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05-11-2009, 10:00 PM #1
distribution of 6pt frame supports
a theory question.
if you have the choice of freely place 6 frame supports in a stringing machine, where would you put it?
the constraints are:
- they are single sided support, either on the inside or the outside, but not both.
most machines put the default locations at 6/12. and then depending on whether they are badminton specific mounting, they can be around hole 10/11 or sometimes higher.
my ASE has the support at 6/12 o'clock, B12 and A11 i believe. the 6/12 are inner supports, B12/A11 are outer supports.
05-11-2009, 10:53 PM #2
A 6pt frame support should be evenly distributed
I would think they should be evenly distributed, to be placed at 6/12, 4/10 and 2/8 o'clock.
05-12-2009, 03:34 PM #3
it is not as simple as that, thus i wanted to ask.
- the badminton racket frame is not a perfect circle
- the way we string 2PTD is not symmetrical
- the strength distribution of the frame is also not symmetrical
05-12-2009, 07:50 PM #4
Well, the mains will try and force the sides of the racket outwards, with the most stress at 3 and 9, so it makes sense to put support closer to the middle than 2/4/8/10 o'clock. I, for example, always have my side supports past where the outermost main meets the frame at either end. In clock terms I suppose it would be 2:30, 3:30, 8:30 and 9:30.
05-12-2009, 08:37 PM #5
05-14-2009, 01:45 PM #6
when doing 2PTD, we string the crosses from the top down. the pressure put on the frame effectively squeeze the racket frame downwards, this creates a bulge at the 4/5 o'clock region which at this point, is unsupported by anything except for the side support. if we move a support away from it, it will be vulnerable to cracking. i have cracked a weak racket frame this way.
so as you see, the question isn't as it looks. i am surprised no other stringer wants to comment here..
05-14-2009, 03:49 PM #7
In all seriousness, this is both a "tough question to answer" and a "trivial problem to solve".
What I mean is that all stringers use their experience to string, like almost all professions. Different stringers will place the supports differently, and they all still string just fine because the tension pulled is still within the safety factor from the racket design. So, chris@ccc did answer your question about "where would you put it?".
If you want to know "what the ideal positions are, such that load from stringing is distributed most evenly across the rackethead?", then that would be very tough for stringers to answer and justify. However, that is a trivial problem to solve with tools such as finite element method (FEM). Creating the rackethead geometry and setting the material properties only constitutes a basic example of FEM. Then setting up the time-varying load profile of the stringing process and run the simulation for various support positions. This way, the perfect support positioning can be found for any rackethead geometry or material.
Note: the word trivial is used to mean that all the individual steps of what I described above is simple to do, for an undergraduate mechanical engineering major (not my major but I have taken the courses and work with some people from MechEng). Time is the only limiting factor for someone who is not familiar with FEM softwares, such as myself.
05-14-2009, 11:42 PM #8
I think whats on mine or Kwun's machine is perfect for 6 point
4 on the side (2 each side) and two for top and bottom.
the side will be outer and the top bottom will be inner.
Reason for this...
For top bottom its inside because when tensioning main, this help (especially the top) holding the upper area of the frame from bending inward.. and because of this, the 4 side put in outer is excellent because it help the top by keeping the side from getting push outward.
For the location of putting the four sides, if I can keep it changing. I like them to be just slightly after the last shared grommets or last main string and toward the side.
the small round is where the mounting is... and the 4 line outside is pointing to the last shared grommet or last main string
Edit: by the way my stringing method is always 4 knot, two piece stringing, bottom up, main from centre to the side.. I use 4 flying clamp for main and two for cross
Last edited by ae86trueno; 05-14-2009 at 11:46 PM.
05-15-2009, 08:59 PM #9
Reason: My current machine side supports are on 2.5/9.5 and 3.5/8.5 o'clock. I stopped doing 2PTD after my SOTX CP5000 broke when I pull the 2nd last string on the bottom cross.
2) For 2PBT, 2/10 and 4/8 for side supports on outside would be fine.
07-08-2009, 07:59 PM #10
kwun, you also need to consider whether its a suspension mount, or hold down type. Suspension mounts are more susceptible to breaking rackets due to a bad mount, where as hold down type are very secure all around. In fact the prince neos, one of the most popular stringing machines is only 2 pt.
07-09-2009, 06:59 AM #11
Hi, I'm a beginner at stringing, probably in playing too
But my simple guess would be that when one strings the main, there are two things to be considered, the points furthest away from the vertical centre would be displaced more?
Second thing, the curvature of the frame (since badminton rackets are neither oval or circular), greater curvature suffers more stress ( i hope i got it the right way round, lol).
Anyway, both of which occurs from mid to lower half of the frame, so I would guess placing two supports near 3, 9 oclock and two 4/5, 7/8 oclock?
The next bit messes my head up, when you string the cross, it really depends on where you start, I will think more about this and post later, lol.
07-09-2009, 09:31 AM #12
ooh good thread... subscribing to get more info. I need this to convert my 2 point machine to a 6 point machine.
In my conversion, the 6/12 positions will be hold down and the rest 4 will be suspension.
07-09-2009, 05:46 PM #13
Well, from my experiences the other 4 side supports no matter where they are located doesn't really matter that much, their job is simply to guard the shape of the frame while tensioning the main only. My gamma X-2 I locate the 4 side supports around the points where the cross starts to go through the shared grommet with the main both up and down. 2 things that I observed, 1) when you pull the crosses basically these 4 side supports don't have any functions to do with the pulling action both left and right, say you are pulling left to right, the frame will be pulled away from the left support, on the right the pulling action is straight through the grommet and is not inserting any force on the right side of the frame at that location, as a result the right side support doesn't have any force resulting to it. 2) when the cross string pulling approaching 2 & 10 o'clock locations you will notice that the frame @ 1 & 11 o'clock locations will deform a little bit when you pull (try for yourself, pull, don't clamp, let go and re-pull). With the side supports mounted as what I mentioned after the racket string is done I notice the side supports @ 2 & 10 o'clock locations are not even touching the frame anymore (2-3mm away). I don't know if there is any stringers out there have the similar observations as mine.
07-09-2009, 09:06 PM #14
IMHO, with the scenario you wrote above, while yes it might not be putting force directly on the right side of support, but racket frame is one piece (by 1 piece I mean, left and right does not work independently. Imagine its like letter O. From what you saying the right side won't have any force, I think its only true when racket frame look like U) so any force on the left pulling toward to the right, will put the force to the right side too.
When I finished stringing my racket, all the support still in contact with the racket frame. I never had situation its not even touching frame anymore, this sound like the top part of frame squashed I imagine.
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