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  1. #358
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    Quote Originally Posted by Neil Nicholls
    are you confusing two different things?

    2nd moment is sum of mass x (distance from axis)^2
    if the axis of rotation stays in the same place (i.e. you hold it in the same place) then adding weight anywhere can only increase this value.

    holding near the cone reduces it, and holding near the butt increases it, because you are moving the axis.

    see also Overall Weight vs Balance
    problem in discussing or debating complex issue is it's easier to disproof a well supported argument by highlighting a few isolated exception not due to fact but due to failure to present a 100% leak proof presentation by the proponent. Eg. OJ Simpson got off incrimination from a undersized leather glove although overwhelminng evidences show OJ did killed his wife. Poor presentation in this case is not really a negative fact since we now know the police planted that glove in hope to seal the case but instead it actually backfired.

    As in here, i'm still stuck at supporting silentheart original point even tho i have said before the tiny weight of a foam overgrip doesnt really change the racket dynamic but rather it is due to 'something' else.

    yes, the mass of the overgrip will increase the moment of inertia (moi) but no one yet explain yet why the racket feel head lighter?

    Neil, what u said isnt 100% correct either. Adding weight anywhere can only increase this value is not 100% true. You had assumed adding mass grip forward but what if i add mass on the other end, like the taping a 2 ounce lead weight on the yonex green butt cap? Total racket mass increased but moi is reduced. Eg, look at a crankshaft Your revving engine will blow up without those 'added' mass. Even taneepak use this concept to mod his rackets

    what i should said earlier with a 1 lb overgrip is the relative moi is reduced. U are applying more energy to rotate the 1 lb overgrip such that it overwhelms your feeling of the frame weight, even if it was an AT700 head heavy frame. Your feeling of frame is masted by the force needed to twist the heavy handle.
    Last edited by cooler; 02-03-2006 at 03:04 AM.

  2. #359
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    Quote Originally Posted by cooler
    Neil, what u said isnt 100% correct either. Adding weight anywhere can only increase this value is not 100% true. You had assumed adding mass grip forward but what if i add mass on the other end, like the taping a 2 ounce lead weight on the yonex green butt cap? Total racket mass increased but moi is reduced. Eg, look at a crankshaft Your revving engine will blow up without those 'added' mass. Even taneepak use this concept to mod his rackets
    still 2 different things I think, but I hadn't thought about it like your crankshaft example before.

    I still stick to "Adding weight anywhere can only increase this value"

    If you add mass to the racquet, the force you have to apply to make it rotate is increased.

    Once it is rotating though, the racquet applies a force back on you at the axis or rotation. Centripetal force.
    An easier to see example might be a ceiling fan. If it is not balanced, one of the blades will pull on the axis more than the other blades and it will make the whole thing wobble.



    P.S. I thought taneepak was always removing weight from the handle to move the static balance point closer to the head, not adding it.

  3. #360
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    Quote Originally Posted by Neil Nicholls
    still 2 different things I think, but I hadn't thought about it like your crankshaft example before.

    I still stick to "Adding weight anywhere can only increase this value"

    If you add mass to the racquet, the force you have to apply to make it rotate is increased.

    Once it is rotating though, the racquet applies a force back on you at the axis or rotation. Centripetal force.
    An easier to see example might be a ceiling fan. If it is not balanced, one of the blades will pull on the axis more than the other blades and it will make the whole thing wobble.



    P.S. I thought taneepak was always removing weight from the handle to move the static balance point closer to the head, not adding it.
    if u add mass as close to the axis of rotation, wobble (moi) is
    reduced even tho the defective fan blade is still as defective as before.

    The racket frame ( and even the whole racket) is analog to a wobble fan blade example because it is totally out of balance relative to your all those swing axises as u rotate and apply force to hit the shuttle. That's why u have to hold onto your racket or it will wobble out of your hand
    Last edited by cooler; 02-03-2006 at 04:36 AM.

  4. #361
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    Quote Originally Posted by cooler
    if u add mass as close to the axis of rotation, wobble (moi) is
    reduced even tho the defective fan blade is still as defective as before.
    the wobble and the moi are not the same thing

    what do you mean when you say moi ?
    is it the same as on this page http://hyperphysics.phy-astr.gsu.edu/hbase/mi.html ?

  5. #362
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    I think that the issues of balance are becoming confused now.

    To clarify:

    Adding a grip to the handle DOES affect the "swingweight" -- slightly. This is because, as cooler said:

    • The mass is not concentrated at the fulcrum, but spread over the whole handle. Thus it will affect the moment of inertia, causing a SLIGHT shift of balance towards the handle.
    • There is no exact fulcrum point anyway. This is a simplifying assumption of my model; in fact, the "fulcrum" is the whole area of the hand gripping the racket.


    Nevertheless, we should recognise that adding weight to the handle has a far smaller effect on the swingweight than adding weight to the head.

    I am convinced that my analysis is qualitatively correct. All this can be done without measurement.

    It is not clear, however, whether my analysis is quantitatively correct. Clearly adding weight to the handle has a much smaller effect than adding weight to the head; but what are the numbers? Is it noticeable?

    My subjective experience suggests that adding a grip to the handle affects the swingweight only marginally. I think I can notice a small difference -- but not enough to change my appraisal of the racket's playing characteristics (its "feel").

    In my view, this very slight change in swingweight is not worth worrying about. If you apply more than two layers of replacement grip, then it might start to be more noticeable.
    Last edited by Gollum; 02-03-2006 at 06:49 AM.

  6. #363
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    Quote Originally Posted by Gollum
    Nevertheless, we should recognise that adding weight to the handle has a far smaller effect on the swingweight than adding weight to the head.
    ...
    It is not clear, however, whether my analysis is quantitatively correct. Clearly adding weight to the handle has a much smaller effect than adding weight to the head; but what are the numbers? Is it noticeable?
    I refer the honourable gentleman to my previous answer
    Racquet Swingweight Measurements

  7. #364
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    Quote Originally Posted by Neil Nicholls
    I refer the honourable gentleman to my previous answer
    Racquet Swingweight Measurements
    OOOh oooh

    There are the numbers! And, of course, you could do a similar experiment to see the effect of adding one/two/three layers of replacement grip.

    Nice. Slightly scary, but nice

  8. #365
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    Quote Originally Posted by Neil Nicholls
    the wobble and the moi are not the same thing

    what do you mean when you say moi ?
    is it the same as on this page http://hyperphysics.phy-astr.gsu.edu/hbase/mi.html ?
    thx but i already went through that site before i made my prior posts

  9. #366
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    Quote Originally Posted by Neil Nicholls
    I refer the honourable gentleman to my previous answer
    Racquet Swingweight Measurements
    thx for providing experimental data that supporing my argument.
    In that Table, it clearly illustrate why less weighted rackets have more MOI than a more heavier racket if u say adding mass always increases MOI? Why some lighter rackets have higher MOI than some heavier racket? Why is two carlton AS1 have large MOI differences when they statically weighted equally?
    Last edited by cooler; 02-03-2006 at 10:39 AM.

  10. #367
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    Perhaps plotting the correlation of balance point and MOI would be useful.

  11. #368
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    Quote Originally Posted by Gollum
    Perhaps plotting the correlation of balance point and MOI would be useful.
    there is no such functional correlation that worth plotting them

  12. #369
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    Quote Originally Posted by cooler
    there is no usable correlation that's worth plotting them
    ...................................
    Last edited by cooler; 02-03-2006 at 11:19 AM.

  13. #370
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    Quote Originally Posted by cooler
    there is no such functional correlation that worth plotting them
    I agree, it's all about the overall feel of the grip. And of course, each person's preference for ideal feel is different.

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    Quote Originally Posted by cooler
    thx for providing experimental data that supporing my argument.
    In that Table, it clearly illustrate why less weighted rackets have more MOI than a more heavier racket if u say adding mass always increases MOI? Why some lighter rackets have higher MOI than some heavier racket? Why is two carlton AS1 have large MOI differences when they statically weighted equally?
    what's your argument again? Adding weight near the axis reduces MOI?

    here's the list again sorted by MOI with added data about the original weight range the racquets were supposed to be (2U,3U,4U) and what sort of balance they are supposed to be.

    number 1, The Rasmussen Superlite is partly why I did these measurements in the first place. When I first played with it I could barely hit clears 3/4 court. not even close to the back. So I wanted to know what was different about this racquet.

    number 2 looks out of place. Maybe I measured something wrong. maybe Carlton had a bad day at QC.

    next up, 3 and 4, the head-light racquets

    5,6,7,8,9,10 the even 3Us and the head-heavy 4Us
    9 appears to have a large MOI for it's weight, but it's balance point indicates it might be head-heavy rather than even. Why? I don't know. Ask Carlton.
    10 is heavier because it has more (and heavier) grip on it, but it hasn't done much to the MOI

    finally, 11 and 12 the heaviest racquets and the largest MOI


    And the AS1s with the same weight but large MOI difference.
    I added weights to different places on the same racquet.
    weight on the head, much bigger MOI
    weight on the butt, hardly any difference
    Attached Images Attached Images  

  15. #372
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    Quote Originally Posted by Neil Nicholls
    what's your argument again? Adding weight near the axis reduces MOI?
    u disputed my statement that ' adding certain mass at certain area/region can reduce MOI' and then went on saying


    Quote Originally Posted by Neil Nicholls
    are you confusing two different things?

    2nd moment is sum of mass x (distance from axis)^2
    if the axis of rotation stays in the same place (i.e. you hold it in the same place) then adding weight anywhere can only increase this value.
    your own experiemental data doesnt support your own statement

  16. #373
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    Quote Originally Posted by cooler
    your own experiemental data doesnt support your own statement
    which particular piece of data are you talking about?

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    Quote Originally Posted by Neil Nicholls
    which particular piece of data are you talking about?
    i like to reference your table that was originally posted in
    http://www.badmintonforum.com/vb/showthread.php?t=25202

    as highlighted by the circles, your measurement or calculated MOI isnt consistent to your statement that, on similar racket, "then adding weight anywhere can only increase this value(MOI)" does not hold. If your statement was true, how can a heavier racket end up with lower MOI in some cases?
    Attached Images Attached Images  

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