Saturday, January 20, 2007

I got up this morning and hydro tested my 3" wound tank. It failed at 200 PSI in dramatic fashion. It shattered into a bunch of little pieces.
As you can see in the picture on the left the PTEG tube has lots of little cracks. After this failure I suspected that maybe something was wrong with my initial small scale test with the Florescent light tube cover. So I retested that, again the fitting leaked and again it held to 1500 PSI. So I suspect that the PETG tube and the FTC tube were made of different stuff. I've decided to disassemble the old small FTC tube, fix the fitting leak and try again. I'm letting the oring overwrap reenforcement dry and when that is done I'll wind another tank and test it on Sunday.

Just in case my spectra tanks don't work out I'm also working on lightweight aluminum tanks. I built a hydroforming fixture out of a large chunk of 12" diameter Aluminum and a 12" diameter steel cover plate.

The frist try at using this fixture was ok, but not great. the only Aluminum I had was 6061-T651 so it was hard and did not yeild well, I've ordered som 6061-T0 and we will see how that works. The resulting end cap from the -T6 was usable, but shallower than I would like. It failed around the edge of the fixture, so my guess is that I need to radius that part of the fixture a bit more. I send E-Mail to two metal spinning companies asking for quotes on having them make 8" hemispheres and I've gotten no answer.

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