String Tension - Evening Out from String to String

Discussion in 'Stringing Techniques / Stringing Machines' started by LOBALOT, Feb 14, 2018.

  1. LOBALOT

    LOBALOT Rookie

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    I have been reading all the posts about proportional stringing and have even performed my string length measurements and prepared my spreadsheet to give it a shot.

    One item I was wondering about was tension changes from string to string after stringing (so to speak as per half it is all just one string). I believe I have read posts on here that tension does not really even out from string to string.

    However, I have observed after stringing a racquet in the evening and then checking on it the next morning that the strings seem to "set up". The looser strings are more taut then they were in the morning. Even the outside mains on a 2-piece stringing are tighter.

    Do others observe this?

    Is this due to tension from tighter strings balancing with less tight strings on the same half of string (assuming 2 piece)?

    Is this due to some other factor?

    Thanks
     
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  2. esgee48

    esgee48 Legend

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    My last mains always feel looser and they do not get any tighter as I play with the frame. Put a tennis ball on your racquet in the center of the string bed. Note that the ball will always hit multiple string of the mains and crosses. Those strings all go around the edge of the frame, so string friction comes into play. Hitting adjacent strings also mean that the forces of the ball impact are countered by the strings going in opposing directions, so the the tension cannot even out. It can if you hit one string, but not multiple ones. Yes, the tension will equalize a lot if you hit around the edge of the frame. But they have a hard time doing it near the center. HTH.

    What racquet are you using? An ESP or Spin effect frame? I can't really see this happening in 16x18 on up to 18x20.
     
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  3. LOBALOT

    LOBALOT Rookie

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    Multiple different racquets. For example, Babolat Puredrive + FSI I just restrung on Sunday. 16x19.

    I don't have 2 fish scales to do it but if I take a 10 foot piece of wire wrap it around a pole (like a pre-stretch) and have a buddy with one scale lean back and pull 80 pounds and attach it to a wall and I take another scale and pull 60 pounds and attach it to the wall. If I come back the next day, depending on friction and elasticity I wouldn't find say 70 pounds on the one scale and 63 pounds on the other?
     
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  4. LOBALOT

    LOBALOT Rookie

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    Well I learned something today and I was incorrect. See below.

    https://en.wikipedia.org/wiki/Capstan_equation

    Not that I feel like doing the math but from what I am reading the friction around the pole provides an exponential benefit, so to speak, helping the lower tensioned side counteract the higher tension on the other side of the pole. An example would be rigging for sails on a boat.

    I still wonder why the strings seem to settle/firm up on a racquet as it sits after stringing. I have heard this from several people that string racquets and I see it myself.
     
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  5. esgee48

    esgee48 Legend

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    When I string up a frame at 52#, I expect Racquet Tune to show 52 - 51.8 # when it comes off the stringing machine. I am using strings that I have measured string factors for and are accurate. If I let the frames rest 24 hours and test the frame again, it may say 51.6 - 51.5#. This is due to strings relaxing or stretching. I can't see how a string could get tighter. I do realize that RT measures the overall string bed in the middle, but what you describe does not seem possible in the real world.

    I will theorize that perhaps what you feel is the strings in a semi fluid state as it is stretching and relaxing. After the strings reach equilibrium, the semi fluid state has to return to an amorphose or semi crystalline state otherwise you will have a set of noodles in the frame. That alone would account for the stiffer feel. It does not mean that the tension is higher.
     
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  6. LOBALOT

    LOBALOT Rookie

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    I concur about string tension increasing. That is impossible. I normally see a decrease on RacquetTune of a pound. My thoughts are/were that over several strings this tension was given up to other strings lower in tension so those would increase (i.e. the outer strings getting a bit more taut).

    I still have no explanation for this as I have discussed this with others that see it.

    Shall I start my next post about how on my stringer, each time I use string from a certain manufacturer, if I convert the beeps produced when the machine reaches tension into morse code I get the lyrics to "Radar Love" by Golden Earring?



    It happens every time... I can't explain it!
     
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  7. 1HBHfanatic

    1HBHfanatic Hall of Fame

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    tnx for this, physics just gave me a round house kick to the face as well..

    this settles it for me "a smaller force can hold a larger force by pulling arround a post"..
     
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  8. Irvin

    Irvin G.O.A.T.

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    I've heard for a long time that the USRSA said that strings so not equalize in proportional patterns. Not sure if they really said that or not but let's just assume they did and they were LIARS. Damn I hate liars. LOL If strings really do even out over time then we should be able to double pull because the tension would even out. We would not have to increase tension for tie off strings because it would even out.

    But on the other hand what if they did say that and they were right? Then double pulling would be a bad thing, and maybe it would be a good idea if we employ procedures to eliminate drawback and tension loss.
     
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  9. LOBALOT

    LOBALOT Rookie

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    Thanks, something is still not adding up for me though as I have been playing this sport for 48 years and from observation I have seen it time and again... That is a freshly strung racquet left for a day "setting up"/"firming up"/"Locking into a Grid" whatever term you want to give it. I even feel it playing with a racquet freshly strung vs. a day or two older.

    "Locking into a grid"... Maybe it is the forces in the other plane of direction like that video of yours on stringing crosses and how they tend to push the string into a smile. Perhaps after strung you have all those humps pushing up and down on the mains locking them in place. I am not sure.

    This does give me more confidence in what I am reading as I head down this path of trying proportional stringing. i.e. the various tensions applied to a piece of string of will remain independent.
     
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  10. LOBALOT

    LOBALOT Rookie

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    Yes, I don't even what to tell you what I studied in college!!!! While not the exact same area of study close enough to have known better!
     
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  11. Irvin

    Irvin G.O.A.T.

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    @LOBALOT was there a question hidden in your post #9?
     
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  12. LOBALOT

    LOBALOT Rookie

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    Hi Irvin:

    I am just wondering if perhaps the forces in the other direction could then explain what I see. I am not sure.

    There has to be an explanation.

    Thanks
     
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  13. Irvin

    Irvin G.O.A.T.

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    I still do not understand your question if there is one. I know that some people like a racket after a day or so or some players actually step on their string bed to get it to soften up before it plays at its best. If you drop your tension so it plays best when it is strung it becomes too soft very quickly.

    My solution to that is to prestretch the string before your racket is strung and or use a prestretch feature on the stringing machine.
     
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  14. LOBALOT

    LOBALOT Rookie

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    Yes, I have seen players stand on their strings to loosen them if they feel they are too tight. That is not my question specifically because one can find in general that they have requested a tension for that particular day's playing conditions and what they want so they feel they need a looser setup.

    My question specifically is what is the root cause of the changes in a string-bed between when the racquet is strung and a period after that causes the strings/string-bed to feel more taut then it did right after coming off the stringing machine. Simply when one takes the racquet off the stringing machine and leaves it for say 24 hours.

    If it were just me saying this then I would chalk it up to my being nuts. However, I have heard this time and again from others who play as well over the years.

    Maybe it is just me and the others who I have spoken with. I don't know.
     
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  15. esgee48

    esgee48 Legend

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    I think you are confusing DT with ref tension. They are related, but not linearly. For DT, interstring friction between mains and crosses play a big factor. Static COF is generally bigger than dynamic COF by 2-5x. Temperature change towards colder will also stiffen up string bed. Not so sure if string lubricant coating drying up or being wiped off has any effect, but that can certainly affect COF.
     
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  16. LOBALOT

    LOBALOT Rookie

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    Hi Irvin:

    Maybe that is where to begin the question.

    Do you have customers that prefer to play with their racquet right after it is strung and others that prefer to wait a day before using the racquet?

    Thanks for your help.
     
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  17. Irvin

    Irvin G.O.A.T.

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    Yes both ways. I have a good friend that told me one time he likes it best just before it breaks. That was on a changeover. He said to remind him to get his racket strung because it was playing great. He went out to receive serve and it broke on the very first service return.
     
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  18. LOBALOT

    LOBALOT Rookie

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    Thanks, that is funny... So I like my racquets to sit for a day before I use them.

    So what do we think it is with the string bed that is changing for one player to like a racquet right off the stringer and another wanting to wait before using it?
     
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  19. jwocky

    jwocky Rookie

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    Does a string bed reach some equilibrium state involving tension balancing? Yes.

    Take the simple case of just main strings – this can be modeled as a multiple capstan/pulley system. Tensions on adjacent strings will achieve an “equilibrium” state after factoring in string material elasticity, string-to-frame coefficients (function of grommet specs and material), tension used, frame deformation characteristics AND time. This “equilibrium” will not result in identical free main string tensions on adjacent mains, but the main strings will settle or reach a state of equilibrium.

    Now introduce interwoven crosses, for example, on a 16 main strings racquet just a simple experiment with over/under 8 mains and only string one out of four crosses (1, 5, 9, 13, 17). If the crosses are at really low tension then they provide some additional resistance to the mains in the “main strings equilibrium” process, and they encounter their resistance from the main strings to achieving a “cross string equilibrium.”

    Continuing this way it is fairly straightforward to see that an equilibrium process does occur and the time to equilibrium is dependent upon string pattern density, string material characteristics, tensions used, frame deformation characteristics, string-to-frame coefficients (function of grommet specs and material), etc.

    Ultimately, I would rather build a skill set that is flexible and adaptable, and not too sensitive to imperceptible differences in DT/SBS. I prefer to just go out and play instead of giving myself a list of excuses based on tens of variables where I have less control in determining tolerance than I think I do.
     
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  20. Irvin

    Irvin G.O.A.T.

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    I’ve seen Technatic test of lockout tensioner so many times it isn’t funny. All it shows is that tension start dropping in a racket after it is strung. Fact of life no way to get around it. Tennis string starts relaxing immediately after it is strung. As the string relaxes tension falls. After a day evidently it falls to a tension you like. As you play with it it falls more, and more ...
     
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  21. tennytive

    tennytive Professional

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    Reported for logic and common sense. ;)
     
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  22. Imago

    Imago Hall of Fame

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    As for the capstan, see this final compensation drop...

     
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  23. tennisbike

    tennisbike Rookie

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    Not sure if this is relevant.. but I noticed that the stringmeter reading can go up as well. I attribute that to temperature variation. I could be measuring a higher reading after getting off the stringer but in the morning when the temperature is cooler. But I should have record the temperature at the time of taking measurement. So still I am just speculating.
     
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