Racquet Mod Formulas: Matching Specs

Discussion in 'Racquets' started by Amone, Sep 25, 2006.

  1. Duzza

    Duzza Legend

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    Conflict between 2 spreadsheets?

    Help me out please, they show a different swingweight, unless the swingweight at 10cm is different?..
    [​IMG]
    [​IMG]
     
    #51
  2. FitzRoy

    FitzRoy Professional

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    I don't know if the cause of your disparity is a problem in the formula or not; it might be. I do know that you aren't going to be able to get the Safin setup with the racquet you're using, because you can't increase swingweight by 37 adding 5 grams to a 348 gram racquet. If you want to match the swingweight and balance of the Safin setup, you'll have to do so with a higher static weight. That's one of the problems of matching his specs - it's hard to do with a lot of the stock player's racquets because they start out with a similar weight but have lower swingweights.
     
    #52
  3. Amone

    Amone Hall of Fame

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    I do know one thing, and that is that your setup there is theoretically impossible; the racquet stops at 68.5, one of the weaknesses of my spreadsheets is that it allows that to come up.

    Yes, I realised that there were disparities, though not that high. Perhaps there's something bigger wrong with mine, I'll need to get in touch with Steve H. or TravlerAjm about the swingweight formula for the original.
     
    #53
  4. Duzza

    Duzza Legend

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    So I'll follow Steve's spreadsheet for this test and say it is 344 swingweight. Thanks, I noticed some of the figures go outside impossible too but that makes perfect sense. 5 grams pfft.
     
    #54
  5. andrew_b

    andrew_b Rookie

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    OK, help please? First, though, thanks for taking the time to provide this to the community! You've obviously put a bitof work into it, and you're not afraid to admit parts have discrepancies and to work to address them.

    So, I played with it with my racket settings and a setup I'd like to try out:

    weight: 340.48g
    Balance: 32
    Swingweight: 335

    Final weight: 352.48
    Final balance: 32
    Final swingweight: 365
    weight mass 1: 7
    weight mass 2: 5

    The above give me locations of (roughly) 14 and 57, which is OK.

    I, too, get a pretty big difference in swingweight when I plug the starting values, weights, and locations into Steve's spreadsheet. It ends up saying the swingweight is 346.

    Sorry I can't post the images like someone else did, don't know how to do that. Any idea why the swingweights are so different, or which one is closer?

    Thanks,
    Andrew
     
    #55
  6. BlackJesus

    BlackJesus Rookie

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    First of all thanks for this usefull tool. The spreadsheet tells the location where adds the weights but I'd like to know how long the pieces of lead tape must be. Thanks
     
    #56
  7. BlackJesus

    BlackJesus Rookie

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    #57
  8. Amone

    Amone Hall of Fame

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    If I could get that to work, BlackJesus, I probably wouldn't have done much more than adapt it to my own uses. But to be honest, I am completely uncapable of meeting that spec.

    The weights assume 'concentrated mass.' In other words, if you must use strips, they can be as long (Or short) as you like, but make sure the center of them is at the point my tool specified.
     
    #58
  9. BlackJesus

    BlackJesus Rookie

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    Thanks a lot Amone :)
     
    #59
  10. Amone

    Amone Hall of Fame

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    If only I felt that helping you would truly give back to the learning I've recieved from the greats of Talk Tennis, or half of it, then I would welcome your thanks with the deepest gratitude. But I haven't, not with the sum of everyone whose seen this spreadsheet and been helped out.

    So instead, I shall reply: "No, thank you."
     
    #60
  11. Duzza

    Duzza Legend

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    Andrew, if the 2 spreadsheets don't agree then it's impossible I've found. If you try to get too big a swingweight it may not work and Steves spread is pretty accurate(to about 0.03 off) so 2 things you can do: Lower the desired swingweight unfortunately, or mess around with the mass in location 1(the one in white) until both spreadsheets agree
     
    #61
  12. Duzza

    Duzza Legend

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    #62
  13. stules

    stules Rookie

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    Hi
    I have taken a few of the formulas that have been on various threads lately,
    and combined them into a more more useable format.
    Thanks to all that contributed. Instructions are included particularly Travlerjm, Amone, and TonyB. Should be self explanetory.
    I hope this helps............
    download it here
    http://www.badongo.com/file/1604939
    You have to go to the bottom of the page, and read the instruction.

    I figure you have Excell on your pc.

    open the spreadsheet.

    There is no need to copy the formula. Across the bottom of the page are 'tabs. I have inserted about 10 popular racquets there, with the specs off TW. click on the tab, and mod away to your hearts content.

    When you wish to use a new racquet,
    'right click' on any tab at the bottom of the page,
    click 'copy sheet'
    tick the sheet you wish to copy
    'ok'
    'right click' on the new tab and rename to the desired name.

    The blue fields need to be filled out, ie if your racqet length is 69.5cm, you need to insert that number in the blue square.

    Fill out the blue 'weight added' squares with grams of lead at a distance from the butt (both figures can be varied) but leave the space blank or with a '0' in it if you don't place lead there. Negative numbers work as well, eg if you trim down the grommets, weigh them before and after, and place the difference as a minus figure at the average distance from the butt where you trimmed.

    TW's figures are close, but they are averages of that racquet, and not for your specific one. ie if you have a 4 5/8 grip it may be heavier, and slightly more head light. With this in mind I weigh the actual racquet I am modding, measure its actual balance point (with overgrip and dampener on) and check the SW using the pendulum method (as per the bottom of the spreadsheet) and then insert these figures into the start of the spreadsheet instead of TW's. Either way is reasonably close.

    Please follow these instructions, and hopefully it will be reasonably self explanatory. If you have any difficulties, please say so, as you won't be the only one. I have tried to label everything on the spreadsheet to make it useable without complicated instructions.

    PS, I don't think there are any mistakes, but caveat emptor...
    Regards Stuart
     
    #63
  14. Duzza

    Duzza Legend

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    Hey stules nice work, what is the quality index? Also i didnt like the way it rounds up on grams added and fyi a standard racquet is actually 68.58 cm ;) and why would you remove the grip and not add a new one on? And why does, with the balance if you have 12.5 inch balance equal 8.5 points? If its a standard 27 inch racquet surely the balance is (13.5-12.5)*8? Also this one also involves trial and error unlike Amones. Maybe if you asked him if you could include his work in yours? What i mean is with Amones you can choose the desired swingweight, balance and then mix around with the 1st location of weight until you find places that work.
    eg. [​IMG]
     
    #64
  15. stules

    stules Rookie

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    Hi Duzza
    Hope you find it useful.
    what is the quality index?
    http://www.racquetresearch.com/complete_idiot.htm

    Also i didnt like the way it rounds up on grams added and fyi a standard racquet is actually 68.58 cm
    Actually not... I measure the racauet and use the actual length in cm's and mms.

    why would you remove the grip and not add a new one on?
    Two reason, to remove abut 13gm from the total weight, and hence give me more room to customise before coming up against my total weight barrier.ie, if the total weight is 343gm and my target total is 346, I can only add 3 gram to the racquet, not much of an adjustment. If I remove the grip, I now get about 16 gram to add anywhere to achieve my atarget weight. Second reason is that I like the feel of the 'sharper edges of the handle with just an overgrip only. It feels to me easier to change grip positons. Personal preference. I buy a 4 5/8, then take off the grip, add an overgrip and have a 4 1/2 handle.

    And why does, with the balance if you have 12.5 inch balance equal 8.5 points? If its a standard 27 inch racquet surely the balance is (13.5-12.5)*8?
    Easy answer, just adjust the Racquet lenght field to 69cm , if it is a 27" racquet. THat example is 68.58cm ie not 27". hence the discrepancy

    Also this one also involves trial and error unlike Amones. Maybe if you asked him if you could include his work in yours? What i mean is with Amones you can choose the desired swingweight, balance and then mix around with the 1st location of weight until you find places that work.
    I find trial and error not too hard. I know how much weight I have to play with ie 330 starting weight, aiming for 346, I know I have to add 16 gm.
    Preference is at least 6gm at 3/9 for stabilty, then I play with thel last 10 to get the total swingweight and balance, which is the juggle. Try it, not too time consuming.
    Regards Stuart
     
    #65
  16. Amone

    Amone Hall of Fame

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    Well, after more consideration, I noticed what caused the problems, and why there were problems:

    Having a low resultant-SW caused it to just plain overshoot the numbers, for whatever reason. The Balance and Weight results, however, were approximately perfect.

    The cause of this was my original equation: The part of the formula I used for weight placement was horrendously over-simplified, and I'm working now on a new one, using a more proper balance marker.

    A new sheet should be out within a matter of hours.

    EDIT: No, not tonight. I will spend some time on it tomorrow in my blow-off classes for the day.
     
    #66
  17. Duzza

    Duzza Legend

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    Thanks for replying

    Fair enough, I just thought it would be a waste of time filling in the numbers of removing a grip and then putting it back on, with an overgrip only of course it makes sense.

    But adjusting the CM length does nothing different because you're equation for calculating the points involved inches, ie. 27*2.54
    EDIT: Hmm I'm a little confused by my own work now, don't worry about it. ALSO: Where do you get the (/0.3) from? Like your equation is Half the length minus the balance point from the buttcap divided by 0.3. I'm sorry but I'm not familiar with why the 0.3 is there. Something to do with the Inch/CM conversion?
     
    #67
  18. stules

    stules Rookie

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    0.3 is 3mm ie 1/8" ie 1 point
    I'll look into the 27" equation. Get back to you on that.
     
    #68
  19. stules

    stules Rookie

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    But adjusting the CM length does nothing different because you're equation for calculating the points involved inches, ie. 27*2.54

    Not sure about that 27. I don't have that number in any equations at all. Just the length that you nominate in the blue box. Its then halved as the basis for the mid balance point.

    If you have modified the sheets equations after unprotecting it, you can always download it again.
     
    #69
  20. Duzza

    Duzza Legend

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    Wouldn't it be 0.3175 then?
     
    #70
  21. stules

    stules Rookie

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    Yep it would indeed. My mistake.
     
    #71
  22. mareli63

    mareli63 New User

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    I notice in Steve's spreadsheet one field called "balance" and one "pro balance". What is the difference between these 2? When I do the Safin setup which is 6.6 HL what balance should I consider? the pro balance or the normal balance
    Thanks,
     
    #72
  23. palikero

    palikero Rookie

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    Amone, so make this simple for me, in plain English.
    Where on the racquet is Weight 1 Location? (Like, how many inches up from the end of buttcap is it? Is Weight 1 Location on the handle?, on the throat?) ... Same question for Weight 2 Location...

    Once I locate on the racquet where Weight 1 and 2 Locations are, I am suppose to add Weight 1 Mass amount of lead tape (in grams, I assume) to this point?

    So confused.
     
    #73
  24. Amone

    Amone Hall of Fame

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    The first answer I'll give you isn't an answer at all. The formula's a waste. Doesn't work. It's wrong. I've been working on a new one, but having gotten this close and failed, it's a little difficult.

    The second is that whatever answer you get in the box marked 'weight 1 location' and 'weight 2 location,' divide them by 2.54 to get the number of inches from the butt cap they are. In they're current form, they're the same number, but in cm.
     
    #74
  25. jace112

    jace112 Semi-Pro

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    spreadsheet is no more available :-(
     
    #75
  26. Amone

    Amone Hall of Fame

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    It didn't work anyways, Jace. I'm sorry. As much as we disagree, if you'd like I can get back to work on it for you. If you want the non-working version, then I could send it to you if you'd like. soulcutterx13@yahoo.com

    EDIT: Never mind, I'm trying to fix it anyways. For a second there I sounded kinda pathetic! ^_^;
     
    Last edited: Dec 29, 2006
    #76
  27. jace112

    jace112 Semi-Pro

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    Yes, we sometimes disagree, but it was just to improve our knowledge ;)

    I'm also doing some kind of SW and other tennis tools spreadsheet, I was looking for some Trav's formulas (SGPR...). I'll post this tool next week. And maybe we'll merge our files?

    Wish you the best for 2007

    jace from Paris
     
    #77
  28. Amone

    Amone Hall of Fame

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    Same to you, Jace. I do have most of those formulas available, if you'd like I can post them here.
     
    #78
  29. jace112

    jace112 Semi-Pro

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    THX! here's my email address : jace_dehodossy (a) hotmail.com
     
    #79
  30. gd!

    gd! Rookie

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    Hi, unfortunately your link and file is no longer available. Appreciate if you could mail it to me --> go_deep@web.de

    Thanks!
     
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