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Monsters of the Potato Gun World (video update 2/3/08)

Built a combustion 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 » Sun Jan 20, 2008 3:25 pm

I'm sorry if I offended anyone with my post, tiredness and rushing to get to work contributed to its poor wording.

How it was childish I have no idea whatsoever. As Mark has shown twice, a gasoline/air mix actually produces less power than the equivalent with propane.

A stoichiometric mix of gasoline and liquid oxygen may have energy densities approaching (or even exceeding) that of dynamite, but other than the previously stated problem of persisting chamber fires, and the slight power disadvantage, using gasoline as a fuel is not a problem, whether you get the mix right or not.

And spudfarm, nobody is 100% safe anywhere, at any time. That is also fact. The aim of building cannons properly is to avoid raising the level of risk too high above ambient.
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Unread postAuthor: SpudFarm » Sun Jan 20, 2008 3:33 pm

thats right you are NEVER 100% safe but making cannons out of plastic is dangerous from the beginig and if a cannon explode it isn`t really a big difference in the boom bechause the pipe will burst on the same pressure.
mabe something like acylene and oxy will build more pressure before the pipe get time to burst not that i know
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Unread postAuthor: DYI » Sun Jan 20, 2008 3:39 pm

Well, I don't make cannons with plastic pipe holding pressure, which is probably the easiest way to increase your safety margins to an acceptable level. If you even worry about your cannon exploding while you're using it, then you don't have a big enough safety margin.

Oxygen/acetylene mixes have very short DDT run up distances, and can quickly end up giving an effect roughly similar to setting of a brick of high explosive in the chamber.
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Unread postAuthor: ALIHISGREAT » Sun Jan 20, 2008 3:44 pm

Uber-noob question alert!!!!! what is DDT?!?
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Unread postAuthor: thespeedycicada » Sun Jan 20, 2008 3:47 pm

Deflagration to detonation transition if it happens in pvc you get well...BIG BOOM!!
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Unread postAuthor: ALIHISGREAT » Sun Jan 20, 2008 3:51 pm

thespeedycicada wrote:Deflagration to detonation transition if it happens in pvc you get well...BIG BOOM!!


doesn't sound good (for the pvc) but what about in metal combustions?
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Unread postAuthor: thespeedycicada » Sun Jan 20, 2008 3:53 pm

It is ok possibly 1 or 2 times but it puts alot of stress on the pipe so its not good in either case.
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Unread postAuthor: rcman50166 » Sun Jan 20, 2008 3:54 pm

noob of noobs wrote:Appologies for my doubt about gasoline. My parents are still concerned that I'm moving towards propane, and I guess some of that paranoia is rubbing off. :oops:
Regardless of it's fueling, they're really nice cannons. Got any damage pics?



I don't have damage pics but if you look at the video it's clear the damage the cannon can do.
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Unread postAuthor: jrrdw » Sun Jan 20, 2008 3:57 pm

What was it you shot at the trash can? A frozen soda bottle?

DYI, it's childish to discord safety advice at any level. I think everyone can honestly agree on that. To say theres no logic in it? Thats just illogical.

Where is Captain Spoc when we need him! :P
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Unread postAuthor: rcman50166 » Sun Jan 20, 2008 5:05 pm

jrrdw wrote:What was it you shot at the trash can? A frozen soda bottle?

DYI, it's childish to discord safety advice at any level. I think everyone can honestly agree on that. To say theres no logic in it? Thats just illogical.

Where is Captain Spoc when we need him! :P


The particular bottle I shot at the garbage can was liquid water, but today I found a bottle I left outside that was frozen so I shot it and it did more damage than thawed bottles. It was also reusable. :idea:
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Unread postAuthor: rcman50166 » Sun Jan 20, 2008 5:08 pm

My cannon is being tested in the winter remember. It is at it's weakest stage in this case. Because of this I am confident with the "General's" ability to contain the blast is high, especially during the warmer seasons. Would it make everyone happier if I put a duct tape "safety glass" feature on the "General"? I've tested the idea with great results. The grenade-in-the-face explosion everyone is wondering about is personally proven with PVC and the duct tape holds back shards while letting pressure to escape. It is a feature on the "Sarge". As shown in this picture.
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Unread postAuthor: noob of noobs » Sun Jan 20, 2008 5:22 pm

Whoa... Looks a lot bigger in that picture... :shock:
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Unread postAuthor: pizlo » Sun Jan 20, 2008 5:40 pm

Hmm I would say all of this arguing was childish, but I thinks its great. different people had different opinions, and everyone has a right to there own opinion. Me and my friends argue alot, but its the only way to keep checks and balances in an unorganized mini society.
Personally I don't really go for huge ass guns, or gasoline, but if that what your doing, just keep focused when you do it, and no drinking for you! I would use gasoline as propellant in my cardboard combustion, because I build bonfires in my backyard so on the off chance that is catches on fire I'm not going to freak out, also I have no fancy crap to prove this but it just seems to me that why would expanding gass blow apart a material when it can push an extremely light pingpong ball out of a tube?
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Unread postAuthor: SpudFarm » Sun Jan 20, 2008 5:47 pm

yeah its really looks bigger in ths picture :D that`s a nice thing tho
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Unread postAuthor: jrrdw » Sun Jan 20, 2008 6:40 pm

We don't have arguments around here, we dicuss. Anyway you look at it, that poor poor trash can has seen better days! :shock: :P :P

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