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.
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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.
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The question is, by knowing all the specific numbers make you a better player?
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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.
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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 inconsistent information of dubious integrity one needs to find a way to cope. Numbers supplied by vendors, sadly, do not alleviate this pickle.
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 inconsistent information of dubious integrity one needs to find a way to cope. Numbers supplied by vendors, sadly, do not alleviate this pickle.
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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.
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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?
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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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.
They could but a false claim can be checked and the damage to the reputation would be severe.
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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.
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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.If you think having objective proof is enough to stop people from buying the next, new shiny object... you don't know marketing!
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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Hi Thomas,
I've now played with it for 10/15 min ( BH D64 + Tibhar Off+ 8,5 ) which is absolutely not enough to describe it but;
It doesn't feel so hard as D05, easy to generate spin and serve, so briefly I found it more accurate for my play than D05, even if, as said I didn't play enough with it to give a real sentance.
Maybe in the next weeks if I bought it ?? ;-)
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As Dr Evil said, it's a no sense to do it like that as you don't play only with a rubber....and each different blade you use with a rubber will affect the result of the bat.
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I can happily report that my first 2-hour session with Dignics80 on bh was better than I'd thought beforehand. I've tried T05 before and I didn't like it, too bouncy. I come from over 2 years of using H3 on bh and this session certainly makes me want more D80, so I'll be using it at our league matches on Tuesday. Only fools rush in, and myself.
Pros:
Linear, good controllable speed, great in blocking game, good touch in service receives, good spin but no spin monster. Gives me confidence to attack with more power since margin for error is bigger compared to H3. If the contact on H3 isn't almost perfect it's difficult to get top speed from it.
Cons: Very heavy! It made my setup jump up from 194 grams to 205 and that made me overshoot many shots mainly from my fh side since the heaviness added power to the stroke when using the same swing speed as before. Had to adjust a bit to that. Not as good as lifting backspin as H3, perhaps unused to the different way to contact the rubber with the ball so I will adjust to it. H3 has a nastier trajectory, it dips more after the bounce than D80 does which puts opponents into some trouble. H3's top speed and spin is better than D80 since H3 hardly ever bottoms out.
All in all, a great rubber that I will continue to use and take it from there.
Pros:
Linear, good controllable speed, great in blocking game, good touch in service receives, good spin but no spin monster. Gives me confidence to attack with more power since margin for error is bigger compared to H3. If the contact on H3 isn't almost perfect it's difficult to get top speed from it.
Cons: Very heavy! It made my setup jump up from 194 grams to 205 and that made me overshoot many shots mainly from my fh side since the heaviness added power to the stroke when using the same swing speed as before. Had to adjust a bit to that. Not as good as lifting backspin as H3, perhaps unused to the different way to contact the rubber with the ball so I will adjust to it. H3 has a nastier trajectory, it dips more after the bounce than D80 does which puts opponents into some trouble. H3's top speed and spin is better than D80 since H3 hardly ever bottoms out.
All in all, a great rubber that I will continue to use and take it from there.
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Hi Langel,
Sorry but what you described is totally unrealistic. they're no interest to measure what you want, so only the rubber properties as you'll never use it alone and must be glued on a blade.
I had the same rubbers glued on 3 different blades ( Garyadia ALC, Garaydia ZLC and Garaydia T5000), I used 2 in the same session to compare and I can tell you the result/feeling I had was really different from each bat and affected my strokes / play.
At the end of the day what's really fit to you is what you feel confortable with.
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Yes, but what you are speaking about is the subjective feeling of the performance of the system rubber+blade+player.
What I'm speaking about is the objective characteristics of the rubber, depending on its particular structure and the corelation between the elements of this structure, each of them with its particular properties.
For example a softer and thinner rubber top sheet put on a harder sponge will have different tangentional impact patterns than a harder rubber top sheet on the same sponge, and these patterns will be different depending on the pips structure and on the top sheet to sponge ratio of hardness and thickness. This is objective and can be measured objectively, you don't have to use blades, just a static hard and stiff surface. And it will be as objective as the sponge hardness, for example, and this hardness does not change with the blade, the performance changes, depending on the system. I understand that the pattern concept might not be of great interest for the majority, but to me it would tell a lot, especially for the expected type of spin generation.
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I think so, and it's not that hard; a fairly straighforward application of Pythogoras' theorem.
Given a circle with r=20mm and that 10mm "dust mark" segment, we have a triangle with two sides of 20mm and one side of 10mm. That triangle can be split into two rectangular triangles with a hypothenusa of 20mm (c) and one side (b) of 5mm. The distance to the circle rim - the penetration depth we seek - is r-a.
Applying pythagoras (a^2+b^2=c^2) we get a^2 = c^2 - b^2 = 20^2 - 5^2 = 400 - 25 = 375.
Taking the square root, we get a=~ 19.36. The distance left to the ball edge, then, is 20-sqrt(375) =~ 0.635mm.
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But the patterns on tangentional impact are not circles.
Whats more - the stamp on the ball will be different than the stamp on the recovered rubber surface, but same /or closer/ to the rubber surface deformation pattern during the impact.
Observing the stamp pattern on the rubber surface after its recovering can tell somethings, but not what I ment.
I'm sorry if the abstraction of the concept is not clear.
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