Tension differentials: electronic vs crank machines

Discussion in 'Stringing Techniques / Stringing Machines' started by Slapper, Apr 28, 2018.

  1. Slapper

    Slapper Rookie

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    I am currently stringing with a tension differential of 5 lbs (crosses strung looser). I use full poly.

    When I get my racket strung on an electronic machine (Wilson Baiardo or Tecnifibre TF8000), I am able to confirm that the tension differential is present by measuring the change in the length of my racket. It is -3 mm. The results have been consistent for different poly strings and different tension setups (48/43 lbs and 45/40 lbs). This is what I want.

    However, when I get my racket strung on a crank machine (Gamma Progression ST II) by a different operator, the racket length is either unchanged or very slightly longer (+0.5 mm), indicating that the desired tension differential is not present, despite the tensions on the machine being set at 48/43 lbs.

    What might be the reason(s) for this failure on the crank machine?

    The crank machine is calibrated and the operator uses the double-pull method.
     
    Last edited: Apr 29, 2018
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  2. Shroud

    Shroud G.O.A.T.

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    I only string on ECP machines but i wouldnt be surprised if the different operator is to blame. Look on these boards lots of pro stringers regard ANY hoop deformation as a problem and a sign of a bad job. They tend to be more arrogant than doctors sometimes so wouldnt be surprised if they just ignored your request thinking you wouldnt notice.
     
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  3. Slapper

    Slapper Rookie

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    While that may be true, in this case the crank machine is operated by my good friend with whom I have had detailed discussions about stringing and differentials. In fact, he started stringing his own racket with a differential after I explained the theory and benefits. So my racket was definitely strung at 48/43 lbs as I requested.
     
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  4. Shroud

    Shroud G.O.A.T.

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    Do his frames shorten?
     
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  5. Slapper

    Slapper Rookie

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    We have not measured them, but I will do so at the next opportunity.
     
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  6. Shroud

    Shroud G.O.A.T.

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    I certainly cant think of a reason for much difference based on the tensioning method. The differential should be there regardless of the string method.
     
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  7. Slapper

    Slapper Rookie

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    That's what I would have thought, too. But apparently it is not the case.

    If the pulling method shouldn't make a difference, what about mounting, clamping etc?
     
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  8. Karma Tennis

    Karma Tennis Hall of Fame

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    Pulling tension on crosses through mains with a LO machine (even with double pulling) will be very different than doing it with a CP.

    In any case the mounting system and clamping system on a $9000 machine will probably be somewhat better than the one on a $700 machine. Pulling one string might not be that different, but doing a whole racquet may well be. Especially if there are different operators.
     
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  9. Shroud

    Shroud G.O.A.T.

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    Could be but all that hopefully would be consistent between the crosses and mains so cant see that making a difference. Were the strings the same on both machines??
     
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  10. Slapper

    Slapper Rookie

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    If so, then I would have thought that the lock out machine would result in a lower tension on the crosses, which would produce a greater tension differential. But that is the opposite of what I have observed.

    That's what I suspected, and I am wanting to know the actual cause, in the hope that we might be able to address the problem.
     
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  11. Shroud

    Shroud G.O.A.T.

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    Sure that all makes sense but we are talking about differentials and tension between the mains and crosses. So what if the machines are different? There should be a differential regardless the type of machine if the stringer is somewhat competent.

    Said another way if you string 48/43 on anytype of machine there should be some shortening of the frame if the stringer is competent.
     
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  12. Slapper

    Slapper Rookie

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    Yes, strings were the same on both machines.
     
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  13. Slapper

    Slapper Rookie

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    As far as I can see, there are only three possibilities here: either mains are looser than intended, crosses are tighter than intended, or both. But how could this unintended result be caused by operator and/or the machine?
     
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  14. Shroud

    Shroud G.O.A.T.

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    Bad knots would affect mains tension more than cross tension I think so it could be the knots. It would be hard to see crosses being higher than intended on a lo. Its a conundrum for sure.
     
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  15. esgee48

    esgee48 Legend

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    Did the stringer double pull the mains and the crosses? Or just the crosses? The other issue is whether LO can remove inter string friction betw mains and crosses. With an eCP, you can move the crosses while the string is being pulled; not so with the LO.
     
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  16. Shroud

    Shroud G.O.A.T.

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    E48 thats the quandry. As you suggest the Lo shouldnt get the crosses as tight as a eCP so there should be more of a differential. Though by double pull i took it to mean tension twice, not pull two strings at the same time.
     
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  17. Slapper

    Slapper Rookie

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    Did double pull on mains and crosses.
     
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  18. esgee48

    esgee48 Legend

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    You interpreted my 'double pull' correctly, i.e. pulling a single string twice. Guess we wait for OP to reply with what the stringer did.

    OP replied. So, my guess just went out the window. It should have resulted in a 'squashed' frame rather than a narrowed frame.
     
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  19. Slapper

    Slapper Rookie

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    Yes, tension twice, not pull two strings at the same time.
     
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  20. Slapper

    Slapper Rookie

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    Suppose the clamps are no good and there is slippage after releasing the tension head. In this case, there might be more slippage of the mains and less slippage of crosses, because string-string friction would limit the amount of slippage with crosses. There is no string-string friction when the mains are strung, so mains slippage would be the greatest (if there is any slippage at all).

    On the lock out machine, the racket length was unchanged with string gauge 1.30, but was +0.5 mm with string gauge 1.25 (same string). I guess this is consistent with the above hypothesis, since there would presumably be more slippage with a thinner string.
     
    Last edited: Apr 29, 2018
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  21. Dags

    Dags Professional

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    Modern frames are pretty robust, and those aren't particularly high tensions. I think your assertion here is somewhat flawed.
     
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  22. Irvin

    Irvin G.O.A.T.

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    If I were going to point fingers I would think the one that shortened your racket were causing the problem / issue. Many frames using the Stringway Tension Advisor have a tensionsion differential dependant on the frame being used and the frame is not distorted. What type frame are you stringing?
     
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  23. Slapper

    Slapper Rookie

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    The problem/issue, as I have defined it, is the lack of shortening of the racket when using the lock out machine. I want the change in racket length to be -3 mm, as it is when strung on the electronic constant pull machines.
     
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  24. Irvin

    Irvin G.O.A.T.

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    I understand that, but asking someone to change their mounting procedure to shorten the racket is easier said than done. Your friend is going to have to change his procedure to allow the racket to compress. They may be a learning process that may or may not produce the desired results at first. When the frame is unmounted there may be an issue getting the frame off the machine, which could cause problems.
     
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  25. jim e

    jim e Legend

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    Simple.
    If you want machine to change racquet length by -3mm then increase tension of main strings by a few lbs more and your goal should be accomplished.
    The main strings are longer so with a constent pull machine it should stretch the longer strings more than a lock out machine, where a shorter string would be less differential between machines.
    Two variables can effect differences between cp and lo machines. One is type of strings ,more elastic will stretch more and
    two would be the string length. main strings are longer.This is documented in the USRSA handbook of stringing techniques under differences between LO and CP machines
    Since you have stringers use same string and tension, longer main strings will stretch more with CP.
     
    Last edited: Apr 30, 2018
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  26. Slapper

    Slapper Rookie

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    OK, but why do you think the mounting would be preventing compression of the head? Are you suggesting that the mounts at 12 and 6 o clock were tighter on the lock out machine compared with the electronic machines?
     
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  27. Irvin

    Irvin G.O.A.T.

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    @Slapper If someone asked me to do that I’d refuse the job. Not trying to be rude but it would best best for everyone to just go to the stringers that are deforming the racket the way you like it.
     
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  28. Irvin

    Irvin G.O.A.T.

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    Not necessarily tighter but farther apart. The 6&12 supports will need to be moved in or the side supports moved out.
     
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  29. Slapper

    Slapper Rookie

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    But of course.

    However, I would like to know the actual reason for the difference between the machines/operators. I'm curious and would like to identify/fix the root problem, if possible.
     
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  30. Irvin

    Irvin G.O.A.T.

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    @Slapper if all the supports are moved in so they are just touching an unstrung racket your goal should be accomplished.
     
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  31. Slapper

    Slapper Rookie

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    Asked you to do what? I have not said that I plan to ask my friend the stringer to do anything.

    Obviously, I would go to the other stringer with the electronic machine, but it's not convenient.
     
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  32. jim e

    jim e Legend

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    Simple.
    If you want machine to change racquet length by -3mm then increase tension of main strings by a few lbs more and your goal should be accomplished.
    The main strings are longer so with a constent pull machine it should stretch the longer strings more than a lock out machine, where a shorter string would be less differential between machines.
    Two variables can effect differences between cp and lo machines. One is type of strings ,more elastic will stretch more and
    two would be the string length. main strings are longer.This is documented in the USRSA handbook of stringing techniques under differences between LO and CP machines.More elastic strings and larger size racquets would require more tension to compensate with a LO.
    Since you have stringers use same string and tension, longer main strings will stretch more with CP.
     
    Last edited: Apr 30, 2018
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  33. Slapper

    Slapper Rookie

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    Yep, by tighter I meant farther apart.

    Of course, all of this is assuming that the mounting is the problem, which might not be the case. However, it seems like a reasonable hypothesis and I will ask my stringer friend about it.
     
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  34. Slapper

    Slapper Rookie

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    Sounds reasonable. Did the USRSA check whether this holds true when using the double pull method on a lock out machine?
     
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  35. jim e

    jim e Legend

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    No.
    But I cannot see exactly how your "double pull" would completely compensate.
    A LO machine set for say 60 lbs. and you pull it twice at 60 lbs. should not equal the same as a CP machine pulling constantly at 60 lbs .for a while before string is clamped. They cannot be exactly the same.
    Seems easier and a little more reasonable to just pull once and increase tension some to compensate as close as possible and of course even that would not be the same. .
    Want it the same, then have similar machine CP string it all the time
     
    Last edited: Apr 30, 2018
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  36. Slapper

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    Do the USRSA data give any indication of approximately how much tighter the mains would have to be pulled on a lock out machine to compensate? I realise there are all sorts of variables here. Just looking for a ball park recommendation. 5-10 lbs?
     
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  37. Irvin

    Irvin G.O.A.T.

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    Impossible to determine, for a string to stretch a certain % you must use a higher tension or pull for a longer per of time. But you’re not talking about stretching (deforming) the string you’re talking about deforming (stretching) the frame.
     
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  38. Shroud

    Shroud G.O.A.T.

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    Well read the op. He takes the same racquets and strings to one stringer and at 48/43 gets a shortened hoop. The other with the racquet being the same and strings and tension the same doesnt produce the shortened hoop. The racquet is a common variable so its flawed to think the racquet has anything to do with it.

    Only variables that are different are machine type and stringer
     
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  39. Irvin

    Irvin G.O.A.T.

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    @Shroud by changing machines there are a lot of variables that can also change. Like turntable stiffness, clamp drawback, and string pull. My guess is the machine is the root of the problem but a similar overall deformation can be obtained if that’s what the client wants and the operator is willing to try changing methods.
     
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  40. jim e

    jim e Legend

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    no doubt it is machine or stringer.
    Like said, just increase tension for mains to get similar 3mm deformation as that is what OP wanted.
     
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  41. Dags

    Dags Professional

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    I read the OP. There appears to be an assumption that the stringer who doesn’t deform the racquet is at fault. With the information provided, I’d suggest that the issue is more likely with the electronic machine and/or stringer.

    I appreciate that the OP prefers the results he’s getting from the electronic machine, but that’s a different matter.
     
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  42. Slapper

    Slapper Rookie

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    The result is consistent for different electronic machines operated by different stringers. Also, a tension differential with looser crosses would be expected to shorten the length of the racket (if there is any change in length at all), and that is what happens when the racket is strung on the electronic machines. On the lock out machine, the racket length is either unchanged or even slightly longer, which is not what we would expect with looser crosses.

    Taken together, this suggests to me that the result from the electronic machines is closer to the intended 48/43 lbs than the result from the lock out machine. In other words, I think the 'issue' is with the lock out machine and/or operator.
     
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  43. Slapper

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    Double post.
     
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  44. Steve Huff

    Steve Huff Legend

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    My guess is that his friend is pulling 6 and 12 tighter when mounting the racket s Irvin suggested, so it doesn't deform as much (called "stretching" the racket by some). That, or the low tension used. Generally, a LO has an end result of approx 10% lower than the end result of a constant pull. Maybe the frame doesn't distort at those low tensions by the LO as it may be just under the threshold of the tension needed to distort it.
     
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  45. Chadillac

    Chadillac Legend

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    Double pull as in pull each string twice or is pulling two strings on one pull?
     
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  46. Slapper

    Slapper Rookie

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    That’s a good point about the threshold. I did wonder about that.

    I get no distortion with mains at 48 lbs on the lockout but I get distortion with mains at 45 lbs on the electronic machine. So, if 48 lbs on the lock out machine is equivalent to 43 lbs on the electronic machine, and if the threshold is between 43-45 lbs, then it could explain what I have observed. I think it is possible but not the most likely cause.
     
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  47. Slapper

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    The former.
     
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  48. graycrait

    graycrait Hall of Fame

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    @Slapper have you considered getting your own stringing machine?
     
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  49. Irvin

    Irvin G.O.A.T.

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    Dah?

    EDIT: how come it took an old retiree to think of that? LOL
     
    Last edited: May 3, 2018
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  50. Slapper

    Slapper Rookie

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    Yes, it probably will come to that eventually. But for the next 6 months or so I’ll have to rely on others to string for me.
     
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