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Why +2lbs On The Cross?

Discussion in 'Badminton String' started by kwun, Apr 7, 2003.

  1. kwun

    kwun Administrator

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    explanation on why 2 more lbs on the cross.

    here i offer an explanation why we need 2 more lbs on the cross string. actually quite trivial and i wonder why no one has brought it up.

    the first pound.

    let imagine the situation in which we have a good 6-pt machine.

    we weave and tension mains string first, and then we weave and tension the cross string. when we tension the main string, the strings are a straight line when tensioned. without loss of generality, let say we first tension the mains to 20lbs.

    then we weave and tension the cross at 20lbs. notice now that after the tensioning, the mains are no longer straight as they are weaved with the cross. the result of the mains being displaced and since the frame isn't moving, the tension will have to go up. by how much is anybody's guess, but my guess would be say 1 lb?

    now, if the mains goes up by 1lb, then we have to increase the cross tension to 21lb to compensate for the difference.

    the second pound.

    i believe if we have good support, 1lb or so is all we need. many have said that if we have a machine with no support, we need 2 pounds to compensate the distorted frame. i think that is a legitimate argument.

    collorary:

    what else can we find from this?

    well, one observation i can see is that, if we tension, eg. 20/22, the resultant mains tension is actually higher than 20. and imho, more like 21 or so.

    does that make sense?
     
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  2. eggroll

    eggroll Regular Member

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    Re: explanation on why 2 more lbs on the cross.

    Kwun, you are right about this. I asked our guy about this and two reasons were given.

    1) Restore raquet to original shape
    2) Original shape more difficult to restore because of weaving and tension diffence on crosses.
     
    nutty likes this.
  3. Yodums

    Yodums Regular Member

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    Makes perfect sense kwun :) Perhaps you should sticky it in FAQs or something.

    Yodums
     
  4. ayl

    ayl Regular Member

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    G'day Kwun,

    For a long while after reading, I was like -> :confused:

    Then I guess after the beer has worn off, I did a big ->:eek:

    Good post! And makes perfect sense! :)
     
  5. jug8man

    jug8man Regular Member

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    let me just say this. if you can string a racquet without needing to adjust the mains and crosses to look neat upon completion (by stringer, not by player after use) then you can skip this whole 2lbs / 10% diff on the crosses. but no real harm generally if still practiced.
    if not then stick to the 10% rule is all i can say to the average stringer.
     
  6. cooler

    cooler Regular Member

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    +10% rule if the desired end result is to have similar tension for both cross and main. :rolleyes: those are what i call regular tension.
     
  7. benibeni

    benibeni Regular Member

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    Just Curious

    Hi, I wanted to ask whether 2lbs difference is the recommended difference on iso shapped racquets?
    Well, jus read the post from mr.lok from a forum where he strung racquets for pros, and he strund Kim's racquet at 27lbs mains, and 21lbs cross... not only was the cross not 2lbs higher than the mains, its way lower..

    Just hope to find an explanation before restringing my racquets.. all of them are quite loose at the moment and i need them redone soon..
    cheers
     
  8. benibeni

    benibeni Regular Member

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    Just asking

    Hi, just a question, whether it will do any harm to the racquet or any change in performance if the cross is strung lower than the mains?
    in one forum, it was stated that Kim DM played with 27 mains, 21 cross, is that ideal?

    Hope to get an explanation
     
  9. bluejeff

    bluejeff Regular Member

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    I believe that's a mis-typed information because a 6 pound difference could potentially damage the racket. I think it should be like 27x31, which is close to the tension that Koreans prefers in Olympics.

    27x21.....the racket will become a full circle :rolleyes: .
     
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  10. Pete LSD

    Pete LSD Regular Member

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    That's not mistyped information. Mr. Keen has special attachments that allows all sorts of tension and tension-ratio combination.

     
  11. Radium

    Radium Regular Member

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    How is the tension measured? I don't string my own rackets, and I was just wondering.
     
  12. Neil Nicholls

    Neil Nicholls Regular Member

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    I'm not sure that 27x21 is KDMs normal tension setup.
    The impression I got was that on that particular day his racquet just felt wrong and he had to keep changing it. Eventually, after several restrings, when it got to 27x21 it felt OK.
     
  13. Neil Nicholls

    Neil Nicholls Regular Member

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    As we've been talking about Main v Cross tension a bit recently, I thought I'd have another look at this. I don't claim to be an expert. Thse are just thoughts and observations.

    From measurements on a strung racquet, I calculate that the mains are stretched by about 0.027mm per cross string. This is for 0.7mm diameter string.

    With 23 crosses this adds about 0.6mm to the mains.
    Centre mains are 24cm, or 240mm
    Stretched length becomes 240.6mm
    An increase of about 0.25% (maybe 0.5% for the side mains)
    Small enough to be ignored (in my opinion. 0.5% of 20lb = 0.1lb )

    So any increase in mains tension as a result of stringing the crosses may be mostly due to the frame changing shape during stringing.

    Another reason for increasing tension on the crosses may be that when you pull the crosses, friction from the mains reduces the effective tension that the string experiences. How much by, I dunno, but we should be able to find out by attaching some string to some scales. Weaving it through some tensioned mains, and pulling tension. Compare what the string machine is set to pull and what the scales read. Probably easiest to do on a drop weight.
    I'll have a go next time I string.
     
  14. jcl49

    jcl49 Regular Member

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    Maybe he wants an oval shaped titanium head-heavy racquet...
    jl
    PS maybe there is a better racquet out there than the cab30ms :p
     
  15. leehsim

    leehsim Regular Member

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    compared with highlight as bold blue

    Quote:
    Contradicting views?

    I thought during racket stringing that if you use a 6-point support stringing machine, the supporting system is able to hold the frame of the racket more or less in its unstring shape.
     
  16. kwun

    kwun Administrator

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    actually, we are talking about the same thing. what you quoted was my first part which assumes a 6pt machine that holds the frame in place. the second part explains the 2nd lbs of tension which assumes no support which is what Neil assumed also.
     
  17. leehsim

    leehsim Regular Member

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    Thanks to your clarification. Help to confirm my understanding.

    Some more thought.

    Thought 1: During stringing of racket on a 6-point, the frame in sahpe but the tension of main may increase due to weaving of crosses.

    Thought 2: After the the racket is dismounted from the stringing machine, the frame of the racket may change due to the reaction of the tension on the mains and crosses.

    Any misconception of my thoughts?
     
    #17 leehsim, Jan 11, 2005
    Last edited: Jan 11, 2005
  18. HORACE

    HORACE New Member

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    Racket stringing. The Answer...

    Hi.
    Very interesting all that. I play tennis, and have a stringing machine ( Tyger Profi 55 ) and although we are talking about different tensions and guages, the principles remain the same ...
    I have been bothered for some time about the fact that the crosses are obviously less tight than the mains because of the reasons already mentioned, i.e. that the crosses tighten the mains as they ( the crosses )are pulled. An effect of this must surely be that the ball/shuttlecock is send back mainly under power from the resilience of the main strings only. The crosses must have little to do with it as the mains reach their maximum stretch point well before the crosses will even be tight !
    This seems like a pretty undesirable situation. Surely if the mains and crosses had the same tension, better ball control would be the result - although, as the crosses are shorter, their maximum stretch point would be reached before that of the mains, so pêrhaps a slightly lower tension is after all desirable for the crosses !
    But how can this be achieved ?... The tighter you pull the crosses, the more tension will be put on the mains, so a much lower tension seems desirable for the mains, and higher for the crosses... But, I've tried this, and it doesn't seem to work, as, the high tension on the crosses just pulls the mains even tighter !
    For information, when I string my racket normally, the mains measure at 25Kilos, but the crosses at at only 12. This is lamentable ...
    The only way I can see to keep tension even would be, starting at the middle of the racket, to string one main followed by one cross, one main, one cross, etc. etc... That way a main will tighten the cross, then a cross will tighten the main etc...
    Trouble is, you will need around 4 clamps to acheive this. It is not possible with just 2 fixed clamps, and resorting to flying clamps results in less accuracy ....!
    Another big problem, is that in normal stringing, each cross string has progressively more friction on it from the mains, resulting in less tension on the final crosses. Most people worry about even tension on both sides of the mains, but look at the way a ball is hit, and you will see that the racket is more in a horizontal position than a vertical one ( in tennis anyway ), so the balance of the crosses on either end is actually more important...
    I remember I once saw on the Fischer website, a factory worker stringing a racket, and he was using a device which held apart the mains, while he strung the crosses. The crosses did not touch the mains, and therefore avoided any friction. But where does one obtain such a device ?....
    One final point. When I have my rackets strung on the big, expensive Babolat machines, they play better than mine ! However, they are strung conventially, with less care and attention than I give. I can only assume that the clamping system is of very high tolerence, with little freeplay, therefore minimizing tension loss. This is perhaps after all, the most important factor of all ... If only I could afford one .... !!
     
  19. catbear

    catbear Regular Member

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    Hi All,

    I just noticed that Yonex recommends 2 pounds higher tension for cross for their old models such as Ti10. But for the latest models, they only recommend 1 tension for both main and cross. Can anyone come up an explanation for it?

    http://www.yonex.co.jp/badminton/old-model/pro2001/racket/ti10r.html
    http://www.yonex.co.jp/badminton/old-model/pro2003/racket/mp80.html
    http://www.yonex.co.jp/badminton/old-model/pro2001/racket/cab20lo.html
    http://www.yonex.co.jp/badminton/products/racket/ns7000.html
    http://www.yonex.co.jp/badminton/products/racket/at800.html
    http://www.yonex.co.jp/badminton/products/racket/mp90.html

    縦 means main. 横 means cross

    Regards,
    CB
     
  20. taneepak

    taneepak Regular Member

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    That is not how I read it. The 1lb difference is between a 2U and a 3U, or a 3U and a 4U. Even when Yonex is more specific, like when suggesting both main and cross tension, the 2lbs difference is a rough guide. A more accurate difference is 10%.
     

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