provide sound physical arguments and/or provide convincing illustrations and/or provide clear demonstrations and/or provide experimental results that back up your proposed theory.

Regards,
Dave

 

[Jaden]

This is the last I'll post on this for now...

This is not a perception. It is a necessary fact. Again, this is fully explained, illustrated, proven with analyses, and verified with experiments from reputable pool-physics experts via the info and links here:

what causes squirt

squirt endmass and stiffness effects

If you still haven't studied these resources in detail, please do so. They might help change your perceptions.

The physics of endmass momentum balancing out the sideways momentum the CB develops (causing squirt or CB deflection) is very straightforward and clearly proven on the resource pages. In simple terms, the reason why the CB gets pushed sideways (causing CB deflection or squirt) is because the CB pushes the endmass sideways (and the endmass pushes back).

Again, if you have any alternative theories to explain squirt, the burden of proof is on you to convince us your theories have any merit. I personally won't be convinced unless you can provide sound physical arguments and/or provide convincing illustrations and/or provide clear demonstrations and/or provide experimental results that back up your proposed theory.

Regards,
Dave

Ok...I understand that. You have an understanding and experience that tells you, that you are right...

I'll try drawing up some diagrams that illustrate what I'm saying...

Jaden

 

[dr_dave]

BTW, I WASN'T the one that said the outward movement of the shaft and tip is what causes the spin. Dave said that.

I don't think I said that; but if I did, I was wrong. What causes spin is the forward force (composed of two components, as Jim has described) acting through a line of action that doesn't go through the center of the CB (due to an off-center hit).

Regards,
Dave