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    #1

    looping racket angle

    WingTT mentioned me.
    This topic is on mytt
    looping racket angle - Alex Table Tennis - MyTableTennis.NET Forum - Page 2
    In short, I agree with pingpongpaddy.
    Rolling your wrist is not good. If you roll your wrist the the angle of the paddle will change from millisecond to millisecond.
    The others do not know what they are talking about.
    Dwell time is not milliseconds under normal play. It is around a millisecond plus or minus microseconds. Contact time is shorted at higher speeds.
    You can't extend dwell time by more that a few micro seconds at best so I don't know how you can feel the difference.
    When I was on mytt I challenge the PhDs in physics to prove they are right and I am wrong and NONE rose to the challenge.
    I haven't seen anybody do the math yet except Baal with his crude "napkin" calculations.

    It is been 12 years now. No physic PhD has risen to the challenge.
    What is the force that is applied to the ball? Make assumptions but then show the math.
    What must the acceleration of the paddle be to increase the dwell time?
    However, if the paddle is still accelerating then it is not at maximum speed.

    This is why the PhDs hire me or did in the past. I am retired now.






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  2. UpSideDownCarl is offline
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    #2
    Baal;343380Actually Sjan, I've
    Baal, Can Peter go back onto MyTT and post so he does not have to try and answer threads from MyTT on TTDaily?


    I bet it would be fine to have him MyTT these days. He has been a pretty productive member of TTDaily for several years.


    I think you guys should have a brief PM exchange on the subject and look into setting it up.


    What say you?
    Last edited by UpSideDownCarl; 04-11-2021 at 12:59 AM.
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    #3
    This isn't up to Baal. I have no issue with Baal.
    Mytt would need to apologize first.
    I could always get back on the forum using a different name. That isn't the issue.
    They do not deserve my answers.
    If the people on mytt want to believe the crap posted there then so be it.


  4. UpSideDownCarl is offline
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    #4
    Okay.
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    #5
    Yeah, cool story.

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    #6
    at the end of the day some cross fertilisation between forums is both unavoidable and beneficial
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    #7
    Proably need a physicist that know tabletetennis a bit aswell? Feel like there are proably many variabes so must be difficult to calcuate.

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    #8
    Quote Originally Posted by Lula
    Proably need a physicist that know tabletetennis a bit aswell?
    I get hired by PhDs. The PhDs could probably solve problems themselves eventually but at what I do I am pretty damn good because I have done many simulations. Sometimes the simulations show the system will not work. If the system exists and doesn't work I can show why and show how to make it better next time.

    Feel like there are proably many variabes so must be difficult to calcuate.
    TT is relatively simple compared to some I have done. System simulations/models take up to 25 variables.
    I have done simulations and control for the FAA and department of energy. They have PhDs but still I get hired.

    On mytt PPP, got it right and still people don't believe. They dig up videos where there may be an arc ( concave or convex ) but I doubt that is intentional or desired. People aren't machines so our strokes aren't always perfect. The diagrams are pretty good. When I get tired I don't get my paddle down far enough like the motion of the amateur. The pros are faster so they able to get into position and their paddles down. Another fault I have is that I tend to scoop the ball when I get tired. My arm motion moves the paddle in a convex motion instead of in a plane. This is not good when trying to return back spin.

    What I found interesting with the diagrams is all the motion AFTER contact instead of slowing down faster for a recovery. It is too bad there aren't plots of the derivatives of position so we could see the velocities and accelerations.

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    #9
    Quote Originally Posted by Lula
    Proably need a physicist that know tabletetennis a bit aswell?
    I get hired by PhDs. The PhDs could probably solve problems themselves eventually but at what I do I am pretty damn good because I have done many simulations. Sometimes the simulations show the system will not work. If the system exists and doesn't work I can show why and show how to make it better next time.
    Feel like there are proably many variabes so must be difficult to calcuate.
    TT is relatively simple compared to some I have done. System simulations/models take up to 25 variables.
    I have done simulations and control for the FAA and department of energy. They have PhDs but still I get hired.

    On mytt, PPP got it right and still people don't believe. They dig up videos where there may be an arc ( concave or convex ) but I doubt that is intentional or desired. People aren't machines so our strokes aren't always perfect. The diagrams are pretty good. When I get tired I don't get my paddle down far enough like the motion of the amateur. The pros are faster so they able to get into position and their paddles down. Another fault I have is that I tend to scoop the ball when I get tired. My arm motion moves the paddle in a convex motion instead of in a plane. This is not good when trying to return back spin.

    What I found interesting with the diagrams is all the motion AFTER contact instead of slowing down faster for a recovery. It is too bad there aren't plots of the derivatives of position so we could see the velocities and accelerations.

  10. latej is offline
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    #10
    Quote Originally Posted by brokenball
    In short, I agree with pingpongpaddy.
    So do I. Thanks PPP, for fighting the good fight out there against the "wrapping of the ball" put forward by poster B...S. When I read that thread I thought it is good that many people on MyTT objected against those illusions. Can anyone find a high-speed camera capture of the TT ball impact from high-level player? I think that could settle it, maybe even the poster B...S would be convinced :-)

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    #11

    maybe someone could arrange a video with someone like boll to explain in detail what he meant by wraparound.
    That would be interesting though I must admit that I know at least 1 international player who talks about letting the ball "sink into the sponge". The thing is he is not technically minded. He is very bright tactically but does not like to delve into the nitty gritty of ball contact.
    Anyway I am going to let them stew in their own ignorance for the moment rather than indulge in a thread of repetion and counter repetition.

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    #12
    Quote Originally Posted by pingpongpaddy
    That would be interesting though I must admit that I know at least 1 international player who talks about letting the ball "sink into the sponge". The thing is he is not technically minded. He is very bright tactically but does not like to delve into the nitty gritty of ball contact.
    Anyway I am going to let them stew in their own ignorance for the moment rather than indulge in a thread of repetion and counter repetition.
    The feeling of impact can be quite thrilling, that is what we want to repeat like junkies. But it is learned after the impact. The impact's duration is cca 1ms. The nerve impulses travel 50-60 m/s. If the arm to brain is say 1m, it takes 16,6ms one way. Let's say we have super fast brain which decides in 10ms (non-sense, it will be more like 100ms), and then way back we have 16,6*2+10 = 43ms, long after the ball left...

    Of course, poster b... can say this is not what I am talking about, I will time the "wrapping of the ball" without feeling it. OK, how much will the change in the angle during the impact be, if the impact is 1ms? Let's say he does monstrous "wrapping of the ball" and the total change of the bat angle will be 40 degrees, now let's say he is capable of timing this rotation in the interval of 10ms around the impact point. That I think is super-human. This will give us change of 4 degrees during the impact. For the record when playing multiple topspins against backspin the bat angle changes (between strokes) for +- 5 degrees, which means 10 degrees interval, 10 degrees angle change between strokes. And with the above we highly unrealistically achieved 4 degrees change during impact, still well within that interval.

    First it is unrealistic, change of <1 degree during impact would be more realistic. And that is negligible. I believe there is no change at all in fact, but only high-speed camera can prove it. Worse is the price we pay for achieving this negligible non-sense. It is non-sense to try to incorporate supination/pronation, it will only screw the stroke. The arm should fly freely, propelled by the leg/hip/body motion. Trying to do something else other than letting it fly brings only harm.

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    #13
    I also think it's not a good idea to do things consciously with the arm while it's being propelled by the body - speaking from own experience I have tried and failed. The legs and body propel the arm and the racket just happens to collide with the ball. Some say they pinch using their fingers and I'm unsure if this is necessary to do consciously - of course you'd have to hold on to the racket slightly firmer as you're reaching max speed or it might fly out of your hand.

    I also believe reliable shots require hitting into the sponge more. The aim to thinly brush the ball I think is a bit of a myth - it happens of course and can be useful, but if we just listen and watch the pros practice they are most of the time getting cracking sounds and aren't using the topsheet much to just brush the ball. I have done this brushing with the topsheet a lot in the past but it has never been consistent and has lead to overuse of the arm. Even against backspin now I'm trying to get this thicker contact into the sponge and it's much more consistent than it has ever been for me - and as a last resort this brushing action can be used, but it's no longer my priority as it was years ago when I was given that advice.






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    #14


    Good, people are starting to think about what the so called coaches say about wrapping the ball.
    There is a lot of fake martial arts in China too. I have only come up against bad engineering research papers student write for graduation.
    Latej gets a thumbs up for his analysis but lets say the paddle angle changes as little as 0.5 degree/millisecond and the player is early or late by 1 millisecond.
    How much difference does that make to the elevation of the ball 3 meters away at the other end of the table. I am assuming that the player is close to the table. At 4 meters away the difference is even more.
    3*math.sin(math.radians(1)) = 0.052357219311850535 meters or about 52 mm or 2 inches..
    How many shots have you missed by less than that?
    I used 1 degree because the error in paddle angle is doubled if you estimate the ball bounce of like a reflection. I know that balls don't truly reflect off the paddle because any tangential contact adds or subtracts from the inertia or spin of the ball which affects the tangential speed or angle too. The error in the ball trajectory angle will certainly be bigger than the error in the paddle angle. Off course errors in estimating spin are probably bigger.

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    #15
    Have never heard the expression wrapping the ball. Care to elaborate? Maybe need to read that thread.

  16. latej is offline
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    #16
    Quote Originally Posted by brokenball
    Latej gets a thumbs up for his analysis but lets say the paddle angle changes as little as 0.5 degree/millisecond and the player is early or late by 1 millisecond.
    How much difference does that make to the elevation of the ball 3 meters away at the other end of the table. I am assuming that the player is close to the table. At 4 meters away the difference is even more.
    3*math.sin(math.radians(1)) = 0.052357219311850535 meters or about 52 mm or 2 inches..
    How many shots have you missed by less than that?
    I used 1 degree because the error in paddle angle is doubled if you estimate the ball bounce of like a reflection. I know that balls don't truly reflect off the paddle because any tangential contact adds or subtracts from the inertia or spin of the ball which affects the tangential speed or angle too. The error in the ball trajectory angle will certainly be bigger than the error in the paddle angle. Off course errors in estimating spin are probably bigger.
    You make good points which I didn't consider. Obviously the bouncing of the ball from the bat doesn't work like light beam mirror bounce because of the rubber but still there will be, in some form, the difference you speak about. If someone manages to wrap the ball by changing the angle during contact by 1 degree, we can estimate the resulting ball is approx., as if he hit it with stable bat with angle changed 0.5 degree (the middle). Which gives us your situation. The ball trajectory is arc, say 4m long, highest point say after 2m, and this means 35mm elevation change (over net), simplified. Which is quite a lot. Those balls when I hit top-spin and it bounces out from the net, I hate the most. So, my "angular" analysis is not so good... Anyway, I'd love to see high-speed camera impact from a top-level player. Cheers.

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    #17
    Quote Originally Posted by Richie
    I also think it's not a good idea to do things consciously with the arm while it's being propelled by the body - speaking from own experience I have tried and failed. The legs and body propel the arm and the racket just happens to collide with the ball. Some say they pinch using their fingers and I'm unsure if this is necessary to do consciously - of course you'd have to hold on to the racket slightly firmer as you're reaching max speed or it might fly out of your hand.

    I also believe reliable shots require hitting into the sponge more. The aim to thinly brush the ball I think is a bit of a myth - it happens of course and can be useful, but if we just listen and watch the pros practice they are most of the time getting cracking sounds and aren't using the topsheet much to just brush the ball. I have done this brushing with the topsheet a lot in the past but it has never been consistent and has lead to overuse of the arm. Even against backspin now I'm trying to get this thicker contact into the sponge and it's much more consistent than it has ever been for me - and as a last resort this brushing action can be used, but it's no longer my priority as it was years ago when I was given that advice.
    Hi Ritchie,
    I’ve seen some vids where the coach advise to pinch with the fingers for serving, it’s supposed to increase the racket speed therefore increasing spin potential, the timing of the ‘pinch’ can vary depending at which point of the stroke / contact point on the ball you want to achieve and therefore the type of spin. So in this instance, when learning to do so, it is a conscious thought, and with practice and time becomes ‘natural’. As do many things when you’re learning, such as footwork patterns etc
    Again the timing is crucial, and as pointed out it probably can’t be done reflexively, on the spur of the moment as it were, because by the time you’ve processed the decision it’s too late!!

    For other strokes such as FH loop I have also read that trying to be ‘In Pai’ (apologies if I’ve spelt it incorrectly) is desirable, relaxed during the stroke before impact, tenser at impact and relaxed after impact. Again this would seem to be natural regarding the hand not letting go of a rapidly move bat!!
    But there could be more to it than just the hand, arm muscles etc, think of a boxer, in order to best transfer all the power produced into the opponent there has be be an amount of tenseness. How often does a commentator use the term that was a really ‘stiff’ jab!! Or ‘solid’ jab!!

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    #18
    As far as ‘rolling the wrist’ is concerned I’d agree that it’s pretty pointless!!
    bat angle at contact is exactly that!!
    bat angle after contact is meaningless!! For example a ‘fake motion’ as part of a serve, the fake motion does not effect how the ball is going to spin, it’s used as DECEPTION tactics!!
    My old golf coach, used to say much the same, after the point of impact the swing follow through is to a certain extent meaningless!! And is really a product of the takeaway / down swing. Yeah, there’s desirable posture and weight distribution after impact, club face orientation etc but he used to say what we train to do after impact is helping to promote what we are trying to achieve for the downswing. Perhaps this maybe the case for rolling the wrist??

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    #19
    Quote Originally Posted by IB66
    Hi Ritchie,
    I’ve seen some vids where the coach advise to pinch with the fingers for serving, it’s supposed to increase the racket speed therefore increasing spin potential, the timing of the ‘pinch’ can vary depending at which point of the stroke / contact point on the ball you want to achieve and therefore the type of spin. So in this instance, when learning to do so, it is a conscious thought, and with practice and time becomes ‘natural’. As do many things when you’re learning, such as footwork patterns etc
    Again the timing is crucial, and as pointed out it probably can’t be done reflexively, on the spur of the moment as it were, because by the time you’ve processed the decision it’s too late!!

    For other strokes such as FH loop I have also read that trying to be ‘In Pai’ (apologies if I’ve spelt it incorrectly) is desirable, relaxed during the stroke before impact, tenser at impact and relaxed after impact. Again this would seem to be natural regarding the hand not letting go of a rapidly move bat!!
    But there could be more to it than just the hand, arm muscles etc, think of a boxer, in order to best transfer all the power produced into the opponent there has be be an amount of tenseness. How often does a commentator use the term that was a really ‘stiff’ jab!! Or ‘solid’ jab!!

    If it helps to think about, then I see no harm. I've been down that path and it never helped me. I don't see the serve as that different from the other strokes. With the serve most modify their grip to hold with mostly the thumb and index finger. When you've reached high racket speed from snapping the wrist back and then forward (along with the forearm and torso rotation) if you don't firm your grip a bit with the fingers (especially since you're most likely just holding on to it with a few fingers) the racket will likely slip out of your hand. I feel like it's fairly intuitive to do as you don't want that to happen.

    You could think about pinching the racket at different points of the stroke and you'd therefore get different contacts and different spins.. you could also think that if you contact the ball in different areas and during different times in the swing you'll get the same effect if you have high racket head speed. You have no choice but to "tense" up or firm your grip slightly at around or after contact. It's possible that if someone is given this advice they'll by accident reach higher swing speed and as a consequence tense their grip a bit more on contact or follow through.

    Let's say you want to throw a ball really far, you'd use your body to swing your arm fast and then let go.. if you want to keep the ball in your hand you'd better hold on to that ball relatively tight by the end of the swing or it'd fly off. Did you consciously tighten your grip of the ball or did it just happen because your body intuitively knew that you'd have to grip the ball a bit harder? If you couldn't get a fast swing going then you wouldn't need to "tense" as much on the follow through as less would be required for you to hold on to that ball. Maybe if someone struggles with this it could help to consciously tighten the grip, but I'm sceptical.

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    #20
    Quote Originally Posted by latej
    You make good points which I didn't consider.
    This is why I have made the big bucks.

    Even small angles of paddle error make a big difference it where the ball will be 3-4 meters out. It is amazing people do as well as they do but it is also easy to see why we miss so many balls.

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