I recommend to let the stringer do his work. FME even some shops don't have the most expensive and solid machines, so I recommend to pick the cross tension you want and let stringer do his work, because he knows his machine best. I couldn't do for you 2lbs difference, the racket would came out a tiny bit narrow. I need to do 1lbs difference to give you the exact shape. If the stringer uses just a 2 point machine it would be very bad to go square.
I actually string the cross with 2lbs more than the main string because: 1. during stringing the cross with constant pull, you will loose some tension here (i think that's because of the weave): http://stringing.info/2015/01/05/nur-jede-zweite-saite-ziehen-double-pull/ ps: my actual stringing machine doesn't have the function 'pre-stretch' 2. to keep the racket shaped 3. my experience during playing: if I string main=cross, I've the problem, that the main string constantly move right/left after every smash. so I've to align the String ... it's nerved and interrupted the concentration during the match! to string the cross with 2lbs more, this problem reduces!
That's a very interesting link. I think @kwun has made the same test in the past with significantly different results when it comes to double pulling the mains. We had that double pulling discussion not so long ago in another thread, I'll edit in the link when I've found it. If you go by the result of this test, you would end up at pretty much the desired tension if you double pull and simply add 15% pre-stretch. EDIT - Here you go: fastest way to string a racket.
Interesting link. It shows that I was right in my stringing method all along, even if I didn't bother measuring it My current preferred method is a 2-piece top-down (2ptd) string job where I do a CP on every single main with the desired tension and a 10% PS pull on every single cross with desired tension+0.2-0.3kg. This yields the best result on my machine, and it's very consistent to the point where two rackets strung directly after another have an almost dead even pitch after evening out for a night (and I've got very sensitive ears). I do it top-down for slightly better work flow and speed, as I can pre-weave a couple of crosses before tightening the mains that would cover the respective grommets. Favorite pattern to string is the Arc7/Arc11 (76 holes, no?). Simple reason why double pulling doesn't work without pre-stretch - friction. The grommets always introduce friction, and much more so when you pull two mains and have a) more grommets - 4 instead of 2 - and b) a less favorable angle at the top where the string is re-directed in a "U"-shape. The pre-stretch is great to overcome that friction, because it pulls harder at first, allowing you do reach the desired tension on the first string, and then drops off to CP to get the same tension on the second string and not a higher than desired one, making it much better than doing a CP at a higher tension than desired. Same process on the single-pull crosses - now you have a second source of friction, the tightened mains, which your cross will displace slightly and rub against. If you CP with the same tension as you CP'd the mains, you'll end up with a weird-feeling string job on most machines, since the overall tension of that cross will be lower than the desired tension, and lower than the mains. The CP doesn't help here, as every single main string can act as a small break, so to speak, and create a certain delta up to which the cross will not move behind it. Once you go over that threshold, your cross moves again and the friction coefficient changes (it's different for 2 static objects vs the same objects moving relative to each other, and usually smaller for the moving case). That's why pulling harder once and then relaxing can achieve the exact desired result, if the overpull (or pre-stretch in this case) is done to the correct amount. I'll actually test and see whether a 15% PS with no added tension on the crosses yields a better result on my rackets than my current method. I'm guessing it'll be virtually the same. Still feeling a bit iffy on double-pulling the mains, maybe I'll test that on my own some time, but will not do that for others without thorough testing.
No doubt it's the fastest way, but is it the better? Would you ever string a racket, where you single pull all mains, alternating between 15% PS and no PS on every other string? (because that is the result of DP'ing with 15% PS). Also, it would have been nice to see the end-result on the test, had it been not the first mains nor the first crosses. For mains, the difference may not be the greatest, but as you get closer to the frame, holes are not aligned 100% with the string, which may affect the results. And especially for the crosses, once you go a few strings up, the resistance grows (which is more or less part of the result seen when DP'ing). That is because when pulling the first cross, the friction is super low, due to the strings not being restricted in up/down movement of the previous cross. And as you move up, the mains become tighter and it will become even more evident. The proper test would have been measuring at the sweet-spot. Result would be, that single-pull would loose much more tension, and double-pull would lose a bit more tension... String roughness/thickness will also affect the results (if my hands are indeed as sensitive as I make my self think, then you can clearly feel the difference when pulling your crosses, depending on the string used (BG80, ZM65 vs slippery and thin stuff)... ----- But it's interesting for fast stringjobs that are not pushing the limit of the string (in relation to the 15% PS).
I don't think it's even up for discussion if double pulling is the better way - or even tolerable at all. I consider it cheating with unpredictable results in the end. Just look at the two different test results. One ends up with almost half the tension, the other one mysteriously close to full tension. There's just too much influence from the grommets and frame involved. However, what I do find interesting is the difference when pre-stretch is used on (single pulling) the crosses. I have noticed that I get slightly higher pings when I use 10% pre-stretch and frankly, I couldn't explain this really. But looking at the test results and considering what @j4ckie wrote regarding the use of the pre-stretch to overcome the friction on the grommets, this is starting to make sense to me.
IMO the most important thing is to keep the shape the same and this is related to the machine. I don't know, just a guess but isn't it better to string main and cross with a fixed ratio to come over the friction part instead of switching on the PS to 15% for the cross? What me made think about it is, that you not just handle the friction part, you also influence the tension loss curve for the crosses drastic, when you just pull the mains only with ECP?! A constant ratio should work more accurate regardless if you do a 20lbs or 30lbs job. 15% mean you pull 3 to 4.5 lbs over the desired tension for a short time. Please don't get me wrong, I don't have thoughts about using PS, when it's also done for the mains as well. But wouldn't this procedure lead to the same issues with very different strings for main and cross, which have a very different tension loss curve? I mean 15% is not a low percentage for PS. Anyway, as long as everybody is happy with his work and results, there is no point to discuss and we all use different machines, so the procedure must also be slightly different. Just my thoughts about adding PS just for the crosses.
Easy fact: Your string also loose tension while you string. The string don't wait to drop until you are finished. That you overcome the loss with PS a bit, results in a slightly higher ping. Should be normal.
That would be an easy explanation, you're right. I'm in general not yet sure about what to do with the pre-stretch function. I have started to use it lately (10%) on all my jobs and all strings (I surely won't bother with changing PS between mains and crosses!), but especially for the LN1 I found that it changes the settling behaviour noticeably - and not for the better. A big strength of the LN1 for me was that it starts to feel best after 2-3 hours of usage and then staying this way. With PS, the settling curve seems to be more flat, leaving the string a bit too harsh IMO. Could also be purely a mind game though. However, I think I will turn off PS with my next LN1 jobs and see if there will be a difference again. For all the big stretchers like BG65, I will for sure keep using the 10%.
At the moment I switch off PS for my own rackets. Clients get 10%. Shouldn't be an issue with BG80. FME my jobs with no PS drop slightly more at the beginning. Anyway, from my feel the PS made my rackets dropping the performance earlier, regardless what the ping says. Since I have a great feel and performance I don't mind about pings, it's just a number and even a high ping can feel dead and a lower ping can feel lively and vice versa. I stopped too much measurements...Was man nicht weiß, macht auch nicht heiß.
I stopped tracking pings over lifetime too a while ago and rely on feel alone too. And the current example proves me right - I'm sure the pings are looking "better" with less drop over time with PS. But still, the string appears to feel more lively without. So currently I tend to go without PS from here on and see if the old LN1 feel will come back. And if I do so, then I will also do it for client's rackets. Why giving them something different from what I prefer myself?
As a stringer people will call you snobby when you get too much into detail and sometimes you must accept them and talk their language. As long as they are happy, they get the same constant result. Most of my requests are below 24lbs and mostly with BG65 or ZM69F. If somebody beside my few mates would know that I restring after a few weeks, they would call my freaky crazy. IMO it really depends on the string.
You will get tighter strings (crosses) with PS, no doubt. It's not the grommets, it's the friction from all the crosses. Say for each cross you loose 0,5% of the pull (made up figure), that sums up to 10% on the far side of the frame. If you PS with 10%, you will get the "right" pull on that far side (just about), and when prestretch goes back, it will easy up mostly on the near side, giving you a tighter pull as the result, and a more balanced one. You end up with the same tension near-side, but higher tension far-side. Of course the string will settle evenly after a while (or a couple of hits). Now, without PS, you will need this extra lbs or two to even out things. Say you are trying to do 24 lbs on your cross, no PS. You pull 24, you get 22 on the far side, and 24 on the near side. After a while, you have 23 all over. I really think the article linked to above, makes a huge mistake measuring on the first cross, since this will get more pronounced at the middle or top of the frame! Constant pull also affects this, not just PS. I found, when going from lockout (crank) to Wise with CP and PS, that I needed to add less to my crosses. Basically about 0.5 - 1.0 lbs less, depending on how hard the job is. I'll go and do these measurements one of the days, I've often been thinking about it
this is my test-result: string: BG80 all main with CP: 11,5 kg all cross with PS (10%): 12,4kg from the middle: near the head:
Did you massage the cross during the pull like in a normal stringing process? Or just let the wise pull it? IMO this makes a huge difference. IMO the measurement don't measure the whole string segment and I doubt due the friction that the measuring point is at a point to guarantee the most accuracy. IMO you measure just the string from your scale to the first weaves and I think that the pulled force will increase when you go towards the tensioner. But this is impossible to measure and to rephrase my Prof. in "Messtechnik" in early days: "Wer viel misst, misst Mist." Also just using one fresh segment tend to be slightly faulty due the fact, that the segement between frame and tensioner got several times pulled, before weaved inside the frame, tensioned and clamped. So a string got previous indirect pulls due the process. Thanks for your experiment and efforts and sorry for beeing such a pea counter. I think as long as a racket comes out at same shape and plays lively we shouldn't get any headaches because of numbers. What me wonder is that the segement with less weaves (at the top) brings the lower number. But I think who ever strung on a DW knows, that some massage can drop the lever. What me also make think is that you have more crosses than mains. So the forces must compensate each other to get the same shape. That 22 mains vs. 23 cross don't apply easily spoken not the same forces in each direction should be clear. I also don't know who spread the myth that the cross must be at exact tension as the mains by measurement? For the mains you pull tension X. While you pull, the tension of pulled mains drop initial. You tie off the mains you get another drop on the mains. Also count in that due the shape the outter mains are clamped a bit away from the frame and generate a loss. Now you do your cross and add some tension (adding 1 lb, 2 lbs or 10% and PS as an option) to compensate the zig-zag of the mains, which increase the tension slightly You also need to get over the friction. I hardly doubt that the sense for stringing a racket means that each segment must be at 100% at the setted tension. I couldn't be and shouldn't be and IMO we overthink here to much about numbers instead of being happy with our work.
I've conducted this experiment because of my interest and for other interested persons ! I let the Wise pull it and don't massage the cross. Of course the measurement only provides results with limited accuracy.. but it's interesting too see the difference between the 2 measures. For the tie of the main, I pulled 12,4kg (10% PS) for the last 2 mains to compensate partly the loss. nobody claim that the cross must be at exact tension as the mains by measurement! through the weave the main get more tension and the cross loose some tension (I believe) ... We all only try to find the best accordance between cross and main! for the cross I would claim: (12,4+10,3)/2=11,35! I always work bottom-up... so the main get tighter the more I reach the top! During mounting the racket, I stress it a bit.. so after the stringing process, the cross get a bit more and the main loses some tension! but like i said: it only provides a quantitativ statement! For me it's important, that the main don't move right/left after every smashes! and like you said: as long as a racket comes out at same shape and plays lively we can be happy with our work!
Hi Lukas, thx for the extra info. I'm not a 100% sure that I understand your numbers correctly, especially compared to the original article. But if I do, it seems that in the original article, and the first lower cross, the tension loss was 0.6 kg (out of 9) without prestretch, and zilch with 15% prestretch. The tension setting was "squared" (cross = mains). This will have an effect as well, as higher tension crosses, will rub the mains harder (it may be a very small effect though). At your 2nd experiment here, you are ONLY testing with prestretch, and at the middle of the strings, there's a more significant tension loss, and at the top of the strings, the tension loss is huge? In other words, if I understand the sum of data correct, tension loss on crosses increase as the string bed tightens up (as my prediction). Correct? Thus the +2 lbs on the crosses makes a lot of sense, but the amount of +++ to put on them, would be affected by things like CP and PS (which also go in line with my observations when going from crank to Wise). Furthermore, this makes me speculate, if perhaps the crosses should be strung by adding +1lbs after the first 3 crosses, then adding another +1lbs when getting close to the middle (at cross 6-7 perhaps)?
In the original article, I've founded the link online. It's not my experiment! You're right: I claim that tension loss on crosses increase as the string bed tightens up.. that's why I make this 2nd experiment to observe it! I believe that during stringing the cross... the friction is higher than expected... because we always pull the cross on the hard weave. here the condition: F1=F2 but I believe F2>F1... if my claim is right : main get more tension the more I reach the top! so that mean A2>>A1 (A1 und A2 cause friction force) Options to reduce this effect: 1. like you say: for example- put 1 lbs on the first 3 cross than put 2lbs on the others 2. begin to string the cross from the middle... constant up and down! this guarantees to get the most right tension for the sweet spot! but no guarantee for this theory!
I think that the massage of the cross had lead to a higher number on the scale. Due the lack of this step (which is standard when you string) the influence of the friction looks higher than it would be in RL. I agree, but would this also be the same when you massage? Also the angle of pulling the cross is very different compared to the top, so I think it sounds logic that the angle plays a role. But you ignore here that also the mains drop tension. Lets say you finish your mains in 10 minutes. The strings drops in this minutes tension. They also drop tension during weaving the cross. By how much the weaving add tension and how much tension is dropped to clamping, tie-off and time, would be intersting. I can't tell a number, but it would be interesting to also see a experiment for the mains with ECP and Lock out or lets say 5 minutes to give the mains the same attention as the crosses. I agree that simplyfied the mains get tighter, when we ignore the drop. But what about it? And by how much they get tighter? It also depends on the thickness of the string. Also the friction part depends on thickness and how rough, slippery the string is. If we have loss and added tension we should offset them to get a tendency. It's like filling a bank account and ignoring the lift-offs. Just one side of the coin. Please take my harsh words not as an offence. I just want to set some light and add all factors instead of just speaking a number for everything which let a few things out.
Your "angle theory" is interesting. The closer to the frame, the higher wrap around angle (and thus more surface and more friction). In addition to this, you have the force that the mains are putting on to the crosses (like a pair of scissors in your diagram). The harder the mains are tensioned the higher force it will apply on the crosses. When you move up the racket, mains will tighten up, and that force will increase. Once we're past the shared holes, I suspect the the difference will start to drop again, because the will be fewer contact points (fewer mains to run across). Cheers, FB
