Dwell Time .....

[UpSideDownCarl]

how long ? idk I never measured this lol.

You get a feeling for weather the blade has a long or short dwell time by playing alot of different blades.
You really feel if the ball sticks into your racket or if it gets like pushed out immediately.

with the innerforce technology you dont have an outer carbon. You have limba wood which is really soft. So the balls sticks into the limba wood first before it hits the carbon.
And this longers the dwell time compared to outer carbon blades where the ball like "explodes" as soon as it hits the blade due to the outer carbon fibre.

If you are more of a spinny player I´d recommend a soft outer wood because you will simply get more spin with it.
and if you´re the hitter you can go for something really fast, hard and stiff.


Correct me if anything´s wrong

I think his point was that a feeling based on vibrations that continue long after the ball is gone is not actual dwell time and what people are feeling and calling dwell time is not the actual time the ball is on the blade face.

You can think about it this way: a good stroke is, maybe a second long in the first place. The racket travels about a meter (3 feet) in a full FH stroke in about a second. If the ball was on the racket for about 3mm (1/10 of an inch) which is a very generous assumption, then how long could dwell time possibly be? And usually it is shorter than that.

So, again, what you are feeling as dwell time is valuable for choosing a racket but it is not actually the time the ball is on the surface of the racket. And as Baal has already said, the amount of time the ball is on the racket is shorter than the amount of time it would take for the nerve impulse to get from your hand to your brain.

Now look at brokenball's video that shows how the vibrations of the blade continue long after the ball has left the racket.

 

[zyu81]

A quick question for hard-headed engineer. Have you used one before? If so, share how it feels in actual play. Otherwise, it gets us nowhere.

No, no, no. Sensation, feeling and perception have nothing to do with playing table tennis. It's strictly governed by the laws of science.

 

[brokenball]

I can't believe it.
You guys can't separate the paddle from the player after over a decade.
Perception and feelings don't change facts.
No one is calibrated do measure intervals as short as microseconds.
The claim above was about inner force technology not perception and feelings.
Perception and feelings are a personal feature/problem.

If you want to increase dwell time then decrease normal impact speed. Brushing will reduce the normal impact speed. This will have a MUCH bigger affect on dwell time than the blade. It will also increase the resulting spin relative to speed.

My questions above were not answered.

 

[zyu81]

If you want to increase dwell time then decrease normal impact speed. Brushing will reduce the normal impact speed. This will have a MUCH bigger affect on dwell time than the blade. It will also increase the resulting spin relative to speed.

My questions above were not answered.

Let me flip the question on you. What will this look like and result in during a table tennis match? What sort of outcomes will there be on the player and opponent? What will happen if you "decrease normal impact speed and brush more" in the context of a point being played?

 

[UpSideDownCarl]

I do think it would be worth it if you guys realized you are talking past each other and on one side people are talking about what they feel and on the other the actual time the ball is on the rubber and blade face is being discussed. Each of these pieces of information has a value. But arguing past each other may not.

How you touch the ball in TT is very important to higher level skills. What you feel in your hand is also very helpful. You might not be able to do much consciously about what you feel on a shot by shot basis. But part of why what you feel--and a blade, like an all wood blade, that gives a decent amount of feedback at frequencies usually blocked by the dampening effects of carbon--helps a developing player learn to get more spin is that you feel when the contact was not good, because it FEELS BAD; and you feel when the contact is good, because the contact FEELS GOOD. Where a carbon blade, even when quality of contact is suboptimal, a lower or mid level player may still feel something good from the mistake and the blade may cause the shot to be a little better than it should be because the carbon still propels the ball out.

How does this help a developing player: over time; on a sub-cortical level (that means, it is not on a conscious level). The player starts to feel how to make those contacts that just feel really good on a more and more consistent basis and as that happens, with less effort, the player gets both more spin and more power.

I also have a feeling that one reason a blade with more flex is useful to a player getting more spin and more control is precisely because the rebound of the flex is much too slow to propel the ball out sooner. So, FOR THE DAMPENING EFFECT of the flex. Just like, sponge does not increase speed. It increases dampening which actually makes it so you can swing harder and keep control if you are making tangential (spin) contact. So, you may be able to hit the ball faster without losing control if you use thicker sponge, but that is because you can put more effort in and use the spin to control the arc of the ball onto the table. I think something similar may be going on with why a blade that is slightly slower and has more flex (vibrations) and why it gives a player more control and an increased ability to learn spin contact. Once a player has a decent quality of contact and can get high levels of spin, it stops mattering what kind or speed of blade he/she uses.

In any case, it is worth distinguishing what you feel from how long the ball is on the blade face. But are important subjects. But they are not the same.

 

[zeio]

Didn't feel like typing out all this crap, but it's necessary or this won't get anywhere.

Below is what I've collected after The Great Brainstorming of 2012.

The dwell we feel and actual dwell time are actually related. The actual dwell time has a direct influence on the vibrations that are excited. Vibrations with a period shorter than the actual dwell time are strongly suppressed. In a way, it's like a footprint, from which you can tell a number of things about the living being that left it behind. You can't tell exactly but you get a rough idea, a ballpark figure, so to speak.

For tennis, the membrane modes(string-bed vibration) are said to have a strong influence on dwell-time and racket power, but has little to do with feel since they don't involve vibration of the handle.

For table tennis, however, the membrane modes could have an influence on feel since the thumb and index finger could touch the blade head. The frequency of the 1st membrane mode for a hand-held racket(blade+rubbers) also falls within the upper end of the Pacinian corpuscle(20-1000Hz). Therefore, there's reason to believe we could feel the membrane mode unlike other racket sports.

Unfortunately, I'm not aware of any table tennis studies or papers that look at both dwell time and the higher modes of vibration. The closest one from Taiwan looks at the dwell time and only the fundamental mode.

 

[brokenball]

Didn't feel like typing out all this crap,.....

The dwell we feel and actual dwell time are actually related. The actual dwell time has a direct influence on the vibrations that are excited.

Notice I made no comment about your post.
The second paragraph

Now that it is established the duration of dwell is generally too short for a normal person to distinguish, it looks like the perception of dwell comes instead from the intensity of a stimulus, as vibration in this case.
[/quote=zeio]
I made no comment about this statement years ago but what you feel is not actual dwell time.

The question next is whether the half-period of vibration of the racket correlates with the dwell time of the ball on the rubber. The half-period is the time it takes for the racket to go from its equilibrium position to fully deflected by the ball and then return to its undeflected position.

Again, I made no comment then because it is a good question. However, TT is not tennis.
If you look at my Toxic5 video you can see the blade is very slow and what you call a half cycle is much longer than the dwell time as in the tennis example. However, that isn't true for my Firewall+ ( see video ).

The question about whether the rubber stays in contact with the rubber is a good question. I doubt that it does but faster rubbers will stay in contact with the ball longer thus returning more energy to the ball.
You can see that my toxic 5 blade returns very little energy to the ball. Most of the "spring" is in what little the pips provide and the deformation of the ball but I can't see the ball deform in the video because of the low resolution.

Zeio's question is also a challenge to JRSDallas's data. I agree that the half cycle time or fundamental frequency is much more important than 4th harmonics.

I remember Anton's obscure question. I posted a link to a video made by Tackshow123 where he was catching the ball. Basically showing that dwell time can be infinite. The tread went on and on because people couldn't separate contact time from the 'touchy feelly' time. Now years later the problem still persists.

 

[zeio]

Apparently that shows you don't understand the different modes at work here. What you're seeing in your slo-mo doesn't exist with a hand-held racket. There's a fitting name for that mode. The fundamental mode of a hand-held racket is different. The higher modes are difficult to capture on video. You need a vibrometer for those. They DO have a contribution in the ball-racket interaction.

My question then was also not a challenge to JRSDallas's data. If anything, what I've come across is consistent with what he has written over the years.

That's it. I've shared what I know so far.

 

[zeio]

No, no, no. Sensation, feeling and perception have nothing to do with playing table tennis. It's strictly governed by the laws of science.

TBH, I want all the time I've wasted back, when I witnessed that FH stroke the first as well as the last time.

All this knowledge is, frankly, helpless in improving play. I got to where I was as a player before all that by playing. Knowing all that only helps to explain/clarify what's really happening, why I'm doing that intuitively etc. It doesn't help/alleviate the burden of choosing equipment either, because you still need to get yourself one to tell how it plays in real life. Last but not least, I've never discussed all this shit at the club because I'm there to play, not to convert.

 

[Der_Echte]

Hmmm... I wonder what the dwell time of Carl's trap door would meter out to be... as the Goonies fall under and slide down the chute to his underground septic basement tank...

Carl, any prelim data on that yet? Is it any longer or short depenting on if you baited the entrence wile a pile of national H3 or your consultant friend in the mini-dress...

 

[brokenball]

Apparently that shows you don't understand the different modes at work here.

A claim without showing the example of what I don't understand.

What you're seeing in your slo-mo doesn't exist with a hand-held racket.

Another vague claim. What exactly are you saying doesn't exist with a hand-held racket?
You didn't see the video where I was holding the Firewall+. No vibration is visible there. I admit the video quality is poor.

There's a fitting name for that mode.

What name? Vague again.

The fundamental mode of a hand-held racket is different.

Why? Did the fundamental node change change?
If the handle flexes then I can see how the fundamental mode would change depending on how high you choke up on the handle but if the handle is stiff then the fundamental mode will not change. The hand will provide more damping than a vise. The damped frequency of oscillation will change because of the change in damping.

The higher modes are difficult to capture on video. You need a vibrometer for those.

While I agree the higher modes are difficult to capture with most paddles you can see the Toxic 5 has a couple of modes that can be seen. A vibrometer usually only indicates the lowest frequency of vibration. It would be better to get a high frequency accelerometer and a spectrum analyzer that way all the frequencies can be seen.

They DO have a contribution in the ball-racket interaction.

How do the higher modes contribute to the impact? Again you make a general statement without proof.
What are the amplitudes of the higher modes? Are the amplitudes of the higher harmonics big enough to have any affect? How does the rubber affect the higher modes?
If they do the effect is extremely small. I would like to see an example where the effects are noticeable.

My question then was also not a challenge to JRSDallas's data. If anything, what I've come across is consistnt with what he has written over the years.

What is consistent? Faster paddles vibrate at higher frequencies? If the paddle vibrates at 500Hz is fast. It s paddle the vibrates and 2000 Hz faster? 4 times as fast? Even after rubber is applied?

Last but not least, I've never discussed all this shit at the club because they are there to play, not to get lectured.

I agree that knowing about dwell time really has nothing to do with actual play. I bet the programmers that program the Omron robot don't even consider dwell time. I can't see were dwell time is part of any speed or spin after impact calculations. So why are people obsessed with dwell time?

 

[Hysteresis]

I agree that knowing about dwell time really has nothing to do with actual play. I bet the programmers that program the Omron robot don't even consider dwell time. I can't see were dwell time is part of any speed or spin after impact calculations. So why are people obsessed with dwell time?

To be fair the Omron robot measures spin but does not apply much of it itself. A (good, relatively orthodox) human player doesn't play anything like that.

I think people are obsessed with dwell time, because they are told more dwell time is good (or at least, equals more spin), which has some merit under certain conditions. They just don't understand what those conditions are.

Given the same equipment, playing a (let's say topspin) shot of equal ballspeed, a shot with more dwell, whether physical or perceived, probably will have more spin.

If you are switching equipment, however, dwell time, physical or perceived, probably tells you nothing useful.

People just haven't had it clarified that dwell time is useful feedback for your stroke, not your blade or rubber.

 

[zeio]

Play both at the same time to "feel the vibe-ration"!

 

[Baal]

To be fair the Omron robot measures spin but does not apply much of it itself. A (good, relatively orthodox) human player doesn't play anything like that.

I think people are obsessed with dwell time, because they are told more dwell time is good (or at least, equals more spin), which has some merit under certain conditions. They just don't understand what those conditions are.

Given the same equipment, playing a (let's say topspin) shot of equal ballspeed, a shot with more dwell, whether physical or perceived, probably will have more spin.

If you are switching equipment, however, dwell time, physical or perceived, probably tells you nothing useful.

People just haven't had it clarified that dwell time is useful feedback for your stroke, not your blade or rubber.

We could suppose this but I would not believe it in the absence of reliable data demonstrating it, key words being reliable and data.

 

[UpSideDownCarl]

Play both at the same time to "feel the vibe-ration"!

I do think this sums things up more completely than anything else I have yet read on the subject.

 

[brokenball]

I think people are obsessed with dwell time, because they are told more dwell time is good (or at least, equals more spin), which has some merit under certain conditions. They just don't understand what those conditions are.

The key words are "People are told". By whom?
It is the brush stroke that is good for more spin. When brushing the dwell time will be longer because the normal speed of impact is slower. Longer dwell time is the result of lower impact speeds and thicker rubbers.

Given the same equipment, playing a (let's say topspin) shot of equal ballspeed, a shot with more dwell, whether physical or perceived, probably will have more spin.

However, it is the impulse ( force over time ) that determines the trajectory and spin. The force can e high over a short time or low over the a longer time and still end up with the same results.

Show me an equation that uses dwell time to calculate spin. Anybody? Please? Pretty please?

Notice that Zeio makes is vague attacks but can't back them up.
I think Zeio should tell us about reduced mass. ( from an old post on mytt ).

To be fair the Omron robot measures spin but does not apply much of it itself. A (good, relatively orthodox) human player doesn't play anything like that.

In the videos between Dan and the robot I couldn't see where the balls were marked so the robot could see spin. It probably used info from Dan's paddle and stroke. It is also possible to estimated the spin by fitting a differential equation to the data gained from the trajectory.

If the robot tried to generate spin the paddle speed would need to be much higher. The machine would probably shake itself to pieces in no time.

I am finishing up an simulation of the impact with the paddle. The impact itself is easy because it is similar to many other applications I have done before. The tricky part was actually raised by zieo above. Actually it was in the mytt thread. When the ball starts its rebound, how long does the rubber stay in contact with the ball?
The rubber can be modeled as a spring with a spring constant and damping. The damping is rather high since I have seen no cases where the rubber oscillates in and out after impact. This means the damping is over damped. If the rubber starts the rebound in contact with the ball but starts slowing down due to the damping as it reaches the original position then sometime while the rubber is expanding it will start moving slower than the ball. This means all the energy the rubber still has is not returned to the ball.

 

[zeio]

That means you haven't seen enough. Rubbers, particularly those with porous sponge, do oscillate in and out after impact, like waves. As I wrote, I have high speed footage but that still won't get us anywhere, only more bickering. I even have the dwell time for different strokes performed by actual players.

 

[Hysteresis]

The key words are "People are told". By whom?
It is the brush stroke that is good for more spin. When brushing the dwell time will be longer because the normal speed of impact is slower.

In the videos between Dan and the robot I couldn't see where the balls were marked so the robot could see spin. It probably used info from Dan's paddle and stroke. It is also possible to estimated the spin by fitting a differential equation to the data gained from the trajectory.

If the robot tried to generate spin the paddle speed would need to be much higher. The machine would probably shake itself to pieces in no time.

Pretty sure you are overthinking this. Normal people on a TT forum don't care to find exact mathematical relations between really any two measurements, especially those actually asking 'which blade has the most dwell time', which in the context of actually playing TT isn't very relevant or useful.

Pretty sure when these people are being told that more dwell time is good, by coaches, other players, or just other people on a forum, 'Dwell time' is just being used as a byword for brushing contact or being passed on as a truism by people who've been told that but don't quite understand the implication.

As for the robot, there is a paper published on that on the Omron site ( kyohei et all) that has a section exactly on dealing with spin estimation. The paper phrases it in terms of calculating the spin from the 'error' between measured position and expected position of a non-spinning ball. But the actual equations used looks awfully like a reorganisation of just fitting spin into the trajectory calculations to me.

My point with the robot however, is that normal human players don't play like the Omron robot, and don't need to (and can't) solve differential equations while playing TT. What is useful for the robot might not be able to a human player and vice versa. It just so happens in this case it's useful to neither.

 

[zeio]

One last post before I stop wasting more life force on this shit.

It's become increasingly clear from the findings in recent years that some ball-racket interactions in actual play are difficult to reproduce in laboratory settings. That means what you observe in the lab is not necessarily an adequate representation of what takes place in the field.

An example is the player grip. It's difficult to model in experiments. Changes in grip pressure affect how the racket behaves and this alone affects how different players perceive the feel and stiffness of the same racket. It's always wise to appreciate the player experience as something tangible and valuable, rather than dismissing it as illusory and disposable.

Can't believe I still remember writing this nearly 1 decade ago when all this shit started...
http://mytabletennis.net/forum/foru...PID=483657&title=paddle-mass-and-speed#483657

There must be a reason when various people feel(as in notice, albeit infinitesimal) a correlation between higher ball velocity and greater paddle mass. As a responsible person who work in the science field, one should, based on all information and knowledge available to him/her at the time, arrive at a reasonable conclusion for a common phenonmenon observed by many others after putting across mathematical explanations supported by experimental data and NOT come up with some shaky assumptions and self-justification that go against empirical evidence and force them on others.

https://www.butterfly.co.jp/story/alc/latter_part.html

例えば、ボル選手は『ラケットAがラケットBよりも弾む』と評価して、水谷選手は『ラケットAはラケットBよりも弾まない』と評価するような場合です。そうした場合、私たちは『ボル選手にとっての弾みとはこういうことで、水谷選手にとっての弾みとはこういうことを意味するのだろう』と推測するしかありませんでした。
しかし、機械測定がより精密にできるようになってからは、客観的な評価、つまり、共通のモノサシができたわけです。そのモノサシを基準に、『この選手のこういう評価は、このような意味を持つ』と判断できるようになりました。
このように選手の感覚的な表現を数値化しやすくなったことで、『このような性能ラケットをつくりたい』と思ったときに狙った性能通りのラケットをつくることができるようになってきたのです」
こうした改善の積み重ねで、『アリレート カーボン』を搭載したラケットは、世界中でますます受け入れられていった。

For example, Boll evaluates that "racket A bounces more than racket B", and Mizutani evaluates that "racket A does not bounce more than racket B". In that case, we had no choice but to speculate that "the bounce means this for Boll, and the bounce means this for Mizutani."
However, after mechanical measurement became more precise, objective evaluation, that is, a common measuring rod, was possible. Based on that measuring rod, it has become possible to judge that "this kind of evaluation of this player has this kind of meaning."
By making it easier to quantify the player's sensory expression in this way, it has become possible to make a blade with the desired performance when thinking "I want to make such a performance blade."
With the accumulation of these improvements, blades equipped with "Arylate Carbon" have become more and more accepted all over the world.

 

[UpSideDownCarl]

This is one of the unfortunate things about this subject is that, it really appears to be rehashed arguments from a decade ago.

My recommendation is to stop posting. Think about it. If people are mentioning a thread from MyTT from a decade ago and still trying to re-litigate arguments from back then, then something is a bit off with what is going on.

There is a reason I made the post below when someone woke this thread up a month ago:

This:

I wonder if frankie knew what he was getting the whole forum into by necromancing this old dead thread back to life?

Frankie has still not made another post and people are still arguing about ancient history without being willing figure out what kind of variables are really in play.