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    1. Top | #41
      Dr Evil is offline
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      Quote Originally Posted by brokenball View Post
      The problem is that no one cares enough to do it right.
      I think the problem is that it would be useless. A sheet of rubber doesn't have a coefficient of restitution. The COR refers to a particular collision, which includes the rubber, the blade, the ball, impact velocity, atmospheric conditions, etc. A useful measurement of the COR for a rubber wouldn't be a single number, but a matrix of numbers from which you might or might not be able to draw useful conclusions based on comparison to the numbers for other rubbers. Much more complicated than you suggest. And much less useful than opinions from players who have used the rubber.

    2. Top | #42
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      Wkat I would like to see is a diagram of the rubber deformation pattern with different ball speed, no spin, under spin and top spin with different speed of rotation, different tangential angles, along with the corresponding contact size and form of the impact stamp on the ball.

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    4. Top | #43
      lasta is online now
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      Quote Originally Posted by langel View Post
      Wkat I would like to see is a diagram of the rubber deformation pattern with different ball speed, no spin, under spin and top spin with different speed of rotation, different tangential angles, along with the corresponding contact size and form of the impact stamp on the ball.
      I don't even need all of that. It would be helpful enough to simply know the precise and replicable measurement of the top sheet material and sponge material hardness separately. The old ITTF Education material already proved that friction of just about all inserted rubber is enough to "completely stop the ball rotation on contact" ie no slippage.

      It seems even that is too much to ask.

      I agree with Brokenball. TT is too much hocus pocus, not enough objectivism.

      On the other hand, if someone jumps out and challenge said subjectivism, they are at risk of being ostracized. Just look at what's happening in the audio community.
      Last edited by lasta; 2 Days Ago at 01:05 PM.

    5. Top | #44
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      The question is, by knowing all the specific numbers make you a better player?

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    7. Top | #45
      lasta is online now
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      Quote Originally Posted by yogi_bear View Post
      The question is, by knowing all the specific numbers make you a better player?
      Absolutely not. But I does make one a more informed consumer. It's better to have more information than you need, than to have the limited available information distorted beyond usefulness.

    8. Top | #46
      yoass is offline
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      Blowing up the argument to an “all” vs. “nothing” is probably not too helpful.

      Fwiw, as a general rule completeness of information is a fata morgana. We usually are not lacking in information — quite the contrary, there’s usually too much of it of unknown/unreliable veracity, marked subjectivity, and (a tell-tale) utterly lacking consistency.

      In this overload of inconsisten information if dubious integrity one needs to find a way to cope. Numbers supplied by vendors, sadly, do not alleviate this pickle.

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    10. Top | #47
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      Quote Originally Posted by langel View Post
      Wkat I would like to see is a diagram of the rubber deformation pattern with different ball speed, no spin, under spin and top spin with different speed of rotation, different tangential angles, along with the corresponding contact size and form of the impact stamp on the ball.
      It is hard to see the deformation at 2000 FPS. One can get an idea by the diameter of the dust mark a dirty ball leaves on the rubber. If the dust mark is about 1 cm in diameter then you know that the ball went into the rubber a little bit.

      Challenge. Can anybody do the math to compute how far the ball went into the rubber?


      Knowing accurate rubber specifications will not make one a better player. It will keep people from buying the next new rubber that is the same as the old rubber.

      Too evaluate the rubber by itself would require mounting the rubber on a heavy block of wood like a cutting board. The cutting board would not absorb much if any energy. The speed can be measured easily just before and just after impact so the air resistance would have a minimal effect.

    11. Top | #48
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      This are the things that are not being considered:
      1. Companies will not release those numbers especially if they are less compared to other rubbers from other companies.
      2. How sure are you they will not change the value of the COR or speed of the rubber?

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    13. Top | #49
      brokenball is offline
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      Quote Originally Posted by yogi_bear View Post
      This are the things that are not being considered:
      1. Companies will not release those numbers especially if they are less compared to other rubbers from other companies.
      I agree, that is the whole point. TT companies don't want an objective way of comparing equipment. They want to sell us the same or stuff with a different name knowing we will buy it in hopes we will play better.

      2. How sure are you they will not change the value of the COR or speed of the rubber?
      They could but a false claim can be checked and the damage to the reputation would be severe.

    14. Top | #50
      LordPippington is online now
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      Quote Originally Posted by brokenball View Post
      It is hard to see the deformation at 2000 FPS. One can get an idea by the diameter of the dust mark a dirty ball leaves on the rubber. If the dust mark is about 1 cm in diameter then you know that the ball went into the rubber a little bit.

      Challenge. Can anybody do the math to compute how far the ball went into the rubber?


      Knowing accurate rubber specifications will not make one a better player. It will keep people from buying the next new rubber that is the same as the old rubber.

      Too evaluate the rubber by itself would require mounting the rubber on a heavy block of wood like a cutting board. The cutting board would not absorb much if any energy. The speed can be measured easily just before and just after impact so the air resistance would have a minimal effect.
      If you think having objective proof is enough to stop people from buying the next, new shiny object... you don't know marketing!

      But what if the rubber isn't designed to be played on a tree stump? lol... they would just say their rubbers are perfect for... THEIR OWN blades! And while the tree stump test may show theirs to be lower on some stats, when you use a fancy blade by them, the true feel of the rubber is unleashed.

    15. Top | #51
      brokenball is offline
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      Quote Originally Posted by LordPippington View Post
      If you think having objective proof is enough to stop people from buying the next, new shiny object... you don't know marketing!
      Actually, I do. However, "there is a sucker born every minute". I actually do a fair amount of marketing but I am mostly an engineer. I do the kind of marketing targeted towards engineers and you can't BS them too much.

      But what if the rubber isn't designed to be played on a tree stump? lol... they would just say their rubbers are perfect for... THEIR OWN blades!
      This is why the rubber needs to be mounted on a hard and heavy piece of wood like a cutting board. Back when Pathfinderpro was making his videos, I noticed that he tested the rubbers on blades and I pointed out that all the blades are different and absorb different amounts of energy. I suggested a cutting board but Pathfinderpro opted for a thick piece of plexiglass.

      The idea it to test just the rubber. If two rubbers are similar they will play in a similar way on the same blade.

      I use a cutting board to mount the rubber on. I don't even need to cut it. I shoot balls at the rubber glued to the cutting board with a robot. The robot is pretty consistent but there is some variability. I need to take an average. I have a small pen laser mounted to the head of my Newgy 2050 robot. The laser bounces off a small mirror glued to the cutting board. The reflection needs to hit the wall at the same place to be sure the cutting board is angled just right. This is cheap and more repeatable than using a protractor. I haven't tried to actually measure coefficients of restitutions but I can tell by how far and what angle the ball bounces of the rubber which rubbers have higher coefficients than others.

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