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My take on a stretch jig
My take on a stretch jig
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Old 13th November 2015, 03:06 PM   #21
405man is offline 405man  Scotland
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Over the month you could check the pressure in the tube every day and pump up as necessary, digital tyre pressure gauges are cheap

Stuart
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Old 13th November 2015, 04:00 PM   #22
WrineX is offline WrineX  Netherlands
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Quote:
Originally Posted by 405man View Post
Over the month you could check the pressure in the tube every day and pump up as necessary, digital tyre pressure gauges are cheap

Stuart
to much hassle im afraid
well its even hard to pump a given amount into the tire, let alone a really tiny amount.

only thing that could be tested is glue it to a stator and see what happens. to the resonance (could drop few hz because of the glue or cutout of my jig is 1mm smaller whatever, but at least it is repeatable), and then see what happens to it over time.
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Old 14th November 2015, 12:16 PM   #23
WrineX is offline WrineX  Netherlands
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Well here a 3d version(without base etc and details ) , i am not sure yet if i should make the small circle that's on the metal tube a little larger, this would increase the maximum length of Mylar it can pull sideways(it pulls 1/4 of the circumference). but it will lose some of the arm so a little more weight might be needed to pull to correct resonance.

in previous post i showed one of these arms, and the weight alone when you hold it at the hole in the small circle has already some force.

i also did a test with some glue on the clamps to see if it can hold Mylar. this is hit and miss. although tolerances are pretty ok there is still a tiny bit of room in the clamping so mylar slips. witch is not weird since my machine wont mill to 3 um precision that would be fun

i might try single sided foam tape, i once used that to hold Mylar between 2 mdf piece of wood, and it never slipped before it broke(and that was 6um)


I did not draw the rubber bands that come between the outer hole in the clamp arm and the top hole in the 1/4 circle. i also only draw one weight(the black circle) just to hope clear how this would work.


Further, there is an option to automate all this, for now i will drill an extra hole in the 1/4 circular piece so i can lock the clamp in the open position. later on i would like it to be automated. when i could get a ram of some sort it can push the 1/4 circles into the beginning position, and at the same time push the clamps against a bar so it will go in the open position. so 4 rams needed in total. or another solution
any suggestions or stuff i miss please let me know. don't want to make soooooo many pieces and come to the conclusion its is a dumb idea haha
Attached Images
File Type: jpg JIG met draaidingen.jpg (81.6 KB, 255 views)
File Type: jpg JIG met draaidingen 2.jpg (320.8 KB, 250 views)
File Type: jpg JIG met draaidingen 3.jpg (271.4 KB, 248 views)

Last edited by WrineX; 14th November 2015 at 12:25 PM.
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Old 24th November 2015, 02:40 PM   #24
bhunter is offline bhunter
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Quote:
Originally Posted by WrineX View Post

So far i gained knowledge that my clamps are holding and my tire is not leaking any air. (not even a tiny bit) at least the panel would be glued by now. since glue dries in 40 to 60 minutes.

last be not least. you can see that just mechanical stretching a membrane then glue it to a stator is not gone give you a steady result. it will drop. be it 2.5 hz over 17 hours, who knows where it will end up

ESL63 wanted to know measurement over a time span of a month. and i am curious to. be it i cant miss my jigg for a month. or i have to buy new clamps.
Interesting and looking forward to your future results. BTW, what glue are you using to attach the Mylar to the frames?
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Old 24th November 2015, 11:25 PM   #25
WrineX is offline WrineX  Netherlands
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yeah i got side tracked again still need to come up with a good and solid way for stretching. i did buy 22 kilo's of scrap lead for weights but i have to melt them down to small compact size. never melted lead so must buy some protective gear first i guess.

i use some sort of polyurethane. 1 component kit . its really fast drying. i delute it with allot of acetone. you then spread it on the foil NOT on the stator, and be sure to apoly a little wider then the stator spacer is wide so there will be glue every where on the edge of the stator. (else it will make anoying sound when playing low frequency) i got a foam strip underneath the the mylar where the stator comes on top so the glue will follow every nook and cranny of the stator, it will be hardened in 45 minutes.

glue brand is bison TIX top speed
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Old 25th November 2015, 09:51 AM   #26
405man is offline 405man  Scotland
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What glue do you use to glue the stator pcb to the plastic frame and how do you apply it.

Stuart
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Old 25th November 2015, 01:07 PM   #27
WrineX is offline WrineX  Netherlands
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i use 2 component epoxy, but its used for mouldings, so its really thin. i mix it with a tiny bit of cotton fibres, thismakes it a bit thicker and it will release epoxy when presured. then use a roller to aplly it on the stator frame. put pcb on top then a trash bag since its PE plastic witch dont stick to the epoxy verry well, then a piece of wood the size of the stator pcbs with the holes at the right place and repeat stack them all, and at the end a heavy weight 60 kilos of crap like sandbags and other stuff the glue need to dry at least a night so better do 8 in one go
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Old 30th November 2015, 05:37 PM   #28
WrineX is offline WrineX  Netherlands
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Well since i am not able to get any wood i don't have a car, neither a license to drive

i tried the tube stretcher once more. i got a new roll of 40 meters 3 micron foil again so this would be the 3'rd roll i spends on this project... nice another 70 euro... hobby aint cheap. well at least i come closer and closer to a original panel. and well it means allot to me to be able to repair these baby's as close as i possible can and preferred closer then anyone else in the Netherlands since quite a few people repair these panels and since i got so many minor problems i ask myself sometimes if people really got rid of them or deliver a lesser/ or at least not equal to original product.

so well i used the stretch jig again. but the resonance needed by quad is pretty close to bursting range, at least at some critical points. so this time i apply the mylar as before with the clamps. but then i line the whole tube part with 2 pieces of tape. this ensures me that the mylar wont stretch in these parts(since its hard to heat these sections), and wont rip either. i then stretch to 70 hz, heat , restretch to 70hz heat, restretch to 70 etc. the drop it makes from the heating will get smaller and smaller. the last drop before restretch was only 3 hz. so verry close to best possible. i now let it rest and measure the resonance every 30 minutes. i so hope this works since my head spins from making a new jigg at the moment and i really would like to be done with these so i got some money to invest in a proper jig (and some one that has a car to get some wood )

so far after 90 minutes it dropped 1.5hz, i wonder if it will settle on the 3 hz it dropped from heating it. this would be anoying but at the same time gives me a guide line to how to do it proper , do the same thing over and over until after heating it settles at 70

Last edited by WrineX; 30th November 2015 at 05:40 PM.
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Old 30th November 2015, 07:59 PM   #29
esl 63 is offline esl 63
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70hz seems a bit low. And that is before coating whis is adding mass and lower the resonance further.
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Old 30th November 2015, 09:20 PM   #30
WrineX is offline WrineX  Netherlands
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Quote:
Originally Posted by esl 63 View Post
70hz seems a bit low. And that is before coating whis is adding mass and lower the resonance further.
here you might have a point!. Thx. i will take a look what happens when glue dried and circles are melted. it kinda of depends indeed on the weight of the coating. i know licron is pretty thin, lets see what it does. i got measurements although the process now, so i could change things accordingly to get a desired result in the end.
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