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  1. #103
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    sure! try it tmr and provide your feed back

    btw ever considered dividing the method into to types of grip, the short grip and the long grip?

    i use the short grip more often as i play doubles almost all the time now, this is when the effect of a weight on the buttcap is the most significant, in affecting the agility of the swing/head

  2. #104
    Regular Member visor's Avatar
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    Quote Originally Posted by visor View Post
    Hi @vajrasattva

    Yes, if you add tape to the head, it will alter the bp and of course increase the head wt proportionally. Try this on one of your rackets and you'll see that the equation is true for both before and after adding tape!

    Additionally, if you add a coin to the bottom of the handle (as in your method to reduce bp), then something important occurs in the ways we both measure "head wt" differently.

    In your case of placing the fulcrum in the middle of the handle
    , the coin will lift the head frame off the scale a little bit, thus making head wt lower.

    In my case, my fulcrum is at the very tip of the handle
    , and the coin happens to be there at the very tip too, so the coin has no effect at all on the head wt!

    Please try this yourself if you can't visualize it. Then only can you see the significance of the difference in our methods of measuring head wt.

    In my method, the elegant equation holds true whether you add weight to the top or bottom or any where in between. Whereas your method, I doubt it.

    Here are some measurements I just took...

    The calculated bp according to that equation is very very close (within 1-2mm) to the measured bp, thus confirming the validity of the equation for the method that I use to measure head wt
    .

    Bare wt Bare head wt Playing wt Play head wt Play bp measured Play bp calculated
    RKEP XP70 84.2g 37.7g 93.1g 41.0g 297mm 296mm
    + 0.7g tape head (84.9g) (38.4g) 93.8g 41.7g 298mm 300mm
    + 0.7g tape head
    + 7.0 g coin bottom
    100.8g 41.7g 280mm 279mm
    Alright, for those who don't see this intuitively, I finally drew a diagram to show how and why head wt, total wt, and bp are related to each other in the equation:

    (Head wt / Total wt) = (bp / Total length ie. 675mm)


    Name:  Head wt.jpg
Views: 820
Size:  18.8 KB

    Does it help? Comments?
    Last edited by visor; 03-13-2013 at 12:54 AM.

  3. #105
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    Quote Originally Posted by visor View Post
    Hi @vajrasattva

    Yes, if you add tape to the head, it will alter the bp and of course increase the head wt proportionally. Try this on one of your rackets and you'll see that the equation is true for both before and after adding tape!

    Additionally, if you add a coin to the bottom of the handle (as in your method to reduce bp), then something important occurs in the ways we both measure "head wt" differently.

    In your case of placing the fulcrum in the middle of the handle
    , the coin will lift the head frame off the scale a little bit, thus making head wt lower.

    In my case, my fulcrum is at the very tip of the handle
    , and the coin happens to be there at the very tip too, so the coin has no effect at all on the head wt!

    Please try this yourself if you can't visualize it. Then only can you see the significance of the difference in our methods of measuring head wt.

    In my method, the elegant equation holds true whether you add weight to the top or bottom or any where in between. Whereas your method, I doubt it.

    Here are some measurements I just took...

    The calculated bp according to that equation is very very close (within 1-2mm) to the measured bp, thus confirming the validity of the equation for the method that I use to measure head wt
    .

    Bare wt Bare head wt Playing wt Play head wt Play bp measured Play bp calculated
    RKEP XP70 84.2g 37.7g 93.1g 41.0g 297mm 296mm
    + 0.7g tape head (84.9g) (38.4g) 93.8g 41.7g 298mm 300mm
    + 0.7g tape head
    + 7.0 g coin bottom
    100.8g 41.7g 280mm 279mm
    True. What you are doing is actually "Summing Moments" and it does have solid background from Statics..

    The moment of a (point load) is naturally affected by the distance from the point you where want to sum moments.

    The only complication is that the racket weight is not evenly distributed along its length. Nonetheless, any distributed load can be replaced by an equal point load...

    see if what your doing relates to the principles in the link: http://www.engin.brown.edu/courses/e...ts/moments.htm

  4. #106
    Regular Member visor's Avatar
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    Quote Originally Posted by bakulaw View Post
    True. What you are doing is actually "Summing Moments" and it does have solid background from Statics..

    The moment of a (point load) is naturally affected by the distance from the point you where want to sum moments.

    The only complication is that the racket weight is not evenly distributed along its length. Nonetheless, any distributed load can be replaced by an equal point load...

    see if what your doing relates to the principles in the link: http://www.engin.brown.edu/courses/e...ts/moments.htm
    Thanx for the link... but way over my head.

    Actually, this equation/relationship was only accidentally noted when I first started this thread. But despited being aware that my approach is overly simplistic in assuming the racket as a uniform beam, the equation still works very well to 3 significant digits.

    Except for certain rackets like Voltrics with those head heavy "Tri-Voltage" bulges at the top skewing weight distribution to the top.

  5. #107
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    2x Carbonex 880 Tour Pro with additional string and grip.

    Length: Both 665 mm (I thought all rackets are 675 mm)

    1. Weight: 100 g. Bp 280 mm. Head weight: 280/665*100= 42.1 grams

    2. Weight: 102 g. Bp 286 mm. Head weight: 286/665*102= 43.9 grams

  6. #108
    Regular Member j4ckie's Avatar
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    Quote Originally Posted by SSSSNT View Post
    2x Carbonex 880 Tour Pro with additional string and grip.

    Length: Both 665 mm (I thought all rackets are 675 mm)

    1. Weight: 100 g. Bp 280 mm. Head weight: 280/665*100= 42.1 grams

    2. Weight: 102 g. Bp 286 mm. Head weight: 286/665*102= 43.9 grams
    Old rackets and some inferior companies' are shorter sometimes. Reason: there's only a maximum length&width stated in the rules (675mm x xxx), so theoretically you can make your racket as short as you want. Why anyone would make it shorter though is a complete mystery to be as it shortens your lever (and thus decreases your power) as well as moving the sweet spot compared to a normal length racket which will cause quite a few mishits if you change between the two.

    Regarding the adding weight to the bottom thing: it might feel quicker/lighter because you're handling a higher overall weight and thus the head wt doesn't feel as heavy in comparison. That feel is just that though - a subjective feeling. Your muscles won't be any stronger or quicker than without that added weight, so they'll move the racket just as quickly as before, if not a little slower (as the weight added at the bottom will increase the moment of inertia if you grip the racket high).

    If you're interested in testing that, take an adjustable dumbbell (those metal ones where you put on weight plates) and swing it around without any weights on the grip. Then add a weight below your hand (important that you grip at the same spot both times) and swing it again - are you really faster now?

  7. #109
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    Quote Originally Posted by j4ckie View Post
    Old rackets and some inferior companies' are shorter sometimes. Reason: there's only a maximum length&width stated in the rules (675mm x xxx), so theoretically you can make your racket as short as you want. Why anyone would make it shorter though is a complete mystery to be as it shortens your lever (and thus decreases your power) as well as moving the sweet spot compared to a normal length racket which will cause quite a few mishits if you change between the two.

    Regarding the adding weight to the bottom thing: it might feel quicker/lighter because you're handling a higher overall weight and thus the head wt doesn't feel as heavy in comparison. That feel is just that though - a subjective feeling. Your muscles won't be any stronger or quicker than without that added weight, so they'll move the racket just as quickly as before, if not a little slower (as the weight added at the bottom will increase the moment of inertia if you grip the racket high).

    If you're interested in testing that, take an adjustable dumbbell (those metal ones where you put on weight plates) and swing it around without any weights on the grip. Then add a weight below your hand (important that you grip at the same spot both times) and swing it again - are you really faster now?
    shorter racket = lower stresses.
    I believe this is mainly influenced by the available materials.

    Technically speaking, better materials with higher yield strengths do enable the racket to withstand higher stress; thereby allowing the design for longer rackets....

  8. #110
    Regular Member visor's Avatar
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    4.1 The racket shall be a frame not exceeding 680 mm in overall length and 230 mm in overall width consisting of the main parts described in Laws 4.1.1 to 4.1.5 as illustrated in Diagram C.

    Looks like it's 680mm max length.

  9. #111
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    Nanospeed 200 with string and grip:

    Weight 98 grams. BP 294 mm. Length 675mm

    Head weight: 294/675*98 = 42.7 grams


    Bravesword 12 with string and factory grip:

    Weight 91 grams. BP 295 mm. Length 675 mm.

    295/675*91 = 39.8 grams


    I'm still not sure what this all means

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    Regular Member demolidor's Avatar
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    Quote Originally Posted by SSSSNT View Post
    2x Carbonex 880 Tour Pro with additional string and grip.

    Length: Both 665 mm (I thought all rackets are 675 mm)

    1. Weight: 100 g. Bp 280 mm. Head weight: 280/665*100= 42.1 grams

    2. Weight: 102 g. Bp 286 mm. Head weight: 286/665*102= 43.9 grams
    Quote Originally Posted by SSSSNT View Post
    Nanospeed 200 with string and grip:

    Weight 98 grams. BP 294 mm. Length 675mm

    Head weight: 294/675*98 = 42.7 grams


    Bravesword 12 with string and factory grip:

    Weight 91 grams. BP 295 mm. Length 675 mm.

    295/675*91 = 39.8 grams


    I'm still not sure what this all means
    You should also weigh the actual "head weight" like in post #1 to compare against your calculations . Otherwise there is no point to it

  11. #113
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    Quote Originally Posted by demolidor View Post
    You should also weigh the actual "head weight" like in post #1 to compare against your calculations . Otherwise there is no point to it
    I did and it seems pretty accurate. NS200 is showing 43 grams while BS12 is showing 40 grams.

  12. #114
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    Can anyone here tell me the significance of head weight and swing weight? I currently interpret headweight as an estimate for ease of use, however I have a feeling that this is incorrect.

    For example. I measured the specs on three different rackets with a karakal PU super grip + strings.

    Vapor Trail Tour: 88.9g playing weight, 40.6g head weight, 310mm BP
    4U Victor artery tec Ti-99: 89.7g playing weight, 40.1g head weight, 301mm BP (modded to this with 1g lead tape at 1' and 11' positions)
    Lethal 70: 98.8g playing weight, 43.6g head weight, 297mm BP.

    The VTT and AT Ti-99 have very similar head weight and are only off by 1g in overall weight, however the victor artery tec feels significantly more head heavy.
    The Lethal 70 is only about 3g heavier in headweight, but it feels tremendously more difficult to use than either the VTT or At ti-99.

    How should i interpret the above data?

  13. #115
    Regular Member visor's Avatar
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    First off, 3g more head wt is a lot!
    It can mean the difference
    between a bs12 and a vztf!

    I can already feel a difference in about 0.3g, so no wonder 10x that is much more noticeable.

    Your ti- 99 head wt, is that measured with the lead tapes on?
    Last edited by visor; 03-15-2013 at 03:22 PM.

  14. #116
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    Hi Visor, thanks for the input!
    Yes, the Ti-99 weight is with lead tape on. Just an experiment to increase the headweight to equal that of the VTT. I was surprised when it felt a lot more head heavy even when it had 0.5g less headweight.

    Could headweight be used as a generalization of racket ease of use (Independent of frame shape/shaft stiffness/etc)?

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    Quote Originally Posted by bobbinbette View Post
    Can anyone here tell me the significance of head weight and swing weight? I currently interpret headweight as an estimate for ease of use, however I have a feeling that this is incorrect.
    already answered:

    Quote Originally Posted by amleto View Post
    It [head weight] doesn't [help with knowing swing weight], really. It's just another static measurement like BP that isn't related to rotational movement so it doesn't accurately describe the feel of a swing where you should instead consider the moment of inertia.

  16. #118
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    Quote Originally Posted by visor View Post
    Alright, for those who don't see this intuitively, I finally drew a diagram to show how and why head wt, total wt, and bp are related to each other in the equation:

    (Head wt / Total wt) = (bp / Total length ie. 675mm)


    Name:  Head wt.jpg
Views: 820
Size:  18.8 KB

    Does it help? Comments?
    it's just a re-hash of my sketch and tbh, I don't really think the relationship is intuitive since 'head weight' isn't a real thing.

  17. #119
    Regular Member visor's Avatar
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    Quote Originally Posted by bobbinbette View Post
    Thanks for the input!
    Yes, the Ti-99 weight is with lead tape on. Just an experiment to increase the headweight to equal that of the VTT. I was surprised when it felt a lot more head heavy even when it had 0.5g less headweight.

    Could headweight be used as a generalization of racket ease of use (Independent of frame shape/shaft stiffness/etc)?
    Strange, perhaps the ti99 is less aerodynamic?

    That's
    what I was hoping. An appproximation
    of swing wt.

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