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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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ME20H-41, by DYI

Unread postAuthor: DYI » Mon May 12, 2008 8:43 pm

Miniature Experimental 20x Hybrid - 41mm

Nothing very exciting here, but due to its extreme affordability and ease of replacement (along with a hell of a lot of wire), I can test it up to its limits, which I haven't managed to reach so far, although I have gained some interesting insights along the way.

Specifications:

Chamber
Material: SCH 40 welded steel pipe, 150 psi rated malleable iron fittings
Volume: ~87ci
Configuration: SCTBDC style, with elbow on back for quick reloading and versatility

Barrel
Material: Fiberglass reinforced SCH 40 ABS pipe
Dimensions
ID: 1.61"
OD: 3.500"
Length: 48"

Fueling
My universal fuel meter, capable of up to 20x air/propane, or up to 24x oxygen/propane

Ignition
Ignition device: 3 camera flash capacitors (wired in parallel) discharged through a 1:100 winding ratio coil, for 33kV.
Spark gap: single central gap, ~0.5mm
Sparkplug: 1/2" epoxy filled brass nipple with two conductors, so that current never passes through chamber material

I've tried it at up to 20x oxy/propane, and I don't intend to try it any higher. Unlike most ridiculous claims, this one comes with video evidence.

And here it is!

Also, I have pictures. I had to make a new Photobucket account just to host them because my old one crapped out on me.

Image

The whole thing, sans sparkplug (it got pwned by 20x)

Image

The barrel, 1.5" ABS inside 3" ABS, with fiberglass filling the gap

Image

The breach. The barrel extends so that it is flush with the sealing face of the union.

Image

Our target barrel, 1/16" steel walls. The scale isn't quite apparent from this picture, but the barrel is over 8 feet high.

Image

The 3" diameter hole in said target after the impact of a supersonic (~1300 fps) golfball core. The biggest fragments of the projectile after it impacted were roughly 1/4" across.

Image

The GHETTOPOD (tm), with its proud creator Kevin, used to hold the camera for the 20x while we retreated to a safe distance behind 4 feet of stone.

Image

A 64 layer alu. foil burst disk after 20x. I know it should have been thicker, but it was all we had left. With an estimated failure pressure of 1kpsi, it certainly wasn't a pushover, and the total combined thickness of the layers was over 1/8". The fact that there was no apparent detonation at 20x with an OXYGEN/PROPANE mix says something about our current knowledge of combustion, in my opinion.

Enjoy, and for God's sake, watch the video.

EDIT: new, longer video.

[youtube]http://www.youtube.com/watch?v=fHzfkUj0W20[/youtube]
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Last edited by DYI on Mon Jun 23, 2008 5:19 pm, edited 2 times in total.
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Unread postAuthor: Rokmonkey » Mon May 12, 2008 8:52 pm

How come the camera guy is so close and your so far away? :P


Thats awesome though, really sweet cannon.
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Unread postAuthor: OuchProgramme » Mon May 12, 2008 8:52 pm

WOW
WOWOWOWOOW
Amazing lol
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Unread postAuthor: Carlman » Mon May 12, 2008 9:02 pm

wow mate just wow!

the video wouldnt do it justice so how loud is a supersonic GB? lol

and how far back were you for the first 20x shot, i wuda been running :D

noice work
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Unread postAuthor: FordGtMan » Mon May 12, 2008 9:11 pm

can 150 psi fittings take that 20 x mix? if its safe, i feel stupid. i was about to buy 3000 psi rating fittings and pipe for a mini hybrid 10 times smaller than that. :roll:
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Unread postAuthor: LynyrdSkynyrd » Mon May 12, 2008 9:12 pm

wow that was awesome. :shock:

I'd be behind a concrete wall when i first fire something like that.

great job.
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Unread postAuthor: Eddbot » Mon May 12, 2008 9:13 pm

good god, i don't think yelling fire in the hole is enough, you should get an air horn, i'm pretty sure you can hear the gun farther away than you could hear someone yelling
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Unread postAuthor: Lentamentalisk » Mon May 12, 2008 10:08 pm

FordGtMan wrote:can 150 psi fittings take that 20 x mix? if its safe, i feel stupid. i was about to buy 3000 psi rating fittings and pipe for a mini hybrid 10 times smaller than that. :roll:

Not in the least! That is why they had the camera set up on a tripod, and they were behind 4 feet of stone.

F\/<king insane, good job!
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Unread postAuthor: DYI » Mon May 12, 2008 10:11 pm

150 psi rated fittings might be able to take it, but considering that the safety factor is dropped to roughly 1.05 (where 3 is safe, 2 is dubious, and 1.5 is "run like hell"), I wouldn't be anywhere near it when it was set off.

The sound is difficult to describe, really. You have to be there to understand it, but it sounds kind of weird because the noise is somewhat directed until it starts echoing. Apparently, on the first supersonic shot at 8x (before the cameraman cleared the area along with me at 12x), the sound made his ears ring from 20 feet away, almost directly behind the launcher.

The sound of our warnings before the dangerous shots would carry far enough to warn any unlucky bystanders to take cover immediately.

On the only 20x of the day, we were 150 feet away, behind a 4' thick stone piling.
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Unread postAuthor: mark.f » Mon May 12, 2008 10:58 pm

That is very nice. That cannon actually mimicked my friend's "magic dust" cannon, which slides backwards about 10 feet when fired (loaded with lead shot and a good quarter cup or so of "dust"), a good feat for a "magic cannon" which weighs a good 130 pounds due to the lead used in it's construction. :roll:

You can see this "magical device" in time lapse 0:08 - 0:14 of this movie.


But, anyways, good job. Certainly a first: 20x oxy/propane. Hope you can keep pushing the limit. :wink:
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Unread postAuthor: bigbob12345 » Mon May 12, 2008 11:03 pm

wow, someone is addicted to insanity :roll:
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Unread postAuthor: starman » Mon May 12, 2008 11:43 pm

That's very impressive David. You certainly like to push things to the limit. I would've been happy with the supersonic GB at 8x... :wink:
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Unread postAuthor: Lentamentalisk » Tue May 13, 2008 12:00 am

Mount a chrony to the end of the barrel and see how fast its going!
Out of curriosity, how did you figure that 8x was supersonic?
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Unread postAuthor: ammosmoke » Tue May 13, 2008 12:02 am

:shock: :shock: :shock: :shock: ...DROOLS AND SHORTS OUT KEYBOARD.... BZZTZ!! BZzzZT BZZzT!!!!
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Unread postAuthor: kablooie » Tue May 13, 2008 12:29 am

Congratulations, seems as though you have made a monster. Way cool. Supersonic BB's are one thing, but golfballs (at least the core), that's insane.

On another note, I can totally see someone saying "nice gun, but look at my awesome advanced combustion!" and then adding a link to their spray and pray. That's more than a little bit random, I guess big booms get me all worked up.
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