The thick sponge and tacky topsheet is no good at all.

[igorponger]

The thick sponge and tacky topsheet is no good at all. Dr. Konrad Tiefenbacher offers strong arguments.

Tiefenbacher's practical investigations of 1994 is well convincing that the best optimal sandwich rubber to play with should be a non-tacky topsheet attached to mid size sponge 1.7 mm. It is a worthful and reasonable choice in every way, to benefit you a lot. Not easy to look out on China marketplace though.

As for myself, I trust Tiefenbacher, I better favor 729 non tacky products in thickness 1.7 plus orthodox compact cell structure. It makes me a king of allround game.

Be happy.,

 

[BaRanchik]

How do you explain H3 spinning the ball more than say Fastarc G1?

 

[ttarc]

Because the study is from 1994 when we had 38 mm celluloid balls and neither Hurricane 3 nor FastArc G-1. Now we have 40 mm plastic balls and a semi-tacky "sticky enough that the ball cannot slide" Hurricane 3

 

[blahness]

Furthermore, momentum absorption is extremely good to have in the short game as well as controlling incoming loopkills, which is always not considered for some unknown reason

 

[Gozo Aruna]

The thick sponge and tacky topsheet is no good at all. Dr. Konrad Tiefenbacher offers strong arguments.

Tiefenbacher's practical investigations of 1994 is well convincing that the best optimal sandwich rubber to play with should be a non-tacky topsheet attached to mid size sponge 1.7 mm. It is a worthful and reasonable choice in every way, to benefit you a lot. Not easy to look out on China marketplace though.

As for myself, I trust Tiefenbacher, I better favor 729 non tacky products in thickness 1.7 plus orthodox compact cell structure. It makes me a king of allround game.

Be happy.,

View attachment 28869

CNT does not listen to Doctor and produces many grand slam winners. Meanwhile, The Motherland produces lots of fantastic dancers...

 

[dingyibvs]

How do you explain H3 spinning the ball more than say Fastarc G1?

Well, first you need to prove that's the case. Measure the RPMs of the ball given the same relative impact speed, angle, and spin. Even assuming the statement is true, higher friction would only result in greater spin if the ball slips on the rubber with the lower friction one. Is that what we experience? We can usually feel and hear when the ball slips (that tssss sound), but that's not what happens with say the G1. It then stands to reason that most likely the H3 generates more spin, assuming that's true, because it has higher tangential elasticity.

With that said, the biomechanics of TT is rather complex, and the Tiefenbacher study only begins to scratch the surface of it. A much more elaborate experiment is needed to answer some of the most common questions in TT.

 

[Johnniedarko]

Igorponger, you are misquoting the paper and both "rules" you made are not to be found in there.

Tiefenbacher absolutely does not say anywhere there that a 1.7mm sponge gives the same Tpar (Tangential efficiency, or in laymens terms: spin and loop ability) as a 2.2mm rubber.

What he says is that the specific tacky/sticky rubbers that they tested at 2.2mm, were as good in generating spin as the grippy rubbers (J1) of 1.5mm. BUT, importantly, the grippy rubbers (J1) of 2.0mm were a lot "faster' (Epar) and "spinnier" (Tpar) than the grippy rubbers of 1.5mm. AND the grippy rubbers of 2.2mm were in turn faster and spinnier than the 2.0mm grippy rubbers.

So your first "rule" ("a 1.5mm sponge will do the job as well as a 2.0mm sponge') is not in the paper, In fact, the opposite is in the paper.
Your second "rule" ("You don't need sticky rubbers") cannot be said with certainty, because that is only true for the sticky rubbers of 1994. Perhaps after a redo of this research could you claim that, but not now.

If you like sticky rubbers for the reasons posted by Blahness, sure, but it's not in the paper.

I added the sponge thickness as described by the text. 2.2 is way more to the right. Tpar is higher and that means it has more tangential efficiency (spin/loop ability).

Furthermore, momentum absorption is extremely good to have in the short game as well as controlling incoming loopkills, which is always not considered for some unknown reason

Tiefenbacher states "If we assume that the aim of a high level offensive player is to produce the fastest ball with the highest rotation, [...]", and also states that that's been the goal of manufacturers (of that time). Perhaps rubbers weren't so fast back then and so control was plenty? I don't know.

Papers I've read the last couple of days (including Tiefenbacher) often state that they use the topspin ball (or topspin vs topspin) because it's either the most common and they want to simplify, and/or it's the most extreme in terms of energy(transfer).

 

[brokenball]

I agree that the Tiefenbacher document needs to be updated. There are much better cameras available now. Tiefenbacher had to use a strobe while the shutter was open. Now there are color cameras that can record at 2000 FPS easily.

Tacky rubbers have an advantage when brushing. They will grip with lower impact force. However, Tiefenbach is right about having to break the tackiness. Tacky rubbers are at a disadvantage when playing away from the table because of the need to break the tackiness grip on the ball.

In the end it is the tangential and normal coefficient of restitution ( Tpar and Epar ) and the tangential and normal impulse that matter when generating spin and speed.

Furthermore, momentum absorption is extremely good to have in the short game as well as controlling incoming loopkills,

You mean energy. Momentum is conserved. Momentum doesn't just disappear.
Kinetic energy is absorbed and converted to potential energy and a little heat. The energy doesn't just disappear. The goal is to return most of the potential energy back to kinetic energy. Not all potential energy gets returned as kinetic energy which is why the coefficient of restitution is always less than one.

 

[dingyibvs]

I agree that the Tiefenbacher document needs to be updated. There are much better cameras available now. Tiefenbacher had to use a strobe while the shutter was open. Now there are color cameras that can record at 2000 FPS easily.

Tacky rubbers have an advantage when brushing. They will grip with lower impact force. However, Tiefenbach is right about having to break the tackiness. Tacky rubbers are at a disadvantage when playing away from the table because of the need to break the tackiness grip on the ball.

In the end it is the tangential and normal coefficient of restitution ( Tpar and Epar ) and the tangential and normal impulse that matter when generating spin and speed.


You mean energy. Momentum is conserved. Momentum doesn't just disappear.
Kinetic energy is absorbed and converted to potential energy and a little heat. The energy doesn't just disappear. The goal is to return most of the potential energy back to kinetic energy. Not all potential energy gets returned as kinetic energy which is why the coefficient of restitution is always less than one.

I think he meant for situations when the goal is to NOT return most of the potential energy back to kinetic energy, like a safe block or a short push.

As for the Tifenbacher study, I think it falls short in a couple of major areas in terms of its design. Aside from the obvious shortcomings due to the age of the study, the biggest issue IMO is a lack of study of the extremes. The common claim re: the superiority of Chinese rubbers is their gears. That is, they can play short balls really well but remains very powerful (i.e. still has great combination of speed and spin) at the high end.

From what I can tell, the Tiefenbacher study really failed in studying the high end. In the Japanese vs Chinese rubber comparison, in Figure 7a the Epar of Japanese rubbers was about 0.62. From Figure 6 we can see that an Epar of 0.62 is achieved with a relative speed of about 11-12 m/s, which is ~40 kph. Now, we know that even with the 40+ plastic balls a pro is able to generate 80+ kph shots against a floaty backspin ball, and probably much higher against fast topspin balls. Then you figure that the player's racket speed is probably higher than 80 kph as well (underhand baseball pitchers can pitch 170 gram baseballs in excess of 120 kph), then in a head on collision the relative speed would be a maximum of close to 200 kph.

Now of course in an actual loop you don't strike the ball perpendicularly, but the relative speed must be significantly higher than 40 kph. What happens to Tpar when the relative speed is very high? Players report a phenomenon of "bottoming out", when a really hard shot only increases speed and not spin with softer rubbers, so does that actually happen? Is it possible that the Chinese rubbers can maintain its Epar/Tpar better at extremely high speed/spin situations?

We already know from the Tiefenbacher study that Epar for all materials are already about the same at relative speed of ~100 kph, so the key question here is what happens to Tpar at high speed?

 

[Der_Echte]

It doesn't matter. If the manufacturer puts half nakkid pics of a popular singer, like say Gloria Tang Sze-wing all over the packaging... then no one cares about the stats.

That is how BTY does it... with sexy stats claiming everything under the sun.

 

[brokenball]

I think he meant for situations when the goal is to NOT return most of the potential energy back to kinetic energy, like a safe block or a short push.

As for the Tifenbacher study, I think it falls short in a couple of major areas in terms of its design. Aside from the obvious shortcomings due to the age of the study, the biggest issue IMO is a lack of study of the extremes. The common claim re: the superiority of Chinese rubbers is their gears. That is, they can play short balls really well but remains very powerful (i.e. still has great combination of speed and spin) at the high end.

I said above that I think the Tiefenbacher test should be done again with modern equipment BUT, the laws of physics haven't changed. The formulas haven't changed. Only the values you put in the formulas have changed.
The different values will result in different results but not much different results.

From what I can tell, the Tiefenbacher study really failed in studying the high end. In the Japanese vs Chinese rubber comparison, in Figure 7a the Epar of Japanese rubbers was about 0.62. From Figure 6 we can see that an Epar of 0.62 is achieved with a relative speed of about 11-12 m/s, which is ~40 kph. Now, we know that even with the 40+ plastic balls a pro is able to generate 80+ kph shots against a floaty backspin ball, and probably much higher against fast topspin

Today it is possible to test how pros hit the ball but back then Tiefenbacher was videoing in the dark with a strobe. A player would have a tough time hitting a ball in the dark with only a strobe lighting it up

balls. Then you figure that the player's racket speed is probably higher than 80 kph as well (underhand baseball pitchers can pitch 170 gram baseballs in excess of 120 kph), then in a head on collision the relative speed would be a maximum of close to 200 kph.

I am glad you used an example that I have used many times before about softball pitchers. Yes 15 yo girls can fast pitch balls much faster than 80 kph. However, are we testing the equipment or the players.

Now of course in an actual loop you don't strike the ball perpendicularly, but the relative speed must be significantly higher than 40 kph. What happens to Tpar when the relative speed is very high? Players report a phenomenon of "bottoming out", when a really hard shot only increases speed and not spin with softer rubbers, so does that actually happen? Is it possible that the Chinese rubbers can maintain its Epar/Tpar better at extremely high speed/spin situations?

"bottoming out" should only happen with a flat hit. In this case one isn't worrying about spin. When brushing the normal speed is reduced and the rubber is effectively thick.

We already know from the Tiefenbacher study that Epar for all materials are already about the same at relative speed of ~100 kph, so the key question here is what happens to Tpar at high speed?

You mean high tangential impact speeds?
More testing can be done but who will do it? You need time, money and knowledge.
I could have but the forums have done so much to p!ss me off and now I am retired. I don't have the time.

Finally, who cares? The forums seem to like people that talk about stuff like dwell time of which they know nothing about. The TT moderators NEVER call BS on false claims. Its all about advertising and views, not facts.

 

[Tony's Table Tennis]

So are the russians using 1.7mm rubbers nowadays?
no wonder I don't see any of them

and igor, you still playing with 38mm balls I presume?

 

[zeio]

スポーツ用具性能の可視化 ～新作卓球ラバーの開発支援～
https://www.itic.pref.ibaraki.jp/publication/doc/result/r4/R4_p.15.pdf
https://www.itic.pref.ibaraki.jp/publication/publication-1957/

Bumping this up because I just ran into this PDF about how Nittaku approached Industrial Technology Innovation Center of Ibaraki Prefecture for help in assessing and translating the performance of Hammond Z2 into digits using scientific methods, which sadly shows how useless they are to the end users because they don't represent play conditions at all.

In much the same way, and as I explained in the other thread, the passive experiment used in the study by Tiefenbacher is of little use to the end users because tacky rubbers are rarely used that way by most people.

 

[riemsesy]

So you’d like the KTL pro xt 1.8 mm?

 

[Johnniedarko]

From what I can tell, the Tiefenbacher study really failed in studying the high end. In the Japanese vs Chinese rubber comparison, in Figure 7a the Epar of Japanese rubbers was about 0.62. From Figure 6 we can see that an Epar of 0.62 is achieved with a relative speed of about 11-12 m/s, which is ~40 kph. Now, we know that even with the 40+ plastic balls a pro is able to generate 80+ kph shots against a floaty backspin ball, and probably much higher against fast topspin balls. Then you figure that the player's racket speed is probably higher than 80 kph as well (underhand baseball pitchers can pitch 170 gram baseballs in excess of 120 kph), then in a head on collision the relative speed would be a maximum of close to 200 kph.

I'm curious what the speeds are. I took Otcharov's record attempt, where he reaches 113 kph ball speed at full power:

Screenshots below are from at 2:15.

Frame 1

Frame 2

Frame 3

2 frames at 50 fps means this swing took 1/25th of a second, or 0.04s. (I double checked that there are indeed 50 frames in a second by skipping 50 frames and seeing youtubes time counter tick over a second).

In these 3 frames his bat covers about 2/3rd of his table half, let's estimate that distance at about 1 meter.
But his bat doesn't move in a straight line. It rotates around his elbow. Let's assume the bat traveled in a circle, with a diameter of 1 meter. The distance traveled is now 1.57m (pi*r).

1 meter in 0.04s is 25m/s = 90 kmh
1,57 meter in 0.04 is 39 m/s = 142 kmh
The bat speed must fall in between (given these estimates).

The balls measured speed at 113kmh seems pretty low but it’s measured after the ball has lost speed due to drag.

 

[dingyibvs]

I'm curious what the speeds are. I took Otcharov's record attempt, where he reaches 113 kph ball speed at full power:

Screenshots below are from at 2:15.

Frame 1

Frame 2

Frame 3

2 frames at 50 fps means this swing took 1/25th of a second, or 0.04s. (I double checked that there are indeed 50 frames in a second by skipping 50 frames and seeing youtubes time counter tick over a second).

In these 3 frames his bat covers about 2/3rd of his table half, let's estimate that distance at about 1 meter.
But his bat doesn't move in a straight line. It rotates around his elbow. Let's assume the bat traveled in a circle, with a diameter of 1 meter. The distance traveled is now 1.57m (pi*r).

1 meter in 0.04s is 25m/s = 90 kmh
1,57 meter in 0.04 is 39 m/s = 142 kmh
The bat speed must fall in between (given these estimates).

The balls measured speed at 113kmh seems pretty low but it’s measured after the ball has lost speed due to drag.

A loop isn't a smash, of course, so we'd need to know what the relative normal speed is. I suspect it's much higher than the ~40 km/h the Tpar tests are done with.

That article overall has far less data than studies I'm used to reading, both in the methods and results section.