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ME20H-41, by DYI

Built a hybrid cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: DYI » Mon Jul 28, 2008 6:52 pm

I probably should have posted the results in this thread earlier, but I completely forgot.

The first shot of the day was with a 500psi disk, which resulted in the golfball going through the chrony at 1031 fps from 10 feet away (so as to not confuse the chrony with the muzzle blast). We saw a strange cloud of black smoke, and were puzzled as to what caused it until we opened up the breach to reload, and found that first 6" of the barrel had apparently flash-boiled to some extent, and that the rest was welded shut. There's no way to get the inner pipe out of the outer pipe, so that barrel was ruined.

The one data point we got indicates that this launcher is definitely supersonic with a proper burst disk at 20x oxy/propane (we never got to test varying percentages of inert gases either, because of a curiously damaged sparkplug), probably in the neighbourhood of 1400-1500 fps. Our results may have been skewed by the destruction of the barrel, but that would only make them low, not high.

Anyway, the ME20H-41 is dead now. It may return at some point, but that is relatively unlikely, unless I decide to try to build a silencer for it. Firing in my shed, which dampens sound quite well, isn't really an option because of the risk of concussion damage (although tests I've done indicate that the windows will survive the deflagration of that volume of oxy/propane, some other things in there don't fare as well). This launcher was too loud and dangerous to be a backyard plinker, but not powerful enough to be a serious destruction gun.
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Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.
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