dwelltime
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Topic: dwelltime
Posted By: mercuur
Subject: dwelltime
Date Posted: 08/27/2013 at 2:53am
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Lot of threads and discussions on the equipment forum involve dwelltime. There seem to be some scientific meassurements with a camera but I can,t find them. What I read now and then doesn,t tell anything about how much it can vary from things as sponge, sponge thickness, blade, different type of strokes, technicque. aso. I have read several times it was in the realm of 0,001 sec. That,s in millisec but a unit says zero nothing about the precision for meassuring variabillity For 1 msec even less then it would for 4 or 5 msec. 1 (with no further digits) can be between 0,5 and 1,5 millisec which has a faktor three (or three hundred percent) possible difference. A fourth digitnumber and how this fluctuated is needed then to know something about the variation in percentage. I don,t know wether the camera measured with more precision or if the measuring data was rounded to millisec. So question is if someone knows more or where I can find this ? ------------- |
Replies:
Posted By: Baal
Date Posted: 08/27/2013 at 7:39am
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ITTF once commissioned some engineers with a very high speed camera to measure the length of time the ball stays on the paddle -- this must have been done at least ten years ago if not more. I have spent some time trying to figure out where on the web this thing is buried, so far without success. The numbers they came up with were presented with standard errors, which were reasonably small. Anyway, the bottom line was that the ball stays in physical contact with the surface for such a short period of time that sensory neurons would not be able to measure the true dwell-time -- and we are talking more than an order of magnitude. I am working from memory here, I read it carefully a couple of years ago, but I don't think they checked multiple blade types, and multiple types of rubbers. Players can clearly discern that different setups react differently, and often refer to some part of the feeling as "dwell" because that is what it seems like, but that is not what they are feeling, at least not directly. My theory is that people feel in their hand a complex vibration probably comprised of many different frequencies that is created from the ball striking the rubber on the blade. Presumably the spectrum of vibrations, and their duration, depend on the blade and rubber, and the vibration lasts much longer than the time the ball is in contact with the blade. It would be interesting to put pressure transducers on various parts of a paddle and shoot balls at the surface to see what these vibrations look like in terms of power spectrum and duration. Those kinds of transducers are not very expensive (compared to the cameras), and it would not surprise me if a company like Butterfly doesn't do something along these lines. Also, to me it seems plausible that something about the vibrations evoked by the ball hitting the surface would have some relationship to the actual dwell time. Maybe an engineer or physicist could weigh in on this?? From the point of view of physiology, though, the neurons in our fingers and hands, sensitive as they are, cannot possibly measure actual dwell time but they can certainly figure out that different blades and rubbers are different. I think there is a thread about this with a link to the pdf of the original study somewhere on OOAK forum. |
Posted By: BH-Man
Date Posted: 08/27/2013 at 8:25am
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LIKE Baal post! ------------- Korea Foreign Table Tennis Club Search for us on Facebook: koreaforeignttc |
Posted By: JacekGM
Date Posted: 08/27/2013 at 9:56am
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To approximate the dwelltime of a blade-rubber combo, one might position the various rackets horizontally flat on a supersensitive and superfast balance and shoot the ball at exactly the same (reasonable) speed vertically from above, at the racket surface. The one different thing about this experiment would be that it ignores vibrations yet yields the real dwelltime (...and you can challenge this assumption, of course). One problem I see here, though, is that I am not aware of balances that would be as fast as a camera, but who knows, these days so much is possible...
------------- (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. |
Posted By: davidz
Date Posted: 08/27/2013 at 11:52am
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About two years ago, I also learned that the dwell time is 0.001 sec. I believe that is rounded result due to relatively slow camera. Unfortunately, it causes some people to consider the dwell time is a constant regardless of blade ruber type, different tech. etc. The sound frequency is more likely between 700 to 1000 Hz when bouncing a ball using a blade with a rubber. This might indicates the dwell time is 0.001- 0.0014 sec. When hiting a ball, the sound frequency decreases a little, suggesting a longer dwell time. When looping, I guess the dwell time could reach 0.002 to 0.004 (? I did not test this). A frequency measure software should be helpful to measure the blade frequecy under different playing techniques. This approach assumes the sound frequency is directly tied with blade dewell time. ------------- PG7 (Skyline 2, LKT XP) YEO (Skyline 2, Skyline 3) |
Posted By: mercuur
Date Posted: 08/27/2013 at 2:48pm
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Handmuscles act on a bat with some muscletension. There is inner awareness for this type of tension from neuronsystem. So hitting a ball, the ball hitting the bat ,this tension interacts and reacts. That can be part of sensing the ball. The other part is more from sensory feel.. These can be combined for the whole experience then. How fast the neuronal system works for that doesn,t matter much. That,s more for processing and combining these two types of feel. I can,t see why that can,t be done afterwards or even other then that. Somewhat similar to the residue vibrations of a blade. Trained more specific this processing and combining would be better and quicker. ------------- |
Posted By: Baal
Date Posted: 08/27/2013 at 3:36pm
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Fatt, I think you are right that we don't actually have to measure it in real time. Over at OOAK forum there is a thread in the blade section by Kees on "The Function of Feedback in Blades" that talks about the point you raise. The idea is that we use mechanical feedback from blades to decide what to do on the next shot, not the one we just hit, which is what I think you are saying. I think that is really important for sure. My idea is little bit different (and not incompatible with that one). It is that something about the vibrations in the handle is directly related to the true dwell time, and that is what the sensory cells in our hands and fingers are picking up. |
Posted By: Baal
Date Posted: 08/27/2013 at 3:51pm
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Mercuur, the sensory elements in the muscles in your hand and fingers (called muscle spindles) detect the length of your muscles, and there are sensory elements in the tendons where the muscles attach to the bone that detect the tension. However, those systems are very very slow, even compared to the vibration sensing neurons in your skin. They would contribute to your ability to measure the size of a handle and how hard you are gripping. They would probably not contribute much to the feeling one has from striking the ball, including the sense of "dwell", whatever it might actually be. Basically, this all comes down to two questions: (1) why do different blades feel different (which you can often tell immediately) and (2) what effect does it have on how you play (which you figure out a bit from trial and error, but making use of this sensory input). Well, also a third question, why do we like what we like? Some people would argue that you should use a blade that gives you as much sensory input as possible, and therefore a blade with more vibrations ought to be better. More information should mean better motor responses, or so you would think. For some reason though, blades that seem to dampen out quite a bit of that vibration (e.g. Butterfly ALC blades) are very popular (I like them better than any other kind of blade myself) and they are even used by top players in the world who don't really need the power that they generate. I have to admit I don't understand why I don't like much vibration in my blade, and why blades like Viscaria, TBS, TB-ALC etc. feel so pleasing to many players. You would think it would make no sense. |
Posted By: tt4me
Date Posted: 08/27/2013 at 3:53pm
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@mercuur, this forum is not the place to ask this question. I would go to a physics forum or even make a request of a TV show that makes high speed videos. Did you post the same question of the German TT forums? Edit: I just posted my comment and I see Baal's above posted while I was writing mine. @Baal, why do you always derail the threads on dwell time? Anton was asking about how long the ball stays on the paddle. mercuur is asking the same thing. You always want to get into the physiology of what is felt rather than the physics of what is really happening. This is why I made the comment about this forum not being the place to ask this question. If you ask the same people the same question you will get the same answers. Look at Baal's comments in Anton's thread and compare them with Baal's comments in this thread. mercuur needs to seek new people. ------------- Samsonov Alpha+H3 Neo+802 1.5mm, the Ball Whacker is revived!<br />Samsonov Alpha+H3 Neo+802-40 1.8mm my back up<br />BCX5+H3+802-1 1.8mm New but promising.<br /> |
Posted By: Baal
Date Posted: 08/27/2013 at 6:31pm
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Well, anyway, the dwell time has been measured and it is really really short and it was measured reasonably reliably in answer to OP. I think the link to the paper can be found in the thread started by Anton. |
Posted By: mercuur
Date Posted: 08/27/2013 at 6:34pm
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Kees his article about feedback was interesting to read back then. All these subjekts seem to overlap anyway. That,s part of it. Kees and I also happen to overlap each other for that I lived in same city for eight years, Never met him tough I think and only played there for competition playing for other clubs. Level back then was higher Dutch national youth league and lower Dutch natonal seniorleague. But his article would also be bull for science when dwell couldn,t be experienced directly at all and compared for things and changes. Or all off this article would also be from residue vibrations. I don,t feel them as too disturbing mostly but also not really contributing for this feedback. I never play with a clock in my hand tough. I don,t compare my experience for TT with reading and seeing a clock. Better keep these things apart offcourse. I learned to play before technical, physics education. That makes it easier for me maybe. But the word dwelltime or dwell doesn,t need the idea of a clock either. Longer or shorter dwell also comes along in reviews for instance. That could just the same be trajektory. I take a sidestep now and then to this type of video,s and this involves a clock then with dwell is 0,001 sec. That,s physics then because a clock, is used as physics tool. Still if we keep these things apart or try this the discussion stays pure and interesting and about tt and equipment also. @Baal, I don,t mean that precisely. It,s more a basetension or sort of an equilibrium build with the bat. The ball comes in reacts on this and what it reacts to also fluctuates from this a little. Enough to sense it in fingers and hands immediately independant of a sensory uptake from the skin contact with a bat. One type of feeling could feel the collision more and other the bats reaction to the collision ? I really don,t believe a sience forum could answer all this or people wouldn,t even go into it.. But I,m not out for finding thruths like that anyway. Not for my own either. Yet it,s fun to conversate about ithis on this forum as I heard last week our summer holliday was extended with another two weeks pause. I suspect this is mostly the reason for my current activity on the forum as a compensation and surrogate for playing. Normally I can deal with it better because I know the date it starts again to look out for. This time they criminally changed the date  .------------- |
Posted By: AgentHEX
Date Posted: 08/27/2013 at 6:58pm
"Dwell" is just a psychological concept we relate to certain feel (perhaps persistence in certain frequencies). There's no way to even tell if what one person means by "dwell" is same as anothers'. All we know is that between product X and Y, if a "reviewer" says X is more in certain feel than Y (as unreliable as that already is), when others try X & Y they each attribute some subset of that diff to the concept. IOW, it's a complete crapshoot what anyone really means by it. Feel is important because it provides info on how the shot was hit thus allowing more prep for reaction, but not trivial to characterize without some srsly sophisticated study. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
fatt wrote:Posted By: cole_ely
Date Posted: 08/27/2013 at 7:31pm
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How do you define dwell to measure it? Do you start from the moment the ball touches rubber and end when it no longer touches? Do you start when the ball stops its forward momentum and stop when it begins to move the other way? ------------- Wavestone St with Illumina 1.9r, defender1.7b Please let me know if I can be of assistance. |
Posted By: AgentHEX
Date Posted: 08/27/2013 at 7:35pm
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There's the physical dwell defined by the former (~1/2 the latter) and psychological dwell defined by the stuff inside people's heads. These two are different enough that using the same word for both is confusing. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: stiltt
Date Posted: 08/27/2013 at 7:51pm
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The way I understand "dwell" it does not need to be quantified and can only be measured relatively to another object. eg XZQ has more dwell than Schlager Carbon; Bluefire M1 has more Dwell than Tenergy 05. For blades it is a mix of flex (more = more dwell) and softness of the outer ply or plies (more = more dwell); for rubbers it's a mix of elasticity of the topsheet (more sling shot effect = more dwell), bounciness of the sponge (less = more dwell) and resistance of the sponge (more about this below). It is interesting to note that more dwell does not necessarily mean less speed and that's why I find the concept intriguing and useful; to explain that we can achieve more speed and spin without loss of control which at first sounds like heresy. About the resistance of the sponge: it can be thought as the time the sponge takes to compress and the time it takes to release the stored energy; on the Bluefire M1 that compressing time is longer (more dwell) than on the T05 and yet the Bluefire is not slower: the sponge takes longer to compress but will release the ball faster (more dwell but no loss of speed). We may need somebody who has an understanding of dwell (other than intuitive like me...) and does NOT lack the scientific background to put it in words that can be accepted by all as useful a tool to describe a rubber. ------------- /forum/topic91512_page1.html#1124698" rel="nofollow - sales - forum_posts.asp?TID=19315" rel="nofollow - feedback |
Posted By: AgentHEX
Date Posted: 08/27/2013 at 9:12pm
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I don't think it's helpful to assume causal relationship between any physical attribute of the blade and psychological terms. For example, it's already established that humans can't necessarily feel the "flex" per se anyway. They can however feel frequency/magnitude of vibrations of the blade. Maybe some people describe high magnitude low freq as dwell, maybe some define it as the height of the shoulder in elasticity function (when a bat's elasticity stops being linear), and everything in between. It's worth noting again that our personal mental feelings/definitions for these words are NOT shared, which makes mapping any such thing to how something feels largely pointless. As a separate topic, it's perfect feasible that a softer sponge (longer physical, not psychological dwell) is also more elastic. But again as established, this is not something anyone can take advantage of themselves. In fact it's when the intuition of softer = slower breaks down that our minds develop even more elaborate myths (like OP) to retain misleading generalizations. This is part of why sharing feelings with others is like a chinese and japanese person communicating in writing. The words look the same but can mean different things. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: tt4me
Date Posted: 08/27/2013 at 9:31pm
No!!! dwell time = contact time. Baal and others have high jacked and misused the term dwell to mean how long you feel the ball. @Cole and @Fatt, the contact or dwell time is the time the ball is in contact with the rubber. Simple. Dwell time is hard to measure unless one has a high speed camera with a very high frame rate. Then one can count the number of frames the ball is in contact with the rubber and multiply that by the period between frames. VLC is very good at step through videos frame by frame or playing the videos back in slow motion. @mecuur, knowing the dwell time is not going to make you a better player. ------------- Samsonov Alpha+H3 Neo+802 1.5mm, the Ball Whacker is revived!<br />Samsonov Alpha+H3 Neo+802-40 1.8mm my back up<br />BCX5+H3+802-1 1.8mm New but promising.<br /> |
Posted By: AgentHEX
Date Posted: 08/27/2013 at 9:36pm
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Again, there's the physical dwell and what people feel as dwell. You cannot deny the latter any more than you can deny sadness because it's not some easily visible physical phenomenon in itself. It if helps you can think of it as any number of words with multiple, equally valid definitions. It's unfortunate if people conflate them, but that's a different problem than validity of each in and of itself. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: AgentHEX
Date Posted: 08/27/2013 at 9:43pm
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This conveniently segways to an illustration worth mentioning. When you
feel, say, "sad", what you're really saying is "this is how I feel when
such and such type events occur" not that the event is itself sadness.
You might be able to empathize when someone else feel emotions akin to
this about it or similar events to the point where you share the same word to describe it, but you never know what they themselves
feel. It's philosophically questionable whether this sort of quite common and valid linguistic
usage is conducive to further clarification beyond a certain level.
------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: smackman
Date Posted: 08/27/2013 at 9:54pm
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chuck Norris is so good at TT he can dwell time loop all the way around the ball ------------- Ulmo Duality,Donic BlueGrip C2 red max ,Yinhe Super Kim Ox Black NZ table tennis selector, third in the World (plate Doubles)I'm Listed on the ITTF website |
Posted By: AgentHEX
Date Posted: 08/27/2013 at 9:56pm
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Chuck norris don't even need to play because his opponents always forfeit. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: tt4me
Date Posted: 08/27/2013 at 10:11pm
This must be some medical term for the delay in sensation that would be better than dwell.
I am not arguing with what Baal says. I simply think it is off topic. It has nothing to do with Anton's or mercuur's original question. Being off topic delays getting to the truth. In this case it has delayed getting to the truth a lot and in general been a big time sink. Reading through Anton's thread again I see mention of dwell times of up to 5 milliseconds. I wonder how that was determined? ------------- Samsonov Alpha+H3 Neo+802 1.5mm, the Ball Whacker is revived!<br />Samsonov Alpha+H3 Neo+802-40 1.8mm my back up<br />BCX5+H3+802-1 1.8mm New but promising.<br /> |
Posted By: AgentHEX
Date Posted: 08/27/2013 at 10:26pm
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It's perhaps OT to the topic of physical dwell but not the topic of the psychological. I'm the last person you need to advise that using technical words to describe the latter can be annoying. However, what people feel is equally "truthy" and probably more material to their game even if it's more nebulous. Frankly nothing I've seen about the technical aspect implies it's that complicated. The only significant ambiguity is that different parts (pips bend, sponge compress) contribute differently to the whole on a contiguous scale that varies according to speed/spin and direction of incoming shot. Eg, japanese synthetic pips have more mechanical elasticity, but how much compared to softer natural rubber? 20%? 50%? How much % does that vary from touch to power stroke? ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: JacekGM
Date Posted: 08/27/2013 at 11:04pm
Cole, In the post (vide infra) I meant dwell time of a racket setup as from the moment the ball touches the rubber of the racket and up to the moment it leaves the rubber. Isn't that the "dwell" we intuitively expect? To approximate the dwelltime of a blade-rubber combo, one might position the various rackets horizontally flat on a supersensitive and superfast balance and shoot the ball at exactly the same (reasonable) speed vertically from above, at the racket surface. The one different thing about this experiment would be that it ignores vibrations yet yields the real dwelltime (...and you can challenge this assumption, of course). One problem I see here, though, is that I am not aware of balances that would be as fast as a camera, but who knows, these days so much is possible... Leaving the realm of physics for this topic may bring us to another lively discussion where everyone is right ... in their own way. However, the experiment needs to be very simple and we need a good tool to measure the dwell. A superfast balance (scales?) with output recording could do the job, as could a number of other devices. ------------- (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. |
Posted By: tt4me
Date Posted: 08/28/2013 at 12:27am
Then why hasn't anybody figured it out? Why do these threads on dwell time reappearing? ------------- Samsonov Alpha+H3 Neo+802 1.5mm, the Ball Whacker is revived!<br />Samsonov Alpha+H3 Neo+802-40 1.8mm my back up<br />BCX5+H3+802-1 1.8mm New but promising.<br /> |
Posted By: JacekGM
Date Posted: 08/28/2013 at 12:27am
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A crude example how such superfast balance would work: Time (milisec) Weight read-out (grams) 0.00 0.00 (Tared) 0.2 0.7 0.4 1.9 0.6 2.9 0.8 3.6 1.0 3.1 1.2 2.2 1.4 1.0 1.6 0.6 1.8 0.2 2.0 0.0 2.2 0.0 Dwell time= 2.0 miliseconds ------------- (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. |
Posted By: AgentHEX
Date Posted: 08/28/2013 at 12:40am
Figured out what? You can model/CAD the bat and use FEA to simulate the physics. But what's the point? ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: JacekGM
Date Posted: 08/28/2013 at 12:43am
For different rubber-blade combos I would rather measure things than simulate. The purpose would be to determine which racket allows a longer dwell time, or the optimal dwell time for a player, etc. ------------- (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. |
Posted By: AgentHEX
Date Posted: 08/28/2013 at 12:57am
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Huh? It should be clear from the info above that dwell time doesn't matter. Who cares if it's 1ms or 5ms? You body can't react that fast anyway, thus it's just matter of feel. How anyone prefers feel is subjective. Btw, this bit isn't necessarily correct:
Why not? Being able to sense the approx "dwell" by proxy of vibrations isn't nearly as hard as reacting within the window. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: tt4me
Date Posted: 08/28/2013 at 1:01am
I agree that measuring is better than simulating but there are too many combinations to measure. How would you measure? Once there is accurate data on each rubber and each blade then one can simulate all the different combinations. We know this will not happen but NO ONE is going to simulate all the combinations of rubber and blades and I don't think that is the point since many rubbers are similar and so are many blade. I don't see why you guys persist in knowing the dwell time. It won't make you a better player. When I play with my hard bat I know the dwell time is short. The dwell time is probably short when I play with my LPs too. It doesn't bother me because I expect it. ------------- Samsonov Alpha+H3 Neo+802 1.5mm, the Ball Whacker is revived!<br />Samsonov Alpha+H3 Neo+802-40 1.8mm my back up<br />BCX5+H3+802-1 1.8mm New but promising.<br /> |
Posted By: JacekGM
Date Posted: 08/28/2013 at 1:04am
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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. ------------- (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. |
Posted By: AgentHEX
Date Posted: 08/28/2013 at 1:04am
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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. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: AgentHEX
Date Posted: 08/28/2013 at 1:08am
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. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: JacekGM
Date Posted: 08/28/2013 at 1:10am
Interesting... Also, I have updated the original post. ------------- (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. |
Posted By: tt4me
Date Posted: 08/28/2013 at 1:21am
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. ------------- Samsonov Alpha+H3 Neo+802 1.5mm, the Ball Whacker is revived!<br />Samsonov Alpha+H3 Neo+802-40 1.8mm my back up<br />BCX5+H3+802-1 1.8mm New but promising.<br /> |
Posted By: AgentHEX
Date Posted: 08/28/2013 at 1:28am
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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. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: Baal
Date Posted: 08/28/2013 at 8:41am
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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. |
Posted By: Baal
Date Posted: 08/28/2013 at 8:53am
Pretty much what I expected. |
Posted By: JacekGM
Date Posted: 08/28/2013 at 10:55am
So, the experiment I offered to measure the dwell time is pretty much conceptually ignorable, is it not? ------------- (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. |
Posted By: Baal
Date Posted: 08/28/2013 at 11:09am
No, I don't think so. |
Posted By: Baal
Date Posted: 08/28/2013 at 11:18am
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. |
Posted By: JacekGM
Date Posted: 08/28/2013 at 11:23am
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. ------------- (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. |
Posted By: Baal
Date Posted: 08/28/2013 at 11:27am
|
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. |
Posted By: tt4me
Date Posted: 08/28/2013 at 11:31am
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. ------------- Samsonov Alpha+H3 Neo+802 1.5mm, the Ball Whacker is revived!<br />Samsonov Alpha+H3 Neo+802-40 1.8mm my back up<br />BCX5+H3+802-1 1.8mm New but promising.<br /> |
Posted By: JacekGM
Date Posted: 08/28/2013 at 11:33am
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.
------------- (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. |
Posted By: Baal
Date Posted: 08/28/2013 at 11:35am
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!!!!!  |
Posted By: JacekGM
Date Posted: 08/28/2013 at 11:42am
... or, lets find a guy with a supersensitive and superfast balance  ! It must exist somewhere... ------------- (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. |
Posted By: mercuur
Date Posted: 08/28/2013 at 1:28pm
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. ------------- |
Posted By: JacekGM
Date Posted: 08/28/2013 at 1:42pm
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?
------------- (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. |
Posted By: Baal
Date Posted: 08/28/2013 at 1:45pm
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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. |
Posted By: JacekGM
Date Posted: 08/28/2013 at 1:56pm
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. ------------- (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. |
Posted By: Baal
Date Posted: 08/28/2013 at 2:00pm
|
You are a crystallographer? |
Posted By: JacekGM
Date Posted: 08/28/2013 at 2:01pm
No, I am not, but quite close, really. Are you?
------------- (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. |
Posted By: mercuur
Date Posted: 08/28/2013 at 2:09pm
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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. ------------- |
Posted By: Baal
Date Posted: 08/28/2013 at 2:17pm
|
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. |
Posted By: JacekGM
Date Posted: 08/28/2013 at 2:27pm
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------------- (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. |
Posted By: JacekGM
Date Posted: 08/28/2013 at 2:29pm
Such as...? ------------- (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. |
Posted By: AgentHEX
Date Posted: 08/29/2013 at 4:12am
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. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: AgentHEX
Date Posted: 08/29/2013 at 4:19am
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. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: Baal
Date Posted: 08/29/2013 at 9:58am
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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? |
Posted By: AgentHEX
Date Posted: 08/29/2013 at 10:24am
 ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: Baal
Date Posted: 08/29/2013 at 10:32am
|
AgentHEX, I have repeatedly maintained on this thread and elsewhere
that the nervous system cannot possibly measure the actual dwell time directly--the
length of time the ball is still in contact with the surface based on
the images taken with a pretty fast camera. Sensory physiology is actually what I do for a living. I also know that different blades feel
different, and a lot of people describe setups as having a feel that
seems like "dwell". I have been playing table tennis seriously since I was ten years old and I do a lot of coaching. You may not believe that people can sense this. However, you state, and I believe you, that you can switch from LP to inverted on your BH with no change in level in an hour. So I simply wouldn't expect you to have developed that feel because I know exactly what that claim means. I suspect experienced players can do this reproducibly, but I know for a fact, however, that they cannot be detecting actual dwell given the ball is in contact with blade for substantially less than 7 ms (and I know what conduction velocities and synaptic delays are).
So what is this feeling? Earlier, you came close to my position by
saying it is a "psychological concept". You then went on to say there is no way of knowing if different people mean the same thing when they talk about dwell. Actually, in spite of the fact that you enjoy being an a$$ho1e about pretty much everything, you have hit right there on the key question -- is there some reproducibility to what people are actually sensing when they talk about dwell? My guess is that there is and that the sense of dwell may related to the duration of vibrations of all frequencies that move down the handle where they can be detected by neurons in the skin of the hand and fingers. Maybe blades like some softer feeling Btfly ALC blades vibrate less at high frequencies, but the totality of the vibrations may actually have longer duration, and so maybe people would say this kind of blade had a longer dwell. Other blades may have more vibration at high frequencies and you would feel more of a buzz, but maybe for less time. There is nothing intrinsically implausible about this. Of course there are no data either, so I could be wrong but it would be really interesting to know. The difference in our position is that you immediately assume that it is all nonsense, that everyone is full of it, and that you are a superior entity and that experienced players are just talking about stuff for the sake of talking about stuff. I assume that people actually have the touch to make quite subtle distinctions. |
Posted By: AgentHEX
Date Posted: 08/29/2013 at 10:58am
I believe people can sense a lot of things, just not necessarily what they claim to sense.
What do "conduction velocities and synaptic delays" have to do with measuring a duration of time? I don't know jack about sensory physiology, but if they mean what they sound like, that statement isn't obvious.
Probably. Just because there's no standard and therefore potentially arbitrary doesn't mean it's random. Though I'm more curious here why you think being an ass and being purposefully correct are mutually exclusive. Certainly this shouldn't be novel to a man of science.
Not sure if you're trying to be an ass by repeating more or less http://mytabletennis.net/forum/forum_posts.asp?TID=62442&PID=743654&title=dwelltime#743654" rel="nofollow - what I already said back to me, but I suppose I have no choice but to agree.
The question beckons, why would you still attribute wisdom to yourself and foolishness to myself given it's more reasonable that history repeats itself? I mean, is your mental representation of me as dumb as that straw man? ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: Baal
Date Posted: 08/29/2013 at 12:03pm
|
...repeating more or less http://mytabletennis.net/forum/forum_posts.asp?TID=62442&PID=743654&title=dwelltime#743654" rel="nofollow - what I already said back to me Read earlier thread started by Anton. I wrote about vibrations and sense of dwell months ago. I annoyed tt4me by bringing it up again in this thread. He probably has a point. What do "conduction velocities and synaptic delays" have to do with measuring a duration of time? Conduction velocities are synaptic delays are the reason why someone would not possibly be able to measure dwell time in time to make use of the information on that shot. Actually, more importantly, the response times of sensory receptors in skin would not respond to a 1-5 ms duration stimulus, which I didn't mention. Why would you still attribute wisdom to yourself and foolishness to myself My wisdom is limited. I did not claim anything more than a theory here about what people are feeling when they report dwell. You obviously know a lot about physics and engineering. You berate people on practically every thread you enter. Your claim to be able to play at the same level with LP and inverted with an adjustment time in hours is not something I would ever dispute, in fact I am quite sure it is true, but it is also very revealing. |
Posted By: tt4me
Date Posted: 08/29/2013 at 12:37pm
i warned you guys. This is ridiculous. Another thread ruined just like Anton's.
Yes, you sure have. It is mostly your fault because you do not address the OP's original equation. In the future why don't you just post a link to what you have said before. That way we don't need to read it over and over again and you will save a lot of time REPEATING YOUR SELF and arguing with others. The only part of Baal's distraction that would been useful is if tell us what the minimum difference in real dwell time we could detect. Even a range of differences would be useful. I laugh when I see most people talk about dwell time. Yes, it is what they feel but it isn't what is really happening. I know they have NO clue. I would not bother to post anything intelligent on this thread now because people would get bored before getting here with all the off topic bickering in the previous 60+ posts. ------------- Samsonov Alpha+H3 Neo+802 1.5mm, the Ball Whacker is revived!<br />Samsonov Alpha+H3 Neo+802-40 1.8mm my back up<br />BCX5+H3+802-1 1.8mm New but promising.<br /> |
Posted By: Baal
Date Posted: 08/29/2013 at 2:04pm
|
tt4me, you are probably right, except that I did answer the OP question in several posts-- less than 7 ms. You are right, though, this is not very interesting anymore. Mea culpa. Note added later in defense: tt4me, I don't think i ruined Anton's thread because if you recall, the information I provided on this is exactly what he wanted to know, as he mentioned specifically in that thread. Don't forget, Anton (who we have no seen here in awhile) is in a graduate program in cognitive neuroscience. He thinks stuff like that is really interesting. I do too. Not everybody does. If you don't like my comments don't read them. But, because I don't want to unnecessarily piss you off, I will avoid this topic in the future. Peace. |
Posted By: AgentHEX
Date Posted: 08/29/2013 at 4:49pm
That's fine, but why repeat some line I've said back to me as if it were novel and that I'm a fool for not considering it?
Sure, that's what seemed superficially obvious from their name but why bring them up when they're not relevant to the issue at hand, ie measuring duration?
Why not mention that the first time when it was pertinent? You're supposed to be the expert here so I'm confused why this discussion doesn't appear that way. By "proxy" of dwell it seems fairly straightforward that if there's a relationship (non-static across blades) between dwell and power of shot, and between that and various vibration characteristics, which seems entirely reasonable, then the player can pick up on any number of proxies for dwell by unconsciously sensing the first order derivative of such a relationship. For example, one blade can be "fast" (imply low dwell) meaning they are not only higher freq (ie hardness/elasticity), but both shorter vibration and lower magnitude of vibration. Then again, this is only one category of possibilities of what dwell can mean. For others the word seems synonymous with flex which perhaps refers to the lee-way before a blade enters non-linear elastic reaction. That's why I implied it's potentially arbitrary, yet not random. The linguistic question I posed is which of these is the real slim shady for each player who only know of "dwell" from context of the word in reviews and such with no external verification of what they're measuring or how to measure it? As you theorized yourself above, some of these proxies might be misleading if they're not consistent across blades, but again some might be rather more consistent. So with no way of even remotely aligning measurement standards across players, what can really be said about the affair? Don't conflate this with saying something about measuring blades in general, just how the completely clueless can speak intelligibly about "dwell". Again, you're the human expert here, but to me it seems a rather intractable issue. It's also worth mentioning since we're talking about proxies that I make the distinction because it's questionable whether the hand can measure dwell directly (like a camera does) anyway. What you feel on the hand is the reaction of the bat to the shot, and the questionable part is whether it even makes sense to talk about "feelling dwell" without that stuff in between, ergo the "feel" is the proxy.
I berate people on posing with introductory terms as much for their own future benefit as mine. One does not need to be any sort of expert here because it's blatantly obvious to anyone who paid attention in their intro classes. I'm often genuinely confused whether they're assuming everyone else present is ignorant or just don't know better themselves. Likewise if I ever do such a thing, let me know so I don't repeat the same embarrassment when it matters.
What is it revealing of? There's provably someone @~2200 who can switch between carbon+max inverted and clipboard w/ only ~100 loss in even shorter period of time. Does it imply I'm worse than them because it may take me longer? Or that my game is very stylistically advanced that it takes so long? I really don't know. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: AgentHEX
Date Posted: 08/29/2013 at 5:34pm
|
Ok, my bad on assuming the posing since it seems everyone was instead assuming zeio can think clearly about basic physics in that former thread. Kind of odd someone can read so many studies and still be so terrible at it. I mean, conflating sample frequency with general timing just because the units match is something you only expect mercuur to do. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: JacekGM
Date Posted: 08/29/2013 at 7:33pm
@ Baal: Man, I sent you a handshake, I thought you would reciprocate ... now I don't even have the time to fully express my resentment because AgentHex may pop up any second now...Seriously, this thread interests me hugely - I feel that there is a high practical potential to the concept of dwelltime when determined strictly and reproducibly for different rackets. Yes, rackets, obviously, because the OP clearly had in mind a blade-rubber combo, and this is what plays in our hand, after all. I have a V1 with a thick Vega Europe on it and this has a huge dwell time - don't tell me it does not... I also have a 95 g Juic SBA with 1.9 Sriver on the backhand side, and the dwell there is much shorter, don't tell me it is not... although I know it is not that short either because I can sens the ball stay there for a little... Anything else - it would be nice to be able to attach a reliable dwelltime number to it in order to compare, please don't tell me it would be useless... I close my eyes and envision a 2020 catalogue offering tables of blade rubber combinations, right next to their dwelltime, for your convenience (and next to respective prices, for your desperation...) . Imagine a scenario when we actually found a really easy way to determine the said dwelltime. Someone here would quickly add a table of many numbers... I bet you we would suddenly start discussing how we relate our game to the various dwelltimes. Regarding wisdom and foolishness... that would belong to a thread in a different forum... but the way I see it - true wisdom is non-aggressive and tends to patiently probe reality because it knows how huge the unknown is and how small is the domain of what is known. And there is so much in between... I had a colleague in high school who had a clear and really very strong aversion to any strict knowledge, but he wrote passionately his literature assignments covering technology issues, sports and other areas of measurable human activity. He was disputing aggressively and making really prickly comments toward those who dared to challenge him, and yes, he offended people badly... Once I asked him what his motivation was.. he told me he wanted to be a journalist. Even though he had to repeat a grade or two, decades later I heard he actually became one... maybe that's it? ------------- (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. |
Posted By: AgentHEX
Date Posted: 08/29/2013 at 7:51pm
No it really wouldn't. First a "dwelltime" in itself is pretty meaningless since it's at least contiguous function against ball speed (likely closely correlated to elasticity in blades) not necessarily reducible to a scalar. Second, even given better characterization, the product of rubber/blade combo isn't necessarily simple convolution esp if you'd want to do more than hit the ball straight on. There are further issues, but at this point I'm not sure how the less technically competent are even supposed to make sense of this in a marketing catalog.
True wisdom is exactly like the name says. Everything else is just practical considerations. For example, some folks simply have less patience for hand-holding than others, and many have a strong aversion to bruised ego. Generalizing from anecdotes is less useful when we know the direct causes. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: Baal
Date Posted: 08/29/2013 at 9:34pm
Sorry man. I needed to actually do the work I'm paid for. It's grant writing season, I'm looking into the brink, and sometimes for sanity I come here and post a bunch of nonsense before getting back to my Significance and my Innovation. Mechanosensitive channels. |
Posted By: JacekGM
Date Posted: 08/29/2013 at 9:48pm
Super... can you selectively block these in bacteria vs in mammals ? Not that I want to dwell (time) on this topic here... ------------- (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. |
Posted By: Baal
Date Posted: 08/29/2013 at 9:58pm
|
Does anybody know if the wood they use for handles these days is pretty much all the same? For sure it didn't use to be! We worry a lot about the plys in the blade itself, but a lot of what we feel has to go through the handle, except for our forefinger on the surface (and for some people the side of the thumb). But we never talk about the wood on the handle and the manufacturers rarely say anything about that either. Handle shape and size matters a lot to me. One of the many things that determines the sensitivity of vibration detectors in your skin is the pressure exerted on the surface (for example how hard you grip something). Changes in the handle shape is going to cause pressures to be exerted in slightly different parts of your hand, which take some getting used to. You would think that how hard the handle wood is might matter too. I am curious that there is not as much said about that. I have the impression that most people are not real crazy about excessively hollow handles, but when they first came out it was the next Big Thing. |
Posted By: igorponger
Date Posted: 08/29/2013 at 11:09pm
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http://protabletennis.net/book/export/html/89" rel="nofollow - http://protabletennis.net/book/export/html/89 Mr. Fullen is right indeed. There is no "absolute" dwell time. The time span that ball sits on the racket will vary distinctly from a stroke to a stroke. Smashing stroke, chopping and stop-blocking will produce different dwell time, and the difference is measured just by few millliseconds, from 0.001 to 0.004, if my memory still serving me. |
Posted By: haggisv
Date Posted: 08/30/2013 at 1:12am
|
It's simply another subjective term, just like 'throw', that's meaningless as an actual number, but useful for comparison to other equipment. If you don't like it or don't believe in it, ignore it, but personally I find it quite useful for comparison. ------------- Smart; VS>401, Dtecs OX http://tabletennisshop.com.au/index.php?main_page=page&id=42" rel="nofollow - Tenergy Alternatives | http://tabletennis-reviews.com" rel="nofollow - My TT Articles |
Posted By: AgentHEX
Date Posted: 08/30/2013 at 1:26am
Vibration modes is primarily function of bat materials (incl rubber) itself since shape is predetermined. Unless the handle is strange it shouldn't matter too much to main area the vibrations are created (in that if you just cut it off, the changes shouldn't be drastic) as long as there's solid connection to the hand. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: AgentHEX
Date Posted: 08/30/2013 at 1:31am
The problem is that even if each individual can reliably feel what they call dwell, there's no reliable way to intelligibly communicate it to others accurately. It's also not quite akin to throw in since throw is more conceptually straightforward and easily verified. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: stiltt
Date Posted: 08/30/2013 at 1:42am
|
At whatever level, a person who tests a lot of rubbers can make the difference between the dwell of one rubber and another; if that person shares the word "dwell" in his/her tt vocabulary with a reader, the latter will understand what the reviewer means: one rubber has more dwell than the other. People who do not like the word "dwell' should propose something else; or they could sit in a meditative stance yelling "DWEEEEEEEEELLLLLLL" and the enlightenment will come. ------------- /forum/topic91512_page1.html#1124698" rel="nofollow - sales - forum_posts.asp?TID=19315" rel="nofollow - feedback |
Posted By: haggisv
Date Posted: 08/30/2013 at 2:03am
I never said it needs to be accurate. Just the information from an experienced reviewer that the dwell time is high (obviously compared to other equipment they've tested) can be quite useful. Similarly the comparison that it's higher than something else (that I may have played with) can be very useful. If you try and put numbers to it, it does indeed too subjective to be useful.
I disagree... throw is also subjective as it depends on too many factors, like the stroke played, how hard you hit the ball, etc. This is why I think it's again mainly useful for comparison purposed, just like dwell. ------------- Smart; VS>401, Dtecs OX http://tabletennisshop.com.au/index.php?main_page=page&id=42" rel="nofollow - Tenergy Alternatives | http://tabletennis-reviews.com" rel="nofollow - My TT Articles |
Posted By: AgentHEX
Date Posted: 08/30/2013 at 2:04am
I've already addressed this but will try to demonstrate using an analogy. A car is often described as "faster" than another, but this can mean any number of things including HP, torque, top speed, etc. These are all well understood correlated measures in an entangled but coherent mesh of relationships, yet describe different aspects of performance. Even using "faster", a more objective concept than "dwell" is rather perilous without careful definition least we consider an f1 car and salt racer both faster than the other. The difference here to TT is that the average player or even EJ simply lacks both the standardized vocabulary and technical sophistication to speak meaningfully of these measures or physical concepts such as acceleration, not unlike an auto enthusiast ignorant of the terms above trying to rate various cars. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: AgentHEX
Date Posted: 08/30/2013 at 2:26am
If you ask ten people how they feel dwell, expect many different answers. If there's not even any sort of shared definable quality to a concept, what meaning is it supposed to represent? Compared this to throw below.
No, throw can be pretty well defined since it's hardly just a nebulous feeling. If a bat is held at same position (or other swung) against given incoming shot (eg robot), it will rebound the ball at a measurably objectively and repeatedly verifiable angle (and speed). ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: stiltt
Date Posted: 08/30/2013 at 2:40am
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right or wrong, using the word "dwell", people exchange information; through trial and error they will eventually reach their goal (good for us) unlike a superior mind who will get it right away (good for him and you). In your analogy if the people use the word "fast" because that's what interests them why should they be pointed at for not knowing about or ignoring torque and the 4-stroke cycle? IOW, why would anybody care? Would you engage with a bunch of teenagers loving their customized honda civic and tell them: "you don't get it; that huge muffler does nothing to you it only costs you money and it's also ugly; your hi-fi system is such an overkill for such a low interior volume and it does not even sound good". ------------- /forum/topic91512_page1.html#1124698" rel="nofollow - sales - forum_posts.asp?TID=19315" rel="nofollow - feedback |
Posted By: stiltt
Date Posted: 08/30/2013 at 2:45am
if 10 people have slightly different definitions of dwell but can arrange 10 rubbers in the same order when comparing their dwell characteristics then the dwell is good a tool to communicate. ------------- /forum/topic91512_page1.html#1124698" rel="nofollow - sales - forum_posts.asp?TID=19315" rel="nofollow - feedback |
Posted By: AgentHEX
Date Posted: 08/30/2013 at 2:53am
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People can do whatever they want, I'm just pointing out in a thread about dwell that the usage of term is fraught with error. I've certainly benefited from thinking a bit about an aspect of a game that interests me, and maybe like minded individual did, too. I've probably also pointed out similar follies in a thread about exhaust systems some ages ago. Maybe someone got upset then, too, but then again it's a bad idea to read the internet for those folks. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: tt4me
Date Posted: 08/30/2013 at 3:01am
No it isn't!!!! One can get a high speed camera a count the frames the ball is in contact with the paddle. It is simple.
Dwell time would be meaningful IF everyone agreed it was the time the ball was in contact with the rubber. There must be some other medical term that covers what Baal is talking about. I am not disputing what he says. I just thing it is off topic. I am not a medical person so I don't know what the term would be for what Baal is talking about. I do know that other sports use dwell as the time that the ball is in contact with what ever they are hitting it with. I KNOW that dwell time can be roughly measured using a high speed camera. If one can do that math and analyze the video they can calculate what happens between the frames. I do agree that throw is a subjective term but useless term until someone defines throw with units. I see all sorts of ways throw gets used like throw distance, throw height or throw angle. In contrast, dwell time is easy to define. It is the time the ball is in contact with the paddle. I suggested earlier. One will not find the answer here. I think these guys can find an answer. http://www.youtube.com/watch?v=xe-f4gokRBs Edit, you guys are wasting your time and filling up Alex's disk with noise. Do you want answers or don't you? ------------- Samsonov Alpha+H3 Neo+802 1.5mm, the Ball Whacker is revived!<br />Samsonov Alpha+H3 Neo+802-40 1.8mm my back up<br />BCX5+H3+802-1 1.8mm New but promising.<br /> |
Posted By: AgentHEX
Date Posted: 08/30/2013 at 3:03am
Or more likely people just subtly align their results with the prevailing popular opinion, which is even worse than arbitrarily varied measures in the first place where at least some useful info might exist. Just like reviews of TBS vs Viscaria, or '96 vs '97 Sonoma Merlot. I distinctly remember stock of P.Noir rising after Sideways not unlike Viscaria after ZJK. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: AgentHEX
Date Posted: 08/30/2013 at 3:06am
Yet this has little to do with what people are referring to as "dwell". Recall this is confusing due to two words/concepts that happen to be spelled the same. You also don't need a high speed camera to measure dwell, just a reasonably accurate one. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: igorponger
Date Posted: 08/30/2013 at 3:08am
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AN IMPORTANTE DISCOVERY. http://tt.tennis-warehouse.com/showpost.php?p=6986320&postcount=27" rel="nofollow - http://tt.tennis-warehouse.com/showpost.php?p=6986320&postcount=27 This is a statement of tremendous importance. This is to end any more disputes about the DW, once and for all. THIS scientific fact states clearly --- it is impossible for a human brain to percept/recognize HOW LONG the ball touches racket on impact. One can only sense the moment of time at which the ball hits racket, but one can never tell the moment the ball comes off the racket. Yes. Yes. Yes. Dwell Time can be measured well with high speed camera, still it is NONE perceptible by human body sensors, and therefore one can't make any practical use of this.. That is that. Great and interesting Discovery. Thanks to Mr. Pvaudio, a science versed forumer from the Tennis Talks. |
Posted By: AgentHEX
Date Posted: 08/30/2013 at 3:12am
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You're making the common mistake of conflating reacting within a span of time vs. simply measuring a duration of time. Propagation speed of neutral signals has no direct bearing on the latter. It would help to read the thread before mouthing off because this was already mentioned. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: tt4me
Date Posted: 08/30/2013 at 3:14am
The ball doesn't care about what people feel. The trajectory of the ball is not influenced by what people feel. Only what actually happens affects the ball.
Show me where dwell is a medical term used to describe how long a ball is in contact with the paddle.
An accelerometer would do if the sample rate is high enough. What else would you propose? Most are probably wondering WTF am I talking about. ------------- Samsonov Alpha+H3 Neo+802 1.5mm, the Ball Whacker is revived!<br />Samsonov Alpha+H3 Neo+802-40 1.8mm my back up<br />BCX5+H3+802-1 1.8mm New but promising.<br /> |
Posted By: AgentHEX
Date Posted: 08/30/2013 at 3:23am
Sure, but people care about what people feel, and how people feel potentially influence their play.
Dwell as people define it seems to be some mix of various items discussed above. Note this is not the same definition as you use. Surely you can understand the concept of one spelling with different meanings given your reasonable proficiency with the english language.
My proposal was already mentioned above. With two sample points for an object, one can determine velocity and the rest is the classic trivial two trains meeting in the middle problem. As long as the samples are sufficiently accurate, it should be possible to determine exact time when both the ball contacts and leaves the bat. This is probably most easily done with fixed bat and camera, in which case only 4 total samples (frames) on ball are necessary, or 6 to account for likely insignificant aero if you want to be really retentive. Not necessarily perfectly accurate on rebound since we need to assume reconstitution of rubber, but certainly good enough for relative comparisons. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: tt4me
Date Posted: 08/30/2013 at 3:50am
I agree that people should use what they feel comfortable with but ignoring what is actually happening is putting your head in the sand.
Show me in a dictionary. Show me that medical people use the term dwell the way Baal uses it.
Show me. It isn't that simple.
OK, I agree but why hasn't anybody done it?
i agree again to a point. Why hasn't anybody done it? If it were easy then someone should have made some high speed videos by now and calculated the dwell time. I know why. There are few people that can fit a system of differential equations to data. ------------- Samsonov Alpha+H3 Neo+802 1.5mm, the Ball Whacker is revived!<br />Samsonov Alpha+H3 Neo+802-40 1.8mm my back up<br />BCX5+H3+802-1 1.8mm New but promising.<br /> |
Posted By: AgentHEX
Date Posted: 08/30/2013 at 4:09am
What's actually happening is quite useless to a player in this case, but how a strike feels so you can predict its path is quite useful.
Language is defined via usage, not by diktat. That's basic linguistics, and quite obvious given that language existed well before dictionaries. Also, Baal isn't "defining" the term, he's just guessing (however accurately or not) at what others feel/mean when they use the word.
What? You want a lesson on how to solve the train problem?
Maybe they already had ready access to the fast camera, and that's more definitive given less assumptions of how the rubber moves along with host of information about impact other than dwell (magnitude of deformity, etc).
These are linear equations. The train problem is a "dummy" math joke for people really bad at math. Smart people probably didn't bother with dwell time much because they know it's a pain in the ass regardless to collect for all range of speeds times range of angles, times #rubber times #blade combos for something that doesn't matter. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: mercuur
Date Posted: 08/30/2013 at 6:04am
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http://ooakforum.com/viewtopic.php?f=38&t=14333" rel="nofollow - http://ooakforum.com/viewtopic.php?f=38&t=14333 This is where my 1000 fps came from. Skipping seconds with the mouse over the runbar shows a filmic effect on itself. That can,t be from one ms frame or two offcourse. But also shows the filmic effect as much shorter then another second for watching the same part on the video. This must have the shorter filmic effect spread over this second. To me this said and says it has more slow-mo technicques combined inside the camera (as a real camera and as a projektor to a screen, two funktions it combines). Even with celluloid film there are different aspects influencing movietime (adapting images/meter celluloid, projektor runspeed as frequency and diameter of the rolled up film ....all combined). So this nothing spectacular on itself for this part. 10 fps display for this camera is plain japanese technical information. It is what it is. Slower or faster to a clock or realtime, whatever that is (or not realtime would have to be), all doesn,t apply to these 10 fps because it simply would be less or more fps then (or the manual lies with this value). No matter how or how much steps it clearly has another slow mow rate of factor 100 before or after as 1000=10*100 (no units) or 1/10 * 1 /100 = 1/1000 (any clock-unit for physics). Otherwise it has 0,01 sec/sec for science-fiction. ------------- |
Posted By: Baal
Date Posted: 08/30/2013 at 7:54am
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AgentHEX is right about duration vs reaction time. The conduction velocities simply mean that you cannot possibly react in time to make a change in what you are doing while the ball is still on your blade. Another measure of interest is that the maximum frequency of a vibrational stimulus that most people can detect with their hands is about 300 Hz (and still discern it as a "buzz"). |
Posted By: mercuur
Date Posted: 08/30/2013 at 7:55am
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This idea of technical steps is way off maybe and asks too much for knowing the technicque inside. Even more for me. But that doesn,t change that 10 fps lasting longer or shorter is science fiction. But Casio wouldn,t inform buyers that bad - I think - that they would keep other slow-mo technicques out from a manual. It,s too easy. But I,m just reading manual information here and try to interpret it for this case. I would hope that,s allowed. The question is what the slow-mo rate to use for correction on frames (or certain amount) is What crossed my mind few times is the mathematical possibillity to go from 1 to 1000 as : 1 * 10/1 * 1000/10 = 1000. Display has a frequency 10/1 and a frequency 1/10 combined toward the camera uptake and toward the screen. But 10/1 =>100/10 ....and 100/10*10/1=1000. 10 stands for ten frames. How shooting film, processing and displaying ten frames relates to time is all different. So it has the possibillity of systematic error.s or interpretation errors in relation between theory and practice. As in this case for a tennisballbounce . http://home.comcast.net/~saintjohnboscooffice/images/martikean/articles/39.pdf" rel="nofollow - http://home.comcast.net/~saintjohnboscooffice/images/martikean/articles/39.pdf ------------- |
Posted By: AgentHEX
Date Posted: 08/30/2013 at 2:53pm
How do I translate this into english? Google translate w/ auto-detect is of no help. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: mercuur
Date Posted: 08/30/2013 at 5:09pm
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10 fps display doesn,t say a frame keeps corresponding to 1 msec for screenplay after the shoot. Shooting an image in 0,001 sec doesn,t say that screenplaying can,t keep a single image in sight for much longer tp even an hour or complete standstill. 10 fps display is just the distribution frequency. So I went to far also in trying to see things from this video. For screenplay with slow motion distributing ten images of 0,001 sec each over 1 sec would show nothing for 0,99 second. That would be seeing a movie with 99 % seeing nothing. So the camera also must have a longer dwell for frames on the display screen.. Casio would adapt all this for best filmic effect and sharpness I suppose. ------------- |
Posted By: AgentHEX
Date Posted: 08/30/2013 at 5:19pm
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Bet nobody anticipated it would be mercuur who goes and parodies mercuur. ------------- Science; upsetting the indignant since http://en.wikipedia.org/wiki/Galileo_affair#Inquisition_and_first_judgement.2C_1616" rel="nofollow - 1616 . |
Posted By: JacekGM
Date Posted: 08/30/2013 at 8:21pm
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Maybe from a different angle: do different rackets have consistently different dwell times? Now, be careful how you answer this. If you say no, you are in trouble. If you say yes, then you probably would admit that this information can be/is useful to TT players. Sorry... ------------- (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. |