Constant pull vs Lockout

Discussion in 'Stringing Techniques / Stringing Machines' started by Irvin, Aug 2, 2011.

  1. fortun8son

    fortun8son Hall of Fame

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    I don't think tensile strength is the only factor here, or perhaps I should say initial tensile strength.
    Nylon and polyester will continue to elongate as long they are under tension. I think you will find that a pre-stretched string no longer has the same tensile strength as the virgin string. The molecular bonds between the polymer strands shear and slip, eventually acting like the pizza cheese.
    Steel is different(suspension bridge analogy). Once it settles in, it stays there. It's molecular structure is uniform.
    Yes, its tension can change, even increase, with temperature changes, but it's tensile strength does not.
    Just ask any guitarist about the difference between tuning a nylon string guitar vs. steel strings.
     
    #51
  2. Irvin

    Irvin G.O.A.T.

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    Come one that is nonsense. I will make a video later to explain how to use a lockout to get a CP result. Got to go now but check in later.

    Irvin
     
    #52
  3. True Gut

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    Looks like I stirred things up good! I like the debate, and I haven't given up yet. ;)
    I have to respectfully disagree with you - at least partially, anyway. The amount of the load determines whether they will stretch to the breaking point. Not just any load will do. If the load is under the tensile strength, a break is not gonna happen. Do you think if you hang a five pound weight on a tennis string it will eventually break it? A one pound weight? A one ounce weight? A 1/10000 of an ounce weight? At some point the weight just isn't heavy enough to permanently move those molecules around. That point is the limit of the string's elasticity. Beyond that it will start to permanently narrow and stretch before it breaks - that's the plasticity part of the stretching. But both are properties come into play to determine the ultimate tensile strength.

    The jury's out on this one for me. I don't see how a pre-stretched string will realistically have a different tensile strength than a virgin string. It will if you don't put it under load, but as soon as you do that, you've levelled the playing field. The way I think about it is, once you put the virgin one under tension, it will stretch, and at some point before it snaps it will match the pre-stretched one for reduced tensile strength since both are then stretched strings. So effectively they have the same tensile strength.
    Steel or nylon, they both have elasticity, plasticity and tensile strength properties. They both play by the same general rules when under tension. Pull hard enough on either one and they will stretch and deform and eventually break. Heat up either and your tensile strength will start to suffer at some point. Way before they melt, they will get soft and gooey and the tensile strength will drop off in both.
    You might think so, but I'm not making this stuff up - hop over to wikipedia and read about it for yourself and let me what you think: tensile strength, plasticity, elasticty.
     
    #53
  4. True Gut

    True Gut New User

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    Which part is nonsense? Or do you mean all of it?
    I never said you couldn't get a CP result on a LO machine, but I would like to see how you do it with only one pull per cross or main on the LO machine. And no matter what happens with this thread, if we get another Irvin video out of it, we all win. :)
     
    #54
  5. Irvin

    Irvin G.O.A.T.

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    That is exactly the part that is non-sense. You can pull the string more than once with a lockout. As a matter of fact if you use a constant pull and the time between when you pull first and the time you clamp off is different for each string you have the same tension on each string but when you pull longer you end up with a string that is stretched farther therefore they are not constant. If you pull with a crank and 5 seconds later or whatever time you choose you pull again you can actually pull about 3" of string more than the initial pull. Once you stop pulling tension the lockout locks out and does not stretch the string any more so you will end up with a more constant tension on all strings. I am testing a way of making a higher quality video and it is taking much longer to load up should be ready shortly. Sorry the same old boring southern draw for audio. LOL

    Irvin
     
    #55
  6. Irvin

    Irvin G.O.A.T.

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    All tennis string will continue to stretch as long as the pulling for remains constant. Some more than others assuming your tension is high enough to stretch the string. So if you have a constant pull the string stretches. As soon as you isolate the constant pulling force the string will not stretch and will continue to lose tension.

    Irvin
     
    #56
  7. Irvin

    Irvin G.O.A.T.

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    #57
  8. rjw

    rjw Professional

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    Personally, I think its baloney.

    Why pull twice? why not pull 50 times or more? Maybe I could string a whole racquet with 5' of string if I pull on it enough?

    I've strung my racquet while double pulling every pull, and it ended up feeling like crap. It lost the whole feel that I normally get from a LO machine.

    IMO, bad idea especially with stretchy strings like OGSM.....

    If there's NO stretch left in the string, how is it going to play and stretch when a ball makes contact?

    jmo

    You can keep the cp machine...not for me
     
    #58
  9. Power Player

    Power Player Talk Tennis Guru

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    You are exaggerating it big time..Most people clamp off each string in 10 seconds or less...the CP does not come close to over stretching the string in that time and is instead very very consistent if you keep a rhythm.
     
    #59
  10. Irvin

    Irvin G.O.A.T.

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    I am not over exaggerating anything. If you wait about five seconds and pull tension again the string will stretch another 2 mm. I am not pulling any harder than a constant pull will pull as I pulled at 57 lbs in that video. If a constant pull does the same thing for 5 seconds it will stretch the string 2mm too. If it does not it is not a true constant pull.

    Irvin
     
    #60
  11. Power Player

    Power Player Talk Tennis Guru

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    I was talking to the poster after you not you.
     
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  12. rjw

    rjw Professional

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    yes, that would be me...

    my point is that double pulling of soft stretchy strings might not be the greatest idea. I've strung 2 sticks, back to back, same tensions, same stick, same string (OGSM), but I double pulled on one and not the other and the results were very different. One played great and the other felt like a board.
     
    #62
  13. GlenK

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    It's kind of like the Toyota commercials.. just buy a Camry. lol...
     
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  14. Irvin

    Irvin G.O.A.T.

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    I think some are missing the point. I was showing you how to get a lockout string job to feel like a constant pull. IF YOU WANT TO DO THAT. I realize some don't and that is fine.

    Irvin
     
    #64
  15. rjw

    rjw Professional

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    I'm just messing with you Irvin....:twisted: for some reason, ogsm 17g and double pulls didn't agree with me.
     
    #65
  16. Up&comer

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    With a constant pull, which are generally elcteic, the pull speed is the same. The extra pull of 5 seconds or so may make a difference of a couple pounds, but that's better than the possible changes of different speeds of pulls.
     
    #66
  17. tes

    tes Rookie

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    Is this the same rjw who posted this less than two months ago????

    What should I be looking for when buying a used one?

    Is this machine considered decent?

    First time machine for me, no exoperience, looking to spend under $500...is this a good way to go?

    Would be used to string 4 racquets , once a month

    Thanks

    WOW... and already messin' with Irvin... yup, I think I'll listen to what rjw has to say instead of Irvin now that he has gone through a couple of string jobs off is first reel of OGSM.
     
    #67
  18. rjw

    rjw Professional

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    That would be me...totally newbie, but still able to voice an opinion...
     
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  19. True Gut

    True Gut New User

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    Thanks for the new video, Irvin. It's really great how you take the time to make those and share with everyone. And I actually think we are saying the same thing - except for your point above about the string breaking if you leave your CP machine turned on a long time. Being hard-headed, I am going to take another shot at convincing you that your hypothetical string will be just fine on your CP stringer for as long as you want to pay the power company to run it.

    I'll assume you believe a 55 lb pull on a CP would break a string within five years, and see if I can get you to change your mind with a little imaginary experiment.

    You take two pieces of identical string - same length, gauge, brand, etc. You string one in a racquet, measure the tension afterwards at 65 lbs and put it in a corner for 5 years. When you pick it after 5 years, the string isn't broken, but the tension is way down, say at 55 lbs. You agree it wouldn't be broken, right? There are plenty of racquets sitting in closets to make this point a no-brainer.

    Now take that second string and hang a 55 lb weight on it (the simplest CP machine of all) and leave it for 5 years. Does it stretch out until it breaks or not?

    For the answer, compare what happens with the two strings. You put 65 lbs of tension on the first string originally, and it was never subjected to less than 55 lbs of tension for 5 years. The second string actually had life easier than the first one, because it never had more than 55 lbs of tension on it in five years. Both strings have the equivalent of at least a 55 lb weight hanging on them for the same amount of time. Both are at exactly 55 lbs tension 5 years later. The second one isn't going to break if the amount of strain on it over the same amount of time is less than the first string's. Both strings will be just fine.

    Convinced? Or just more of my nonsense?

    If you still aren't convinced, your new video offers proof, too. You showed that each time you wait and pull, the distance the string stretches decreases. Imagine how tiny the stretch will be after 10 pulls - 100 pulls - 1,000 pulls - 1,000,000 pulls. Eventually the stretch is so smalll it just isn't a factor any more. The string effectively stops stretching under the weight. If your string isn't stretching enough to be measured any more, it ain't gonna break.

    Q.E.D.

    Bonus question for anyone who actually even cares at this point. In the example of the two strings, which string will be longer after five years? <insert evil 6th grade teacher laugh here>
     
    #69
  20. fortun8son

    fortun8son Hall of Fame

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    I suppose it would be simple enough to try a Mythbusters-type experiment with a length of string, a yardstick and a 55lb dumbbell. Take daily measurements to see if it continues to stretch and at what rate and if it ever breaks.
    I'm not gonna do it, though. :)
     
    #70
  21. Irvin

    Irvin G.O.A.T.

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    'True Gut' I tried something a little different. I hung a 5 lb dumbell on a #32 rubber band. If it falls I win if it doesn't you win. I will give it a day two at the most.

    [​IMG]

    It looks like it is almost on the floor but it is actually about 6" above the floor.

    Irvin
     
    Last edited: Sep 13, 2011
    #71
  22. SW Stringer

    SW Stringer Semi-Pro

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    Bogus test, it really proves nothing either way.
     
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  23. Irvin

    Irvin G.O.A.T.

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    It proves that gravity is stronger than a rubber band. So far though after almost 3.5 hours the rubber band is winning. But if the weight does not touch the floor and take the pulling force off gravity will win.

    Irvin
     
    Last edited: Sep 13, 2011
    #73
  24. Irvin

    Irvin G.O.A.T.

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    4 hours 46 minutwes and the wait is over. The rubber band snapped.

    Irvin
     
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  25. Up&comer

    Up&comer Hall of Fame

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    What was the point of that test?
     
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  26. Posture Guy

    Posture Guy Professional

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    Perhaps to show he needs to buy a better quality of rubber band?
     
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  27. SW Stringer

    SW Stringer Semi-Pro

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    Bogus test now becomes so much BS.
     
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  28. Irvin

    Irvin G.O.A.T.

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    Why experiment?

    The longer anything elastic is subjected to a constant force the more it stretches. The longer it stretches the thinner it gets. The thinner it gets the lower the tensile strength (and the lower the elasticity of the elastic.) When the tensile strength is less than the force applied your elastic will break.

    No amount of experimentation can ever prove me right; a single experiment can prove me wrong. - Albert Einstein

    I did the test to prove you could break a rubber band with a constant force lower than the tensile strength. If I had put a 1 pound weight on the rubber band it still would have broke just not as fast. If I used a #64 rubber band with the 5 pound weight it would have broke too just not as fast.

    Let's get back to the original idea of the post Constant pull or lockout question. If you have followed the thread I hope you realize when a tennis string is pulled it starts to lose tension immediately after the full pulling force is applied. The loss of tension is directly proportional to how long the force was applied and how long it has been since it was applied. If you, or y our stringer, use a constant pull and clamp the string as fast as you can you defeat the purpose of the constant pull. And if you double pull your strings on a lockout you can achieve just a tight a string bed as you can with a constant pull.

    Irvin
     
    #78
  29. SW Stringer

    SW Stringer Semi-Pro

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    Abjectly wrong on many levels, the interested student can do a cursory examination of elasticity and the elastic limit to understand why. Nice quote from AE but it doesn't make your assertion any less wrong.

    "[FONT='Arial','sans-serif']The difference between genius and stupidity is that genius has its limits.[/FONT]
    [FONT='Tahoma','sans-serif']- Anonymous[/FONT]

    [FONT='Arial','sans-serif']When asked to spell Mississippi the boy asked, "The river or the state?"[/FONT]
    [FONT='Tahoma','sans-serif']- Anonymous[/FONT]

    [FONT='Arial','sans-serif']Some drink from the fountain of knowledge - others just gargle.[/FONT]
    [FONT='Tahoma','sans-serif']- Anonymous"[/FONT]
     
    #79
  30. rjw

    rjw Professional

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    the rubber band on this thread has snapped ...and from the getgo
     
    #80
  31. fortun8son

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    Time to revisit the original post.
    The question is: Is CP better than LO?
    The answer is: No.
    Mounting, clamping, and stringing technique are all far more important in achieving a consistant, quality stringjob than the mechanism used to pull the strings.
    You can get both great and lousy results using either.
    Is an electronic tension head faster and less physically demanding?
    Of course it is...and a lot more expensive, too!
     
    Last edited: Sep 13, 2011
    #81
  32. rjw

    rjw Professional

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    Very well put

    While I have very limited experience in all this, I do have a bit. I watched my racquets being strung on a very expensive CP machine and I will never go that route again, even though I now realize that the operator actually did a good job.

    There's nothing that feels as good in my hand as a racquet strung on an LO machiine, as long as the pulls are not too fast and consistent.

    While I've gotten a lot better at sizing things up, weaving crosses, etc I actually take as much or more time than initially, because the results are worth the extra time and effort. You can really feel how the string is stretching. It's something that every stringer should FEEL, and this cannot be done on an electric CP machne.

    jmo
     
    #82
  33. fortun8son

    fortun8son Hall of Fame

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    I like the feel of pulling the crank, too.
    If I was stringing 15 racquets a day, I'd want one of those fancy jobs!
    Oh, my aching back and feet!
     
    Last edited: Sep 13, 2011
    #83
  34. mad dog1

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    when i owned my gamma 6004 LO crank machine, a friend let me borrow his stringway MS200dx manual CP machine to try out. i strung 2 rossi F-200s - 1 on each machine w/ gosen syn gut. the one done on the gamma LO machine, i strung up 10% higher in tension than the one i did on the stringway CP machine. my technique was slow, deliberate and consistent. when i took both sticks out to playtest, i far preferred the feel of the stick strung on the stringway CP machine. it was this experience that convinced me to get a CP machine but there were some minor things about the stringway that i wasn't crazy about. i decided that CP was the feel i preferred so i ended up w/ a babolat sensor. the resulting feel of stringbed on the racquets that come off the babolat feel like the CP stringway strung racquets than the gamma crank strung racquets. so i sold the gamma and kept the sensor. :)
     
    #84
  35. rjw

    rjw Professional

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    I guess that's why there are hundreds of different racquets, hundreds of different strings and dozens of stringing machines.

    Everyone has their preference......it's all a matter of personal taste and whatever floats your boat
     
    #85
  36. Irvin

    Irvin G.O.A.T.

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    A direct quote from an older USRSA Stringer's Digest:

    "Your stringing machine can make or break your stringing business. Be sure to thoroughly investigate the machines in which you're interested. Ask the distributors about warranties, availability of replacement parts and basic maintenance. Pay particular attention to the vise, tensioner and clamps of the machine - a machine which distorts frames or breaks strings won't be of much use to your stringing business. A professional, top quality machine can maximize every frame's playing potential.

    Editor's Note: An intense controversy exists among stringers regarding the professional ability of stringing machines. Many stringers believe that a knowledgeable and careful stringer can manage "perfect" string obs on any machine. Other stringers maintain that a professional quality machine is a prime factor in producing a professional string job.

    In working with the frame companies and aware of the exorbitant number of mangled frames strung on inadequate machine and returned "on warranty," the USRSA believes that a professional quality machine is paramount in producing a professional Job. The USRSA, while an unbiased organization, strongly recommends that stringers who provide a professional service to paying customers utilize the best equipment available."

    Irvin
     
    #86
  37. Posture Guy

    Posture Guy Professional

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    the technical aspects of this discussion are way beyond me, but from a simplistic point of view, here's a question:

    Irvin, are you saying that ANY gauge of rubber band when pulled by ANY amount of weight will eventually break if given enough time?

    I don't believe that would be true. If you get the thickest rubber band your office supply store sells, and then you hang something from it that weighs half a pound, I would expect that the rubber band would stretch to a certain point, reach what I think a prior poster referred to as it's limit of elasticity, and then if that's at a point where the remaining tensile strength of the rubber band is greater than the weight, then the weight will just hang there statically with no further stretching and no breakage.

    am I wrong?
     
    #87
  38. Irvin

    Irvin G.O.A.T.

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    That is exactly what I am saying. What if I used two rubber bands that will give me two times the holding power. It will hold the weight longer and initially higher but I will get the same result.

    Irvin
     
    #88
  39. barry

    barry Hall of Fame

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    I still believe constant pull is a marketing term. In effect you pull tension to the desired poundage, you camp the string and you lockout the benefit of any CP. No matter how you look at it, CP is only significant if you have variable pulling clamps (not invented yet).
    I use an electronic constant pull (Wise) machine for ease, sometimes pre-stretch, but for as CP producing a “better” string job, one would have to define “better”. To be honest, I have 2 identical rackets, one I string with constant pull on, the other with constant pull off. 15 minutes on the court I can’t tell the difference. Once you have strung a few hundred rackets, the machine is insignificant of the process, and only makes the process easier. For example 360 rotations, 2 point mounting, spring assisted base clamps are more important than constant pull. An electronic tensioner is pretty well dummy proof, drop weight is a craftsman tool, and cranks are in between. Since I have all three types of tensioners, it takes me 25 minutes using the Wise, 33 minutes on the drop weight, and about 30 minutes on the crank to string a racket.
     
    Last edited: Sep 14, 2011
    #89
  40. mad dog1

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    could very well be true for you. in my case, the racquets i strung on my CP always maintain higher tension than the ones i strung on my crank. with the 2 rossi F-200s i strung, i hit w/ both of them and found myself using the one strung w/ CP. after a few weeks, i tried hitting w/ the one strung w/ the crank and the stringbed was still looser than then CP strung one and the CP strung one saw alot more play time. in my experience, the racquets i string on my CP machine never lose much tension. they lose some, but not much.
     
    #90
  41. mad dog1

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    agreed. use whatever gives you the preferred results.
     
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  42. SW Stringer

    SW Stringer Semi-Pro

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    .

    Posture Guy you are correct. With a thick enough rubber band, or enough rubber bands, the applied weight will be less than the elastic limit of the material under stress.

    How do you know if the elastic limit for a material under test has been exceeded. Answer: Plastic deformation, the material will not return to it's original shape.

    Aesop’s Fables — The Bundle of Sticks
    An old man on the point of death summoned his sons around him to give them some parting advice. He ordered his servants to bring in a ***got of sticks, and said to his eldest son: “Break it.” The son strained and strained, but with all his efforts was unable to break the Bundle. The other sons also tried, but none of them was successful. “Untie the ***gots,” said the father, “and each of you take a stick.” When they had done so, he called out to them: “Now, break,” and each stick was easily broken. “You see my meaning,” said their father. Union gives strength.

    Even before rubber bands were invented, Aesop knew that with enough bands the weight would hang forever.​
     
    #92
  43. Posture Guy

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    Irvin, ok, then let's take this principle to an extreme. I take a thick rubber band. I then hang a paperclip to the end of it. Eventually, you believe the rubber band will deform to the point that it's going to break?

    Your posts seem really solid and I enjoy reading you so I don't mean this in an antagonistic or disrespectful way, but that seems ridiculous to me.
     
    #93
  44. diredesire

    diredesire Super Moderator

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    Sorry, but this logic/reasoning doesn't make sense to me. While you may have more measurable benefit from "mounting, clamping, and stringing technique" (which, IMHO, is only partially true), what difference does it make when we're talking about ONLY tensioning? For the sake of argument/discussion, we ASSUME all else is equal. As far as my point of view, clamping is the biggest variable out of those you mentioned. Technique is operator dependent, so it should remain the same between systematic changes. Mounting is generally cost limited, and I would point out that the frame mounting is also operator dependent. While you can "pre-lengthen" frames and do weird stuff IF you want to, it's not common.

    Clamps (specifically drawback) are systematic variables. You can pre-load clamps to minimize drawback, but it is still native to the system.

    Long story short: you can't abstract away tensioner differences by saying "other stuff" is more important. That's not the purpose of the discussion. Do I agree with you? Yes. You have to define better, but you have to have the right reasons, IMO. My reasons are: they're different and can only be compared with strict criteria.

    Yes and no. Rubber bands are both good and bad comparison materials for strings. While they're great for picturing elasticity and tensile strength vs stretch concepts, they're terrible in terms of realistic comparison due to material properties.

    While I understand the point Irvin is trying to make, and he's using a simplistic model to do so, I don't think the material is right. Rubber in general will undergo drastic changes in material properties when dry and/or brittle. Nylon is much more stable. We're also talking about significantly different tensioning situations, here. The difference between a constant-pull pull and a lockout pull is going to be a few mm of pull length and a fraction of a second (max 2s) tensioning duration.

    The rubber band example is exaggerated by design, but I'm not sure how much sense it makes in terms of our discussion.

    What if you had 1K rubber bands holding up a 1 lb weight? Rubber bands would break due to age/drying out before their "tensile strength" would cause them to break [yes, the tensile strength will drop as a material property due to age/degradation, but I don't think nylon would exhibit the same properties on a comparable time scale].


    All said and done: I'm just making counter-points for the sake of discussion, I don't personally think one system is strictly "better" than the other. They both have pros/cons, and I prefer the feel of a lockout, but not everyone does.
     
    #94
  45. Posture Guy

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    but if the core point of the thread is that double pulling on a lockout machine will result in less initial tension loss than single pulling, I can buy that. That does seem like a reasonable assertion to me.

    I've seen threads here recommend that if you have had your racquets strung on a constant pull machine at a certain tension and then switch to a lockout, you'll need to bump the tension up maybe 5-10% to achieve a similar feel. I don't know if that's true or not, but it seems reasonable.
     
    #95
  46. Irvin

    Irvin G.O.A.T.

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    OK let's go to an even farther extreme. I believe if you tie a rubber band on your strings for a vibration dampener, given enough time it will dry rot and fall off under it own weight. Any force you exert on the rubber band will cause it to reach it elastic limit or yield strength sooner.


    Irvin
     
    #96
  47. Irvin

    Irvin G.O.A.T.

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    Yes you are right that is just like putting the paper clip on the one rubber band. But then you are going to the same extreme. Let's get more realistic. I will put enought weights in a 5 gallon bucket to bring the weight up to 65 lbs and suspend it on a tennis string. Will the string break? I think it will.

    Irvin

    EDIT: Problem is more than likely it will break whereever I tie a knot or clamp the string but it will break.
     
    #97
  48. Irvin

    Irvin G.O.A.T.

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    How can that possibly be reasonable. 5% or 10% is a big difference. At 60 lbs that is 3 lbs. Why not just double pull at the tension you want then there is no guessing?

    Irvin
     
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  49. diredesire

    diredesire Super Moderator

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    But how long will it take? I'd guess on the order of > 1yr. This is assuming like you said that there are no weak spots. (String jobs typically don't break at knots unless it was operator error, so it's a valid assumption). Also assume the string isn't subject to ridiculous temperature/environmental variance [this includes prolonged exposure to sunlight {on the order of >8 hrs a day}].

    I think the paperclip example is a little extreme, but the tensile strength of the nylon is really, really high (relatively speaking).
     
    #99
  50. Posture Guy

    Posture Guy Professional

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    well I used the paperclip example for a reason. Irvin seems to be asserting that ANY weight on something elastic will, given enough time, eventually distort it enough to snap.

    I do not believe that to be true.

    and snapping because the material dehydrated or 'rotted' is a completely different argument than the one we're discussing.
     

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