Dwell Time .....

[IB66]

But what does the "touchy feelly" time have to do with the equipment?
You guys are talking about the player using the 'feel' of impact to modify strokes.
These are two different discussions.
The OP have made it clear this thread is about the blade not perception. The rest is off topic.
Tell us all. Would this blade feel like it has more "dwell time" because if vibrates longer?
[video]https://deltamotion.com/peter/TableTennis/Toxic%205%20in%20Vise.mp4[/video]
You can see the contact time is short compared to the time the paddle vibrates.

This video shows why JRS Dallas' research was misguided. Look at it carefully.
The video is shot at 2000 FPS but the paddle is in a vice so I didn't need to stand in front of hot halogen lamps.
What you should notice is that the ball leaves the paddle before the paddle can spring back to aid in the pushing the ball back. All the paddle absorbs a lot of energy when being pushed back that isn't returned to the ball. Yet you can see the paddle almost shimmer with higher frequencies that also don't help in pushing the ball back. A faster paddle will will bend a little at contact but maintain contact with the ball as it springs back. This will result in more of the impact energy being transferred back to the ball.

It is the primary mode of vibration that is important, not the fourth.
Ideally the paddle will rebound and keep in contact with the ball as long as possible to return more energy if that is what is desired. This really should be looked at through the lens of a spring board diver where the spring board is adjusted or 'tuned' be vibrate in sync with the diver.

Hi BB, please don’t take this post the wrong way, I don’t mean any disrespect and I am not trying to find fault, you are far far more qualified, knowledgeable and experienced than myself on these topics. I’m just trying to learn and see if my thoughts are somewhere near the mark, as it were!!

Touchy feely time, or perhaps the touchy feely information conveyed and received for a given impact is surely dependent on the equipment used combined with the type of impact. ??

the video was great, clearly showed the vibrations.

I take it that if the clamp were slightly looser the amount of vibration seen would be less ?? Or is that a misconception I’m making?
if the blade had a softish sponge only on it, the amount of vibration would be less?? ( if sponge absorbs impact forces)
if the sponge was harder then the vibration seen would be more than soft sponge but less than blade only??

The OP asks for ‘which blade has the longest dwell time’ so unless someone has measured the dwell time for every blade out there no one can really comment !!
Especially as the duration of impact / dwell time is really very small !!
and I would think that for a given impact Such as in the video clip, the measured differences of impact duration / dwell time for different blades are even smaller!!!

impact duration / dwell time for a different type of impact, with a blade only, say brushing impact, I (we) assume [ makes an ASS out of U and ME or could do!!) would be longer?? Blade with sponge and top sheet longer still.
Now the touchy feely information received is changed.

would the blade feel like it has more ‘dwell time’ because it vibrates longer?? Dunno !!! Reckon it would feel pretty wooden though!!!

if we can’t really comment on dwell time, then what do we have left?? The ‘feeling’ received / perceived from the impact event. So I think that’s why we talk about dwell time in terms of feeling.

These threads are ‘old hat’ to a lot of the members, but to those of us new to this site, they are as bright as a shiny new button!! So please keep going!!!!

regards

IB66

 

[Baal]

Hi BB, please don’t take this post the wrong way, I don’t mean any disrespect and I am not trying to find fault, you are far far more qualified, knowledgeable and experienced than myself on these topics. I’m just trying to learn and see if my thoughts are somewhere near the mark, as it were!!

Touchy feely time, or perhaps the touchy feely information conveyed and received for a given impact is surely dependent on the equipment used combined with the type of impact. ??

the video was great, clearly showed the vibrations.

I take it that if the clamp were slightly looser the amount of vibration seen would be less ?? Or is that a misconception I’m making?
if the blade had a softish sponge only on it, the amount of vibration would be less?? ( if sponge absorbs impact forces)
if the sponge was harder then the vibration seen would be more than soft sponge but less than blade only??

The OP asks for ‘which blade has the longest dwell time’ so unless someone has measured the dwell time for every blade out there no one can really comment !!
Especially as the duration of impact / dwell time is really very small !!
and I would think that for a given impact Such as in the video clip, the measured differences of impact duration / dwell time for different blades are even smaller!!!

impact duration / dwell time for a different type of impact, with a blade only, say brushing impact, I (we) assume [ makes an ASS out of U and ME or could do!!) would be longer?? Blade with sponge and top sheet longer still.
Now the touchy feely information received is changed.

would the blade feel like it has more ‘dwell time’ because it vibrates longer?? Dunno !!! Reckon it would feel pretty wooden though!!!

if we can’t really comment on dwell time, then what do we have left?? The ‘feeling’ received / perceived from the impact event. So I think that’s why we talk about dwell time in terms of feeling.

These threads are ‘old hat’ to a lot of the members, but to those of us new to this site, they are as bright as a shiny new button!! So please keep going!!!!

regards

IB66

See my previous two posts. Assuming that people can reliably and reproducibly sense differences in something we can call touchy feely time (because it's not the dwell time), we are thinking alike in that it may be the duration of a vibrations caused by ball impact, which may be some sort of marker for how it plays and a reult of blade composition*.

I'm not 100% convinced people can reliably discern differences in touchy feely time between different blades and I don't know if its ever been put to a proper blind test. I allow that it is certainly possible. Different blades do feel different overall. (I wonder how much we are unconsciously using sound, though).

* Arylate and zylon are liquid crystal polymers in ALC and ZLC blades and they are known to filter out high frequency vibrations, and to me this always seemed like added "dwell". So maybe we are sensing the power spectrum of the vibrations and calling it dwell.

 

[IB66]

See my previous two posts. Assuming that people can reliably and reproducibly sense differences in something we can call touchy feely time (because it's not the dwell time), we are thinking alike in that it may be the duration of a vibrations caused by ball impact, which may be some sort of marker for how it plays and a reult of blade composition*.

I'm not 100% convinced people can reliably discern differences in touchy feely time between different blades and I don't think its ever been put to a proper blind test. But it's definitely possible. Different blades do feel different overall.

* Arylate and zylon are liquid crystal polymers in ALC and ZLC blades and they are known to filter out high frequency vibrations, and to me this always seemed like added "dwell". So maybe we are sensing the power spectrum of the vibrations and calling it dwell.

Many thanks Baal,

in one of my posts I reported that it felt that a certain rubber had more Dwell, looking back I think that this ‘feel’
was probably softer, it felt like the ball sunk further into the sponge/top sheet combination, because you think that the ball penetrated further into the rubber, you assume that there must be more ‘dwell’. That the ball is being held for longer!!!

 

[IB66]

Here is another thing I wonder about. Let's say we took five offensive blades of various sorts, and ten experienced players chosen to be at a playing level close to the median of the members of this forum, whatever that is. Let's say we put Tenergy 05 on the blades. How much aggreement would there be on the relative "dwell times" of the blades? I'm guessing maybe not that much.

yeah, I think you’re right, what everyone feels is personal, also it depends what your brain is up to !!
i saw a programme about pain, pain levels felt and rated out of 10, the sort of questions asked by doctors.
this fella had suffered some really nasty burns to his legs, when the bandages were being changed this was when he reported that the pain levels were off the scale. So instead of giving pain killers before the bandages were to be changed, they plugged him into a VR head set and he had to play a basic game, throwing snowballs at penguins!!!
he had to punch a button to Chuck the snowball.
Then end result was that the pain levels were drastically reduced because his brain was concentrating on something else, he ended up almost looking forward to having the bandages changed!!!! Almost!! his perceived pain levels were rated much lower.!!!

so the variables for ‘feel’ during play also must include how ‘tuned in’ you are to receiving the feelings.
How many times have you heard someone say something like “ it was a perfect strike, I didn’t even feel the ball leave my foot, the next thing the ball was in the net !!! “

 

[brokenball]

@IB66 I know that different blades will cause the same person to perceive similar impacts differently.
In the end we are going to play with what ever we like.

Loosening the clamp would probably have no effect until the paddle dropped out of the vise. Wrapping the paddle's handle in cloth before putting in the vise would sure damping the vibrations a little.
The second paddle is a Toxic 5 that I used as a my favorite hard bat. There is no sponge so the rubber seems harder than normal inverted rubber. The ball rebounds differently off the paddle depending on how far the ball impacts the blade from the handle.

The dwell time for the blades is going to be pretty much the same because it will be dominated by how the ball pushes off the blade. In effect there are two springs, the blade and the ball. Both will compress or bend a little at impact. For maximum COR the two items should return to initial state while still in contact. If the ball pushes off the blade or rubber too quickly some energy in the blade is lost.

The harder or softer sponge question is a good one. In any system that oscillates, extra mass slows down the frequency of oscillation. Stiffer rubbers will tend to damping the oscillation by keeping the blade from flexing. It is hard to relate that to hard and soft because a material that is hard may be thing and light weight so not reduce the frequency or damping much.

The second video is a hard bat but most of us play with double inverted. In this interaction of the sponge and ball will dominate the dwell time. The first video doesn't show any vibration or flex in the paddle at all because the blade is thick.


@Baal, you should know of a better term for the time it takes to sense or the length of time one senses the ball.
Dwell time should be the contact time and stick to the proper definition. In engineering terms it is a time when the state ( position, velocity , acceleration ) is stationary. In motion control, dwell time is the time an actuator will be still at the end of a move.
Baal should find us a medical term for this phenomena.
I had to laugh when you used my term "touchy feelly"

@gwenved. The OP was asking about equipment.
There have been statements made on this thread that dwell time increases spin. I have shown in a video that that if the ball bounces of the blade before the blade can rebound that energy is lost.
Again, people should relate this to a spring board diver.
Dwell times as long as 10 ms are extremely rare.

 

[IB66]

@IB66 I know that different blades will cause the same person to perceive similar impacts differently.
In the end we are going to play with what ever we like.

Loosening the clamp would probably have no effect until the paddle dropped out of the vise. Wrapping the paddle's handle in cloth before putting in the vise would sure damping the vibrations a little.
The second paddle is a Toxic 5 that I used as a my favorite hard bat. There is no sponge so the rubber seems harder than normal inverted rubber. The ball rebounds differently off the paddle depending on how far the ball impacts the blade from the handle.

The dwell time for the blades is going to be pretty much the same because it will be dominated by how the ball pushes off the blade. In effect there are two springs, the blade and the ball. Both will compress or bend a little at impact. For maximum COR the two items should return to initial state while still in contact. If the ball pushes off the blade or rubber too quickly some energy in the blade is lost.

The harder or softer sponge question is a good one. In any system that oscillates, extra mass slows down the frequency of oscillation. Stiffer rubbers will tend to damping the oscillation by keeping the blade from flexing. It is hard to relate that to hard and soft because a material that is hard may be thing and light weight so not reduce the frequency or damping much.

The second video is a hard bat but most of us play with double inverted. In this interaction of the sponge and ball will dominate the dwell time. The first video doesn't show any vibration or flex in the paddle at all because the blade is thick.


@Baal, you should know of a better term for the time it takes to sense or the length of time one senses the ball.
Dwell time should be the contact time and stick to the proper definition. In engineering terms it is a time when the state ( position, velocity , acceleration ) is stationary. In motion control, dwell time is the time an actuator will be still at the end of a move.
Baal should find us a medical term for this phenomena.
I had to laugh when you used my term "touchy feelly"

@gwenved. The OP was asking about equipment.
There have been statements made on this thread that dwell time increases spin. I have shown in a video that that if the ball bounces of the blade before the blade can rebound that energy is lost.
Again, people should relate this to a spring board diver.
Dwell times as long as 10 ms are extremely rare.

yeah Touchy feely has a few connotations!!!
I’m in the lounge , it’s fairly late here and by the sounds of it my neighbours are having a touchy feely duration right now !!!

 

[Baal]

I will hereafter just refer to it as TFT (touchy feely time), because abbreviations make it sound scientific.

I could use a term like "perceived dwell" or "subjective ball contact time " .

But TFT has many advantages and is consistent with Rule 88.

 

[UpSideDownCarl]

[video]https://deltamotion.com/peter/TableTennis/Toxic%205%20in%20Vise.mp4[/video]

I have to say, that is a great video.

 

[Gwenved]

@gwenved. The OP was asking about equipment.
There have been statements made on this thread that dwell time increases spin. I have shown in a video that that if the ball bounces of the blade before the blade can rebound that energy is lost.
Again, people should relate this to a spring board diver.
Dwell times as long as 10 ms are extremely rare.

Hi Brokenball, I put 10 milliseconds as 1 milliseconds, I don't know exactely how long it is apart some miliseconds. It's just to explain you have for the same dwell time a lot of possibilities.

That's not dwell time who increase the spin but the material you use and your stroke.

Regards

 

[Liquid Sky]

There ist scientific evidence that the dwell time is quite constant at about a thousand of a second.
This is so short that I highly doubt that anybody is able to recognize differences in the dwell time by playing with different rackets.

For me the concept of dwell time therefore does not make a lot of sense.

However what you really notice is that at the point of ball - racket contact different amount of "deformation" is taking place: at the same amount of force softer rubbers stretch more, flexible blades bend more,...

So my guess is that players feel that there is difference in the amount of "deformation" and the term "dwell time" is used to describe that, although there is scientific evidence that more deformation does not necessarily take more time.

 

[brokenball]

There ist scientific evidence that the dwell time is quite constant at about a thousand of a second.
This is so short that I highly doubt that anybody is able to recognize differences in the dwell time by playing with different rackets.

For me the concept of dwell time therefore does not make a lot of sense.

However what you really notice is that at the point of ball - racket contact different amount of "deformation" is taking place: at the same amount of force softer rubbers stretch more, flexible blades bend more,...

So my guess is that players feel that there is difference in the amount of "deformation" and the term "dwell time" is used to describe that, although there is scientific evidence that more deformation does not necessarily take more time.

While I agree that dwell time is too short for people to notice the difference, I don't agree the dwell time is constant. It will vary with impact speed. If the ball impacts the paddle at 20 m/s vs 10 m/s the dwell time will be much shorter. Does that mean one will get less spin when impacting the ball at 20 m/s? No! What really matters is the impulse applied to the ball. That is the force over time. An impulse is ∫f(t)*dt over the dwell time. If the force is constant this simplifies to Fx∆t. The problem is that the force is not constant because is is small at first contact and increases with penetration into the rubber.

My point is that the impulse can also be tangential and create spin. Increasing dwell time doesn't necessarily increase spin. Increasing the tangential impulse does.

 

[Liquid Sky]

While I agree that dwell time is too short for people to notice the difference, I don't agree the dwell time is constant. It will vary with impact speed. If the ball impacts the paddle at 20 m/s vs 10 m/s the dwell time will be much shorter. Does that mean one will get less spin when impacting the ball at 20 m/s? No! What really matters is the impulse applied to the ball. That is the force over time. An impulse is ∫f(t)*dt over the dwell time. If the force is constant this simplifies to Fx∆t. The problem is that the force is not constant because is is small at first contact and increases with penetration into the rubber.

My point is that the impulse can also be tangential and create spin. Increasing dwell time doesn't necessarily increase spin. Increasing the tangential impulse does.

When I wrote that there is scientific evidence, then I meant that there are scientists that actually measured the dwell time! They found that the dwell time is more or less constant at around 1/1000s.

To me that means that dwell time varies in a magnitude of less than 1/1000 of a second.

I can feel that the ball-rubber-blade interaction can be quite different but
I don't think that it is the difference in dwell time that people are feeling.

 

[brokenball]

When I wrote that there is scientific evidence, then I meant that there are scientists that actually measured the dwell time!

How?

They found that the dwell time is more or less constant at around 1/1000s.

To me that means that dwell time varies in a magnitude of less than 1/1000 of a second.

I don't consider 1ms ± 1ms to be very constant. That is a lot of variation relative to the average.

 

[Baal]

Even if the dwell time varied by much less than 1 ms or about 1 ms, I doubt we could sense the difference.

TFT is measuring something else.

The vibrations BB shows in his amazing video are obviously lasting a lot longer than the dwell time.

 

[Liquid Sky]

...I don't consider 1ms ± 1ms to be very constant. That is a lot of variation relative to the average.

Who said 1ms+-1ms ???

 

[langel]

In real play the actual dwell time of every single shot is different and may vary in great margins.
The dwell time depends on many factors, but the most important is the particular technique used for the shot, so it depends on the player, not the equipment. Equipment matters, meaning that a player A can feel the best and be most effective on certain techniques with setup X, but for the same techniques player B would prefer setup Y.
With that respect synthetic tests on blade dwell make no sense.
An experienced player can hold the ball with a 1 meter motion, accelerating it from almost 0 m/s to 10, 20 or 40 m/s and the resulting dwell time will be from 1/5 of the second to 1/20 of the second. And thats between 200 and 50 times longer than the synthetic dwell of the blade. Or it may be a sharp 1 inch snap and the dwell will be really short.

 

[Liquid Sky]

@langel
I wonder where you have those numbers from? Assumptions?

I was talking about information that was provided by Dr. Nicklas (founder of Donic and ESN, https://www.esn-tt.de/en/company/history).

To me this guy looks like he might know what he is talking about.

 

[langel]

Those numbers do not need a comp, calc, or even a pen and paper.

Those guys do know what they are talking about.

But I start to think that to understand what they are talking about, one must be able to find these numbers with no need of a comp, calc, or even a pen and paper.

 

[Liquid Sky]

Those numbers do not need a comp, calc, or even a pen and paper.

Those guys do know what they are talking about.

But I start to think that to understand what they are talking about, one must be able to find these numbers with no need of a comp, calc, or even a pen and paper.

Oh, I see!!
So only assumptions...

 

[brokenball]

Just when I though this matter was getting settled.

The dwell time depends on many factors, but the most important is the particular technique used for the shot, so it depends on the player, not the equipment.

It depends mostly on impact speed.

An experienced player can hold the ball with a 1 meter motion, accelerating it from almost 0 m/s to 10, 20 or 40 m/s and the resulting dwell time will be from 1/5 of the second to 1/20 of the second.

Definitely wrong! The numbers are way too long. Look at the videos.

And thats between 200 and 50 times longer than the synthetic dwell of the blade. Or it may be a sharp 1 inch snap and the dwell will be really short.

What is a synthetic dwell time?

The dwell time is the time the ball is in contact with the rubber.