I think at that point it’s a trade off between durability and performance. Couldn’t make an arc fb with amazing durability and the same weight, at least not currently. But yeah as you noted, narrow 6 o’clock supports do damage rackets. I think with a load spreader you’re fairly safe. After that, I think the 10/2 positions are most vulnerable, so current 6 point setups are well designed. It’s very unlikely a racket would break between the side support and 12 o’clock as the diagram suggests.
I have far too much time it seems. I don't intend to speak for everybody at badmintoncentral.com, but I have been a stringer for long enough to have developed the current understanding of the usefulness of 6-point mounting systems in badminton. This is my current understanding of stresses introduced when stringing racquets. Note that I have been stringing maybe 3 years with 200+ racquets strung, with none broken. I have strung up to 15kgs on steel-framed racquets without collapse with this in mind. My level of confidence on stringing the bottom crosses at 15kgs on a steel framed racquet without direct supports on the outside at 10/2 oclock? Well, I would be telling my client there is a 99% chance are not getting their racquet back in the original condition they gave it to me. *Note that the difference in 2 & 3 is a load spreader. In fact, i might as well just say that the 6 point mounting system is no better than a 2 point mounting system for mains-stress causing breakage. But a load spreader mitigates this risk so much that we are not worried about this. The sole reasons for 10/2 o'clock supports is to mitigate the stresses caused by stringing crosses. By not positioning the 10/2o'clock supports correctly, the risk of breakage is increase on the mains due to the aforementioned induced stresses, but more critically because they are not adequately mitigating the bottom cross-induced stresses. On the same logic, the inside supports looks like a decent way of supporting a racquet for a top-down stringing pattern (since the bottom half of the racquet is typically much stronger), but that was not a benefit or pre-requisite that was presented.
I fully agree again. My diagram does not tell that the racquet will break with the supports at 10 and 2 oclock. The diagrams shows that if you get closer to 3 and 9 oclock the stress in the racquet goes up. And that is what my Japanes agent also told me
And here I get totally confused. You develop and sell machines since decades but can't tell me what I need to add on the crosses to maintain the shape? I kindly disagree. FME it really depends on a machine and how good it supports the racket. The Klippermate need 2lbs to 10% on the cross for badmintonrackets to maintain the shape. On my 6-point with loadspreader and Chudeks I need to go +0.5kg/square on the cross to maintain the shape. Most Badmintonrackets are Iso shapes and have 72/76 holes. Your answer is very vague. If you done everything back in the 90's but can't even tell how you would string a standard badminton racket on your machine, which you sell leaves me really puzzled. I agree with you, but would add that the whole shape should come out close to unstrung. And to reach this, each machine is different and need more or less additional tension on the cross. I did this as a stringer for some time and also measured it during the life time of a stringing jobs and the conclusion is that unstrung = right of the machine is not enough. Since the string settle and loose some tension the W and L change very very slightly. Nothing special but noticeable with the eye. What's your opinion on this one? That's fine, but as long as you are here on a badminton board and not on a tennis board this don't help much to answer my question.
Great information DarkHiatus In tennis all racquets must be strung top down because the top is more vulnerable. This also has the advantage that the force on the 2 and 10 oclock supports goes down with every cross string that is added. My questions are: - Are badminton racquets stronger at the throat? - If so why is the advise to string the crosses from bottom to top then? OR is that not true?
Badminton racquets are much stronger at the throat, just as tennis racquets are - the material is generally thicker around these areas. The advice to string bottom to top comes because of the way 6 point machine are set up i.e. because the direct support is positioned to mitigate the bottom-up stringing method. If you strung top-down, there would be zero support for the top (weakest part) and it is more likely to collapse. The recognition is that the stresses generated by direct stringing of crosses on the strung half is greater than the stresses that are pushed onto the unstrung half. Therefore given the preference, we would actually want to support the inside of the strung half, and support the outside of the unstrung half, during crosses. This would appear to be the ideal design, but i'm guessing is quite difficult to make, since you need 2 support structures that are different on the same machine. Or maybe nobody has thought of it yet, because it has yet to be a problem Come to think of it, someone needs to design a clamp that is able clamp vertically, then it can both support the inside and outside of a racquet so it doesn't matter how you string it. Hmm...again, perhaps this counts as overengineering since it isn't a problem...yet!
No because that has to do with the balance between the forces of mains and crosses AFTER stringing. So it has nothing to do with the machine. This depends on the dimensions of the racquet head and number of strings and………………. On the quality of the stringer. If he looses too much tension in the crosses he needs more tension there. We have the tension advisor since 1989 and we calculate from the desired SBS.
not true. different machine has different stiffness. go and try different machines models from different manufacturers. Some are build like a bomb like Yonex ES machines. Some are pretty soft like Gammas. If you measure the head length after tensioning mains strings, you will find that the racket head will be compressed differently. That need to be compensated by different cross tension. I have done comparing stringing on 2 different machines (Yonex ES5Pro and Alpha Ghost). Both done using the same main/cross ratio comes out sounding and feeling different.
Of course Kwun it depends on the machine also and that is why every stringer has to check his stringjob. But the major thing is that there are no remaining stresses ( zero deformation) in the racquet after it is taken out of the machine.
I fully agree. OF course there is a difference in tension on the crosses when you compare stiff outside support machine with a 2 point machine. We are not going back to the 90’s with our tension advises but we calculate from the stiffness with our TA and this is not done in badminton at all.
@ DarkHiatus About your nice pictures: The bending stress in the racquet depends strongly on width of the supports. Is it possible to show the picture with wider supports inside about 20 mm wide? Or replace the inside supports by 2 inside supports 20 mm apart? We are interested to know the difference.
I have machined Delrin before. it has a smooth surface but at the same time rather soft material compared to metal. to use it as a bearing is a good cost cutting measure but won't be as good (in terms of stiffness and smoothness) as a proper steel ball bearing used in higher cost machines. my Gamma has a pair of steel ball bearing cartridges and they are very very smooth. With Delrin you will have to compensate for the softness with geometry. from your video it seems like there is some deflection. Not that crucial but not something to be proud of.
HI guys Because we are debating the racquet protection and because the conclusion can be that it dangerous to string the crosses from bottom to top: Did you discuss this way of stringing badminton on this forum? Because the crosses on both ends lower the pressure on the outside support earlier this could be very good for the racquet
We use delrin bearings in all our machines. The important thing is that the pressure per square mm is lower than 5 kg/ mm^2. So there should be enough surface to cope with the pressure. The bearings in our alu table last "for ever". Apart from the pressure it is also a matter of design, it is not so easy to fix a ball bearing in the tube of the turntable of the MS140.
The #1 racquet manufacturer in badminton is Yonex. To claim a Yonex warranty, the Yonex stringing pattern must be used, which is a 2 piece stringing pattern that must have crosses strung either top down or bottom up. There are many variations of the stringing that minimise stresses on various parts of the racquet, including the one you linked us a video of. Many forum users discuss these variations and use them personally, which reduces risk of racquet breakage significantly such that you get to the point where we are relatively confident stringing any racquet with a common 6 point support to the maximum warrantied tension (and even beyond) Problem is that Yonex will not honour a warranty if you use any such patterns. Therefore, for our clients we would normally use the manufacturers requirement such that a client can claim the warranty if it breaks on our machine (as then the only fault will be a manufacturing defect if the stringer is competent).
Is this not a little bit amazing? Is Yonex in contact with the stringers about this kind of matters? It should be in their advantage when the stress in the racquet remains as low as possible. Do they have their own technical philosophy?
the ultimate will be: wide inside support for the mains at 6/12 o'clock wide inside support for the cross at 3/9 o'clock procedure is quite straight forward: - tension middle 12 mains at desired high tension - tension middle 12 cross at desired high tension - tension the remaining main/cross at lower tension i believe this will be the ultimate in terms of racket safety. the middle are all internal supported, there will be very little stress. the corners aren't tensioned, so there will be little stressed at the beginning, at the end, they will just naturally support the corners and will relieve stress when racket unloaded/unsupported. the balanced tensioning of the cross/main string will give best feel. the only caveat is you will need our Ultimate support, which doesn't exist at this point.
Not really amazing at all, Yonex are very conservative on their warrantied tensions. A better pattern might allow higher warrantied tensions, but how exactly does that help Yonex make money? It doesn't, especially not if none of their main competitors are not pushing for higher warrantied tensions. The stringing pattern is one of the fastest, so their approved stringers have less work to do. The only racquets that regularly break are professional racquets, and those are a tiny price to pay compared to the amount of sales each sponsored player brings in. They are regularly strung above maximum warranty maximum. Kolding said he breaks a racquet every week for example. Even Axelsen breaks 1 a month, and his can't be due to clashes since he is a singles player. Ultimately Yonex sell racquets. Amateurs do not generally string above 26lbs, and with a bottom up 2 piece pattern on a 6 point rig, Yonex have determined the chance of breakage of their racquets is low enough that they are willing to replace any racquets that do break below the warranty maximum tension. They can upgrade to 28, 30, even 35lbs if they want to (other racquet manufacturers have!), but there is not much market demand for extra high tension racquets, and putting in effort to redevelop stringing/racquets is not worth the minimal extra sales.
5 kg / mm2 is nearly 50MPa. which is starting to tread into the non-linear part of the stress/strain curve. Given that it is compression and much less likely for the material to give, it does partly explain the deflection seen in the video. And this a similar one i can find for steel. which means it is hundred/thousands time stiffer. granted that this joint is not critical and low speed and low movement, so the wear isn't an issue. but the smoothness and stiffness is more important and that contributes much more to the feel and quality of the machine. even my cheapo Alpha Shuttle Express has steel bearings.
