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power vs weight
https://ooakforum.com/viewtopic.php?f=9&t=14337		 Page 4 of 5
Author:  haggisv [ 10 Dec 2010, 20:24 ]
Post subject:  Re: power vs weight
Great post, thanks JRSDallas! :clap: :clap: :clap:

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.
Author:  JRSDallas [ 10 Dec 2010, 23:00 ]
Post subject:  Re: power vs weight
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.
Author:  so_devo [ 11 Dec 2010, 06:52 ]
Post subject:  Butterfly keyshot light
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.
Author:  JRSDallas [ 11 Dec 2010, 19:27 ]
Post subject:  Re: power vs weight
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.
Author:  haggisv [ 11 Dec 2010, 21:30 ]
Post subject:  Re: power vs weight
JRSDallas wrote:
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.
Author:  JRSDallas [ 12 Dec 2010, 00:00 ]
Post subject:  Re: power vs weight
Pnatchtwey - The ball is in your court. There is more to be gained from saying OK.
Author:  hookshot [ 12 Dec 2010, 04:42 ]
Post subject:  Re: power vs weight
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.
Author:  pnachtwey [ 12 Dec 2010, 14:53 ]
Post subject:  Re: power vs weight
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.
Author:  tatlwai [ 12 Dec 2010, 17:35 ]
Post subject:  Re: power vs weight
pnachtwey wrote:

The point is that I don't need this forum. People that are willing to spend the money and time to do testing will alway find a place to publish their results. I know I have the resources to publish where I want. Those articles that I have posted links to cost me about $5000 apiece to get published. I doubt most of you have those kinds of resources.

Note I just got back from here.
http://www.airporttech.tc.faa.gov/naptf/
The testing on done here makes sure that the heaviest aircraft like the A380 will not damage the runways, too much. This data is shared by the US all over the world.
I expect an apology if you want me to contribute here. I wastn't the person that started the derogatory comments. It is that simple.


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. :)
Author:  RebornTTEvnglist [ 12 Dec 2010, 22:35 ]
Post subject:  Re: power vs weight
tatlwai wrote:
Oh, BTW, I am an old crusty engineer too. :)


Lol Tat! :lol: You're a bit more advanced though....with speed from pimples I mean :lol: :lol:
Author:  JRSDallas [ 13 Dec 2010, 01:32 ]
Post subject:  Re: power vs weight
pnachtwey wrote:

The point is that I don't need this forum. People that are willing to spend the money and time to do testing will alway find a place to publish their results. I know I have the resources to publish where I want. Those articles that I have posted links to cost me about $5000 apiece to get published. I doubt most of you have those kinds of resources.

Note I just got back from here.
http://www.airporttech.tc.faa.gov/naptf/
The testing on done here makes sure that the heaviest aircraft like the A380 will not damage the runways, too much. This data is shared by the US all over the world.
I expect an apology if you want me to contribute here. I wastn't the person that started the derogatory comments. It is that simple.



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.
Author:  decoy [ 13 Dec 2010, 11:03 ]
Post subject:  Re: power vs weight
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
Author:  82828282 [ 14 Dec 2010, 18:11 ]
Post subject:  Re: power vs weight
Perhaps the increased weight is just a side effect of what really makes the blade faster. Which may be the denser material that returns more energy to the ball.

That's all pnach had to say, but instead he uses this idea to go on an ego crusade.

Forums are meant for communication, so that members may share and benefit from the experience of others. We notice the weight increase with power, so we say a heavier blade will be (significantly) faster. While it may or may not be 'scientifically' correct to link the power increase directly to the weight, it is a colloquial phrase that communicates wisdom that is useful to a table tennis player.

Pnach's arguments (insults, unrealistic expectations of forum members, and misuse / no use of scientific method) defeat the purpose of the forum because it misguides people into thinking that if they buy a lighter bat, they will be able to produce faster balls - and that this would be true for everyone.
Author:  JRSDallas [ 15 Dec 2010, 09:41 ]
Post subject:  Re: power vs weight
decoy wrote:
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.


Decoy -- The acceleration function used to bring the collision point on a paddle up to an observed collision velocity does not effect the collision result. The result is strictly a function of the observed collision velocity. Now, a rotation of the blade (from any cause but with the typical cause being the player's swing) will result in a non-uniform distribution of speeds across the face of a paddle but the only speed that matters will be the speed at the point of collision at the moment of collision. At that "3-5 msec instant" and point of impact, the impact injects a collision impulse into the paddle that will result into a rotation about a different axis (typically localized to the paddle with possible hand influence but certainly not the original axis of rotation established by the swing), and a translation impulse into the paddle. The interaction of the rotation and translation components of the impulse will deform the blade and couple the deformation impulse into the vibrational modes of the paddle. The impact also deforms the rubber and couples potential energy into the rubber.

NOTE: There is no increase in the mass of the blade through either linear or angular acceleration prior to collision providing we limiting our swing speed to non-relativistic velocities, i.e. velocities not approaching one thousandth the speed of light. There is increased resistance to acceleration felt in the hand and arm joints due to the rotational and translational acceleration of the arm and paddle by the body but these are simply equal and opposite reaction forces arising from the force of the body putting power into accelerating the paddle via the player's swing. If the final collision velocity is the same, then the force used during the swing is only a measure of the power of the player to achive the observed velocity with the observed swing.



decoy wrote:
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


I am sorry but if you are on a faster spinning planet, you would weigh less (not more). In fact if you speed up the earths rotation by 25 times, an object placed at the equator would have a velocity of approximately 25,000 miles per hour, which is approximately the velocity needed to escape earth's gravity. In spinning up the earths rotation by 25x, you would also probably cause much of the earth to fly apart. This planet example does not explain anything about the swing of the paddle.

I believe you are confusing the reation force felt by the acceleration during the swing with the mass of the paddle. The reaction force felt is due to the acceleration and not the mass. The force increases but the mass (and/or rotational moment of inertia), remains unchanged. F = ma, Torque = (Moment of Inertia)(angular acceleration)

In the case of a swing with rotation, you are feeling the Moment of Inertia effecting the resistance to angular acceleration. The Swing Weight of the paddle is equal to the Moment of Inertia of the paddle about a particular axis of rotation.
Author:  decoy [ 15 Dec 2010, 10:02 ]
Post subject:  Re: power vs weight
you are right there dalas , i kinda made the balls of it :P, probably explains why im repeating this year :o

i did forget about angular acceleration, as well as the PE of the rubber elasticity, / the ability to spring back

also forgot that that is what keeps the earth from falling apart= spin. also i have troubles with understanding the concept of inertia. but at the same time, take your arm and rapidly accelerate it in a rotational motion ( basicly swing your arm with the center of your body as the fulcrum ) you will notice your blood rushing to your finger tips.
by you saying from what i said earlier , the faster the spin would basicaly cause the earth to split apart. but the reason it doesnt is because the core/over all mass of the earth is so great the, gravitational pull generated from the stable rotation and mass allows it from falling apart.
this takes us back to the table tennis stroke, where the mass of the player isnt great enough to pull blade towards the player no matter how fast he spins, because he cant spin fast enough to create a gravitational pull, hence the outward/sentrifugal/G-forceforce exerted on the blade causing it to feel heavier.

just to point out i am jsut trying to put forward what i think makes sense to me. you are probably most likely correct, as my knowledge of physics isnt great, as ive only been studying it for the last 2 years. and i know nothing about impulses so far/yet

but still its the technique that matters in table tennis, if your technique is flawless then your ball speed can only bee so fast, upto the point where it becomes irrelevant/imposible.
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