Help with Mini-Combustion

PyroManiac.666 · Thu Feb 23, 2006 3:57 am

HEY ALL, I have a question for someone experienced here, SORRY I'M A NOOB, but I wont be for long. Anyway I just got started with this spud gun thing and I figured I'd start small before I go BIG, So heres the question. I made a Mini-Combustion cannon as seen in attached pics, it is a prototype just built in like an hour and easily disassembled for tweaking, but for some reason it will not ignite the fuel. For fuel I use butane, as seen in one pic I inserted a butane fill valve in the cap of the bottle for easy fueling

, but for some reason I cant get the fuel to ignite. I used a normal lighter Piezo ignitor and it jumps nice 1/4" sparks so I doubt it's that, and when the cap is off it will ignite sometimes so I figure its not getting oxygen, what could I do to remedy this so I can get it to fire before I build a sturdier one? Different fuel maybe? ANY comments are greatly appreciated!

Rambo · Thu Feb 23, 2006 4:15 am

The concentration of butan must be around 5% not 130%.You may use metanlol or ethil alkohol.A few drops.After fireing you must vent the chamber.

PyroManiac.666 · Thu Feb 23, 2006 4:53 am

OK what do u mean 130% i'm not retarded. when i use the butane i barely let any in, and i always vent the chamber by blowing air thru the back out the barrel to get fresh air in, but on another note, i HAVE gotten it to fire very reliably with very small amounts of CaC2 (AKA Calcium Carbide) and water (CaC2 reacts with water to form ACETYLENE GAS), similar to a toy bangsite cannon from the old days, and boy does it make a nice flash and flame out the barrel!!

I may post a pic or vid of it firing if i can.

Urban Ninja · Thu Feb 23, 2006 6:58 am

I just use a disposable ligther with a hoseon, put it in there and let 5 secs off. If not use cologne, although if you use liquid fuels you will have to clean it after use, the residue is a bi#*! after a while.

Rambo · Thu Feb 23, 2006 12:34 pm

You may use H2 instead of H2C2.It is easyer to make.Or petrol and O2 but with safty glasses on.The air from your month isn't wery O2 rich.

PyroManiac.666 · Thu Feb 23, 2006 5:06 pm

How is hydrogen easier to make than acetylene when all I have to to is drop a tiny chunk of CaC2 into the chamber and add a few ml of water? I can get a few shots off b4 I need to add more because after it fires it seems to suck air back into the chamber from the barrel so theres no venting needed.

And how do YOU make hydrogen other than the electrolysis method, and how do you store it? I sure wouldn't want to. I know adding water into the chamber is a little messy and it needs to be cleaned but hell, it takes like 10 seconds and I can get many shots off b4 cleaning.

cardinals08 · Thu Feb 23, 2006 5:26 pm

Hey dude, thats an awesome looking mini. I would be careful with that acetylene, that sh1t is very dangerous. (as if you didnt know that already). The Calcium Carbide doesnt seem to forgiving either. That would suck to accidentally swallow some. If I were you I would add some type of magazine and some kind of continuous ignition to make an auto. You say it doesnt require venting and if it truly doesnt this would easily be done. Again, nice work on the mini, I like it.

PyroManiac.666 · Thu Feb 23, 2006 6:10 pm

Hey I figured I'd post a pic of it firing, not much but you get the idea, i was able to pull of 5 consecutive shots, (3 good ones) without venting b4 the CaC2 was used up. Not too shabby i think!

cardinals08 · Thu Feb 23, 2006 6:24 pm

sweet dude, hey, if you dont mind me asking, what kind of bottle did you use for the chamber? I cant find any good ones to use, all I have found are pill bottles wich work like crap. Also, where do you get your CaC2 from?

PyroManiac.666 · Thu Feb 23, 2006 7:09 pm

Actually the bottle I used was from a hair dye kit, Revlon to be exact $3-$4, you can either actually use the kit up and save the bottle or find one in the trash like I did. If I see a small bottle that I can put to use, I keep it. I collect chemicals and things from different suppliers online that I use to do various experiments with, and small bottles like that are perfect for keeping small samples from my larger stock. The carbide I bought was from eBay, you can get about 11oz for 12.50 delivered, its cheap, just search for it there or go to the source at http://www.calcium-carbide.com/ And be very careful with it, a little goes a long way!

P.S. - Someone tell me why this is happening....when I try to use butane from a canister, it wont ignite, but when done from a lighter it will. I also cant get Axe to work properly, anyone have an explanation?

Rambo · Fri Feb 24, 2006 3:13 am

The acetylene make a higher tempreture then the butane and axe.It also lights in lower tempretures=> it don't need to be in the right proportion.I think that this sucking effekt wich I well know too, suks.This was a very nice gun months ago beafuore ....It was compleatly destroed..

PyroManiac.666 · Fri Feb 24, 2006 3:57 am

OK, I had to try this out. I slightly modded my mini by replacing the .177 caliber barrel and adding a 36" .40 caliber blowgun barrel. To my surprise not only did it launch the needle dart incredibly well, it buried it 3/4" into SOLID pine from about 5 feet. I was amazed as I can barely get one to go in 1/4" with lung power. I cant wait to try it with paintballs.

I attached a pic showing the new addition. SWEET

P.S. I used cologne for fuel and the chamber volume is about 4.6 CI.