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Old 11th November 2015, 05:03 PM   #11
WrineX is offline WrineX  Netherlands
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Did some testing with stretching mylar 3 um and 6 Um heated and not

i must admit for the 6 um stretch i used another inner tube. i wanted to use it on the 3 um but i ran out of 3um Mylar 40 meters gone without even fixing one ESL i am persistent to have it correctly working , i already ordered new mylar just 3 stretches before i ran out so when it arives i use it with the same tire once more. but still there are some funny things happening



by the looks of it the 6 Ûm is most stable. but since i changed inner tube i still have to do it once more with the 3Um oh god. (might have been the tube at fault , that would be a waste)

Another thing to notice that the heated foil drops quickly and then setles in compared to the ongoing unheated 3 um foil witch keeps dropping.


One thing i can say about the test is that it shows that my clamps are holding, at least. so next up to rule out is the inner tube.
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Last edited by WrineX; 11th November 2015 at 05:08 PM.
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Old 11th November 2015, 08:02 PM   #12
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Like to follow your diagram over a timespan of at least a month..
IŽll be waiting...
How do you measure the tension/relaxation?
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Old 11th November 2015, 08:39 PM   #13
WrineX is offline WrineX  Netherlands
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Quote:
Originally Posted by esl 63 View Post
Like to follow your diagram over a timespan of at least a month..
IŽll be waiting...
How do you measure the tension/relaxation?
would be nice but ...... i cant wait a month.

i measure it with a mic on top of the stretch jig and a hole the size of my quad panel in the jig, with a loudspeaker underneath. i use holmimpulse to sweep and see where the peak is.
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Old 12th November 2015, 08:05 AM   #14
WrineX is offline WrineX  Netherlands
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Update on the measurements
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Old 12th November 2015, 08:06 AM   #15
WrineX is offline WrineX  Netherlands
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i wish i had some sort of automation, its annoying to measure every hour.
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Old 12th November 2015, 08:08 AM   #16
WrineX is offline WrineX  Netherlands
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i might do a heated 6 Um today to see what it does, since the normal 6um does pretty ok already. hope we can see a flatliner ;0
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Old 12th November 2015, 02:33 PM   #17
WrineX is offline WrineX  Netherlands
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so far when i stretched the mylar to a health 93 hz before i used the heat gun.(with 6um mylar thats pretty doable)

Then i heat the 6 um mylar especially where the tire stretch it. i heat it until the inner tube does not grow in size anymore, thats the maximum the mylar will stretch with this heat and tension. and then do some passes over the top.

now the res drops considerably straight down to 67 hz. and now for a change i wont correct it to the 74 hz like the rest. because i am wondering if the last action need to be the heating. in the quad jig it get the same tension all over the proces even in the oven it gets stretched. what i and many others do is just stretch or what i did so far stretch heat stretch to correct resonance.

there might be a difference in where the mylar will settle after it stretched with heat and where it will settle after heat + mechanical stretching.


i am not sure yet if i explain this correctly. i am just noticing that with this instance i dont seee the huge drop that all panels have common in the early 20 minutes.
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Old 12th November 2015, 04:03 PM   #18
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hmm some interesting is happening, i will do a post of my finding tomorow when i got some more data.

ooooh exciting
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Old 13th November 2015, 08:33 AM   #19
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beep beep beeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee eeeep
................................beep beep.


Well there is your flatliner. although something weird happens after 17 hours it seem to come alive. it did not drop but increases resonance haha not think this is a trend that continues to be honest but i leave it on the jigg to get some more data about the rise.


So stretch then heat. pretty solid outcome. at least more solid then stretching 6 um alone. but stretching heating and then stretch the last 10 hz does not work.


when i got some more data about the rising , i will try a this:


Stretch
Heat
measure
Stretch
Heat
measure


until i get the resonance i want. (prob when the foil does not want to stretch more with the heat.)

I test this because this is the only way to do it with 3Um foil.
Since 3um will break when stretched to 95 hz before you heat it, it cant stand it, max is around 74-78hz.
And i dont want to waste another 40 meter of Mylar , so i will be stretching it to around 65 then heat etc, and go to 70 hz in small steps.
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Old 13th November 2015, 10:08 AM   #20
WrineX is offline WrineX  Netherlands
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Ok 2 hours later. it looks like the rise was a faulty measurement. after 2 hours it it was back to 67.4.

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.

another issue might be that a inner tube will lose some air over a month i bet!, so result will be slightly skewed. but on the other hand you can see the drop of the not heated membrane versus the heated quite clearly. so there will be a usable result with a small error margin.

conclusion thus far: if you design a ESL with a preferred resonance you cant just stretch it up and see what happens. this might only work if you know at wich resonance it will settle over time. this will cost you a long time figuring out, since there is no rule of thumb to the relaxation of the foil. it might not be linear at all.
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Last edited by WrineX; 13th November 2015 at 10:11 AM.
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