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Pulling two strings at a time

Discussion in 'Badminton Stringing Techniques & Tools' started by merciadriluca, Feb 25, 2013.

  1. Alex82

    Alex82 Regular Member

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    I had a short discussion at the weekend with a stringer which string on some small tournaments around here. He pulls two strings at a time (with a Pro's Pro Pilot) and he says, that he has tested this and this would not be noticeable. I remember how Kwun measured this a year ago, so I have copied his technique (sorry Kwun :rolleyes:) and tested this yesterday evening, this is the result:

    Pull on one string at the mains with prestretch (20%) enabled:
    IMG_0185.jpg

    Pull on two strings at the mains with prestretch (20%) enabled:
    IMG_0186.jpg

    Pull on two strings at the mains without prestretch but constantpull:
    IMG_0187.jpg

    Pull on one string at the crosses with prestretch (20%) enabled:
    IMG_0189.jpg

    Pull on one string at the crosses without prestretch but constantpull:
    IMG_0190.jpg

    Pull on two strings at the crosses with prestretch (20%) enabled:
    IMG_0192.jpg

    Pull on two strings at the crosses without prestretch but constantpull:
    IMG_0191.jpg


    Every time I have pulled with 9kg (~19,84 lbs).

    Also i measured two finished string jobs with the ERT 300 (this is a small tool to measure the "dynamic tension" of tennis rackets). Normally the ERT 300 works for badminton rackets too...

    First i strung this racket with pull on every main with 9 kg (~20 lbs) and prestretch 20%. On the crosses I've pulled two strings at the same time with 9,6 kg (~21 lbs) and prestretch 20 %.
    The result of the ERT300 is 38.
    (My heard was bleeding while i strung this racket with pulling two strings at a time...)

    Second i strung the same racket with the same string with pull on every main with 9 kg (~20 lbs) and prestretch 20%. On the crosses I've pulled every strings with 9,6 kg (~21 lbs) and prestretch 20 %.
    The result of the ERT300 is 44.

    The procedure with pull pulling two strings at a time is more than 15% lesser than the normal one.
    The ERT300 is not optimal for badminton rackets, but i think its a good reference value...
     
  2. Mark A

    Mark A Regular Member

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    ^It's more noticeable with crosses because a double pull doubles the cross friction, which is far higher than grommet-borne friction.

    Losing 0.3 lb on a main isn't exactly the end of the world, but I wouldn't be satisfied with it;).

    P.S. I'd be very interested to see a hand prestretch vs. ECP prestretch result for a "normal" string job...
     
  3. kwun

    kwun Administrator

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    awesome work Alex!!

    15% loss is quite a bit. if we do a 20lbs job, instead of 20lbs we will end up with 17.

    two more observation:

    - the loss on cross and main is different. what it means then is that it will change the main/cross ratio. and as we know, main/cross ratio has a very big influence on the playability of the stringjob
    - pre-stretching reduces the effect. which is interesting as it means it is forcefully overcoming the friction before settling down on the actual tension. make sense, but it also might mean we are not getting the pre-stretch'ing which is one of the factor contributing to the reduce ERT reading.
     
  4. Blitzzards

    Blitzzards Regular Member

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    It looks like this would justify the "add 10% to cross strings" practice. Seems that by doing uniform tension on both main and cross strings, the cross strings will also end up with slightly less tightness thus making the tension "not scientifically uniform" anymore.

    However, a better way might be to just string the mains at the desired tension, and then the cross strings with pre-stretch on (not sure if 10% is enough or we really have to go all the way to 20%).
     
  5. kwun

    kwun Administrator

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    still not quite the same.

    as the result, while have similar tension on average, will have interleaving strings, one at higher than norm, the other one at lower than norm.
     
  6. Blitzzards

    Blitzzards Regular Member

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    That is true, but shall we not let "feel" be the best judge of all? ;)

    I myself have been doing uniform tension, but at the same time having the "centre cross strings" (i.e. between bottom 5 and top 4/5) pre-stretched to 10% when stringing. Thus far this new tensioning practice of mine is giving me a little different "spark" in string feel compared to strictly uniform tension and uniform tension with all strings pre-stretched to 10%.
     
    #26 Blitzzards, Apr 8, 2013
    Last edited: Apr 8, 2013
  7. kwun

    kwun Administrator

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    I do similarly for center strings (i add 10% tension instead of turning off pre-stretch)

    but that's quite different than alternate strings. i guess we need to try it out to see how it feels.
     
  8. DarthHowie

    DarthHowie Regular Member

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    [MENTION=21606]Alex82[/MENTION] & [MENTION=1]kwun[/MENTION]
    I noticed that when you measured the tension on your electronic calibrators you have what looks like a PVC tubing tied on one end. Is this acting as a substitute to clamping the other end of the calibration unit?

    I'm also assuming that you just went to your local hardware store to buy the tube and hand cut it yourself? Can you give me the specific tube type if possible?

    Thanks. I find it rather ingenious.
     
  9. kwun

    kwun Administrator

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    Mine is a PVC tube from the hardware store. 2.5" outside diameter. 5" long. I used a hole saw to cut a hole as the string side opening.
     

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  10. kwun

    kwun Administrator

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    The tape is for protecting the frame. I used a few a layer of masking tape.
     
  11. aloy66

    aloy66 Regular Member

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    From this experiment, it seems that the final tension is higher if you use the prestretch function. From my other post http://www.badmintoncentral.com/for...41-Actual-pulling-tension-of-machine-with-ECP, I was trying to find out if the actual pulling tension from prestretch function is actually higher than constant pull tension.
     

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