main support deforming under load

[speCulatius]

ok, i see. i will try to make a video, sure a lot of fun, the problem is luck of time to do it properly.

Well, it's not much effort. @s_mair asked for a specific l, fixed angle, you don't need to worry about much, it doesn't need to be perfect.

Or at least reply to questions....

Question: After tensioning the first two and first 4 mains, how big is the gap that is opening up between the frame and the support piece or the load spreader respectively?

Does your machine look like this?

If yes, what if that screw/bolt doing there?

... but I'm sure there's more if those that are still unanswered.

 

[s_mair]

ok, i see. i will try to make a video, sure a lot of fun, the problem is luck of time to do it properly.

I just went back to the very beginning of this thread. And it looks like we've jumped way ahead of ourselves before actually knowing what's happening.

So let's imagine we are back in the first 10 posts of this thread and start with some basic questions. You can skip the video and all the other questions for now tbh:

1) Have you ever even measured anything on the machine itself, for example the distance between the two main support bits before/during the job?
2) If not, what makes you think and say that the supports are deforming in the first place? I mean... a deformation of ~5 mm in the hardware would be easily visible with bare eyes.
3) After tensioning the first two and first 4 mains, how big is the gap that is opening up between the frame and the support piece or the load spreader respectively?
4) Are you sure that all the supports are tightened sufficiently before you start the job?

Here's a video that I shot for another BC colleague who also had issues with rackets coming out round from a StringMaster machine and maybe it gives you a reference on how tight you should go:


And as indicated in post #24, I made the exact same mistake when I started with the StringMaster and went with too loose side supports. The result was... guess what... round heads.

 

[konstancij]

well, to your questios, i think i do the mounting correctly and there is table+posts system that is little bit bending under load.
The small hex screw that you marked is rather interesting topic, because it is one of 8 screws, that allow to fix the central support securely to the tower, eliminating screw-rod bending. But was it the orginal idea if designers? - i dont know, as it hard to call a convinient solution.
I thing the intire multiverse of possibilities will be closed with one short video, if i succed to make it, so be patient until sunday.

 

[s_mair]

well, to your questios, i think i do the mounting correctly and there is table+posts system that is little bit bending under load.
The small hex screw that you marked is rather interesting topic, because it is one of 8 screws, that allow to fix the central support securely to the tower, eliminating screw-rod bending. But was it the orginal idea if designers? - i dont know, as it hard to call a convinient solution.
I thing the intire multiverse of possibilities will be closed with one short video, if i succed to make it, so be patient until sunday.

Still open:
1) Have you ever even measured anything on the machine itself, for example the distance between the two main support bits before/during the job?
2) If not, what makes you think and say that the supports are deforming in the first place? I mean... a deformation of ~5 mm in the hardware would be easily visible with bare eyes.
3) After tensioning the first two and first 4 mains, how big is the gap that is opening up between the frame and the support piece or the load spreader respectively?

Again... skip the video for now and start measuring if you haven't done that yet.

 

[konstancij]

hi, as promised, a video. a word caution, it is really boring slow, 1 h long and made in especially poor english. if you ok with that, u're welcome to see and comment.

TLDR:
only mains were tensioned to 11.5 kg.
racket dimentions:
no strings: 23.6 / 18.5 mm
mounted: 23.9 / 18.2 mm
mains pulled: 23.4 / 19.05 mm

distance between metal parts of central supports:
racket mounted: 21.7
mains pulled: 21.4 (actually 21.35)

So in process of mains pulling, the racket becomes shorter by 5mm and wider by 8mm. Out of these 5mm, 1.5 is in load spreaders, and 3.5mm by entire machine deformaton.

it looks like initial question is sufficiently discussed. if i will end up with nice modification preventing machine table deformation, it will be another topic.

 

[s_mair]

hi, as promised, a video. a word caution, it is really boring slow, 1 h long and made in especially poor english. if you ok with that, u're welcome to see and comment.

TLDR:
only mains were tensioned to 11.5 kg.
racket dimentions:
no strings: 23.6 / 18.5 mm
mounted: 23.9 / 18.2 mm
mains pulled: 23.4 / 19.05 mm

distance between metal parts of central supports:
racket mounted: 21.7
mains pulled: 21.4 (actually 21.35)

So in process of mains pulling, the racket becomes shorter by 5mm and wider by 8mm. Out of these 5mm, 1.5 is in load spreaders, and 3.5mm by entire machine deformaton.

it looks like initial question is sufficiently discussed. if i will end up with nice modification preventing machine table deformation, it will be another topic.

Thanks for the video. But I have to say, you're not making this easy with the viewing angle that you chose. It's pretty much impossible to see anything in detail about what's going on in the support area. Apologies for skipping roughly through the video and not spending an hour on this.

However, I feel like the issue has to do with the stuff that you show after 5:30 regarding the support pieces, those rods that come out of the main towers and the hex screws. I am 99% sure that the rods that stick out of the main towers are supposed to be permanently fixed to the support pieces, using the hex screws. So they should be moving in/out of the main tower as you move the support with the wheel. That way, you get a lot more stability in the whole system. They way you currently have set them up doesn't make any sense since they are basically completely useless and can't do anything. What you are doing at 20:40 is clearly not meant to happen and is super inconvenient.

Can those two rods move in/out of the main towers? If so, attach them to the support pieces and leave them there. I don't really like that they are using those hex screws to connect those stabilising rods to the support. That is solved better on the Deluxe machines.

Some further things:
You, again, didn't check for any play at 6 o'clock after pulling the first two main strings after 29:48. And you don't have to look to see a gap, you'd have to re-tighten it on the wheel and see if it is loose. You can't see any gap when there is the load spreader deforming and covering the area. Same at 31:16 - you won't be able to see it, you'd have to feel it with the adjustment knob.
Although I don't think this is a crucial point.

The mounting looks okay from the few things I can see.

 

[konstancij]

thanks for watching and comments.

>Can those two rods move in/out of the main towers?
no, these are fixed on thread in towers.

 

[s_mair]

thanks for watching and comments.

>Can those two rods move in/out of the main towers?
no, these are fixed on thread in towers.

That doesn’t make sense to me at all. So you also cannot loosen them in any way and the machine arrived that way from the beginning?

 

[s_mair]

I finally got some feedback from Tennisman regarding this topic. It seems as if the problem really lies with the machine and that the construction of the main supports is a design flaw. The way you are dealing with the hex screws is correct.

He was kind of surprised to hear about this issue and has adressed it towards the factory to be improved with the next batches, most likely looking like this then (click to enlarge):


This looks better, but tbh still significantly less robust than how it's done on the full-size StringMaster Deluxe variants. I wouldn't have thought that there are such big differences between the tennis and the badminton-only variants and it makes me wonder how much sense those badminton-only machines really make.

 

[konstancij]

the best improvement would be to test prototypes with pro stringer before going production. somebody should tell them.

as to badminton only machines as such, it can offer unique features, like better precision, lightweight, compact size, more adjustment options, specialised central supports, may be even ring design.