Racquet Headspeed.

Discussion in 'Tennis Tips/Instruction' started by Chyeaah, Jan 11, 2012.

  1. Chyeaah

    Chyeaah Professional

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    So my unleaded BLX Pro Open, i thought was abit head heavy maybe 3-4 points so i stuck some coins in the butcap (roughly 8 grams maybe?). And now it seems to swing faster.

    So my question is, do headlight racquets swing faster?
     
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  2. thug the bunny

    thug the bunny Professional

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    Yes. By putting more weight in the handle, your moving the center of gravity closer to your hand, thereby making the effective length of the lever shorter, as long as your arm/body can handle the total weight.
     
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  3. LuckyR

    LuckyR Legend

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    I believe you are confusing balance and swingweight. Adding weight to the butt (as opposed to reducing weight from the head) will change the balance, obviously. But it will not change the amount of mass at the head that your arm needs to plow through the air resistance (swingweight).
     
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  4. DjokovicForTheWin

    DjokovicForTheWin Banned

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    I thought changing balance did change swingweight.
     
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  5. TimothyO

    TimothyO Hall of Fame

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    Given the same static weight a more HL frame will generally swing faster than a more HH frame.

    But adding weight to the butt won't allow you to swing faster. In fact, since the SW stays the same, some strokes such as serve will be slower because you have more mass to move around.

    Oddly enough you can have two frames of the same weight and balance but one have a higher SW! It all depends on the distribution of the mass.

    A heavier, HL frame like the one you've ended up with will feel more whippy with more mass in the butt. And it will be more stable on the long axis to some degree. There's simply no free lunch when it comes to certain strokes. It's always harder to heave 12 oz over your should when serving than 11 oz. Even if both frames are HL.
     
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  6. TimothyO

    TimothyO Hall of Fame

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    Depends on where the weight goes.

    Adding weight at the butt can't reduce SW. It does increase static weight but doesn't change Sw much.

    Adding weight towards the head increases SW, plow through, and static weight.

    I enjoy a frame aroind 12 oz but need it to be HL so the SW isn't too high. So I buy frames around 11 oz plus and a little HL so I can customize them to my liking.

    You can always increase a frame's SW but you can't lower from the mfg specs.
     
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  7. Zachol82

    Zachol82 Professional

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    It does. The change in swingweight depends on where the balance point is but overall, shifting the balance will definitely change the swingweight.

    If you would just imagine holding a baseball bat normally and swinging it by holding at the butt VS flipping the bat around and swinging it by holding at the tip, you would definitely notice a difference in swingweight. Since the balance point of a baseball bat is nearer to its tip than its butt, simply flipping the bat around changes its balance point based on your perspective.
     
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  8. julian

    julian Hall of Fame

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    Last edited: Jan 14, 2012
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  9. julian

    julian Hall of Fame

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    please see another thread as well

    Please see another thread as well
    http://tt.tennis-warehouse.com/showthread.php?t=408703&page=2
     
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  10. TimothyO

    TimothyO Hall of Fame

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    That's a VERY misleading analogy.

    Adding weight to a rkt's handle does NOT reduce the swing weight like flipping a baseball bat.

    An accurate use of the bat analogy: take two frames of equal weight, one HH and one HL. The HH one will feel like a properly swung bat. The HL one will feel like a bat swung from the fat end. Same static weight, different swing weight.

    Staying with the bat analogy, take a bat swung from the handle, add weight to the handle. Does it swing easier? NO! In fact, since you're swing more mass, your shoulder will be doing a lot more work. The swing weight won't increase much but the static weight will.

    The only way additional weight might make a frame feel faster is its effect on wind resistence. Greater mass for a given surface area will smash through the air more easily once you get it moving. Thus a heavier bullet can travel farther than a lighter bullet assuming equal dimensions and equal starting velocity. Or a plastic golf ball can't be thrown as far as a real golf ball.

    More weight under the grip won't effect swing weight or plow much but it will improve tortional stability a bit along the frame's long axis.
     
    Last edited: Jan 13, 2012
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  11. bhupaes

    bhupaes Professional

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    This is a good question, one that I have pondered over many times. The OP should take a look at travlerajm's posts.

    My own take is that at the hand, one feels two aspects of the racquet (not counting wind resistance). One is the static moment, and the other is the moment of inertia or swingweight.

    There are also two main characteristics to a swing: the linear aspect, and the rotational aspect.

    Totally linear swings are easy - the only thing that matters is the static weight of the racquet. It is much easier to move a racquet faster in a straight line if it is lighter. That said, most strokes are not purely linear...

    Now assume you are applying a fixed torque at the handle, centered around the handle. The higher the static moment of the racquet, the slower it will rotate in a given time. Now "headheaviness" is a measure of the static moment, so in general, the more headlight a racquet is, the faster one can rotate it, given a fixed static weight.

    Swingweight, for a fixed racquet length, is a measure of how the weight of the racquet is distributed. A high swingweight means there's more mass near the head of the racquet. The effects of swingweight come into play after you get the racquet moving, and it comes into contact with the ball - a high swingweight, meaning more mass at the head, will be good for plowing through the ball (crushing it).

    So - if you have two racquets with the same mass and length, the one which is more headlight can be rotated faster, and the one which has more swingweight will have more plow through. To me, it seems that high moment is the enemy of all strokes. Even for linear strokes, high moment will cause discomfort. So for a given racquet weight, I would try to make it as headlight as possible (minimize moment) and maximize swingweight - a conflicting requirement, undoubtedly! - to the extent possible.
     
    Last edited: Jan 13, 2012
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  12. Chyeaah

    Chyeaah Professional

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    If you can rotate faster it means more spin right?
     
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  13. bhupaes

    bhupaes Professional

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    More racquet head speed, and more spin.
     
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  14. julian

    julian Hall of Fame

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  15. julian

    julian Hall of Fame

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    Specific examples

    A very good post
    http://tt.tennis-warehouse.com/showthread.php?t=408703&page=2 #22
    provides a very good example ( C & D) for comparison.
    Maybe you would care to comment about comparison of C & D
     
    #15
  16. bhupaes

    bhupaes Professional

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    Thanks, Julian, I had missed that post - I mostly only look at the Tips and Health/Fitness sections.

    The comparison seems to be between two racquets with the following characteristics:

    C) Weight: 12 ounces
    Balance: Even
    Swingweight: 330

    D) Weight: 12 ounces
    Balance: 9 points HL
    Swingweight: 330

    I would wager that racquet D will perform better in every way, and will be much more comfortable to play with. It will feel a lot whippier than racquet C, since one will be able to rotate it faster around the grip, and so will better for spin production. D will also be a lot more maneuverable than C, and so better at net. And having the same SW as C will make D at least equally effective in plowing through the ball.

    To me, this makes D the preferable racquet for ground strokes as well as net play. I don't understand what corners means when he says that C will come around faster. It is possible that a person with long, linear strokes will like the feel of C better... humans are so gloriously unpredictable! :)
     
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  17. bhupaes

    bhupaes Professional

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    Looking at the following comparison:

    A) Static Weight: 12 ounces
    Balance: Even
    Swingweight: 330

    B) Static Weight: 12 ounces
    Balance: 6HL
    Swingweight: 340

    I will agree with corners on this, on second thoughts!
     
    Last edited: Jan 14, 2012
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  18. bhupaes

    bhupaes Professional

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    Finally, for the case:

    E) 12 ounces
    Even balance
    330 swingweight

    F) 12.5 ounces
    6 points headlight
    330 swingweight

    Again, on second thoughts, I will agree with corners - it's hard to say which will swing faster. By my calculation, F should feel easier on the arm, marginally, if the static weight is acceptable to the player.
     
    Last edited: Jan 14, 2012
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  19. fruitytennis1

    fruitytennis1 Professional

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    bhupaes...ABCD rackets comparisons don't make sense
     
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  20. bhupaes

    bhupaes Professional

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    I agree... there's no substitute for actual play testing. We are only talking about theoretical guidelines, which don't take into account many other factors. If they were exact, there would be only a few specifications that everybody used!
     
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  21. julian

    julian Hall of Fame

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    Could you explain why?

    Could you explain why?
     
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  22. julian

    julian Hall of Fame

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    Serve is different than groundstrokes

    Serve is different than groundstrokes
    Balanced rackets are better for serve
    So I disagrree with your sentence "I would wager that racquet D will perform better in every way,"
     
    #22
  23. bhupaes

    bhupaes Professional

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    Just curious - is there a physical explanation for this? Or is it empirical knowledge? Thanks.
     
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  24. julian

    julian Hall of Fame

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    A part comes from Vic Braden

    A length of a lever should be as long as possible for serve.
    Shifting a location of a mass towards a head helps the issue
     
    Last edited: Jan 15, 2012
    #24
  25. bhupaes

    bhupaes Professional

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    You mean shifting mass towards the racquet head, right? Sure, I buy that. You could make the racquet pretty head heavy, and if the player can handle it, he'll be able to hit even harder serves, I am sure - if that is his priority. But headlightness leads to greater maneuverability, which means the racquet will be much easier on the wrist, so one will get other benefits that are at least as important as brute force.

    In the end, this is all qualitative analysis that falls into the realm of general guidelines. In practice, the absolute values matter IMO, and the physical attributes of the player - how strong his shoulders, arms, wrists are, for example - will determine what the optimal values of static weight, balance, SW, head size, etc. are for that player, I believe.
     
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  26. julian

    julian Hall of Fame

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    I corrected the error above

    1.Some players like Chang used 27.5 inch long racket
    2.The OP question was about speed
    There some theory behind what I have said but it requires drawings
    3.The problem depends on quality of serve/elevation/etc
    There is a set of differential equations by Cross describing dynamics
    4.There is a paper by Cross related to the subject above
    5.I post more at tennisplayer.net
     
    Last edited: Jan 15, 2012
    #26
  27. bhupaes

    bhupaes Professional

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    Thanks, Julian, appreciate your drawing my attention to this very interesting topic.

    BTW, regarding point 2 in your list, the OP refers to racquet head speed. Not sure if you mean the same thing... head heavy racquets are good for ball speed, but not RHS, I believe.
     
    Last edited: Jan 15, 2012
    #27
  28. julian

    julian Hall of Fame

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    racket head speed

    I meant racket head speed
     
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  29. julian

    julian Hall of Fame

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    Acronyms

    What is RHS?
    ...spin?
     
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  30. bhupaes

    bhupaes Professional

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    Racquet Head Speed. Sorry, it's an acronym that's commonly used in this forum.
     
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  31. julian

    julian Hall of Fame

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    Justification?

    What is justification of "but not RHS"?
    Is it based on a two pendelum model/theory?
    PS Two pendelum model is described in two references below
    R. Cross, A double pendulum model of tennis strokes, Am. J. Phys. 79, 470-476 (2011). See also http://twu.tennis-warehouse.com/learning_center/doublependulum.php for videos of double pendulum action.
     
    Last edited: Jan 16, 2012
    #31
  32. fruitytennis1

    fruitytennis1 Professional

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    If everything is measured correctly A would have the higher sw
     
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  33. julian

    julian Hall of Fame

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    Contradiction?

    Are you saying that three numbers describing A CONTRADICT each other?
     
    #33
  34. corners

    corners Legend

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    No. You don't understand the difference between balance and swingweight. Don't feel bad, most people don't. But this is Racquets 101 stuff.
     
    #34
  35. fruitytennis1

    fruitytennis1 Professional

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    If its the exact same racket and the the balance is HL...in other words more weight in the handle it would have a lower sw;correct me if i am wrong.
     
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  36. julian

    julian Hall of Fame

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    #36
  37. bhupaes

    bhupaes Professional

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    Julian, I have read this article. Maybe I am missing something, but it doesn't seem to relate the terminal velocity of a racquet to the racquet's properties.

    Anyway, pendulum theory is interesting, and I have studied it in the distant past, but I don't believe it is directly applicable to what we are talking about here. Because in this case, the pendulum is not swinging passively in reaction to an external force (gravity) - its components (wrist, elbow, etc) are actively generating internal torque, in a manner that can only be described as uneven, to put it mildly!

    Coming back to the question of a heavy racquet with large static moment and swingweight and how it responds to a force/torque: it takes a larger force to linearly accelerate a larger mass, and it takes a larger torque to angularly accelerate a larger swingweight. At every step of the way, there is either a linear force or a torque or both active, and when faced with a heavier mass or swingweight, the force/torque will produce less acceleration. Thus, for a given maximum force/torque, a lighter racquet (static weight and SW) can be made to move/rotate faster. If I am wrong, please tell me why.

    BTW, the reason I hate large static moment is that I roughly equate it to the initial force/torque one needs to get it moving. Thus it's simply a drag on the arm, and the wrist in particular. But I suppose performance athletes will choose to live with whatever works for them when in competitions with large sums of money and prestige involved.
     
    Last edited: Jan 16, 2012
    #37
  38. julian

    julian Hall of Fame

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    Paper

    The article addresses rackets with THE EVEN balance with different
    swingweights.Some factors you are talking about are hidden in constants
    named couples (C1 and C2)
    The relevant figure is Fig 5
    Some other papers loosely related
    Cross, R. (199 8). The sweet spots of a tennis racket. Sports
    Engineering, 1, 63–78.
    Cross, R. (1999). Impact of a ball with a bat or racket. American
    Journal of Physics, 67, 692–702.
    Cross, R. (2001). Customising a tennis racket by adding weights.
    Sports Engineering, 4, 1–14.
    Cross, R., & Bower, R. (2006). Effects of swing-weight on swing
    speed and racket power. Journal of Sports Sciences, 24, 23–30.
    Cross, R., & Nathan, A. (2009). Performance versus moment of
    inertia of sporting implements. Sports Technology, 2, 7–15.
    The date of the first reference is 1998-I do NOT know why it did show up as smiley
     
    Last edited: Jan 16, 2012
    #38
  39. bhupaes

    bhupaes Professional

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    ^^^ Got it, Julian - thanks. I will read at least some of these when I get a chance.
     
    #39
  40. julian

    julian Hall of Fame

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    Peachy

    Just for the record I do NOT understand your post #37
    I do NOT understand why the FIRST paper by Cross ( American Journal of
    Physics) does NOT relate to OP
    BTW:an arm is involved as one of pendelums-we have 2 pendelums,NOT ONE
    I expanded my post #38
     
    Last edited: Jan 16, 2012
    #40
  41. bhupaes

    bhupaes Professional

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    Well, I have never studied double pendulums (the single idealized pendulum I believe is easy enough to be a high school math/physics exercise). Also, I don't have access to Rod Cross' paper, and I certainly don't want to buy it for the $30 that it costs! Looking at wikipedia, it seems like the double pendulum is modeled using Lagrangian equations that can only be solved numerically - ouch! I am not too keen to get into all that again, so you'll have to excuse me. :)

    But if you could provide a high level view of what answer it implies to the OP's question, I will be delighted.

    My own view, admittedly very subjective, is that pendulum theory does not apply here because the nature of the forces involved are too different from gravity. I don't think I have any other insights or knowledge to warrant more posts on this subject...
     
    #41
  42. julian

    julian Hall of Fame

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    A FREE link for the double pendelum model

    1.As indicated in one of my previous posts the double pendulum model
    is described in
    http://twu.tennis-warehouse.com/learning_center/doublependulum.php

    Another article is available for reading at
    http://www.physics.usyd.edu.au/~cross/PUBLICATIONS/49. TennisDPend.pdf
    You may go to
    http://www.physics.usyd.edu.au/~cross/publications.html
    It contains the list of publications.
    Clicking the title brings the pdf file of a corresponding paper
    I have checked that I can see the important Fig 5

    2.We may discuss at some moment why the double pendulum applies here
    So I disagree with your last sentence
     
    Last edited: Jan 17, 2012
    #42
  43. bhupaes

    bhupaes Professional

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    Fair enough. One of these days, after I have had the time to slog through the Rod Cross paper, we should have the discussion.
     
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