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The Balance of a Racquet

Discussion in 'Badminton Rackets / Equipment' started by R20190, Oct 5, 2012.

  1. R20190

    R20190 Regular Member

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    Over the years I’ve noticed that a lot of people have taken different views over the question of balance point and have confused balance point with racquet weight. So I’ve tried to put together a few of my thoughts down and try to explain my take on it and hopefully clarify this important racquet property (I got a little carried away and wrote a little too much in the end!).

    Balance point (BP) is basically the position of the centre of mass of the racquet, measured from the butt of the racquet handle. This gives some indication as to whether it is deemed head heavy, head light or even balanced in its original state.

    The overall length of modern racquets are generally around 665mm - 675mm but with most racquets now at the longer length of 675mm, here are my suggested BPs for these racquets.

    Head Heavy (HH) > ~295mm
    Even Balanced (EB) = ~285-295mm
    Head Light (HL) < ~285mm

    Obviously, this is just for guidance, in reality the classification is never as clear cut as this. For example, some may regard 300mm is still even balanced but at the higher end of the EB scale or <280mm to be considered HL. It is quite subjective.

    The weight of a racquet is not the same as the balance. The weighting of racquets are generally in increments of 5g less than 100 grams and a racquet of any weight can have different balances. However a HH “U” weighted racquet and a HL “4U” racquet may be difficult to play with.

    U: 95g
    2U: 90g
    3U: 85g
    4U: 80g

    We mostly feel the effects of a racquet’s balance through the weakest component of our stroke, our wrist/hand. Although it can affect the elbow, shoulder etc, we are more sensitive to its balance in our wrist/hand and in particular strokes that use predominately the wrist such as BH/FH drives, flick serves, BH net kill etc etc...

    In other strokes such as a FH clear/smash, that reliance on the wrist is reduced so we tend not to be affected by racquet balance as much, but is more a case of adjusting the timing of the stroke.

    The conventional way of determining a racquet’s balance is to find the distance of its centre of mass from the butt end of the racquet. Indeed this is the way racquet manufacturers would determine the balance. However there are some limitations to this method.
    1. It is only applicable to a racquet that is not modified or altered from the original specification in any way.
    2. It is a static test method.
    Badminton racquets are seldom kept to the original specification throughout its life. Whether this is through replacing grips, grommets, enlarging the handle, adding weights, using different type/gauge strings etc. All these “changes” would affect the balance point of the racquet to some extent and may change its weight class (U’s).

    The drawback with a static test, is that it does not take into account the aerodynamic effects of the racquet. A head light racquet with poor aerodynamics that generates greater air resistance may hinder its ability to manoeuvre quickly and conversely, a head heavy racquet with good aerodynamics will improve its manoeuvrability to some extent. Given that most of us don’t have a wind tunnel, this factor is usually neglected but it does show that balance point is not the only consideration.

    The Confusion

    A lot of confusion seems to arise from the assumption that if we apply more grips on the handle, thereby shifting the balance point towards the handle it would make the racquet more head light. Certainly the new balance point would indicate that it is now head lighter, but is it actually more head light?

    The answer is no – unless you play by gripping the racquet above the handle!

    The reason is this...

    A racquet is primarily rotated about the players hand/wrist and as this is where we would mainly feel the differences in balance, the “fulcrum” should be roughly where the hand/wrist is. So adding weight near or at the fulcrum would have no real effect on the head weight of the racquet since the moment approaches to zero.

    To explain it further, if we assume (in a static model) the weight of the racquet is broken down into three main parts, head, shaft and handle. To get the real "balance" feel of the racquet I believe we should take moments about the players hand not the centre of mass of the racquet (which is what has been done conventionally).

    A moment is simply the turning force applied on an object. In this case, the static loads are from the weight of the parts of the racquet.

    Racquet Diagram.jpg

    [​IMG]
    The moment therefore is simply the sum of the leverarms of the elements multiplied by their respective weights. M = FxD.

    M = (Head Weight x D1) + (Shaft Weight x D2) + (Handle Weight x D3)

    Where the leverarm distances D1, D2, D3 are the distances from the centre of mass (centroid) of the constituent part to the fulcrum (players hand). So generally speaking the higher the moment M, the more head heavy the racquet will feel. (Note: This is based on our static model, in a dynamic model, moments of inertia should be considered).

    As you can see, in reality adding extra weight to the handle does not make much difference to the balance at all, since the additional weight of the overgrips are near/at the fulcrum (the players hand) making the leverarm D3 essentially zero. What it does do though, is increase the overall weight of the racquet, so it’s just excess weight! The additional grip(s) effectively just increase the overall weight of the racquet. Given that the weight classes are only 5g apart, adding a few overgrips to say a 3U racquet may turn it into a 2U racquet!

    However, if we were to alter the weight of the head for instance, say by adding lead weights, this would indeed alter the balance feel of the racquet as it is at a fair distance from the fulcrum.

    This is simple statics, but should help to explain the balance confusion. Though for the more enthusiastic members amongst us, calculating the moment of inertia, aerodynamic effects (racquet + string) etc would give a more accurate picture.

    Which balance is right for me?

    A racquet’s balance is quite a personal choice, and is one that most people will gradually discover a preference for over time. But there are some indicators/rules of thumb that can help with narrowing down that search.

    Generally speaking:
    • Head-Heavy Balanced – For powerful, strong players who can exploit the extra head weight for greater power. Singles players (who have more time to play shots) that rarely need to play backhands and fast exchanges.
    • Head-Light Balanced – For weaker but fast players who like to dominate fast exchanges, at the net and in defence. Control players, fast doubles and mid-court players.
    • Even Balanced – For all players, doubles, singles, mixed etc.
    Head heavy racquets carry more inertia and so are more efficient at transferring momentum to the shuttle. However in order to take advantage of the extra inertia, one would need to be strong enough (BH&FH) to be able to maintain good racquet head speed. For example, in terms of smashing, weaker players using head light racquets may be able to generate the same racquet head speed as a strong player with a head heavy racquet but the resultant smash would be somewhat slower due to the reduced inertia in the head. But this is by no means the be-all and end-all of it. Other factors such as string type, tension, racquet characteristics, technique etc will also play a part.

    However the bottom line is that only you as the user will know what suits you best. Whenever I look to buy a new racquet, I always give it few swings, normally backhands flicks as this seems to give me the best feel for the balance. Although unstrung racquets are more difficult to tell.

    I often get asked what balance would be good for a beginner. This is quite subjective question and is one that a lot of players/coaches would debate on. But my personal view would be to use head heavy balance racquets. This is because the beginner will need to train their muscles needed for badminton and also to help develop the correct technique. Head heavy racquets are also generally more stable and will help smooth out inconsistencies in a novice’s stroke as well as to encourage the “follow-through”. They are also generally more durable given the extra material in the frame. At beginner level, time invested in getting the correct technique and developing the right muscles is immensely valuable. As the player gets better, they may then want to try different balances.


    Summary
    • The conventional method of determining the balance point of a racquet is only meaningful if the racquet is not modified. If it is indeed modified, measuring or comparing the new BP against other racquets will not be very reliable/meaningful.
    • Adding grips or removing grips from the handle will not make the racquet any head lighter or head heavier (respectively) but will change the original BP of the racquet.
    • Only the user themselves will know what balance is most suitable for them. At the end of the day, it’s what matters to you that counts. If you feel it’s too head light, then it probably is - for you.
    • Beginners – Head Heavy (my opinion).
    Hope it helps ;)
     
  2. visor

    visor Regular Member

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    One word: swing weight.

    Much better measure of racket's playability than a simple static bp and wt measurement.
     
    #2 visor, Oct 5, 2012
    Last edited: Oct 5, 2012
  3. gundamzaku

    gundamzaku Regular Member

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    now that i finally got a stringing machine, my next toy will be a machine that measure swing weights of rackets. unfortunately they are really expensive!!
     
  4. visor

    visor Regular Member

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    If you have an iPhone you should check into swingTool app. Only a few $ but very useful.
     
  5. gundamzaku

    gundamzaku Regular Member

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    sweet!!!! thank a bunch, visor!
     
  6. !¿Clue?!

    !¿Clue?! Regular Member

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    Very interesting observations. Thanks for sharing! :)
     
  7. decoy

    decoy Regular Member

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    I can never get my phone still enough to get an accurate reading. How do you usually set it up?
     
  8. latecomer

    latecomer Regular Member

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    Since you have so much time at your disposal, could you string my rackets next time I come to Califorina.
     
  9. CarbonexFan

    CarbonexFan Regular Member

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    Well explained. I never give balance point in mm, but compare them directly to another racket in the same weight class. I use the same grip for all of my rackets, so the margin is minimal, given the same grip size. I never understood why some rackets has balance adjusters in the handle to make it head lighter. Did you know that you can also make the racket more maneuverable by holding the racket higher, like most double players do? There is a reason why some double rackets have a long handle.
     
  10. vajrasattva

    vajrasattva Regular Member

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    weighing down the handle by a bit (in terms of grams) does make a difference to the feel of how the racquet plays and hits...

    i've added 2 small strips of weight tape from yonex (abt 2.6 grams worth) to the sides of the buttcap of a Z-slash and the racquet plays differently. it makes the z-slash much easier to handle now.

    the balance point of the racquet shifted by a few millimetres.

    need more people to test it out though..
     
  11. gundamzaku

    gundamzaku Regular Member

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    come to think of it i do have a lot of free time during the winter because it's not really cycling season, at least not for me. if you do come to norcal bay area, no problem :)
     
  12. kwun

    kwun Administrator

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    no excuse! i have been going out cycling when it was down in the 30F's...
     
  13. kwun

    kwun Administrator

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    back to swingweight though, i have borrowed a swingweight machine to play with a little bit. the machine is ok, but the granularity is not small enough. the range for the heaviest to lightest racket i have measured were in a range of 15 units. which is not enough as most rackets come into the range of 7 units.

    the machine is the Alpha Accuswing 2. i don't recommend it.
     
  14. vajrasattva

    vajrasattva Regular Member

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    The Balance of a Racquet is easily affected by the Grip!!!!

    [​IMG]
    just for fun, i added a 1.2 gram strip to the butt of my NS9900 purple, the balance point shifted from 29cm to 28.5cm there abouts (measured with a ruler)

    [​IMG]
    balancing on the edge of a pair of forceps till its horizontal

    effect of 1.2 grams only!...... that was why 2.6 grams on my Z-slash made it feel like IZ-Slash :X

    some of the popular grips used...
    [​IMG]

    18.76 grams on that karakal grip or 5.68 grams on the overgrip... it definitely will change things!
     
  15. vajrasattva

    vajrasattva Regular Member

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    yonex super grap is abt 4.7 grams


    all in all the moment about the fulcrum/pivot (wrist) is dependent on the distance of the centre of gravity away from the pivot, so by shifting that, racquet swing timings change, making difficult to use racquets, i.e. z-slash, z-force, seem more manageable
     
  16. visor

    visor Regular Member

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    @vajrasatvva : we've been thru many times in previous threads. Obviously +1g on the top of the frame would have a significant effect on swing weight. But at the handle or butt, very negligible. Try wearing a heavy ring on your racket hand next time and see if you notice any difference. ;)
     
  17. R20190

    R20190 Regular Member

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    You probably have noticed that I've drawn the pivot point not right at the end of the handle. This would imply that if you add a significant mass to the end of the handle, you may feel a difference in the way the racquet swings/plays.

    However, for the size of the mass you have used (a few grams) and given the distance of this to our assumed pivot (~2 inches?), I would be surprised if you noticed much difference during play. Yes, in theory any mass applied to the other side of the fulcrum would counteract the applied moment but if you're saying you can feel difference with 1.2g applied at say 50mm from the pivot I admit I find it hard to believe.

    A lot of players add thin lead strips to the top of the frame. These are usually in the order of about 2g in weight (depending on preference - possibly more) which is applied about 675-50=625mm from the pivot. This would give a different feel to the racquet but the static moment is:

    0.625m x 0.002kg x 9.81 = 0.0123Nm (which we can certainly feel)

    However, going by your test of adding 1.2g at the butt, this would give an approximate moment of:

    0.050m x 0.0012kg x 9.81 = 0.00059Nm.

    This is less than 5% of the effect you would feel from adding 2g weight to the head of the racquet (if my quick calcs are correct). If we turn this around, it is equivalent to (statically) the difference in feel by adding 0.096 grams to the head of the racquet. I certainly wouldn't be able to feel that! It's probably less than the difference in swing weight by changing from thick strings to medium/thin strings.

    I believe, what you may be feeling is the difference in the slight variance in the diameter of the handle which certainly would affect playability as tightening of your forearm muscles are affected.
     
  18. vajrasattva

    vajrasattva Regular Member

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    it is not! on my z-slash i paste the tape around the sides of the butt cap only, i'm extremely picky about the diameter of how my racquets are gripped and have a plastic vernier caliper to measure each time i re-grip my racquets. my target is usually 25mm x 28mm if not i will re-grip it (sorry.. pedantic scientist here..)

    little bit of tape peeking out from side of butt cap
    [​IMG]

    [​IMG]

    both Z-slash and I-slash are gripped to 28mm x 25mm


    your calculation in using the distance 0.625m to calculate the moment is interesting, i would prefer to calculate it based on the centre of gravity since we are looking at free swing. the moment acts through the centre of gravity (there is no external force applied since there is no shuttle contact)

    [​IMG]

    the reason why i chose exactly 2.6 grams on butt cap, was because i wanted to replicate the similar swing feel of the i-slash on the Z-slash, i have the BP down to exactly 283mm from the usual 295mm of the Z-slash, identical to the i-slash. this was how i managed to adapt to the Z-slash's swing speed immediately, with no need to re-calibrate my hitting timings at point of contact

    I slash moment = W1 x D1
    Z-slash original moment = W1 x (D1+12mm) since the centre of gravity was 12mm away

    [​IMG]


    so what happens if i add lets say 1.2 grams on the head of the i-slash..
    the BP shifts by abt 5mm!..
    so in principle the moment that i will feel now, is (W1 + 5mm) x D1

    [​IMG]

    vice versa.. which is why headheavy, even balance or light head balance is just a permutation of a narrow range of a couple of centimetres, yet significant swing differences..
     
  19. vajrasattva

    vajrasattva Regular Member

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    having a ring on the racquet hand doesnt change anything significant because the ring is on the pivot!.. having some weight on the buttcap changes things because it affects the centre of gravity of the racquet by which the moment is calculated....

    i know this had been debated before, but i thought i had to revive the discussion because i have a different opinion as to how the physics should be calculated...
     
  20. vajrasattva

    vajrasattva Regular Member

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    just to be clear here, i disagree with only the separate calculation of W1 and W2 in the original diagram in post 1.. i dont believe W1 and W2 to exist separately in a circular moment about a pivot.

    i believe the contributions of both W1 and W2 (weights of shaft and head) to exist combined at the balance point of the racquet, because if you shift the pivot to below the balance point, the racquet is horizontal, the sum of moments is zero. there is no separate W1 and W2, if not the racquet will be lop sided if W1 is independent.
     

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