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dwelltime |
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JacekGM
Platinum Member Joined: 02/17/2013 Location: USA Status: Offline Points: 2356 |
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Because I find it hard to believe that differences in physical dwelltime between different rubber/blade combos are not relevant to the feel of the racket, and hence to its performance in the hands of a player.
This value (dwelltime) can be measured precisely, and can be reported, for all the imaginable combinations, the same way the specific weight of a rubber is reported. It could be potentially even more useful than the reported specific weights. This is why I became interested in this - new to me- topic. Edited by JacekGM - 08/28/2013 at 1:08am |
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(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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AgentHEX
Gold Member Joined: 12/14/2004 Location: Yo Mama Status: Offline Points: 1641 |
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The point in bringing up simulation is that the system shouldn't be difficult to fully characterize. Simulation generally requires some level of measurement anyway even if only for sanity check.
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AgentHEX
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It is relevant to the feel of racket, but feel of the racket doesn't matter to performance in anything but very short term because your senses will remap a given feel to certain expectation automatically. For example, I can switch to inverted BH instead of LP (surely more than most changes) and only experience temp drop of performance for maybe few hours. |
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JacekGM
Platinum Member Joined: 02/17/2013 Location: USA Status: Offline Points: 2356 |
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Interesting... Also, I have updated the original post.
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(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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tt4me
Gold Member Joined: 01/17/2013 Location: RC Poverty Zone Status: Offline Points: 1019 |
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These questions about dwell time will stop and the people that claim the dwell time is 5 milliseconds will be proven wrong except in some rare cases. There was an Andro video that showed FEA simulation not too long ago. I bet Andro knows what the dwell time is under multiple conditions. The point is that it would answer Anton's and mercuur's question and there wouldn't be any bad information like 5 millisecond dwell times. |
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AgentHEX
Gold Member Joined: 12/14/2004 Location: Yo Mama Status: Offline Points: 1641 |
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Well, if you think information will stop dumb claims and crackpot theories have I got some great investment opportunities for you.
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Baal
Forum Moderator Joined: 01/21/2010 Location: unknown Status: Offline Points: 14336 |
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I found one study (but it's not the one I am looking for, at least I don't think so).
http://www.ittf.com/ittf_science/SSCenter/docs/200200027%20-%20Tang%20-%20Speed.pdf This one used a golf-swing robot and a camera operating at 4500 Hz. All you can see from this one is that dwell time is less than 7 ms (still to fast to measure with your neurons). What they were mainly trying to do is compare 38 and 44 mm balls. I am still trying to remember where to look for the other paper that measured dwell with a bit more resolution. |
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Baal
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Pretty much what I expected. |
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JacekGM
Platinum Member Joined: 02/17/2013 Location: USA Status: Offline Points: 2356 |
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So, the experiment I offered to measure the dwell time is pretty much conceptually ignorable, is it not?
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(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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Baal
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No, I don't think so. |
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Baal
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I'm not sure I understand your point. If the subject is uninteresting to you, why do you weigh in on the thread? I am pretty sure I am not getting what you are saying because you did seem earlier to be interested. I'm not trying to be hostile at all, I just don't get what you are saying here. I am sure there are all sorts of different ways one could measure the dwell time given the funds to do it. There is a consensus that the true dwell time is too fast for nervous system to measure it directly, and yet people have preferences for blades, rubbers, etc. I find this interesting and am curious how people can do it, and do it fairly reproducibly. This is a forum about all aspects of table tennis, and some things are interesting even if they don't make you a better player. Edited by Baal - 08/28/2013 at 11:19am |
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JacekGM
Platinum Member Joined: 02/17/2013 Location: USA Status: Offline Points: 2356 |
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Yes, absolutely. This is what I wrote above about it: ... I find it hard to believe that differences in physical dwelltime between different rubber/blade combos are not relevant to the feel of the racket, and hence to its performance in the hands of a player. This value (dwelltime) can be measured precisely, and can be reported, for all the imaginable combinations, the same way the specific weight of a rubber is reported. It could be potentially even more useful than the reported specific weights. This is why I became interested in this - new to me- topic. |
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(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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Baal
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Jacek, I also agree that the actual dwell time of the blade is strongly correlated with some other aspect of the blade that gives rise to something we can detect, and I would be very curious to know what it is. The most likely thing (if I am correct in this) is the pattern of vibrations that move down the handle, characteristics of which would presumably depend on blade and rubber.
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tt4me
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If the camera could record at 4500 FPS then why didn't they do so when they had the chance? This is a missed opportunity. |
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JacekGM
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Absolutely, yes. I just thought about this issue last night.... So, the experiment I offered would require that the horizontally (flat) oriented paddle be held in some kind of palm-like clamp, which should be very doable. As you suggested, the (complex) vibration pattern will certainly influence dwelltimes of various rackets.
Edited by JacekGM - 08/28/2013 at 11:33am |
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(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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Baal
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I know. It is frustrating that the only picture they show is at 7 ms! I think there is another article where they actually did measure it. Even more frustrating is that I can't find it!!!!! |
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JacekGM
Platinum Member Joined: 02/17/2013 Location: USA Status: Offline Points: 2356 |
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... or, lets find a guy with a supersensitive and superfast balance !
It must exist somewhere...
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(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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mercuur
Super Member Joined: 01/06/2004 Status: Offline Points: 384 |
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Please don,t laugh to soon for this .
I first wondered how a 1000 hz camera can possibly make a movie/video of 0,001 sec (the relevant part). 1000 Hz corresponds to a frequency 1 /ms. One frame for a millisec would more be a fotograph. A slowmotion of a photograph does nothing for that. So then I wondered how they dealt with slow motion and change of sequency for slowmotion. Slow motion affects clocks seen on video also. So did they correkt the cameraclock for this or not or does it do this by itself ? Assume for a moment that it wasn.t corrected and let me try to make a scenario of what could have happened.... Videos like this don,t show running clocks filmed simultaneous with the bounce right ?. Suppose a video would show this. Clocks in slow motion are also slowed down. So it would also show more time then the cameraclock for say ten (10) frames for making the relevant part of these videos. Simply because the frequency got sequency is slowed down ánd this clock also ftom slowmotion but not the cameraclock if it runs the same as for making the video. When a clock runs too fast it shows less timereading for same period. The timereading would be shorter then. Edited by mercuur - 08/28/2013 at 1:44pm |
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JacekGM
Platinum Member Joined: 02/17/2013 Location: USA Status: Offline Points: 2356 |
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In a situation where someone is not a specialist, as a rule of thumb it is safe to assume that there may be situation of which the person is not aware. To me, it would be highly surprising if super-fast recording equipment was not available in science, technology, or even industry for that matter. I would rather try to find what is available on the internet, and then, if nothing of value to this topic is available, I would think of running experiments myself, and if that is not possible... well, just hang in there and see what others can come up with. Does this sound like a plan to you?
Edited by JacekGM - 08/28/2013 at 1:57pm |
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(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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Baal
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Well, the study I mentioned used a camera at 4.5 khz. So if the true dwell time was 1 ms, Nyquist theorem says they should have been able to see it.
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JacekGM
Platinum Member Joined: 02/17/2013 Location: USA Status: Offline Points: 2356 |
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Of course. The same is true e.g. in modern crystallography, where bonds that are 1.3-1.9 Angstroem are well visible with the resolution of 3 A.
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(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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Baal
Forum Moderator Joined: 01/21/2010 Location: unknown Status: Offline Points: 14336 |
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You are a crystallographer?
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JacekGM
Platinum Member Joined: 02/17/2013 Location: USA Status: Offline Points: 2356 |
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No, I am not, but quite close, really. Are you?
Edited by JacekGM - 08/28/2013 at 2:05pm |
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(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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mercuur
Super Member Joined: 01/06/2004 Status: Offline Points: 384 |
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I don't take all science ecually serious.
They likely use a camera packed out of a box with a manual that tells nothing about science use like this. A frequency of 1000 hz is definitely too short for 0,001 sec to give a filmic illusion. These where the values that did go round here. I even used them myself few times in my posts without noticing. These values combined are ridiculous. But I let it rest further here. Edited by mercuur - 08/28/2013 at 2:12pm |
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Baal
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4500 frames per second camera is what they said they used. But in any case, they didn't show an image except at 7 ms, ball was already off the paddle.
I don't know where the 1000hz number came from. Jacek, I work on ion channels. |
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JacekGM
Platinum Member Joined: 02/17/2013 Location: USA Status: Offline Points: 2356 |
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I used to work on selective GABA-blockers... you got me now, . Currently synthesizing all kinds of really complex ligands for RNA-like molecules. Exciting stuff. With kind regards. jgm
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(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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JacekGM
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Such as...?
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(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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AgentHEX
Gold Member Joined: 12/14/2004 Location: Yo Mama Status: Offline Points: 1641 |
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No there isn't. In fact, I'm not sure you think it's true at all.
The vibration freq/magnitude are indicative of mechanical energy loss, which is causal to general elasticity. Dwell time itself is irrelevant in this given a material can be soft AND elastic, or hard AND less elastic. |
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AgentHEX
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Nyquist is so completely irrelevant here that frankly I'm not even sure how anyone can possibly think it is. This isn't some randomly occurring or high frequency event where aliasing might be an issue. The almost exact moment of contact (AND end of contact) can be linearly extrapolated from flight path of ball (and bat if need be). So the minimum requirement here is only two accurately timed samples each for in/out reasonable aero assumption.
Resolution limit (ie diffraction/mtf/etc) isn't same thing as nyquist limit. Nyquist isn't even physics, but rather math. Edited by AgentHEX - 08/29/2013 at 4:29am |
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Baal
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OK, Fine Your points are granted. Anyway, the camera was at 4500 frames per second. The exact dwell time is very short. Anything else you want to add?
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