Racquet Force swing weight...

Discussion in 'Badminton Rackets / Equipment' started by visor, Feb 9, 2020.

  1. Prince Light

    Prince Light New Member

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    I believe they did, as they used the drag coefficient for a circular cross-section to model the drag of the strings.

    All the other details you are mentioning, which the model in the thesis likely did not account for, tends to increase the share of drag for the stringbed (probably not by much though), not lower it.

    Anyway, I found it useful to get some info about the air drag components in a racket. Sorry that you didn't.
     
  2. speCulatius

    speCulatius Regular Member

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    And they calculated the drag for one string. I'm still not sure that that's a good idea for all the reasons above. It wouldn't be that hard to measure the drag for a strung and an unstrung racket and compare, but they're not trying to do research.
    That's passive aggressive and just wrong. Information would have been useful. Great that you think you got information... sorry to say that you didn't. If there was research in what Kwan did, what is the hypothesis? Please don't answer to me...

    Using your calculations, you get a bigger difference due to the weight difference between thicker and thinner strings, I hope you saw that. The paper also says that the weight overall it's the more important aspect than the aerodynamics, though they're - once again - more than vague on how they compare that and at which swing speed and acceleration. It's all not that easy.

     
  3. Swat

    Swat Regular Member

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    Regarding aerodynamics and swing weight - would, in theory, two rackets with the same swing weight number, and let’s say same stiffness, where one is box frame and the other is sword/aero, have equal smashing power?
     
  4. Ch1k0

    Ch1k0 Regular Member

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    Tbh I don't think they would be equal. Non scientific opinion here cos IME box frames have always had better power transfer as compared to aerodynamic frames.

    Sent from my SM-G975F using Tapatalk
     
  5. Budi

    Budi Regular Member

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    The problem is that swing weight machine used by RF & many others is just to catch the head force with very slow swing. It didnt test for high speed swing to see how the aerodynamic takes affect.

    Box frame give better energy transfer but aero frame cut air better resulting faster swing thus also higher power. But how faster a swing speed add on aero frame compare to how efficient a box frame can give on energy transfer, its kinda complicated i guest.
     
  6. Swat

    Swat Regular Member

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    Didn't know the machine was such a slow swing... I haven't seen it in action. So that makes things different at high speed of course.
     
  7. Budi

    Budi Regular Member

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    i saw it once on racket video review but forgot which one show the machine in action.
    The machine is blue colored, the same as what used by RF on their photo. The machine didnt spin the racket like crazy but it just (what to call it... Wobling wigling... :confused:)... Errrr it just swing it kinda like 10 degree to left slowly & then 10 degree to the right few times repeatly.

    Well it just short video showing the machine run when testing, maybe im wrong & the video didnt show full mechanism of the machine, but considering how the machine lock/grip the racket i doubt it will be high speed swing.
     
  8. Ales Berce

    Ales Berce New Member

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    I am in a dilemma regarding publicly available swingweights measured with commercially available machines (Yonex Precision scan and Victor's machine) and possible too see on reviews via YouTube. I myself acquired a laboratory exact swingweight machine produced by Stringlabs in Italy designed and handmade by engineers. It is provided with a calibration bar for tennis and badminton which exac
     

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  9. Ales Berce

    Ales Berce New Member

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    .....The bar comes factory calibrated with values to precision of 0.1kg/cm2. The measured values I get with tennis are about the same as values available online and reproducible from measurement to measurement. Even attaching a dampener changes SW a bit so sensitive is the machine - so I trust it. The values I get with badminton rackets are about 5 units lower then those measured by Yonex precision scan and Victor machines according to the videos/data possible to see online for example on racket reviews on YouTube. I get around 73-74 for 4U (100zz and 88d) unstringed and around 4 more for 3u. LiNings Turbocharging 75c which is a 3u head heavy 87.5g racket gives me a value of 80.5-81.0 kg-cm2 unstringed and 85.5 with liningnr.1 and one overgrip over original grip. I don't get nowhere near those numbers over 90 stringed no matter which 3u racket I tried. I talked to the manufacturer and they laboratory measured badminton rackets and agree that the numbers from commercially available machine are about 5 SW units (kg-cm2) too high. Open for discussion.
     
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  10. Ales Berce

    Ales Berce New Member

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    Here are some other measurements for example. Stringed Ax88d is in the 78 kg/cm2 range.
     

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  11. Ales Berce

    Ales Berce New Member

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    Tennis racket ATP specs head heavy - Tecnifibre tf40 stringed. Sw around 360 kg/cm2 which is correct.
     

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  12. s_mair

    s_mair Regular Member

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    There’s not a lot to openly discuss tbh since nobody else will be owning the same machine. What does the manufacturer say regarding the reasons for the deviations with badminton rackets? I mean… that’s a pretty significant difference to the values measured be the commercially available machines.
     
  13. SSSSNT

    SSSSNT Regular Member

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    As long as the discrepancy is consistently around ~5 kg-cm2, why does it matter if the Yonex or Victor scanner is inaccurate?
     
  14. s_mair

    s_mair Regular Member

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    Two options:
    1) the existing machines from the big brands are wrong
    2) their own machine is the one which is inaccurate

    And if it’s 2 (which is more likely tbh), then something seems to be wrong with their measurement method or the design of the machine. And if I was the manufacturer, I would want to find out what and correct it instead of keep on selling a product that delivers wrong results.

    If I spent money (and I guess quite a lot of it) for a device that is supposed to measure swing weights, then I’d expect it to produce correct results. Period.
     
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  15. Asmo

    Asmo Regular Member

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    I guess a way to further narrow down the issue would be to compare with more machines than the two you mention. There is for example Babolat racquet diagnostic center that I think is pretty common.

    Does the Yonex and Victor machines give the same values within margin of error? If another third (or more) machines agree with the other two it would be difficult to draw any other conclusion than that yours gives too low values for some reason. On the other hand if there is significant difference between other machines I guess that means that swing weight machines don't give reliable data that can be compared between different machines. The youtube channel badminton guide that does racket tests claim that swing weight machines don't give useful data but don't offer any further explanation. So I'm a bit skeptical of that claim. It's my understanding that it's a pretty widely accepted metric.

    In any case if the data is consistent as you say at least you should be able to reliably compare different rackets you test yourself. I don't know how many you have access to and have been able to test but myself and I'm sure others would be interested in seeing your measurements if you would like to publish them.
     
    #75 Asmo, Apr 18, 2022
    Last edited: Apr 19, 2022
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