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    1. Top | #141
      Hysteresis is offline
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      Quote Originally Posted by brokenball View Post
      The dwell time is the time the ball is in contact with the rubber.

      Which is why it's then weird that we are taking an estimate of the actual dwell time from a video of a head on collision of a ball with a blade with no rubber on it. Literally the one way of doing it that is likely to produce the shortest possible "dwell time".


      I know the original topic is for the dwell time of different blades, but I think at some stage we have to accept that the original question isn't really meaningful, because in a game of TT, the ball isn't supposed to be contacting the blade directly anyway.


      And while the blade MIGHT affect the dwell time, just hitting the blade head on with a ball is probably not even a remotely enlightening model of how long the ball is in contact with a rubber.

      Which brings us to:

      Quote Originally Posted by Liquid Sky View Post
      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.
      Do you have the actual study, or the context for when he made this claim? While I believe in the scientific rigour of whatever study he may have performed, the actual methodology matters a lot, and tells us a lot about what exact conclusions we can reasonably make from the results. If he did something like bounce a ball from some bats head on, then it might well be correct to say the dwell time remains mostly constant between blades, but in reality it would be a poor model for actual contact in a game situation, and actually tell us very little that is useful. If instead he took lots of extreme high frame rate video of a wide range of people playing, then it would be very compelling evidence.

      And as BB eluded to, the actual variance of these contact times, it makes a lot of difference exactly how much this time is expected to vary (assuming good and useful methodology). The mean contact time might well be 1ms, but like if BB said if this is 1ms +-1 ms, that is a pretty big difference between a long and a short contact.

      Also lets all be clear, your hand is not actually touching the ball, so irrespective of how long the actual physicial contact time is, be it 1ns or a whole minute, we will never 'feel' the actual contact, it's always inferred, the actual physical dwell time is irrelevant to whether or not we can 'feel' the contact, you are always just inferring it from whatever you do feel, be it vibrations in the blade or just the slight decceleration of the bat.

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    3. Top | #142
      langel is offline
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      Quote Originally Posted by brokenball View Post
      Just when I though this matter was getting settled.


      It depends mostly on impact speed.


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



      What is a synthetic dwell time?

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

      You have the figures, needed to do a simple calculus.

      If you can't, don't say that you're an engineer.

    4. Top | #143
      Hysteresis is offline
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      Quote Originally Posted by langel View Post
      -------------------
      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.
      --------------------

      You have the figures, needed to do a simple calculus.

      If you can't, don't say that you're an engineer.
      I don't think the calculations are the issue in this case, it's where you are getting the numbers from.

      I am deeply sceptical of this 1 meter figure, and 40m/s is faster than what a simple google search will tell you the world record is, which was made outside of normal match conditions.

    5. Top | #144
      langel is offline
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      Google more, though I'm not sure that Google can give an answer to everything, and even it could, sometimes it depends on what and how you do the search. 40m/s is 144 km/h. The max speed in TT is over 150. BUT - more adequate for the particular scenario - arm acceleration, is the max speed a baseball pitcher can deliver - 168.98 km/h. But - this maximum speed gives the shortest "dwell" in the scenario. Its much better to consider the slower max speeds with much longer dwell.

    6. Top | #145
      Dr Evil is offline
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      Quote Originally Posted by brokenball View Post
      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?
      https://deltamotion.com/peter/TableT...0in%20Vise.mp4
      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.
      Nice video, brokenball. A technical question. How exactly did you clamp the blade? Was the handle wrapped in a towel, or was the vice grip applied more directly? After reading things like this ("One might be inclined to believe that a hand-held bat should be treated more like a clamped-free (cantilever) beam. However, research has shown[1] that while the hands quickly damp the bat vibrations, a hand held grip (even tightly gripped) does not significantly change the vibrational frequencies or the modeshapes. The frequencies and shapes for a bat which is free at both ends, sufficiently describe the vibrational behavior of a held bat.") I wonder if it might be an issue. Maybe not so much; a tt blade isn't a baseball bat. But maybe it would make a meaningful difference.

      Edit: Another interesting quote from the same source: "The higher bending modes probably have little influence on the feel of the bat, but computer calculations have shown that they can significantly influence the post-impact ball speed.[3,4]"
      Last edited by Dr Evil; 1 Week Ago at 06:40 PM.

    7. Top | #146
      langel is offline
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      ... And here comes the difference between a Pitcher and a Batter...

    8. Top | #147
      Hysteresis is offline
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      Quote Originally Posted by langel View Post
      Google more, though I'm not sure that Google can give an answer to everything, and even it could, sometimes it depends on what and how you do the search. 40m/s is 144 km/h. The max speed in TT is over 150.
      Again, where are you getting these numbers?

      Because this done recently, , has Ovtcharov, straight up smashing a ball as hard as he can, out of match conditions at only 113kph.

      Sure, they've only done this between the 3 of them, and Ovtcharov is a professional TT player, not a professional 'smash the ball as hard as you can'er so Ovtcharov isn't likely to actually to just get the fastest smash ever on camera, but you'd expect he'd get close. Certainly faster than you would expect people to make in match conditions.

      But given how far away from 150 kph he is (he is after conversion, actually remarkably close to the googled record), I think your your casual and extraordinary claim that max speed is over 150 kph would require some equally extraordinary proof.
      Last edited by Hysteresis; 1 Week Ago at 07:44 PM.

    9. Top | #148
      brokenball is offline
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      Quote Originally Posted by Dr Evil View Post
      Nice video, brokenball. A technical question. How exactly did you clamp the blade? Was the handle wrapped in a towel, or was the vice grip applied more directly? After reading things like this ("One might be inclined to believe that a hand-held bat should be treated more like a clamped-free (cantilever) beam.
      In the first video I was holding the Firewall+ with T25. The second video show a Toxic 5 hard bat held firmly in a vise. The vise did have rubber pads to keep from marring the handle.

      However, research has shown[1] that while the hands quickly damp the bat vibrations, a hand held grip (even tightly gripped) does not significantly change the vibrational frequencies or the modeshapes. The frequencies and shapes for a bat which is free at both ends, sufficiently describe the vibrational behavior of a held bat.") I wonder if it might be an issue. Maybe not so much; a tt blade isn't a baseball bat. But maybe it would make a meaningful difference.
      Yes, hands will dampen the higher frequencies quickly. Although one can see all sorts of vibrations of the paddle the only thing that really matters is that the ball bounces off the paddle before the paddle itself can rebound and help push back. The energy used to deflect the paddle is lost.

      Think of jumping on a trampoline. You must time your jump to occur when the trampoline is starting to push you up. Jumping to early or too late isn't as efficient. Now one talks about how the timing of the rebounds between the rubber and the ball affects the speed after impact.

      Edit: Another interesting quote from the same source: "The higher bending modes probably have little influence on the feel of the bat, but computer calculations have shown that they can significantly influence the post-impact ball speed.[3,4]"
      If the bat springs back to keep contact with the ball then yes. I have seen high speed videos of a hard ball and bat impact and the ball deforms significantly.
      However, that is not the case in the hardball video. The ball doesn't deform in any detectable way and it leaves the paddle before it can rebound.

      I used a vice because when I was holding the paddle in the first video, I was trying to hit the ball staring into very hot and very bright lights. It was hard to even hit the ball and standing there in the hot lights wasn't an option.
      The halogen lights we had back then could melt plastic at a distance. Now I have LED lights and a color camera that is also much more sensitive so image looks more natural.

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    11. Top | #149
      langel is offline
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      Quote Originally Posted by Hysteresis View Post
      Again, where are you getting these numbers?

      Because this done recently, , has Ovtcharov, straight up smashing a ball as hard as he can, out of match conditions at only 113kph.

      Sure, they've only done this between the 3 of them, and Ovtcharov is a professional TT player, not a professional 'smash the ball as hard as you can'er so Ovtcharov isn't likely to actually to just get the fastest smash ever on camera, but you'd expect he'd get close. Certainly faster than you would expect people to make in match conditions.

      But given how far away from 150 kph he is (he is after conversion, actually remarkably close to the googled record), I think your your casual and extraordinary claim that max speed is over 150 kph would require some equally extraordinary proof.

      The TT ball is very light and once it leaves the bat it decelerates very fast.
      In the scenario we don't care about the flight speed, but the initial and the final speed of the arm swing.
      The final speed of the arm swing is the initial speed of the ball flight.
      The baseball ball is much heavier and decelerates less. So its measured speed is much closer to the final speed of the arm swing. Thats why I gave a baseball example.
      But again - for the abstract of the idea its good to look on the slower swings too, where the dwell is much longer, and extremely longer than the milliseconds, measured on static bats, snaps, etc.

    12. Top | #150
      langel is offline
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      BTW the initial speed of the ball on that snap should be very close to 150 km/h, or even more.

    13. Top | #151
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      Quote Originally Posted by langel View Post
      The TT ball is very light and once it leaves the bat it decelerates very fast.
      Yes, the air resistance is proportional the the velocity squared. The ball will slow down by half after about 5 meters. One must solve a differential equation to figure this out.

      The final speed of the arm swing is the initial speed of the ball flight.
      ???????

      The baseball ball is much heavier and decelerates less. So its measured speed is much closer to the final speed of the arm swing. Thats why I gave a baseball example.
      Not a good example if you are comparing pitching fast balls with the impact of the ball and paddle.
      If you are comparing with batting then the arm swing isn't as important as the speed of the bat.


      But again - for the abstract of the idea its good to look on the slower swings too, where the dwell is much longer, and extremely longer than the milliseconds, measured on static bats, snaps, etc.
      [/quote]
      Are you talking about TT or BB dwell times?
      Have you done the math to justify your statement that dwell time is extremely longer. What is extremely longer?

      Too many TT players believe everything they read. That goes for reading and believing TT manufacturer's marketing and forums. No one asks for proof. I keeping challenging statements like this because I know they will be repeated for years unless they are debunked. I know better. I want proof.

      The dwell time can be infinite as demonstrated by TT players catching the ball on their paddles. What are the conditions that must be met to do this? No one has provided and answer.

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    15. Top | #152
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      Quote Originally Posted by frankie View Post
      Donic Appelgren or Xiom Allround S, with a (medium-)hard rubber 47degr+ will give you control and lots of dwell time.
      Quote Originally Posted by UpSideDownCarl View Post
      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 not made a post since necromancing this thread. I think he is laughing up his sleeve about what a commotion he has caused.
      Spin Everything.

    16. Top | #153
      ttarc is offline
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      Quote Originally Posted by langel View Post
      The TT ball is very light and once it leaves the bat it decelerates very fast.
      In the scenario we don't care about the flight speed, but the initial and the final speed of the arm swing.
      The final speed of the arm swing is the initial speed of the ball flight.
      If one would throw a TT ball as one would a baseball than this would be true but not when a TT ball impacts/leaves a racket. We have the impact and deformation of the ball when it's contacting the rubber, then the compression of the rubber/sponge, the deformation and flexing of the blade and the restitution of the blade, sponge and ball.
      Each of these of course obey conservation of momentum but a lot is "wasted" as heat or vibration.

      Kinematics of table tennis topspin forehands: effectsof performance level and ball spin, 2009, Yoichi Iino, Takeji Kojima
      In this paper both racket speed and ball speed before and after impact were measured:
      Advanced players doing topspins against light and heavy backspin
      Light backspin: Mean ball speed before impact 3.0 m/s, after impact 18.7 m/s, mean racket speed at impact 19.4 m/s
      Heavy backspin: Mean ball speed before impact 3.4 m/s, after impact 18.6 m/s, mean racket speed at impact 19.6 m/s
      Light backspin: 11.4 +- 1.5 rps (684 rpm) after the first bounce, heavy backspin: 36.8 +- 2.5 rps (2208 rpm)
      (three of the advanced players had "world rankingpoints between 100th and 300th places")

    17. Top | #154
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      Quote Originally Posted by langel View Post
      If you can't, don't say that you're an engineer.
      Are you serious!

      If you are then I challenge you to come up with the formulas for catching the ball and extending dwell time.

      BTW, I have done the basic differential equations long ago assuming the ball is just hitting the paddle and bouncing off.

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