Thread: CONTEST: Guess the tension loss (with MORE PRIZE!!!)

1. Originally Posted by istringforyou
For a direct pull on the 1st top/bottom cross, what is the max tension you guys here have done?

My personal experience is nothing more than 28LB be it using a commonly used tennis starting knot, Parnel + 2 half hitch or 3 half hitches. Seriously a direct pull on the starting knot is highly dangerous. One of the interesting methods i ve seen is using a starting clamp on b9 (for bottomup) and after doing a handful of crosses, pull the string from b9, clamp it and tie off at b6/b7. I have personally tried this once in 30LB on BG80 and it seems to retain tension well until you hit it for 2hrs and immediately get 2-3LB off.
agree on the starting clamp. but the question is then, how much tension do we lose from doing the knot afterwards? seems like another experiment is in order.

2. Originally Posted by istringforyou
@Kwun

Between pre-weave and weaving as you tension, which do you believe has less tension loss?
a full pre-weave of both mains and cross, there will be string friction when tensioning the mains. compared to weave as we go, there is no string friction at all. this will resulting in tension loss in the mains and the effective tension is lower. furthermore, less time is spend on the machine if one do pre-weave (as you do fast tension->tension turnaround) so that allows less time for the string to settle.

as for tensioning the cross, the tension loss from string friction should be similar if not the same. however, same argument for fast tension->tension turnaround, so there will be less time for the string to settle as well.

so my guess would be the effective final tension on pre-weave will be lower. furthermore, the main/cross ratio will have mains even lower when compare to cross.

3. Originally Posted by a|extan
this is fun

can we have another contest?

guess the tension gain?

hee...
Originally Posted by Mark A
I'd rather play "guess the pitch" - kwun strings a racket at 30 lb in Z62 or something, and we take punts on the Hz (or MHz, in that case).
we can do both, keep the suggestions coming.

4. Originally Posted by kwun
the question is, does that matter?from the tension point of view, the side strings aren't really doing any real work to hit the shuttle. so 25%, 50% loss is almost a don't care.but for mishit protection, is it better to have a lower tension to give it more of a soft buffer, or is it better to have a higher tension to give it more support when the shuttle hits here?
My vote goes in favor of a higher tension yielding greater support on a mishit. By higher I mean only up to not greater than the main tension. It's the same analogy to how adding an extra cross at the top gives you more protection. At 50% or lets say you remove it altogether being 0%, there's no "brace" to prevent the mains from snapping. Strings tend to break on mis hits at the top only because the main strings are essentially flexible one one end yet "fixed" to the frame on the other side allowing for the smallest range of travel before it gives. It's true that lower tension does mean more durability, but that only holds true when it's proportionate to the main tension. In this case, you can't have the first cross acting as a brace when the tension is that much lower. I've put this theory through vigorous testing and each time the top crosses are lower (double pulling) there's a higher chance of breakage on miss hits.

5. Originally Posted by kwun
we can do both, keep the suggestions coming.
OK, how about "pitch drop" (not the tar-in-a-funnel experiment)...

String a racket and get the immediate pitch, then take two more pitch readings after 24 and 72 hrs with the racket having been unplayed.

Or, string two identical rackets identically, play with one but not the other, and guess the tension loss difference after X amount of play.

I should be pitching to ITV - they've bought dafter sh*t than this before!

6. Originally Posted by kwun
and with this, we have a winner, is he is:

om4r_s, whose answer of 29.7lbs and 15.4lbs is the closest. only off by 3.35lbs.

CONGRAULATIONS.

honorable mention is maa2003 whose answer of 30lbs and 15lbs is off by 3.49lbs, merely 0.14 lbs from om4r_s. it was a close one.

om4r_s, please PM me your address so we can send you the price. the NBG99 will be sent to you later this month when it is release. MBS will send you the prize directly.

thank you everyone for playing this contest. we will for sure have more!
congratulation to the winner ....

the 1st measurement result really shocked me, but the 2nd measurement simply just divided by 2.
at the tennis forum, someone in his video (Irvin ?) ever mentioned that if you pull 2 string together you will get half of the pulling-tension.

really interesting contest, and thanks kwun for your effort on this measurement (maybe can be put as sticky as reference)

7. Great work kwun, as always.

So I rechecked my machine and my technique and realised a few important things about stringing especially with your findings here:

Originally Posted by kwun
the question is, does that matter?

from the tension point of view, the side strings aren't really doing any real work to hit the shuttle. so 25%, 50% loss is almost a don't care.

but for mishit protection, is it better to have a lower tension to give it more of a soft buffer, or is it better to have a higher tension to give it more support when the shuttle hits here?
1. If you do the Yonex string pattern on the main strings with flying clamps, meaning that you are coming out from bottom 9 into bottom 12 then loop around and exit from bottom 10, and you tension both the last two main strings at once then clamp off, you should be getting about half of your pulled tension at the last main string.

Practically speaking, this may not matter much or if at all as the very last main strings at the edges will hardly ever come into contact with the shuttle during play and with the friction from the two grommets at the edge, the tension loss should hardly ever creep into the second last main string. Even if there may be a little tension creep from the second last main string to the last main string, from my calculations you can just add about an average of 2lbs to your tension on your final main string before tie off to mitigate all the tension loss from the friction and subsequent tie off. Another good thing to have slightly lower tension at the very edge main strings is that the very sides of the racquet will not be pulled at such a high tension where the frame has a curve and thus have less stress on the sides especially when stringing really high tensions.

2. The same thing goes for the first cross string for both top down and bottom up string patterns. Firstly as [kwun] said, the shuttle will hardly ever come into contact with the top most and bottom most cross strings during play anyway so having then at exactly the same tension as all the other strings will not be of such importance anyway.

8. Originally Posted by Blitzzards
Great work kwun, as always.

So I rechecked my machine and my technique and realised a few important things about stringing especially with your findings here:

1. If you do the Yonex string pattern on the main strings with flying clamps, meaning that you are coming out from bottom 9 into bottom 12 then loop around and exit from bottom 10, and you tension both the last two main strings at once then clamp off, you should be getting about half of your pulled tension at the last main string.

Practically speaking, this may not matter much or if at all as the very last main strings at the edges will hardly ever come into contact with the shuttle during play and with the friction from the two grommets at the edge, the tension loss should hardly ever creep into the second last main string. Even if there may be a little tension creep from the second last main string to the last main string, from my calculations you can just add about an average of 2lbs to your tension on your final main string before tie off to mitigate all the tension loss from the friction and subsequent tie off. Another good thing to have slightly lower tension at the very edge main strings is that the very sides of the racquet will not be pulled at such a high tension where the frame has a curve and thus have less stress on the sides especially when stringing really high tensions.

2. The same thing goes for the first cross string for both top down and bottom up string patterns. Firstly as [kwun] said, the shuttle will hardly ever come into contact with the top most and bottom most cross strings during play anyway so having then at exactly the same tension as all the other strings will not be of such importance anyway.
also notice that if you do that, the 11th main is actually connected to the 9th, and any loss in tension in 11th might be carried to 9th.

not sure if that's of any significance though. hard to reason one way or another without experimenting it.

9. When i start crosses i do it like kwun starts his mains (in his video) ... clamp outside the frame on the last/first cross and pull the next one and clamp toegther. Then pull a couple more as normal, then repull the end cross and clamp/tie off as normal. That way (at least in my mind) i get the desired tension (less tie off slippage) on all the crosses.

As for the outer most mains, i have my own solution.

10. Originally Posted by _Rav_
When i start crosses i do it like kwun starts his mains (in his video) ... clamp outside the frame on the last/first cross and pull the next one and clamp toegther. Then pull a couple more as normal, then repull the end cross and clamp/tie off as normal. That way (at least in my mind) i get the desired tension (less tie off slippage) on all the crosses.
with more and more thinking, i think the method describe (with either starting clamp or flying clamp) is the best method to start the cross. the drawback is that there might be tension loss when tying the knot though.

alternative is to have a super strong knot that can take 30+lbs tension.

11. Originally Posted by kwun
with more and more thinking, i think the method describe (with either starting clamp or flying clamp) is the best method to start the cross. the drawback is that there might be tension loss when tying the knot though.

alternative is to have a super strong knot that can take 30+lbs tension.
If we're only getting half the tension on the outside string with a double pull, then we'd have to have a really sucky tie off to lose that much. I would estimate at the very worst case that you'd lose 25% from a tie off, so you're still better off that way.

Fixed clamps are certainly better for starting , since you can clamp one string in mid air, but i would still probably re pull it afterwards since i suck at starting knots :P

12. Originally Posted by kwun
also notice that if you do that, the 11th main is actually connected to the 9th, and any loss in tension in 11th might be carried to 9th.

not sure if that's of any significance though. hard to reason one way or another without experimenting it.
Yes sir, I agree.

How I came up with the +2lbs on the last main string tension is actually from your experiment right here. So assuming that coming round the bend from the 11th to the 9th you have almost zero tension on the starting end, a pull of 30lbs at 9th will give you 26.63lbs on the untensioned/free end.

26.63/30 = 0.887666667
So for a desired tension of 30lbs on the 9th,

30 = (X + 0.8876666667X)/2
X = 32lbs~

Originally Posted by _Rav_
If we're only getting half the tension on the outside string with a double pull, then we'd have to have a really sucky tie off to lose that much. I would estimate at the very worst case that you'd lose 25% from a tie off, so you're still better off that way.

Fixed clamps are certainly better for starting , since you can clamp one string in mid air, but i would still probably re pull it afterwards since i suck at starting knots :P
Yes sir, and on this other end if you do lose 25%, with the calculation I posted above, the amount you should be adding would be 4.5lbs rounded off. But as kwun as pointed out, is there really a point to have each and every string on the string bed to have exactly the same tension especially at the very ends where the shuttle will not even contact the string?

Thus I believe the +2lbs for the last string pulled formula which I just posted should be just enough to mitigate any tension loss crept into the last strings

13. Originally Posted by Blitzzards
Yes sir, I agree.

How I came up with the +2lbs on the last main string tension is actually from your experiment right here. So assuming that coming round the bend from the 11th to the 9th you have almost zero tension on the starting end, a pull of 30lbs at 9th will give you 26.63lbs on the untensioned/free end.

26.63/30 = 0.887666667
So for a desired tension of 30lbs on the 9th,

30 = (X + 0.8876666667X)/2
X = 32lbs~

Yes sir, and on this other end if you do lose 25%, with the calculation I posted above, the amount you should be adding would be 4.5lbs rounded off. But as kwun as pointed out, is there really a point to have each and every string on the string bed to have exactly the same tension especially at the very ends where the shuttle will not even contact the string?

Thus I believe the +2lbs for the last string pulled formula which I just posted should be just enough to mitigate any tension loss crept into the last strings
Well, theoretically, any tension loss will distribute some loss to the neighbor strings. I could potentially see a 4lbs decrease on the last two mains be a .1 - .5lbs decrease in the middle mains (numbers are totally random). This is nothing confirmed, but it would seem logical that it happens.

14. Originally Posted by yan.v
Well, theoretically, any tension loss will distribute some loss to the neighbor strings. I could potentially see a 4lbs decrease on the last two mains be a .1 - .5lbs decrease in the middle mains (numbers are totally random). This is nothing confirmed, but it would seem logical that it happens.
Yes sir, but do remember the friction in the grommets that led to a drop of 3.37lbs from 30 to 26.63lbs. IMHO the possible tension loss on the last two mains may be only 1lb each and that would not worry me at all.

On my next string job I shall try tensioning the last two mains separately then add +2lbs before the main tie off to see if I can feel a difference to pulling both the last two together before tie off like I usually do as my machine doesn't have fixed clamps. We have to first take note that these very side strings hardly ever contact the shuttle during play..

15. What about a starting knot?

Originally Posted by kwun
with more and more thinking, i think the method describe (with either starting clamp or flying clamp) is the best method to start the cross. the drawback is that there might be tension loss when tying the knot though.

alternative is to have a super strong knot that can take 30+lbs tension.

16. Originally Posted by Pete LSD
not big enough.

17. Originally Posted by kwun
alternative is to have a super strong knot that can take 30+lbs tension.
I really need to make a video of my starting knot...

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