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paddle mass and speed |
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zeio
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Here the reduced mass is appropriate once you learn to differentiate it from the total mass. The total mass or combined mass refers to the mass of paddle(171g) and arm(1kg) combined which comes out at 1.171kg, but keep in mind that this number is valid only for shots made at a right angle at the Center of Mass(COM) of the paddle, which is 147mm measuring from the end of handle. This is where the confusion arises. Any time you make an off-center shot, the total mass that gets put into the shot(effective mass) would always be less than that of one made at the COM(by the Moment of Inertia and Center of Percussion), hence the term reduced mass.
Mathematically speaking, the ball velocity increases little for anything over 20 grams, and the same holds true for the COR. Nonetheless, Fig.19 and 20 demonstrate that slight increase could make all the difference. Impact locations A (Mr~=78.1g) and D (Mr~=165g) result in rebound power coefficient e's of approximately .357 and .378, respectively. And at their respective coefficient e's and 30m/s of impact velocities, the ball velocities end up at 10.71m/s and 11.34m/s, a .63m/s difference which translates to a 5.88% increase. Disregarding drag and spin acting on the ball, the slight difference would still constitute a substantial pressure over reaction time, which comes out at 257.4ms and 243.1ms, given that a typical table tennis table has a length of 2.74m and the minimal trajectory(2.757m at 6.434° over the table) necessary for the ball to travel from one end to the other and over the net(15.25cm + 20mm(radius of the ball)). For reference, the median reaction time of a human is 215ms, as shown by data collected of a simple click test.
Technically speaking, it is the Moment of Inertia that the Angular Kinetic Energy and Moment of Force(Torque) depend on proportionally, but not neccessarily linearly. The moment of inertia for a point mass is defined as the mass times the radius from the axis squared. For a collection of point masses the moment of inertia is the sum for the masses times their respective radii from the axis of rotation squared. Continuous mass distributions, which is the case of a paddle, the moment of inertia is equal to the integral of all the point mass moments that make up the whole.
By the above, one can deduce that an 80g, head-heavy blade can feel as heavy as a 90g, well-balanced blade simply because a greater amount of mass of the 80g blade is distributed at the far end thus resulting in a nearly equal moment of inertia as that of a 90g during the same swing. Hence, for rotational motion, one has to look at both the mass and radius from the axis of rotation to determine the angular kinetic energy and torque associated with the motion. And nowadays in a world where speed-glue/booster has been outlawed, and one's swing mechanics has reached its maximum potential, what would that person, be it a pro or an amateur player do then? |
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Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare) + Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃) = 184.8g |
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walleyeguy7
Super Member Joined: 12/11/2009 Location: Paducah, KY Status: Offline Points: 409 |
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i would agree, having a super heavy setup of a 95-100 gram blade and two 60g (cut) rubbers can be very slightly detrimental, but a 75-80 gram blade and two 40g (cut) rubbers can be equally detrimental. it really can not be so easily boiled down to a science of course, preference plays a large role. younger, stronger, and larger framed people may possibly feel the effects a little less. overall lighter is usually better, imo, but too light can leave a feeling of instability and possibly hinder your control slightly.
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pnachtwey
Platinum Member Joined: 03/09/2010 Location: Vancouver, WA Status: Offline Points: 2035 |
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as
Edited by pnachtwey - 03/20/2012 at 4:30am |
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zeio
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Exactly what I am getting at. Given what have been discussed so far, it is fairly safe to say that it is ideal for people to pick the heaviest blade they can handle and feel best(head-heavy, well-balanced or even handle-heavy), while factoring in their swing mechanics.
I am persuaded that you simply refuse to communicate. After such an extensive and in-depth dialog, you still cling to a distorted perception and dwell on unphysical and unrealistic reasonings that base around severing the tie between the mass(labeled now as reduced mass formula) and COR(as speed-after-impact formula) that stems from oversimplifying the issue at heart, essentially to the point of detriment to the core value of Collective Intelligence. There must be a reason when various people feel(as in notice, albeit infinitesimal) a correlation between higher ball velocity and greater paddle mass. As a responsible person who work in the science field, one should, based on all information and knowledge available to him/her at the time, arrive at a reasonable conclusion for a common phenonmenon observed by many others after putting across mathematical explanations supported by experimental data and NOT come up with some shaky assumptions and self-justification that go against empirical evidence and force them on others.
6 degrees of freedom? Oh, my. The phrase in bold makes up the fundamental moment of inertia formula for a point mass. And for a point mass there are only three DOF and they are all translational(up/down, left/right and forward/backward.)
By your logic, the same can be said where the increased mass does little on increasing the angular kinetic energy required to get the paddle to the desired speed.
Another one like this? Thanks, but no thanks. |
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Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare) + Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃) = 184.8g |
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pnachtwey
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as Edited by pnachtwey - 03/20/2012 at 4:30am |
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zeio
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What an appalling statement. You do not seem to ever be aware that the data presented in Fig.13 are collected using reduced mass derived from their respective moments of inertia at different predetermined locations(including center of mass and off-center) across the length of the paddle face, yet you take that part out of context at face value and manipulate your interpretation to the advantage of your twisted conclusion. The moment of inertia, upon which all subsequent findings in that study are built, has long ago entered the fray ever since I posted the abridged study and first appeared in Table 1.
I seriously doubt your reading comprehension. In Figure 4, the caption for the impact model reads "Single degree of freedom model of impact between a racket and ball by introducing a reduced mass of a racket-arm system." And that single DOF is acheived by limiting the motion of the paddle to pitching only(tilting forward and backward), hence the impact and center of mass locations chosen "along the longitudinal centerline on racket face". Again, Fig.13 bases on that. Given the findings in that study support the hypothesis that paddle mass and COR are correlated, it is logical for one to approximate the off-center mass to a lighter paddle and center-of-mass to a heavier paddle and estimate the effects.
Since JRSDallas has commented in an elegant way about this on OOAK, I will save my own trouble and quote below:
Look now who is bringing up obscure topic to the thread without any substantial reference. |
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Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare) + Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃) = 184.8g |
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pnachtwey
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as
Edited by pnachtwey - 03/20/2012 at 4:30am |
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tompy
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I haven,t read this all but nowhere accelleration is mentioned as a way to lengthen the trajektory on ballcontact. Also referred to as "hitting through the ball".
Longer ballcontacttime offcourse means longer trajektory (In cm,s (if someone would want to do that but - at least qualitywise for understanding - time can also be considered trajektory). If a paddle is accellerated to max speed before ballconstact allready and then only - sorta - follow through, maybe the arguments make sense. But that,s not how you ever manage to get the best loops. Then it,s impact and almost immmediately the ball is gone with a short trajektory, low energy lots of vibrations. With a whipping accelleration starting shortly before ballcontact and continuing during ballcontact the ball can,t escape from the blade as easy. Contact is longer and with that trajektory and with that ...energytransfer. Hitting through is actually not the best choice of words..."accellerating through" would be better. And from max speed there is nothing to accellerate from anymore. A case where this is more obvious in daily live would be a shoppingcar that rolls towards someone. Hit it with maximum speed mostly results in sour hands. Take it in relaxed, accellerate gradually (all tuned and timed to the incoming objekt, taking it in feeling it,s energy) the trajektory can be lengthened and therefor -much - better energytransfer with no vibrations and a more smooth action. Edited by tompy - 01/17/2011 at 3:28am |
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sweetstrike
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There's a really scientific discussion going on here and it's very educational. I think this figure posted by Zeio is the most important concerning the argument that a lighter blade is better. This plot of the reduced mass across the face shows that the Mr decreases as you make contact away from the sweetspot. I wish they had made multiple plots for blades of different mass as I'm pretty sure the Mr plots will be slightly higher for a heavier blade at the sweetspot, but the curve will be flatter meaning there will be a lower reduction of Mr for off center shots.
This means that a heavier blade is more forgiving with a larger sweetspot. This is probably why many players prefer a heavier blade. Although it requires more force to accelerate, the end result is a more consistent shot.
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tompy
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All these figures and formula,s go from the idea of a speed on impact not acceleration during impact. (That,s timing and technicque also). Speed on impact means before it. The technical ability decides whether someone can release energy in the arm during the short moment of impact. The blade is a tool to make that possible and it needs weight for that (much more then the rubber) otherwise it,s resistance to energytranfer is too high due to a balsa core for instance.
The light head will also loose speed from if the player would not put momentum on the blade (like clamping it) even if you hit it in the sweetspot. Clamping a racket with the hand it becomes difficult to tranfer the energy from arm out to the ball during impact. I believe the ideas of preservation of impact and momentum are highly primitive. In my experience with tabletennis impuls can transform to momentum. If you would look at both then there could be some preservation but apart from each other they are not preserved the impuls before collision can be lower if the momentum (or impuls of momentum how do you call it ?) had increased. I experience this for instance with how a ball with spin accellerates from a rubber and jumps of. To me that,s a plain case of increased impuls (and decrease of momentum). It,s a decrease ofmomentum anyway because the momentum of the blade doesn,t change and the ball does. The sum is lower then. This comes out as an increase of impuls. I think that,s the weak thing with all these formula,s. They are far too simple even if they may seem complex. Edited by tompy - 01/17/2011 at 7:29am |
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pnachtwey
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as
Edited by pnachtwey - 03/20/2012 at 4:31am |
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sweetstrike
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If blade properties like thickness, stiffness and moisture content are kept the same, the only way to test a heavier blade is to use a larger sized blade. And the larger blade face will yield higher ball speeds across the face than a smaller blade face.
Mr has to be greater for the blade+arm system than for the blade alone. Say your arm weighs 9 lbs and the blade is 1 lb. When you make contact with the ball, the reduced mass (essentially the weight of the hit) will not be less than 1 lb.
I agree with you the effect does not appear to be substantial and that rubber/sponge choice has a much greater effect on the overall speed than varying the mass of the blade. Edited by sweetstrike - 04/04/2013 at 8:52pm |
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Viscaria FL
FH: Tenergy 05 2.1 BH: Sword Scylla OX |
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yogi_bear
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SIDomized thread
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Best99
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Wait wait wait...
We should also take into account other blade's characteristics, such as stiffness and hardness. Appart from that, let's think it this way. Let's consider 2 blades, A and B, which are made from the same material, have the same shape, the same size but that have different weights (which is physically speaking impossible). If A is heavier than B, its density will be higher, so A is denser than B. A denser material will have less COR, because the molecules are closer to each other. It doesn't matter the material, its characteristics, its density, etc, if two paddles are the same shape and size but one is heavier than the other, the heavier WILL be faster. |
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Blade: Timo Boll ALC 92 g.
Forehand: Tenergy 05 2.1 mm. (black) Backhand: Tenergy 05 2.1 mm. (red). Perfect loops |
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figgie
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mass and speed or mass and velocity? What about acceleration? Kinetic Energy? Moment of Inertia? elastic or inellastic collision? Entropy of the system? How much wood would a wood chuck chuck if a wood chuck could chuck wood?
Edited by figgie - 01/17/2011 at 9:27pm |
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Speed glue, booster, tuner free since 2006!!!
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hulkpens
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The professions/education of this forum's members is showing thru this thread.
When you guys are done, let me know what the consensus is. |
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Anton Chigurh
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The empirical consensus is already in, and it is that heavier blades are usually faster. For example, I've experienced firsthand how two blades of the exact same model, only differing in weight (by about 7 grams), are noticeably different in speed. However, it is pnachtwey's claim via his equations that are causing the controversy. It is quite possible that pnachtwey's claims are correct, as not all things in the "real world" match up with our intuitions. But I'm skeptical, especially because assumptions must often be made when crunching the numbers and those assumptions can sometimes miss crucial data. This conversation has gone far beyond my abilities to comprehend so I'm sticking with my intuitions. Zeio's claim that the COR actually does take into account the paddle mass, just at a lower level of abstraction, made sense to me... but that was many posts ago and I've already forgot why it did. It doesn't really matter to me in practical terms because I'm going to use whatever is comfortable. But theoretically I wouldn't mind knowing the "right" answer to this query just because I'm compulsive like that. |
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Neo H3 40D| Offensive S | Tenergy 80
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pnachtwey
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as
Edited by pnachtwey - 03/20/2012 at 4:33am |
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Anton Chigurh
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I've never used a DEF blade so I cannot speak from firsthand experience. However, I've been told by more than one defensive player the DEF blades are not "slow", by any means. Regarding your comment on the enormous weight of 200g and 300g, I think you're being disingenuous... and I think you know it. Obviously, whatever benefit is gained from a heavier blade, there will eventually be a point of diminishing returns with regards to maneuverability, etc. But don't get too defensive. I did leave room in my comment for the possibility that your evaluation is correct. But if I had to make a guess today then I'd say I don't think it is, simply because of my own experience and the input of many, many, many others whose experience exceeds my own. |
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Neo H3 40D| Offensive S | Tenergy 80
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infinite_loop
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The root cause of the "controversy" is pretty simple: mismatch in expectations of which variables are kept fixed in the experiment. Generally, when players talk about of effect of varying mass, they implicitly assume that the thing that is kept fixed is the type/construction of the blade. Players talk about difference in speed between a 88g TBS vs a 95g TBS vs a 102g TBS. The heavier blades tend to be made of denser wood and have higher COR. Or, blades of the same family with similar construction. e.g. a 80g OC vs a 95g Clipper. Heavier blades tend to be thicker and/or use denser wood and have higher COR. If you are more of a physicist, keeping COR fixed is a natural thing to do in this experiment. If you are more of a player than a physicist -- most forum members are -- keeping something like COR fixed is unnatural. If the fixed part of the experiment is conveyed properly in a way everyone really understands what it is, there is unlikely to be much disagreement. e.g. a 78g Yinhe T2 vs a 95g Clipper. Players of course know that a lighter blade can be as fast or faster in that case. In fact, if we eliminate the mismatch in expectations, I am pretty sure we will arrive at this conclusion: what players informally describe as blade speed is COR. Anyway, this thread reminds me of a joke. What is the difference between an engineer and a theoritical physicist? Edited by infinite_loop - 01/18/2011 at 2:34am |
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tompy
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That,s also what I was told. But I happen not to agree with this idea. To me the sum of momentum and impuls has to be constant but not on themself. How they relate seperately and together to energy then (also assumed to be preserved) I don,t know how of if that could be put in formula,s but still I disagree with this idea of preservation of momentum and impuls as seperate in the sense of qualitywise for my understanding. If I keep a bat with grippy rubber still not doing anything and touch a spinny ball with hardly any impuls the ball jumps off with a significantly higher speed and a decrease in spin. To me that,s a clear example where spin (momentum) converts into impuls. If fysics tells me this is impossible because both are supposed to be preserved then I don,t take the fysics too serious on that. Examples in tabletennis where impuls converts in momentum are also plenty to think of. Like a block on a smash only keeping the blade and catch the ball in the rubber. a ball with no spin can jump of with spin. decrease in impuls (for the blade and the ball together before and after offcourse) and increase in momentum. On a billarttable it maybe shows even better how a spinning ball can accelerate from the side of the billart. If there impuls and momentum are preserved seperately then I have to imagine that the billart moves and rotates afterwarts. That,s too much for my imagination. I see the total of impuls and momentum preserved in such cases maybe but not both seperate. |
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yogi_bear
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why would someone be that stupid to buy a 200 gm blade and play with it? this is far from reality since most blades with rubbers on both sides weigh from 160-175 grams. heavier and slower defensive blades have different wood constructions? why not compare blades on the same speed rating or compare 2 blades with 2 different weights like a clipper wood classic which is 84 grams and 92 grams for example. with the same rubbers on both sides and test it on a radar speed? tsk tsk tsk SID
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pnachtwey
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as
Edited by pnachtwey - 03/20/2012 at 4:32am |
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yogi_bear
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"Good question, but there are still those that think that heavier paddles result in more speed so why not buy a 300gm paddle if they really think it is true? What I am trying to debunk is all the posts that say heavier paddles have more power. By that I think they mean a higher speed after impact for the ball.
The mass alone doesn't make that much difference to the speed. It is obvious that you haven't read or understand the posts and the point I have been trying to make and just want to criticise." says who? who are the ones who think that using a 300gm blade will make their game faster? you are making up stories again to support your claims! it is also obvious that you don't have the logic to support and clarify your statements.. Nobody is stupid enough to think they would get 300gm paddles, you are the only one thinking about that not us! |
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pnachtwey
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as
Edited by pnachtwey - 03/20/2012 at 4:33am |
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yogi_bear
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my 105 gm DHS 08 is faster than my 92 gram ebenholz both with neo skyline 3 on them,
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pnachtwey
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Edited by pnachtwey - 03/20/2012 at 4:32am |
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yogi_bear
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why separate the material and mass when both are components of a racket? as what i have been saying in the past posts prove it in real experiments not just theories.. you always fail to put into account the practical applications! would you like me to remind you about your posts on "throw angle is bull"?
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pnachtwey
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Edited by pnachtwey - 03/20/2012 at 4:32am |
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yogi_bear
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What about the slow and heavy defensive paddles? Explain that! You have to know that increasing the mass alone does not result in more speed. If you thought otherwise you would have a 300 gm paddle. you seem to have no idea about defensive paddles do you? our number player in our country is a defensive player and a chopper. his blade is not slow. a fried of mine who uses joo see yuk blade (it is considered a defensive blade for a chopper). it is not a slow blade and it is heavier than normal bladeS! stop making up stories about 300gm blades! people will not use it nor us here! if you consider yourself a true logical person why disregard other factors and just use the ones you think are for just backing up your claims? why not use all of them? that's what makes your claims unrealistic
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