OOAK Table Tennis Forum

And believe me, ReBorn had written some very very long posts himself.

Ahem, ah well yes, I guess I have some experience in the matter Tat

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I'm always in the dark, but the Dark sheds lights upon everything!! Beauty is only pimple deep! Beauty is in the eye of the pipholder!
S/U 1: Blade: Bty Gergely . FH Black Andro Rasant 2.1 . BH Red Tibhar Grass Dtecs
S/U 2: Blade: Bty Gergely . FH Black Hexer+ 2.1 . BH Red GD Talon
S/U 3: Blade: Bty Gergely . No rubbers...thinking of adding Red Dtecs and Black Rasant
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I am going to start with simply stating what I believe to be my insight into why we physically experience a positive correlation between blade power and blade weight, when the equations of center of mass collision impacts presented earlier in this (or other) threads indicate that the effect of the blade mass should be small. I am not presenting these equations here but some have used MathCad modeling to show the effect on rebound speed is 2% versus racket mass, while experienced players feel that this doesn’t match the effect they are feeling.
I may try to work out a detailed analytical presentation but I’m not going to even be able to look at that until over the holiday break so no promises. I’m going to present an energy argument and presenting a lot of equations (from my pervious experiences) generally results in road kill (and personal satisfaction at understanding it in detail).

So in short, the issue of rebound speed is driven by the previously discussed but not analytically presented effective coefficient of restitution (ECOR), or simply ‘e’. The COR and eCOR are physical measures of rebound that occurs in a system as a function of where the collision occurs between the two objects in question and the energy (velocity) of that collision.

When the COR and eCOR equal 1, the collisions are elastic which means that no energy is lost in the collision but energy may be redistributed between the objects as a result of the collision. When COR = eCOR = 0, then the collision is perfectly inelastic and the two items stick to each other as a result of the collision. In this case both end up with the same final velocity.
The general equation for rebound velocity for center of mass collisions is:

V2 = ( e )( V1 ) + (1 + e ) V Where:

e = eCOR = rebound measurements of V2/V1 in a lab
V1 = inbound velocity of the ball
V2 = rebound velocity of the ball
V = inbound velocity of the Racket

NOTE: This equation doesn’t have any blade mass or ball mass terms at all! However, this doesn’t mean they don’t have an effect. What it means is that effects of mass and energy loss are taken into account when measuring the efficiency of rebound in the first place. As a result, it is not particularly illuminating, other than to show that all of the arguments so far are in the complexities of ‘e’, and for this equation is boil down to the unimpressive result that “the ball rebound velocity is what we measure it to be in the lab”.

OK….so let me jump to my arguement:

Faster blades have higher ‘e’ due to these blades having lower energy losses during collision.

The energy losses generated by a blade during collision come from the vibration energy created in the blade by the collision with the ball. These vibrations show up as a superposition of vibration modes that have different vibration frequencies. The sound the blade make when the ball hits it is the result of these vibrations. The energy of lowest frequencies of blade vibration are rapidly absorbed into the hand and lost (and you don’t even hear the low tones that are occurring) You can start to hear them if you do the hand clamp and ball drop test I explained earlier in this thread.

Higher ‘e’ blades are stiffer so that the ball collisions cannot bend it as much and thereby couple energy into the vibrations of the blade, most of which will be lost during the collision.

Since all blades are 85% - 100% wood, making a blade stiffer generally results in the use of more wood which results in more mass and thus this is the source of our experience of a correlation between blade mass and blade speed. Faster blades do need more wood or denser wood to be stiffer and thereby have lower energy loss during collision. Composite blades can be stiffer than all wood blades or lighter and/or thinner than an equally stiff all wood blade but even here at least 85% of the blade is still wood. Composite blades designed to be as stiff and light as possible will have less of a mass correlation but the difference may not easily perceived. Still, we all do experience the perception that a stiff composite blade like the Schlager Carbon is faster than other blades, even equally heavy all wood blades.

If one were to make a radically stiffer 100% composite blade comprised of a carbon shell and thicker interior foam core that was well lighter than wood and without compromising physical integrity of the shell during impacts with the ball, then I think one would be able to achieve a faster blade than is currently allowed at a lower mass than is currently experienced. This low mass would also allow players to swing faster and thereby increase the V and V2 of the rebounding ball.

Great post, thanks JRSDallas!

Balsa blades would be a real example of a stiff and fast blade, that is also light. The characteristics of Balsa are quite non-linear though, perhaps making it impractical to use it as an example.

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Balsa wood has a very very low modulus of elasticity, i.e. source of stiffness.
Balsa wood is the best material to choose as the foam filling the core, but it is a lousy material to choose as the source of structural strength and stiffness for a blade.

This is why you most often find balsa or other light woods being used as the center ply in a blade. It is being used as a foam-like core. to separate the outer stiffer plys.

A single ply balsa blade may need to be much thicker than a hinoki 10 mm blade before it becomes equally stiff.

Jsr, can i simply say it is a pleasure to see you are posting here. I have read your posts elsewhere and they are fascinating. You will find an appreciative audience here.

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Timo Boll ALC ST
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Thank you so_devo.

The power vs weight issue has been brought up a few times of late (in multiple places) by people who have been striving for a serious explaination and I would like to thank all of them for their efforts and interest. Life is a better pleasure when you can hear, speak to and work with people who are themselves interested in a topic.

With the forum's permission, I would like to request that the ban on Pnachtwey be lifted based on the sincerity and value of his efforts.
I would also ask that both Pnachtwey and the forum members accept that they were on both sides too quick to attack and defend rather than simply move on. People argue and so do I, but I continue to learn that my ego has no value in the real world and I waste my time when I listen to it. Lets forgive, forget, and move on....please.

I can't speak for the other mods, but if Pnachtwey can show respect for other people's opinion and posts (even if they're wrong) then I personally have no problem with him returning, since I also value his contribution.

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OOAK Table Tennis Shop | Re-Impact Blades | Butterfly Table Tennis bats
Setup1: Re-Impact Smart, Viper OX, Victas VS 401 Setup2: Re-Impact Barath, Dtecs OX, TSP Triple Spin Chop 1.0mm Setup3: Re-Impact Dark Knight, Hellfire OX, 999 Turbo
Recent Articles: Butterfly Tenergy Alternatives | Tenergy Rubbers Compared | Re-Impact User Guide

Pnatchtwey - The ball is in your court. There is more to be gained from saying OK.

JRS,
You know this is not the only forum where he raised the hackels of people that are normally calm?
I find your posts enlightning and enjoyable. Your post about COR and eCOR has told me all I need to know to answer the questions I had about two apparently identical bats except for weight. I am sure you could go even deeper into the subject but I have enough now.
I think the ban was justified. And I do not think he could change his tone even if he tried. It is his nature. I do not miss him.

Edited out by Speedplay, as Pnachtwey didn't get the hint, but decided to return with more insults, continuing to call people idiots. Well, at least now there is one less idiot here since we have a tendency to ban them.

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I play TT for the health of it.
Samsonov Alpha FH Apollo BH Mark V max 178 gm Testing if tacky rubbers are better for serving.
My Blocker, 729 Bomb, FH Reflectoid 2mm, BH Pogo 0X 150.51 gm $40

First, I don't think anyone here will apologize to you, and
Second, this forum was doing perfectly fine without you.

Goodbye and please, don't come back.
Oh, BTW, I am an old crusty engineer too.

Lol Tat! You're a bit more advanced though....with speed from pimples I mean

_________________
I'm always in the dark, but the Dark sheds lights upon everything!! Beauty is only pimple deep! Beauty is in the eye of the pipholder!
S/U 1: Blade: Bty Gergely . FH Black Andro Rasant 2.1 . BH Red Tibhar Grass Dtecs
S/U 2: Blade: Bty Gergely . FH Black Hexer+ 2.1 . BH Red GD Talon
S/U 3: Blade: Bty Gergely . No rubbers...thinking of adding Red Dtecs and Black Rasant
Aussie Table Tennis Shop / Aussie Table Tennis Facebook Page / Equipment Review Index / Read my Reb Report Blog: click here.

pnachtwey,

I wasn't watching so please forgive me if I have misinterpreted, but, if the above is actually what you wrote in reply to the open hand I asked be extended to you, then I would have to say that it is a disappointment. I hope you don't behave this way at work but people's personalities in public venues are often the same in the work environment. If true for you, know that everyone you work with, and management especially, are exquisitly aware of your interpersonal style. You may think that the people at work respect you and that there is no correlation, but I would point you towards the Kruger-Dunning effect which demonstrated that incompentent people overestimate their competence and that they don't even have the competence to recognize their incompetence when faced the facts of it.

perhaps this may have been posted before
(i am 3rd year mechanical engineer.)im not brilliant in many senses, but its fun course

perhaps first mistake that people go with is linear acceleration, which does not apply to table tennis as the majority of strokes are rotational

as for power vs weight, if you have the power/strength to hit the ball with the same acceleration + top speed just before hiting the ball with the heavy bat. then again hitting the ball fast is one thing but its the acceleration that is the main component, which will increase the mass of the blade, not physically but through acceleration, but not acceleration on one plane, im talking about centerfugal/ or rotational acceleration. for example:

take two planets same size and mass but one spins faster than the other , hence on the faster spinning planet on the surface on the planet you experience strong gfoces thus, you instatly weigh more, the more acceleration the more mass

so the weight is dependant on th person strenght/ability to accelerate the bat in a rotational movement.
a weaker player with a lighter bat can accelerate much faster and develop more acceleration than he would with a heavier bat.
the difference may only be slight but hat player wont have the consistency of acceleration due to stamina, the heavier blade with wear them out, especially when performing flicks/wrist movements.

technicaly speaking heavier blade will be faster ( ball speed after impact) than a light blade with the same acceleration..

also the blade construction takes into effect soft vs hard/stiff

as well as technique which is the crucial point in table tennis as theres is no point of being able to hit the ball ffaster than others if you are just going to miss. its not how fast/hard its how well you apply your shot. its all about consistancy and being able to keep the ball on the table without messing up while at the same time being able to force the other player to make mistakes ( variation of spin/exploitation of their weakness)

also to mention the location of the mass : ideally the majority of mass would need to be at the outermost tip of the blade allowing for stronger centrifugal force
this is why i made my mutilated my blade handle to be so short sending the weight to the outer most part from the fulcrum( center of the body)

as for a small test that everyone can do:
try hitting the ball without pivoting the body, and just using your arm :
now, jsut pivot your body and keep your arm in one position with the same speed

you will now notice that the ball will travel somewhat faster. by adding the two movements together the speed+spin is even greater now

hope this helps

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