well this is good, obviously you don't assume deformation like you said, but i have some of this: http://www.mcmaster.com/#8980k54/=6ksz6v
so i don't think i'll get too much deformation before it bursts. i'll have to read that other analysis too.

EDIT: dHall, I'm using 80% of the yield strength ...

yeah, I'm no longer worried. Also where are you getting CrMo from? DOM tubing is usually 1026 mild steel. No backpurge, as the end plugs were well machined to close tolerances, and about .75 inches thick, so the gas wouldn't help too much.

thanks for teh comment on mah welds. I love my miller

I was planning on getting the two from mcmaster (f'in love that place despite the high prices) but i just got impatient, so i used what i had (I'm sure you know what that is like)

any pics of the inner workings of that schweet arse reg you built?

It has numbers every 5 psi, major gradations every psi, and then minor gradations every half psi. Also I have been using my meter pipe for the latest tests, but I think the meter pipe method actually adds more inaccuracy to your measurement system because it necessitates a volume measurement ...

I'm sorry, I should have read your posts more thoroughly.

Anyway, right now I'm using the 0-30 psi gauge that came with my lpg regulator. (I think it's probably the most accurate gauge I have now, but I plan to get some better ones) Thus I am limited to 2x mixes.

I do have a spare welding ...

Oh I don't skimp on hearing protection. I'm studying to be an audio engineer, so my ears are a huge asset. I'm actually worried that even with adequate protection the sonic boom from higher mixes will deal me some permanent damage.
Also,
" The smoke you've experienced in the chamber could be due ...

Well, finally got some consistency Five 2x shots in a row. Still only 6 layers, but I'll take what I can get. Gunna try some higher mixes when I can find a huge field far away from my city house

Tried a couple of 2x shots and so far all have ignited, but I still can't use any more than 6 layers of foil. I'm going to try and tune the mix to see if I can get better combustion. Also there is still quite a bit of smoke left over in the chamber after firing, so that is another hint that my mix ...

hm, ok i'll try that tomorrow and post results. I still haven't added the orifice. Also the times that i have been able to achieve combustion, there was always smoke in the chamber. Does this indicate a rich mix?

Propane is heavier than air if I recall correctly....wont it separate from the mix by then?

So I began work on my first hybrid a few months ago. It's designed for 20x mixes, made of DOM steel, and has been hydrotested to 3500 psi. Unfortunately, it doesn't fire half the time :-(.

I've looked all around this forum, read the wiki, and read Hybrid Fueling 101. First I tried using the ...

Thanks for clearing that up. So I guess the method detailed on that other site gives you mass percent, which is useless in this case since we are measuring by volume. (stupid mistake on my part)

Sorry to correct the thread again :roll:, but there is one more thing I thought I should add: the proper ratio of air to propane is actually 15.6:1, or 93.9% air. In the first post it is listed as 95.8% air which is a bit lean (too much air). The ratio can be calculated using the method detailed on ...

I was reading over this sticky as it is my first time building a hybrid, and I thought I'd like to point out what I think is missing information.
Regarding the chamber pressure method of measuring mixes, you would first calculate the correct amount of propane for say a 10x mix:

Vp = ((100/.958 ...