So I'm all excited finally getting the JS12 in the mail, so went to string it right away. It's a 3U model. I finished string and the mains, and was about 2/3 through the crosses (I string top down), that's when the racquet cracked. Here are some details Racquet: JS12 3U, brand new String: Aerosonic Tension 28.5x31lbs String machine: Eagnas pro combo 910 with 2089 Wise tensioning head & Chudek side supports I know the tension is quite high, however I've strung the past ~100 racquets at this tension, and maybe the past 200 racquet at 1-2lbs lower. With this setup, I have never broken a racquet, until now. Attached are pictures of the setup. I had already cut the strings before I took the pictures, but one picture with a string showing illustrates the location of the string that I was pulling when the racquet cracked. A couple more pictures show the detail of the crack (at about 8 o'clock position). Is there something wrong with my setup? perhaps the lower side support should be moved lower? Any chance it could be racquet manufacturer defect? I have string a couple of hundred racquets at this setup and have never once broke a racquet... Somewhat fortunately, I have a 2nd JS12, however now I'm afraid the string that one.
the lower (4/8 oclock) supports are too high / too close to the middle. for top down, there is an incredible amount of stress on the frame at exactly where your racket cracked. you need to shift the support at least 3 grommet spaces down. how do I know? many many years ago, when I first started, i strung a slim frame racket and it cracked at 24lbs at that exact location. btw, sorry that your racket cracked. RIP.
Thanks Kwun, I'll give that a try and put the 2nd JS12 to the test. I guess doesn't hurt to ask the seller to see any chance this could be covered by warranty.
So I lowered the bottom side supports as suggested and strung up the 2nd JS12. No break this time! Hopefully I'll never break another racquet ever again!
Personally, I think you were just unlucky. Sure, you could move the bottom supports down a tad, but given that you've already sent so many through with no problem in the past... (The only racket I ever broke was a top down, and exactly where yours went. If you're going to use serious tensions, I would recommend switching to bottom up - Yonex did so because so many of their frames were cracking under tournament conditions.)
Well, it was 28.5 (at least I would call it that if asked about it). I think there's a good chance that you can get a new racket. Given it's all new and the other one is OK. In all fairness, it probably had a weak spot, since it's the first of 200 rackets to break. Now, you probably want to adjust your method anyway to avoid more breakage. I'd suggest for your machine, to move the Chudek supports to the set of holes, near the end you're stringing towards! So if you go top->but move the supports to the lower holes. If you go but->top, move them to the upper holes. Does that make sense? And then you could always consider if top->but is worth it? I always do but->top unless a client specifically asks for anything else.
Yeah I'm going to start stringing bottom up instead. I've always stuck with top down because I've never had problems with it. Now that I broke a racquet, I'm going to start doing bottom up.
If you are going to convert to bottom-up, I would suggest you place your supports as follows: lower - at the fattest part of the racket (usually just below the mid-point); this is where it will deform most under mains tension. upper - between the two shared holes (with respect to the JS12/Thruster/Meteor patterns); this is where the stress will peak as the crosses go in from the bottom. I am sending 4U rackets through at 34/35 with this arrangement - no problems yet. It will look odd at first - as though the racket is "too low" in the machine - but that's the idea.
You know, I have been wrong in the past. I bought two NR-ZSP in JP code before trying them out, let's not forget.
I want to add one thing: Do you regular readjust the 6 o'clock support? Especially the Load spreaders cause that some frames sink a bit in the load spreader, when you tensioned and clamp the first mains. You can easily see a gap. I also think that with this setup and ratio you cranked it up. I never understand these 10% guys with 6-points.
There are much more experienced stringers than I in this thread but I'll throw my two cents in... This is another reason I enjoy the Paizhuan method. You do the top 4 and bottom 4 crosses very early on, meaning you get the really stressful pulls out of the way, anything after it toward the middle of the frame and unlikely to break anything. What's more is if you double pull these you can get a good tightness on them (not like the slack of a tie off string), but not enough that it's quite as tight as the actual crosses you expect to hit with. Considering it's a new racket definitely worth rolling the dice to see if they'll replace it. Think it's just a bit of bad luck as others have said.
Another good point - always worth checking 6 o'clock and closing the gap after the first two mains. Any space here means more load on the shoulder supports later on. (At my tensions 6 o'clock separates a bit every single time as the load spreader takes the strain.)
If you and Paul need a trainee for the next AE, I will have time. I'm not too bad at changing grommets, pre-weaving the mains and cleaning the clamps.
I used to use one there but I came to realize all it does is put more flex into the system. Not what you want at all. I did (pro)file my 6 o'clock to match the curvature of the frame, though.
Interesting. So it seems like I will have to get rid of my 6 o'clock load spreader from here on too. I also noticed that it seems to add some extra movement to the whole system - and if it doesn't have any real benefit, then off you go!
