All about dwell time, maybe, but only if there are enough people interested.

[NextLevel]

i really don't understand why you all can't acknowledge that pnacht speaks a language very different to you. he takes things literally and his table tennis skill is at a low level but his knowledge of physics is actually very real. no, the rubbers aren't actually under tension, it's just an expression because they feel bouncy. from a physics stand point the back swing and the follow through are not important but from a bio-mechanical stand point the do very much because NOBODY is so precise to consistently and powerfully hit the ball without a good back swing and follow through.

izra, give me a break. Isn't the whole point of my posting some of these things and the whole point of Carl's post to alert people to the fact that OP is not speaking the same language as others if they care to know, whatever you think of my taste or Carl's?

Tension and elasticity are linked concepts in physics. But OP is the same person who has said that blades do not have power, people do, or that you can produce the same spin with Mark V as with Tenergy 05. So obviously, he is look at things from a very literal and impractical standpoint. And if you defend him, sure. But it is clear to me that topsheets in modern rubbers are stretched, elastic and relatively thin and bouncy. Just like trampolines are. But if someone could always persuade me otherwise with something demonstrable, not lots of linguistic gymnastics.

From a physics/math standpoint, don't the backswing and the follow through affect the point vector you are looking at in a continuous function? And if we are going to discuss situations that do not illuminate our understanding of TT, then why should someone pretend to educate us by doing so?

Like I said, we can all sound smart on the internet. In the end, demonstration is what matters.

 

[izra]

...
Let's take the simple case where a ball with no spin is coming towards the bat face in a direction perpendicular to the plane of the face. When a ball is incoming with speed towards a rubber, it makes contact at speed, starts deforming the rubber and burying itself into it, all the while coming to a gradual stop on the surface of the rubber, and then accelerating roughly back the direction it came in and leaving with a speed not more than the incoming speed for a stationary bat, or with a speed higher than this minimal case of a stationary bat if the player moves the bat towards the ball at impact.
This process of the ball coming in with speed, losing speed, coming to a stop, then accelerating away from the bat, implies a net force on the ball, else its velocity relative to the bat would not change. From the moment the ball contacts the rubber surface to when it leaves the surface, the ball and rubber are in contact, and yet there is no equality between the force of the ball on the bat, and the bat on the ball. This is in direct opposition to our friend's claims. And this simple model is also more representative of the situation of gameplay than the ball idly sitting on the surface of the bat with "infinite dwell" as in our friend's example.

nope, he's still right. when the ball is just beginning to touch the rubber it is actually applying very little force on the rubber itself. think of it as a man jumping on a trampoline, when his toes touch the trampoline there is very little pressure on the trampoline and the force between the two only gets stronger when the man sinks deeper and gets stopped by the trampoline.

izra, give me a break. Isn't the whole point of my posting some of these things and the whole point of Carl's post to alert people to the fact that OP is not speaking the same language as others if they care to know, whatever you think of my taste or Carl's?

Tension and elasticity are linked concepts in physics. But OP is the same person who has said that blades do not have power, people do. So obviously, he is look at things from a very literal standpoint. And if you defend him, sure. But it is clear to me that topsheets in modern rubbers are stretched and relatively think and bouncy. Just like trampolines are. But if someone could always persuade me otherwise with something demonstrable, not lots of linguistic gymnastics.

From a physics/math standpoint, don't the backswing and the follow through affect the point vector you are looking at in a continuous function? And if we are going to discuss situations that do not illuminate our understanding of TT, then why should someone pretend to educate us by doing so?

Like I said, we can all sound smart on the internet. In the end, demonstration is what matters.

if the topsheet was stretched out and glued to the sponge it would curl up. maybe they stretch it at some point during the manufacturing process but if it stays the same shape and size without something or someone holding it there it's not under tension any more. the whole tension thing is just marketing because when they made the rubbers bouncy enough the rubbers started feeling like stretched out versions of their older counter parts.

speaking of a continuous function, you could make the whole swing just an inch long or even shorter and as long as you did it with enough speed you could ignore everything that happens before and after. this is where the limits of our bodies come in, so like i said: this is a matter of body mechanics more than it is of physics.

 

[Grandpa]

nope, he's still right. when the ball is just beginning to touch the rubber it is actually applying very little force on the rubber itself. think of it as a man jumping on a trampoline, when his toes touch the trampoline there is very little pressure on the trampoline and the force between the two only gets stronger when the man sinks deeper and gets stopped by the trampoline.

What you say is correct. However, it does not make his point valid. I didn't say that the force from the rubber on the rubber was constant in time, or make any comment on the behaviour of these things. Only that the ball's velocity relative to the bat changes significantly, the force is due to the impact with the bat, and this implies inequality of the force between the two forces. And all this time the ball is in contact with the rubber, directly against what our friend said. If you can directly refute any of what I have written, I'd be glad to hear it.

 

[NextLevel]

if the topsheet was stretched out and glued to the sponge it would curl up. maybe they stretch it at some point during the manufacturing process but if it stays the same shape and size without something or someone holding it there it's not under tension any more. the whole tension thing is just marketing because when they made the rubbers bouncy enough the rubbers started feeling like stretched out versions of their older counter parts.

If they said elastic topsheet, would that make you feel better? Like I said, tension and elasticity are linked concepts.

speaking of a continuous function, you could make the whole swing just an inch long or even shorter and as long as you did it with enough speed you could ignore everything that happens before and after. this is where the limits of our bodies come in, so like i said: this is a matter of body mechanics more than it is of physics.

So how is this useful to a practical player? And while I disagree with you, without it being something demonstrable, our debate is largely useless. What is far more important is that how you swing at the ball does influence the ball trajectory in practice and proper strokes in modern TT are designed to produce topspin and a reasonable clearance. And you can get the wrong impression from a statement like yours or OP and infer that follow through is only important for recovery and not for producing a desired swing trajectory.

 

[izra]

What you say is correct. However, it does not make his point valid. I didn't say that the force from the rubber on the rubber was constant in time, or make any comment on the behaviour of these things. Only that the ball's velocity relative to the bat changes significantly, the force is due to the impact with the bat, and this implies inequality of the force between the two forces. And all this time the ball is in contact with the rubber, directly against what our friend said. If you can directly refute any of what I have written, I'd be glad to hear it.

oh but you did not refute his point. he just said that in his example of a ball stationary on a bat the force caused by gravity and the force stopping the ball from moving are equal and he is exactly right. so without going further into the whole man-on-trampoline-thing, it seems you made an entire theory just to prove him wrong over something he didn't even say.

If they said elastic topsheet, would that make you feel better? Like I said, tension and elasticity are linked concepts.

it would make me feel better if you and pnacht stopped jumping at each other's throats over unimportant things. i'm telling you there is no actual tension (an unimportant point) just as i am telling him it's just an expression (an unimportant point). yet both of you seem to have a problem with it.

So how is this useful to a practical player? And while I disagree with you, without it being something demonstrable, our debate is largely useless. What is far more important is that how you swing at the ball does influence the ball trajectory in practice and proper strokes in modern TT are designed to produce topspin. And you can get the wrong impression from a statement like yours or OP and infer that follow through is only important for recovery and not for producing a desired swing trajectory.

and that's why it would be great if you stopped implying pnacht doesn't know his physics (he does) and started explaining to him why his theory isn't applicable in practical terms.

 

[Grandpa]

He said that "In all cases the force of the rubber on the ball must be roughly equal to the..... is the ball is going to stay in contact with the rubber." I showed that, in fact, in the cases that we are interested in (In play, with a ball coming towards the bat with some speed), he is wrong, and his equilibrium analysis is misguided and largely irrelevant.

 

[izra]

he said:

"In all cases the force of the rubber on the ball must be roughly equal to the force of acceleration if the ball is going to stay in contact with the rubber."

so he was still talking about a ball that is stationary on the rubber. he didn't get anywhere near a practical example, i don't see why you can't just play along before he gets to something more practical.

 

[NextLevel]

it would make me feel better if you and pnacht stopped jumping at each other's throats over unimportant things. i'm telling you there is no actual tension (an unimportant point) just as i am telling him it's just an expression (an unimportant point). yet both of you seem to have a problem with it.

Hahahaha... izra, nice description, but I don't think you know what you are talking about wrt to me and Pnatchwey. I actually wrote at more personal length to explain why I consider people like him dangerous because they don't understand enough TT to understand the limits of their thinking. Pnatchwey would not write the stuff he writes if he was a better player. Better players tend to appreciate the complexity of the issues far more.

When you *demonstrate* to me that there is no tension in the topsheet, I will agree with you. I don't disagree that the topsheet is not appreciably stretched relative the sponge. But that is not the only definition of tension.

https://thoughtsontabletennis.wordpress.com/2015/03/09/introduction-to-table-tennis-chemistry/

and that's why it would be great if you stopped implying pnacht doesn't know his physics (he does) and started explaining to him why his theory isn't applicable in practical terms.

He needs to understand table tennis before he understands the limitation of this thought process. But since you understand him so well, I will leave that to you.

 

[Grandpa]

So he said "In all cases" and you're arguing that by "All cases" he meant "this one very specific and irrelevant case". I guess we're just interpreting it differently, but I find your interpretation absurd. Add to that that all his following comments only included equilibrium analysis and its clear to see what he meant.

 

[izra]

if i understood correctly he was talking about a ball "staying in contact with the rubber" the whole time.

 

[izra]

pnacht i'll be here patiently waiting for you to give us all some practical insight into dwell time.

 

[TTFrenzy]

if only people spent more time actually playing the game than analyzing

no excuses please, you can always do shadow practice at home!!

 

[fais]

Break it down. Acceleration and velocity can be treated differently. Velocity is deflected using the conservation of momentum and acceleration is neutralized (equal and opposite reaction).

A ball resting on the paddle is exerting an acceleration due to the force of gravity, which is neutralized/cancelled with the paddle "pushing back" with equal and opposite force.

A ball bouncing on the paddle has the velocity reflected based on the coefficient of restitution of the contact surfaces.

 

[pgpg]

if i understood correctly he was talking about a ball "staying in contact with the rubber" the whole time.

And I'm still waiting for a decent explanation why his particular example matters as far as TT is concerned.

The gist of original post: "Dwell time is a hot topic in TT, but no one knows anything. It's a myth anyway. Did you know that dwell time can be infinite? Look at the ball sitting on the paddle and doing nothing, so it's irrelevant. If you want more deep insights like this, I'll explain it to you in simple words you can understand".

Meanwhile here I am playing with my slingshot - telling me that it does not work if you just put a small stone in there and lay it down on the ground, is not really that profound.

 

[TTFrenzy]

And I'm still waiting for a decent explanation why his particular example matters as far as TT is concerned.

The gist of original post: "Dwell time is a hot topic in TT, but no one knows anything. It's a myth anyway. Did you know that dwell time can be infinite? Look at the ball sitting on the paddle and doing nothing, so it's irrelevant. If you want more deep insights like this, I'll explain it to you in simple words you can understand".

Meanwhile here I am playing with my slingshot - telling me that it does not work if you just put a small stone in there and lay it down on the ground, is not really that profound.

couldnt agree more. im fed up reading too much scientific analysis about the obvious. scientific theory is a depiction of reality using mathematics and physics in this case. scientific explanation of why and when the dwell time is infinite or "you produce spin & speed/control not the paddle" is plain useless

pnachtwey is acting like a poser & attention prostitute (i didnt say whore, dont ban me pls )

 

[BeGo]

Dear All,

Is anyone of You got speed camera?

Looking for a video for table tennis ball impact on table tennis blade.



Sent from my S5G using Tapatalk

 

[Pnachtwey]

Hahahaha... izra, nice description, but I don't think you know what you are talking about wrt to me and Pnatchwey. I actually wrote at more personal length to explain why I consider people like him dangerous because they don't understand enough TT to understand the limits of their thinking. Pnatchwey would not write the stuff he writes if he was a better player. Better players tend to appreciate the complexity of the issues far more.

Math and physics are the same for everyone. There isn't my physics or math and your physics and math and every one else's physic and math like one the fool moderators on mytt suggested.
Steven Hawking can't play at all so you must think he is the stupidest of all people on earth. Your 'logic' escapes me.

When you *demonstrate* to me that there is no tension in the topsheet, I will agree with you.

This is easy. There is nothing holding keeping the top sheet stretched. Cole of Colestt even said that when they separated the top sheet from the sponge the top sheet didn't shrink.

I don't disagree that the topsheet is not appreciably stretched relative the sponge. But that is not the only definition of tension.

https://thoughtsontabletennis.wordpress.com/2015/03/09/introduction-to-table-tennis-chemistry/

I talked to JacekGM about this on the other forum. There are all sorts of pushing and pulling going on internally at a molecular level in a rubber but they they must balance out or the rubber will either shrink or expand until the forces equalize. There is even tension at the nuclear level. Everything has tension. Imagine that. Now where is this tension that TT players talk about? If I take this top sheet that you say isn't appreciably stressed and chop it up into 1 cm squares to they shrink? If I chop it up into even smaller pieces will the shrink? How small must the top sheet be chopped into to see any shrinkage due to tension?

At the level of a TT ball and paddle there is no tension. Again if there was the rubber would shrink until tension was relieved or some opposing force kept the tension from shrinking the rubber any more. The article doesn't explain what keeps the polymers in tension. There still must be an opposing force to keep anything in tension from shrinking.

I am playing with you but I am also wasting my time.

He needs to understand table tennis before he understands the limitation of this thought process.

I understand much better than you do wannabee. There aren't any limitations to my though process.

But since you understand him so well, I will leave that to you.

The problem is that you don't understand anything. You are the typical go along to get along guy that doesn't questions myths and do much to propagate them. That is not helping TT as a sport. You went along with all the fools on the other forum on this topic and others. Don't feel too bad. There are a lot of fools on those forums.

Now lets play a different game. If you are so damn smart why don't you tell us how tension would make a rubber play better if it exists. I DARE YOU! I will play with you like a cat plays with a mouse. In the end it would only be helpful if this mythical tension increases the COR. The article above doesn't say how tension helps with the COR. It doesn't even mention COR. So what good is tension if it exists? I am talking about at the level of balls and paddles and not molecules and atoms.

Also tension and elasticity are two different things. Tension is a force. Elasticity is the ability for things to return to their normal shape and size after any distorting force has been remove. Things can be elastic without being in tension. Things in tension may or may not be elastic. YOU ARE WRONG AGAIN. You are thinking of an elastic modulus.

So what have you done of any significance besides hit a TT ball around that proves you really know something?

You really should have heeded your own advice and ignored this thread.
BTW, the video above still shows I can return extremely spinny back spin balls with T25 which is something you said you couldn't do. So how is it that a self proclaimed know it all TT player has problems return chopped balls with T25?

Keep it up NextLevel. I don't forget. I don't forgive.
So now you are on the hook for explaining how tension is helpful. Ah, come on. You can do it.....well probably not.

 

[Archosaurus]

Can you produce a single post without letting your insecurity bleed through via insults?

 

[Shuki]

Why is this thread still open.

 

[NextLevel]

I talked to JacekGM about this on the other forum. There are all sorts of pushing and pulling going on internally at a molecular level in a rubber but they they must balance out or the rubber will either shrink or expand until the forces equalize. There is even tension at the nuclear level. Everything has tension. Imagine that. Now where is this tension that TT players talk about? If I take this top sheet that you say isn't appreciably stressed and chop it up into 1 cm squares to they shrink? If I chop it up into even smaller pieces will the shrink? How small must the top sheet be chopped into to see any shrinkage due to tension?

It isn't appreciably stressed relative to what? I wrote something specific which you edited. It's easy to make people sound stupid when you misquote them in the first place. If you really believe that the fact that everything has tension means that everything is equally internally stressed and that everything is equally elastic, then say so.

There is a reason the topsheet of Tenergy is far more brittle than the topsheet of Mark V after some use. Why?