Proof that snap does not spin the ball

[Attila_the_gorilla]

You made the claim that snapback is a catapult effect and now you refuse to stand by your own claim.

These are your exact words:

The reason the ball leaves the stringbed is the strings starting to snap back. That's the catapult effect

This is to attribute to the 'release' far too great an effect.

You should give up your catapult theory. Or if you intend to stand by it then at least justify it.

Sorry mate, I was out living a bit. Once again I think there's some language issues.

I have never refused to stand by my claim that the snap-back is a catapult effect. Well actually it's a trampoline effect, but the same idea. I've been explaining this through many posts and cannot be any clearer than I have been. Strings act as a trampoline. Or catapult, that's semantics. They act that way if they have freedom to move, stretch and snap back. The snap back is the trampoline action of the main strings along the crosses. The reason this provides extra spin is because the trampoline effect results in vertical frictional contact speeds that are much greater than just your swingspeed. It's the main strings that provide this frictional force on the ball.

No explanation can be much clearer than this. Or do I need to quote some scientific study?

I never thought about this subject until I saw this thread. Have never read other people's ideas about it. It's just common sense and a bit of unbiased, clear thinking.

 

[Bartelby]

The 'snap back' idea comes from some images made by a Japanese photographer that were taken up and studied scientifically.

I don't think I've ever rejected the idea that 'snap back' contributes to spin. I've merely tried to place it in a wider context.

I don't know how you disentangle and quantify its effect, but some terms seem to exagerrate the effect.

 

[maxpotapov]

The 'snap back' idea comes from some images made by a Japanese photographer that were taken up and studied scientifically.

I don't think I've ever rejected the idea that 'snap back' contributes to spin. I've merely tried to place it in a wider context.

I don't know how you disentangle and quantify its effect, but some terms seem to exagerrate the effect.

Balanced and fair! Can we now close the thread please?

 

[BreakPoint]

If the ball does not slide the string neither grabs nor releases, so it is a sequence.

If you want to isolate snapback, you are the one who needs to, and has not so far, justified your view of it as a catapult.

The physics of catapults should be pretty clear since they've been around for an extremely long time.

The strings grab the ball when the ball compresses (flattens) against the stringbed and the strings dig into (bites) the nap of the ball. And since the strings are in motion upwards during your stroke, they grab the ball and rotate it producing the spin.

If the ball was sliding across the stringbed then the strings are not grabbing it, which is why I don't believe the ball slides that much across the stringbed. As soon as the strings grab the ball, the ball should stop sliding. And this grabbing of the ball occurs even before its maximum compression against the stringbed.

 

[maxpotapov]

The strings grab the ball when the ball compresses (flattens) against the stringbed and the strings dig into (bites) the nap of the ball. And since the strings are in motion upwards during your stroke, they grab the ball and rotate it producing the spin.

If the ball was sliding across the stringbed then the strings are not grabbing it, which is why I don't believe the ball slides that much across the stringbed. As soon as the strings grab the ball, the ball should stop sliding. And this grabbing of the ball occurs even before its maximum compression against the stringbed.

Or the mains start sliding together with the ball!
You're almost there, come on!

 

[Bartelby]

No one said the strings were sliding on a frictionless surface, as you clearly imply.

The whole point of texture, edges and twisting on spin strings is to create more friction.

The strings grab the ball when the ball compresses (flattens) against the stringbed and the strings dig into (bites) the nap of the ball. And since the strings are in motion upwards during your stroke, they grab the ball and rotate it producing the spin.

If the ball was sliding across the stringbed then the strings are not grabbing it, which is why I don't believe the ball slides that much across the stringbed. As soon as the strings grab the ball, the ball should stop sliding. And this grabbing of the ball occurs even before its maximum compression against the stringbed.

 

[BreakPoint]

Strings trampoline. Both vertically and horizontally. The more freedom they have to move, the faster this trampolining is.

If you don't believe in this trampolining effect, then you don't believe in snapback spin. Which is fair enough, it's your opinion.

The problem I have with that theory is this:

If you have a rough multi that doesn't snap back at all in the plane parallel to the stringbed (i.e., what you call "vertically") due to its high coefficient of friction, then shouldn't this same high friction also cause it not to snap back or at least significantly slow down its snap back in the plane normal to the stringbed (i.e., what you call "horizontally")? And if so, wouldn't that significantly reduce the effect of its elasticity and restitution energy back to the ball (what you call "catapulting" or "trampolining")? If so, then why are multis so much more powerful than polys?

Likewise, shouldn't a very slippery poly snap back very quickly in both the vertical AND horizontal directions? If so, wouldn't that make polys very powerful? But we know that's not the case since polys are very low-powered compared to multis.

We know Kevlar strings do not snap back so it makes sense that they are very low-powered. But since polys do snap back very quickly, they should be very high-powered, however, they are not.

 

[SpinToWin]

Can somebody please get unorthodox stringing here and let him do an experiment...

1 racquet strung with a 16x10 String Pattern with a soft, smooth and slick poly (prince Tour XC or head Lynx should work) at a suitable tension.

Another racquet strung with a 12x22 string pattern and Kevlar mains with syn gut crosses at a tension that doesn't kill his arm and is as high as possible.

Then let him compare how much spin he gets with the respective stringjob.

 

[dominikk1985]

the effect of snapback is probably overrated (friction is still more important- as even locked beds do generate spin) but I do think that it does matter. a springy, Slick bed will provide more spin.

I still would asume that snap only produces the last 20-30% of spin, 70-80% is probably string on ball friction.

 

[Attila_the_gorilla]

The problem I have with that theory is this:

If you have a rough multi that doesn't snap back at all in the plane parallel to the stringbed (i.e., what you call "vertically") due to its high coefficient of friction, then shouldn't this same high friction also cause it not to snap back or at least significantly slow down its snap back in the plane normal to the stringbed (i.e., what you call "horizontally")? And if so, wouldn't that significantly reduce the effect of its elasticity and restitution energy back to the ball (what you call "catapulting" or "trampolining")? If so, then why are multis so much more powerful than polys?

Likewise, shouldn't a very slippery poly snap back very quickly in both the vertical AND horizontal directions? If so, wouldn't that make polys very powerful? But we know that's not the case since polys are very low-powered compared to multis.

We know Kevlar strings do not snap back so it makes sense that they are very low-powered. But since polys do snap back very quickly, they should be very high-powered, however, they are not.

With freedom of movement I was only referring to vertical snapback, cos that's where the differences are. In the horizontal plane, I don't think string surface makes a difference with regards to snapback speed.

 

[maxpotapov]

With freedom of movement I was only referring to vertical snapback, cos that's where the differences are. In the horizontal plane, I don't think string surface makes a difference with regards to snapback speed.

Oh, you mean vertical/horizontal in relation to court surface, OK

 

[Attila_the_gorilla]

By vertical I mean parallel with the cross strings, and by horizontal I mean perpendicular to the stringbed plane. That may have caused some misunderstanding, it's just quicker for me to say it that way.

 

[Bartelby]

TWU - a small excerpt from its multi-part discussion of strings:

It is also apparent how convoluted the process can become. There are a lot of moving parts and forces that change magnitude and direction throughout the duration of the impact. Some factors accummulate to contribute to spin and others to diminish it. It is too complicated to keep an energy accounting at each step of the process. What concerns us is the net effect. All the separate, local events and associated forces and energies will add up to a net effect. Figure 1 (thanks to Rod Cross) shows a simplified conceptual model of the snap-back process.

In the figure, the strings are simulated as a rigid surface attached to a riged wall (the racquet) connected by a spring.

Figure 1 — The Snap-back Model of Tennis Spin.

[strings - stretch - snap back]

String movement as in (b) stores elastic energy in the strings, which is then given back to the ball in (c) in the form of extra spin due to the friction force at the bottom of the ball.

 

[Attila_the_gorilla]

^^^ Care to elaborate on that? Do you feel it's something different to what's been said before?

 

[Bartelby]

Bold is my emphasis:

The videos (here and at the links above) show that string movement does indeed occur at the angles and speeds tested. It is also shown that the strings do snap back for all setups and they do so, for the most part, in less than 1/1000 second. We can't see the details of what occurs during that 1/1000 second between video frames, but the evidence makes it reasonable to assume that the strings are indeed spinning the ball. Furthermore, even when there is no visible movement, the strings can still stretch laterally between string intersections and snap-back to produce over-spin. The end result is that string movement and snap-back very strongly correlate with more spin. These tests were performed at 52 mph.

What is further apparent is that the results of three previous experiments are qualitatively similar: polyester in general moves more than nylon or gut and produces more spin. That does not mean that individual strings of a particular material cannot perform much better than the average for that material. However, because spin performance does seem (at least at present) to correlate to material, the question is what is it about the string/material that makes it move and stretch laterally? The candidates from TWU string properties testing would suggest stiffness, tension loss, and slipperiness as the main candidates. Polyester is stiffer, loses more tension, and is slippery. The stiffer material may be more able to overcome interstring friction or move faster, the lower tension decreases interstring friction enabling more movement, and slipperiness (low coefficient of friction — COF) also lessens interstring friction. These may all act in interactive combinations to facilitate string movement and snap-back. The precise mechanisms of snap-back are yet to be determined.

But it must be remembered that just because a particular string has better spin properties, that does not mean that the player will be able to hit more spin with it. The main contributors to spin, over and above the equipment, are the speed and angle of the swing. If the equipment setup causes the player, for control, strategic, or confidence reasons, to alter the swing, then there may be a decrease in spin. Contrawise, the player might speed up the swing or increase the attack angle or racquet tilt and get even more spin. That, probably, is the reason that lab tests and playtests don't always agree for everyone.

 

[Bartelby]

Conclusion: The snap back denialists like Irvin and Breakpoint have a lot of work to do to prove their case, but the theory is still very incomplete.

It's also clear that snap back is part of a larger explanation of what causes spin.

 

[Attila_the_gorilla]

Do you still disagree that snapback means the string's trampoline movement back into its resting position?

 

[RanchDressing]

The problem I have with that theory is this:

If you have a rough multi that doesn't snap back at all in the plane parallel to the stringbed (i.e., what you call "vertically") due to its high coefficient of friction, then shouldn't this same high friction also cause it not to snap back or at least significantly slow down its snap back in the plane normal to the stringbed (i.e., what you call "horizontally")? And if so, wouldn't that significantly reduce the effect of its elasticity and restitution energy back to the ball (what you call "catapulting" or "trampolining")? If so, then why are multis so much more powerful than polys?

Again, you need a lesson on how friction works. Friction works when surfaces slide against each other.
You just twisted everything I said and put it in totally backwards. I recommend you look up how force vectors work.

The ball pushes on the strings in two directions. So the strings react in two different directions. The strings will "Trampoline" forward regardless what the friction is. The friction only slows/stops the side to side motion of the strings, which affects the spin. Which is why multis (which have high string on string friction) have plenty of power but can seriously struggle to produce spin.

I could draw this out, with vectors, but I don't have time right now.

Likewise, shouldn't a very slippery poly snap back very quickly in both the vertical AND horizontal directions?

Starting with this.
No. The mains don't snap back in the vertical direction, they stretch and return to original position. Snapping back is referring to the mains sliding back to their original position. The forces in play to these two motions are different, even though the strings involved are the same.

Take your racquet and push the main into the bed. Now compare how difficult this is to sliding the main to either the right or the left. When you push the mains into the bed with your hand you also have to push on all the crosses behind it, which push on all the other mains... If racquets weren't woven like this, beds would behave differently.

When you slide the string sideways, you clearly have much less resistance (only the crosses against that individual main). The mains can act much more independently.

If so, wouldn't that make polys very powerful? But we know that's not the case since polys are very low-powered compared to multis.

We know Kevlar strings do not snap back so it makes sense that they are very low-powered. But since polys do snap back very quickly, they should be very high-powered, however, they are not.

Power has to do with tension and stiffness. I don't know how you don't already know that. Snap back has to do completely with friction, as that is the main force resisting the return of the main to its original location (other than the ball).

 

[maxpotapov]

Conclusion: The snap back denialists like Irvin and Breakpoint have a lot of work to do to prove their case, but the theory is still very incomplete.

It's also clear that snap back is part of a larger explanation of what causes spin.

 

[Bartelby]

Not for the first or second time, I have to tell you that this was never my thesis. You simply kept on reading my statements to mean what you wanted them to despite my clarifications.

This is, I repeat again, the thesis of Irwin and Breakpoint, so you need to address yourself to them.

Do you still disagree that snapback means the string's trampoline movement back into its resting position?

 

[SpinToWin]

 

[RanchDressing]

Those that haven't gotten it now never will.

 

[maxpotapov]

 

[Povl Carstensen]

By definition, it they "move away", they cannot be "right there".

They are moving with the ball, grabbing it.

 

[Povl Carstensen]

If the strings move with the ball, then they are not biting deeply into the nap of the ball. And if the strings bit deeply into the nap of the ball, the ball would stop moving relative to the strings. That's when you grab the ball with the strings and rotate it to put spin on it.

You grab better when strings are not stiff like a garbage can lid, remember?

 

[Povl Carstensen]

The strings moving downwards with the ball is a phase that produces less "grab" than if the strings were locked in place.

Not if they skid of, like of a garbage can lid.

 

[Povl Carstensen]

Just take a racquet strung with full poly and pull the main strings aside with your fingers and then time how long it takes for the strings to snap back into place. I know everyone has tried this but no one will admit that it takes much, much longer than the 2 to 5 milliseconds that the ball is in contact with the strings. 1/2 a second is 500 milliseconds.

This has been adressed long ago in the thread.

 

[Povl Carstensen]

No one here is saying that snap back does not occur. It obviously does - that's why with slippery strings the strings go back to being straight after each shot. The question is if this snap back effect adds much or any spin to the ball.

It is at least as much the phase before snapback.

 

[Povl Carstensen]

Or the mains start sliding together with the ball!
You're almost there, come on!

Yes, it could happen....

 

[BreakPoint]

Can somebody please get unorthodox stringing here and let him do an experiment...

1 racquet strung with a 16x10 String Pattern with a soft, smooth and slick poly (prince Tour XC or head Lynx should work) at a suitable tension.

Another racquet strung with a 12x22 string pattern and Kevlar mains with syn gut crosses at a tension that doesn't kill his arm and is as high as possible.

Then let him compare how much spin he gets with the respective stringjob.

Of course the 16x10 pattern strung with poly will get more spin because it is an more open pattern than the 12x22 strung with Kevlar/Syn gut.

16x10 = 160

12x22 = 264

Big difference. And we already know that more open string patterns generate more spin for reasons we've already stated, even without snap back.

 

[BreakPoint]

With freedom of movement I was only referring to vertical snapback, cos that's where the differences are. In the horizontal plane, I don't think string surface makes a difference with regards to snapback speed.

Why not? Then your theory is completely inconsistent.

Snap back happens or doesn't happen due to the coefficient of friction between the mains and the crosses. That occurs whether the snap back is vertical (lateral) or horizontal (perpendicular). If a string snaps back quickly vertically due to it's low coefficient of friction (i.e., slippery), then it should also snap back quickly horizontally. Likewise, if a string doesn't snap back at all horizontally due to its high coefficient of friction (i.e. sticky), then it should not snap back at all or significantly slow its snap back horizontally. Isn't this your theory of "catapulting" or "trampolining"?

 

[BreakPoint]

They are moving with the ball, grabbing it.

If the strings actually grabbed the ball, they would stop the ball from moving. So if they are moving with the ball, they haven't grabbed it. Instead, the strings are being pushed aside by the ball.

 

[BreakPoint]

You grab better when strings are not stiff like a garbage can lid, remember?

Not necessarily true. A stiff stringbed causes the ball to pancake more against it which allows each string to dig deeper into the nap of the ball, thereby grabbing it better. The garbage can lid doesn't have holes/gaps on the surface so it doesn't behave like a stringbed.

 

[Povl Carstensen]

The strings moving with ball is actually proof they have grabbed one another. If it was not uniform movement it would not be grabbing.

 

[BreakPoint]

This has been adressed long ago in the thread.

Where? Please show me. I have not seen anyone in this thread post the time they personally measured for the mains to snap back after they pulled them aside with their fingers.

 

[Povl Carstensen]

Not necessarily true..

And not necessarily untrue.

 

[Povl Carstensen]

Where? Please show me. I have not seen anyone in this thread post the time they personally measured for the mains to snap back after they pulled them aside with their fingers.

Much earlier it was adressed that snapback is a bit of an unprecise term because most of the interaction takes place before.

 

[BreakPoint]

The strings moving with ball is actually proof they have grabbed one another. If it was not uniform movement it would not be grabbing.

Pushing the strings aside is not grabbing it.

If your friend comes near you and you pushed him aside, have you grabbed him?

 

[Povl Carstensen]

The garbage can lid doesn't have holes/gaps on the surface so it doesn't behave like a stringbed.

But apparantly stiff kevlar strings are more like a garbage can lid than more flexible polyester strings according to for instance Agassi.

 

[BreakPoint]

Much earlier it was adressed that snapback is a bit of an unprecise term because most of the interaction takes place before.

But the time it takes for the strings to snap back is at the crux of this topic since if it takes 1/2 (500 ms) or even 1/4 (250 ms) of a second for the strings to snap back, that's way longer than the 2 to 5 ms that the ball is in contact with the strings.

 

[BreakPoint]

But apparantly stiff kevlar strings are more like a garbage can lid than more flexible polyester strings according to for instance Agassi.

Do you seriously think Agassi knows what it's really like to play tennis with a garbage can lid?

 

[Povl Carstensen]

Pushing the strings aside is not grabbing it.

If your friend comes near you and you pushed him aside, have you grabbed him?

No and I have not even tried to grab him. If you miss catching a ball because of keeping your hand too rigid/stiff, then you have not grabbed it. If you manage to catch it by moving with it then you have grabbed it.

 

[Povl Carstensen]

Do you seriously think Agassi knows what it's really like to play tennis with a garbage can lid?

I think he has great experience in playing with different string beds, which he conveyed convincingly in figurative speech.

 

[Povl Carstensen]

But the time it takes for the strings to snap back is at the crux of this topic since if it takes 1/2 (500 ms) or even 1/4 (250 ms) of a second for the strings to snap back, that's way longer than the 2 to 5 ms that the ball is in contact with the strings.

Yes and this point has been adressed and taken into consideration a long time ago.

 

[BreakPoint]

Again, you need a lesson on how friction works. Friction works when surfaces slide against each other.
You just twisted everything I said and put it in totally backwards. I recommend you look up how force vectors work.

The ball pushes on the strings in two directions. So the strings react in two different directions. The strings will "Trampoline" forward regardless what the friction is. The friction only slows/stops the side to side motion of the strings, which affects the spin. Which is why multis (which have high string on string friction) have plenty of power but can seriously struggle to produce spin.

I could draw this out, with vectors, but I don't have time right now.



Starting with this.
No. The mains don't snap back in the vertical direction, they stretch and return to original position. Snapping back is referring to the mains sliding back to their original position. The forces in play to these two motions are different, even though the strings involved are the same.

Take your racquet and push the main into the bed. Now compare how difficult this is to sliding the main to either the right or the left. When you push the mains into the bed with your hand you also have to push on all the crosses behind it, which push on all the other mains... If racquets weren't woven like this, beds would behave differently.

When you slide the string sideways, you clearly have much less resistance (only the crosses against that individual main). The mains can act much more independently.



Power has to do with tension and stiffness. I don't know how you don't already know that. Snap back has to do completely with friction, as that is the main force resisting the return of the main to its original location (other than the ball).

Frictional force is always present, whether the strings move laterally (parallel) or normally (perpendicular). When you hit a ball completely flat, so that the ball and the racquet face are perpendicular to each other and the ball sinks into the stringbed, it first has to overcome the sum of all the frictional forces of all the intersections between all of the mains and crosses on the stringbed. Only then will the strings move backwards, stretch, and pocket the ball. The coefficient of friction is the same and the mains and crosses still have to slide against each other when the strings pocket the ball. And when the strings snap back to their original positions either laterally or normally, they again have to overcome these frictional forces. The strings cannot move in any direction without first overcoming the frictional forces at the intersections between the mains and the crosses.

Imagine having a string that's so rough that they have teeth on them like gears. You could hit a ball perpendicular to the stringbed and when the stringbed stretched backwards to pocket the ball, the gear teeth catch each other and the stringbed never rebounds. Well, a rough multi should snap back (rebound) much more slowly due to all the frictional force, which is the same frictional force that prevents the string from snapping back at all in the lateral direction. And the opposite should be true of a slippery poly. Since it snaps back laterally so easily and quickly due to its slipperiness, it should also snap back (rebound) more easily and quickly in the perpendicular direction. However, if you hit a ball completely flat with a multi versus a poly, the multi will be much more powerful. That is contrary to the trampolining both vertically and horizontally theory.

 

[BreakPoint]

No and I have not even tried to grab him. If you miss catching a ball because of keeping your hand too rigid/stiff, then you have not grabbed it. If you manage to catch it by moving with it then you have grabbed it.

When you grab the ball, you are changing the ball's direction and spin. If the strings are moving with the ball, then the strings are not changing the ball's direction and spin. The ball is having its way with the strings instead of the strings having its way with the ball (which is what happens when you grab it).

 

[BreakPoint]

Yes and this point has been adressed and taken into consideration a long time ago.

But you have not shown me where.

I want actual times from posters here timed with a stopwatch.

 

[SpinToWin]

Povl, put BP on ignore and let's end this tedious debate, okay?

There are people that can't be reasoned with

 

[Sander001]

Frictional force is always present, whether the strings move laterally (parallel) or normally (perpendicular). When you hit a ball completely flat, so that the ball and the racquet face are perpendicular to each other and the ball sinks into the stringbed, it first has to overcome the sum of all the frictional forces of all the intersections between all of the mains and crosses on the stringbed. Only then will the strings move backwards, stretch, and pocket the ball. The coefficient of friction is the same and the mains and crosses still have to slide against each other when the strings pocket the ball. And when the strings snap back to their original positions either laterally or normally, they again have to overcome these frictional forces. The strings cannot move in any direction without first overcoming the frictional forces at the intersections between the mains and the crosses.

Imagine having a string that's so rough that they have teeth on them like gears. You could hit a ball perpendicular to the stringbed and when the stringbed stretched backwards to pocket the ball, the gear teeth catch each other and the stringbed never rebounds. Well, a rough multi should snap back (rebound) much more slowly due to all the frictional force, which is the same frictional force that prevents the string from snapping back at all in the lateral direction. And the opposite should be true of a slippery poly. Since it snaps back laterally so easily and quickly due to its slipperiness, it should also snap back (rebound) more easily and quickly in the perpendicular direction. However, if you hit a ball completely flat with a multi versus a poly, the multi will be much more powerful. That is contrary to the trampolining both vertically and horizontally theory.

Either you're trolling or you're being intentionally obtuse, there is no other possible explanation for this drivel.

 

[BreakPoint]

Either you're trolling or you're being intentionally obtuse, there is no other possible explanation for this drivel.

So are you admitting you're not smart enough to understand it? Because it's incredibly simple.

The strings don't move in any direction (laterally or perpendicularly to the stringbed) without first overcoming frictional forces at the intersections between the main strings and the cross strings. There, is that simple enough for you?