Dwell time

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I've always wondered what dwell time really is.

It's been known that the contact duration between a ball and a blade is 1 millisecond. It's same for pimple in, out, anti and even for a blade without rubber.

Do we think the particular rubber/blade have more "dwell time" because it's more spinny? It "feels like". pimple out has less dwell time to me, but the actual contact duration is same. What is the actual cause for the sensation of more dwell?
 
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Dwell is a feeling
One can feel a good dwell vs a bad dwell even though the actual contact is 1 millisecond

Dwell definition, i'm sure you will know.
So in players vocab, it is the feeling of the rubber, and how easy one can control it
Pretty much a softer rubber offers better dwell, something more hard has less. pimple out like OX will have close to zero, whereby SP with 2.0mm soft sponge still has dwell.

So my explanation - Dwell is the felling
 
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Dwell is a feeling
One can feel a good dwell vs a bad dwell even though the actual contact is 1 millisecond

Dwell definition, i'm sure you will know.
So in players vocab, it is the feeling of the rubber, and how easy one can control it
Pretty much a softer rubber offers better dwell, something more hard has less. pimple out like OX will have close to zero, whereby SP with 2.0mm soft sponge still has dwell.

So my explanation - Dwell is the felling

But human's reaction time is 10 millisecond so we can't sense 1 millisecond of dwell time right?

I agree that softer rubber feels like it has more dwell. On the other hand, hard chinese rubber feels like it has more dwell too.
Fast and not so soft Tenergy(or MX-P) feels like it has exceptional dwell.
Hard and slow rubber such as OX has good control but feels like it has less dwell.

All of them has physical dwell time of 1 milisecond so is it the coefficient of restitution that causes the false sense of longer dwell? Or is it the stickiness of the rubber? Or it there some other facter involved?
 
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There is a classic post on this issue by killerspintt that Carl likes to quote - I hope he can find it. Killerspintt was responding to an arrogant engineer who likes to argue that dwell time is not important because it is the actual physical response is so short.

First of all, the sensation is related to the nature of the rubber and blade. The experiments this blog writer here proposes to the reader to perform with Audacity later in this blog post give you an idea of where the sensation of dwell is coming from:

https://thoughtsontabletennis.wordpress.com/2015/04/25/introduction-to-table-tennis-blade-design/

Secondly, just because the actual contact is supposedly short doesn't mean that the attempt to change the feeling doesn't have actual effects on the ball. It is like saying that only what happens when you hit the ball is important, forgetting that how you hit the ball requires a swing that accelerates, which often means that you need a backswing and a forward movement and a follow through, all of which affect how the ball is hit at contact since the swing is a continuous movement. The feeling of what happens matters, even if you think it does not.
 
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There is a classic post on this issue by killerspintt that Carl likes to quote - I hope he can find it. Killerspintt was responding to an arrogant engineer who likes to argue that dwell time is not important because it is the actual physical response is so short.

First of all, the sensation is related to the nature of the rubber and blade. The experiments this blog writer here proposes to the reader to perform with Audacity later in this blog post give you an idea of where the sensation of dwell is coming from:

https://thoughtsontabletennis.wordpress.com/2015/04/25/introduction-to-table-tennis-blade-design/

Secondly, just because the actual contact is supposedly short doesn't mean that the attempt to change the feeling doesn't have actual effects on the ball. It is like saying that only what happens when you hit the ball is important, forgetting that how you hit the ball requires a swing that accelerates, which often means that you need a backswing and a forward movement and a follow through, all of which affect how the ball is hit at contact since the swing is a continuous movement. The feeling of what happens matters, even if you think it does not.

You mean this one, right:

@Pnachtwey

If youthinks that he is looping the robot ball, clearly there is someting mistaken about looping. Once again it's only because the contact point is ultra high that the ball is going over the net (I could get this beckspin ball past the net even without moving my racket, yup with a static racket, it would be ez, same are some adjustments anyone here will be able to falt hit the ball, you just have to adjust the racket angle).
It really looks like flat hits on underspin ball, the ball is going down right after the ball contact. With the same technique it will be impossible to loop this ball with a contact point under the net.

Pnachtwey you should try the same thing but just waiting for the ball to be under the net and try to loop it back by giving it an arc, with this level of underspin (150+rev/s) just to understand what we are saying here first. Then for improvement, a good thing will be to do exactly the same exercice as we see on the second video with his play mate..........but doing it seriously, meaning huge backspin on the serve, if possible huge backspin + short serve (for more advanced players, requires far more touch than huge backspin + long serve) and then a 3rd ball FH topspin.

Here I don't see the point, the serve is long without spin, the return hardly has any backspin and then a FH topsin that is not even meant to be a winner.......there much better usage of precious training time to be done !!!!

The serves have to be REAL serves, meaning that you concentrate on it to get maxium backspin (long serve if you cannot achieve short serve with huge backspin), this way you also benefit of this training to get also better serves. The training partner takes the ball right after the bounce to input huge backspin (the more backspin you put into your serve, the more backspin yopur partner will be able to input also, while keeping the ball low) into a low a long ball into your FH and then you execute an opening FH loop or killing 3rd ball attack. Repeat it hundreds of time.

This will be truly productive.

And, one more thing, there is no meaning executing 3rd ball attack drills if you don't have, at least, a huge backspin long serve, really, there is no meaning in it.
Table tennis is a constructive sport, its not like I can begin to train someone to do killing 3rd ball attacks if this guy doesn't have the serve skills to benefit from this traing. You won't be able to do 3rd ball FH attacks if your serves are so bad that it is easy to attack your serve.
Most of time, the coach instruction, during those type of exercices, is to attack right away if the serve is long for example....

Also, 9mm balsa core, please don't tell me there is also carbon in it, like a Joola Kool or Yinhe T11, what you are lacking the more right now is touch, not even speaking about technique or anything else, it is to FEEL the ball, to feel when you are giving spin (or not), to feel when your contact is good (or not), to FEEL. This is far more important at your level than the astronomical power of a 9mm balsa core. Get a 5 ply 6mm tick allwood with a lot of flex and if possible a ton of feedbacks (vibrations, sound), something like Stiga Offensive Classic.

Pnachtwey, you are right about the fact that when you topspin a backspin ball, the ball will always rotate (in the referential of the floor), but Carl is not an engineer and what he describes can be wrong if taken litteraly but it is so true when taken from a lambda tt player with a very good feeling.

Carl is describing his feeling, he has the feeling that when he executes a very good stroke, he can "grab" the ball. As I explained, here is just the feeling of being able to deform the rubber, maximizing dwell time and spin, the feeling you get when you have good arm/wirst accelaration. He wanted to explain that there is much more than your simple way to see physics in table tennis and he's done it based on his feeling (and I'm sure he has a pretty good one, because is table tennis "intuition" based on his feeling actually matches very often the physics, even if it's not 100% accurate, but dude......Carl is not a physics nerd and an engineer like I am, or you are, he tries to describe his FEEL with mere words, thats all).

Certainly the same feeling Schlager gets on all his serves, the amazing spin is not created by raw bat speed, it is creating by a combination of very big but very short acceleration (not long enough to reach very high bat speed, as I said I think anyone here can reach higher bat speed on a pendelum serve than Schlager on most of his serves, but nobody here will come close to his level of spin). This way, Schlager is able to maximize dwell time and to deform his rubber far more than anyone of use.

This feeling, to deform the rubber much more than a usual stroke would, even on serves, has been described many time with his own words by Carl.........for example Der_Echte will call it by the famous expression "Bang Impact", a compination of "Hand pressure mastery" and huge acceleration. Werner Schlager, the Elite, is able to get this "bang impacts" even on serves.

But I trully think you lack feeling, with more feeling you will understand far better what Carl is saying, feel is the alpha of table tennis, the omega is the touch and I think it is very very difficult to get a good technique without good touch and feeling.

To me, it looks like you are wanting to overcome your lack of feeling and touch by the usage of low grade physics, and judging from the video it doesn't look like this is a good trade for your improvement, for example you think that you are doing topspins against the robot backspin, it's not true, there is no spin in your ball, you can't feel it but you can at least SEE it, your balls have no spin, just watch the video.

See this video of Freitas touch and feel :

See what he is doing at 1:15 "the backspin catcher". A guy like Carl will instantly understand what Freitas is doing and the level of touch behind it, based on his own feeling. And you won't understand this based on low grade physics applicated to table tennis, because like many scientist would do and has you said, you will consider the dwell time as few milliseconds and thuus........somehow a constant parameter. You even wanted to "expose" the "myth" of long/shord dwell time....etc....but man, a guy like Carl will instantly understand what Freitas is doing the "backspin catcher", indeed he is minimizing dwell time as much as possible, so much that the ball is keeping its backspin after multiple contacts with the rubber, try to guess what will happen with a longer dwell time, try to do it yourself and try to FEEL the ball, the dwell time...etc..., there is now way to understand it with low grade physics once again, even introducing a friction coeficient....etc...won't help you here.

Now I understand why you wanted to "expose" the "long/short dwell time myth" on your famous topic, I trully think that you lack touch and FEEL, and into your hand there is no short or long dwell time blade/rubbers/whatever and you trully believe(d ?) it was a myth. But it's not a myth, you just can't feel it.
 
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That video which shows in many ways how Marcos Freitas is able to do magic tricks with the racket and the ball as a result of his touch is pretty fun to watch.

But I think this one is worth posting as well.

I know, Liten, but sometimes it's so hard to resist.
So one more chance:
Here, Mr. Pnachtweyh, we made this one for you. It was actually just a test of one club members new GoPro.
We placed it at the net, while my buddy and me were doin' a Falkenberg Drill.
Well this is my buddy. He wasn't even swingin' fully. But we slowed it down at the right point (i hope).
Just watch how he 'grabs' the ball and spins it.


Do you actually see a slight difference to what you've been doing?? I really hope so, otherwise you might need new glasses.
I don't wanna show off but just hope you get it this time, what everybody else is seeing. (This isn't me anyway. I was the one blockin')

@Baal: does this dude look familiar?

In the pull ball in Suga D's video, you can kind of see how, as a result of the players touch, the ball does stay on longer than a normal shot.

The difference between .5 miliseconds and 1 millisecond is 100%. I would say that the dwell time on that pull ball is several times longer than the dwell time of a flat hit.

So, if someone is trying to say that dwell time is always the same regardless of what you do, I am going to say that is inaccurate. And the kind of racket you use, particularly the kind of wood, can make it easier or harder to hold the ball on the racket surface for more or less time.

So yes, there are different dwell times, not just feeling. And even if we are still dealing with ridiculously small amounts of time, a slight increase means a lot in terms of letting the rubber deform and rebound while the ball is on the surface of the rubber. Again, the difference between .5 milliseconds and 1 millisecond is a 100% time difference. And .5 milliseconds is the number Pnatchtwey kept repeating. And I would be willing to bet that the dwell time difference in that pull ball is a greater difference that .5 milliseconds to 1 millisecond.

It is clear that dwell time is not always the same.


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Thanks, Carl.

Still, to this day, as far as I'm concerned, that post by KillerspinTT is one of the best posts ever.


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You mean this one, right:
[quote="Killerspintt] [...] Also, 9mm balsa core, please don't tell me there is also carbon in it, like a Joola Kool or Yinhe T11, what you are lacking the more right now is touch, not even speaking about technique or anything else, it is to FEEL the ball, to feel when you are giving spin (or not), to feel when your contact is good (or not), to FEEL. This is far more important at your level than the astronomical power of a 9mm balsa core. Get a 5 ply 6mm tick allwood with a lot of flex and if possible a ton of feedbacks (vibrations, sound), something like Stiga Offensive Classic. [...]
[/QUOTE]

It seems that the blade makes a big difference to develop feeling.
I'm using DHS PG7...could you tell me if this is a good blade for it? I'm a beginner

I have some difficulty to brush/loop...people often tells me to brush more. Sometimes I think I made a good loop with lots of spin, but my partner is able to block without much problem. Could it be because I lack feeling?
 
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There is no way that dwell time is always EXACTLY the same. Even I can feel that nowadays.


We also need to consider that maybe we don't really feel the ball as it's on the racket as much as the forces that ensue from what happens when it's on the racket. Maybe that's why higher level players feel like the ball's on the racket for a good while.
 
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There is no way that dwell time is always EXACTLY the same. Even I can feel that nowadays.


We also need to consider that maybe we don't really feel the ball as it's on the racket as much as the forces that ensue from what happens when it's on the racket. Maybe that's why higher level players feel like the ball's on the racket for a good while.

And that's sport (and life) in general
At a different stage, ones realisation and understand will be different.
This is called progress :)
 
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How does one maximize dwell time or minimize it? Does this occur with practice, training and time? Most of the time a player would want to maximize dwell, when would a player ever want to minimize dwell time?
 
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Accelerating through the ball while spinning the ball will increase dwell time, at least to me.

If you don't accelerate, but decelerate, you will get less dwell time. The most basic** short push (or dropshot, some people like to call it) kinda of involves this. Most people are really used to accelerating through the ball, and have a hard time hitting the ball while slowing down.

**Better short pushes might involve jabbing at the ball a little bit to put a little spin on it.
 
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That video which shows in many ways how Marcos Freitas is able to do magic tricks with the racket and the ball as a result of his touch is pretty fun to watch.

But I think this one is worth posting as well.



In the pull ball in Suga D's video, you can kind of see how, as a result of the players touch, the ball does stay on longer than a normal shot.

The difference between .5 miliseconds and 1 millisecond is 100%. I would say that the dwell time on that pull ball is several times longer than the dwell time of a flat hit.

So, if someone is trying to say that dwell time is always the same regardless of what you do, I am going to say that is inaccurate. And the kind of racket you use, particularly the kind of wood, can make it easier or harder to hold the ball on the racket surface for more or less time.

So yes, there are different dwell times, not just feeling. And even if we are still dealing with ridiculously small amounts of time, a slight increase means a lot in terms of letting the rubber deform and rebound while the ball is on the surface of the rubber. Again, the difference between .5 milliseconds and 1 millisecond is a 100% time difference. And .5 milliseconds is the number Pnatchtwey kept repeating. And I would be willing to bet that the dwell time difference in that pull ball is a greater difference that .5 milliseconds to 1 millisecond.

It is clear that dwell time is not always the same.


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Nice one, Carl.
[Emoji106]
 
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Something about the way the ball-evoked vibrations are transferred to the hand gives people some sensation they interpret as "dwell", but which is in fact something else. The vibrations occur simultaneously at more than one frequency (same reason a violin sounds different from a flute even when both play the same note). The amplitude of the lowest frequency vibration is the blade flex. But higher harmonics and other frequencies give rise to other feelings like softness, buzz, dwell, etc. But the thing you are feeling is not the exact dwell. It is possible that there is something in that vibration that is some reproducible function of the actual dwell, but it would require some very expensive and difficult measurements and analysis to know for sure if that is true. You would need very accurate robot. High speed video. And very sensitive mechanical transducers connected to computers that could do spectral analysis (Fourier) of the vibrations in the handle.

Dwell times are in the 1 millisecond range (this has been measured). Human skin mechanoreceptors cannot detect responses that brief.

Pnachtway always seemed to believe that blades played themselves, (and had some strange misconception that his forehand resembled a loop). He does not know any physiology. There was another notorious engineer at MyTT who started a flame war about sensory capabilities that was pretty absurd.

When the ball strikes the blade we can feel it because the vibrations last longer than the dwell time, long enough to deform the cell membranes of nerve terminals in our skin, which themselves are soft and rubber like.
 
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The OP's question is something I've given a lot of thought to. I actually have some qualifications to answer, because I am a physiologist, and my own research actually pertains to mechanical sensation by cells (although not the cutaneous receptors in the hand that hold the blade).

Part of the issue is the mechanical compliance of the cells that detect vibration. People might have noticed sometimes if they have a cheap garden hose that when the turn on the water, it takes a while for the water to come out, and then when they turn off the valve, the water keeps coming out for awhile, as the hose stretches back into original shape. Also, very brief changes in pressure don't really cause an change in the flow rate if the hose can stretch. The compliance of the wall filters out the very brief pressure changes. (Same reason you can build an electronic filter out of capacitors and resistors). The compliance of sensory nerve cell membranes in skin will similarly not respond to a 1 millisecond long stimulus. It can't. Physically impossible (because of the compliance of the nerve cell membranes, their surrounding glial cells, and the matrix in which they are imbedded). And yet, we know from high speed video measurements that the true dwell time of ball on rubber is around 1 ms, or so, which probably varies a bit from one rubber/blade to another, but never in a range we would detect. The cells that CAN respond to very short stimuli use vibration of a cilium (for example, the hair cells in our ears).

Which raises another interesting question a golfer at OOAK FOrum once pointed out to me. Sound matters, even when we aren't aware that we are using it. An analysis of golf clubs apparently once showed that golfer's impressions of the flex of the club, and other things they care about, had a lot to do with the sound the thing made. I wonder if some of that might be true in our sport too. I rejected the idea at the time, but with time and reflection I know think he may have been on to something.

Now without question we can feel the ball striking the blade, but only because the vibrations in the setup induced by the ball last long enough for our cutaneous receptors to detect them.

Archosaurus translated what I wrote into something easy. We can't measure dwell directly with our hands. But maybe we measure something else that is related to dwell. The thing is, though, I don't think we know with 100% certainty if the thing was interpret as dwell has any relationship at all to actual dwell. I honestly can't even make an educated guess whether that idea is true or not.
 
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Actually, to elaborate on this, we have structures in our skin that are specialized for detecting changing and short stimuli, known as Pacinian corpuscles and Meisner's corpuscles. In normal life, these things help us detect textures when we rub our hand over a surface (or when we make stone tools by chipping one stone against another). They are adapted for short and rapidly changing stimuli. But even those guys are not going to respond to a 1 millisecond stimulus. Bear in mind too, that these cells fire an action potential when stimulated above their threshold, but the action potential itself will last longer than the dwell time of any racket/rubber combination. However, they must respond to the buzz of vibrations in the whole blade that occur when the ball strikes the blade because we can certainly feel that.

I share the OP's wonder that these different blades and rubbers feel as different as they do. It is quite remarkable, whether it has anything to do with dwell or not. When you know more about the underlying physiology it becomes even more amazing, not less!!!! I honestly have no idea how we are able to do this.
 
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Look, this is easy. A flat smack, a smash, a punch, very little dwell time and you are not trying to increase the dwell time with those shots. You are making direct impact and trying to hit the ball as fast as you can.

The more spin you are trying to put on the ball, the more you want to hold the ball on the rubber for longer and accelerate the speed of the racket while the ball is on the rubber.

So a racket that makes it easier to do that is good for helping you learn to spin more.

An elite amateur or a pro level player have developed the touch to do that so well that they can use pretty much any racket they want and still hold the ball on the blade long enough to get that high level of spin.

Learning that technique of holding the ball on the blade face is very important for learning to generate more spin.

As David said, there are times when you want to decelerate to get less dwell and less spin. And as I indicated, there are reasons for smacking the ball flat. And those are ways to get less dwell time.

Now, a soft blade with Limba top ply, on one of those flat hits might not get the ball going quite as fast as a blade with a harder Koto top ply. But the reason the blade with the Limba top ply is a shade slower would also allow you to hold the ball on the blade face longer.

The amount of time in milliseconds might seem incredibly small. But the different of a half a millisecond is actually huge in terms of allowing the topsheet to deform more, the sponge to compress and then rebound more and to allow the elasticity of the rubber to increase the spin.

All this is also what KillerspinTT is talking about when he references how many people can get much more racket speed that Werner Schlager but his touch is so good that he still gets more spin regardless of overall racket speed.

That info may have been in another post of KillerspinTT's. I can't remember. But he gave loads of great information on this subject.


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