13 replies to this topic

[Petrie]

The other day I was looking up how to make a spud gun on howstuffworks.com and figured I could use those same concepts to make a combustion powered. (kinda like boltsnipers combustion gun)

The cb-1 is baisicaly a 6 inch piece of 1/2" pvc with one end plugged by a rubber stopper with a butan valve and a grill lighter epoxyed on. I also put on a coupler and some 19/32" brass to shoot micros.

the ranges are about 65-70 feet that i measured with a 25' tape measure end to end

real bad picture I know


The major draw-back is that it takes about 25-30 minutes for the fumes to accumulate. That is way too slow of a ROF.I have tried all kinds of fuel but they all seem to take a while to get to the point where it can be lit.
any suggestions?

Edited by Petrie, 26 April 2006 - 09:31 PM.

[WratH]

If it takes that long to be able to light it, then it is just condensing on the walls of the chamber, therefor you are using WAAAYYYY too much fuel. Try something like a 1/4 second spray for something that small, then wave it in the air once or twice.

[Carbon]

This is pretty cool. If it turns out the butane lighter is flowing a little slow, it might be possible to keep the sparker from the lighter, and provide fuel from an actual can of butane.

[Pineapple]

Looks like a little grenade with a barrel (or in this case, rocket) on the end.

The guys above have it down. A second or two, tops, with that size combustion chamber.

And PLEASE, be careful. You guys know how much I'm against combustibles for Nerfing. But that's my opinion.



-Piney-

[fobpawwor]

Ive tried these kind of things before, and you need a very small chamber. Your chamber seems pretty big so it will take long to fill and it wastes a lot of butane. Ya, but 70 feet for a butane powered rockect, not bad.

[GeneralPrimevil]

I see the brass. I take it you don't like Venturi Burning?

Combustion seriously has its ways with Nerf. I mean, a good sized chamber, with 1" FBR Stefans, using a powerful chamber fan and propane? Easily,several shots within a minute can be acheived.

There's a problem with the fan melting (Proton Pack made by someone on spudtech.com/forums), but big deal. There are metal fans pushing 60+ cfm out there.

Anyway, nice work. The problem with small chambers, as mentioned previously, is that the mix of air:fuel is even more important than larger counterparts.

[davidbowie]

Ive tried these kind of things before, and you need a very small chamber. Your chamber seems pretty big so it will take long to fill and it wastes a lot of butane. Ya, but 70 feet for a butane powered rockect, not bad.

A few inches of 1/2" pvc is a TINY chamber. If anything, it should be a lot bigger. It's hard to get a proper mix in something that small. It's not going to take more than a second to fill to a proper mix, and it's not going to eat up butane.

One thing you could try for getting a better fuel mix is to fuel it from a propane torch with the venturi tip attached. It won't be perfect, but it will help.

Also, get rid of that rubber stopper. Immediately.

Here's what I think you should do:

Use a much bigger chamber, because it leaves more wiggle room in the fuel mix. You should have a bigger barrel to use the extra power.

Cap the back end with a check valve. Make sure you install it in the right direction. The flow end should be pointing into the chamber. This way, you can vent the gun by blowing into the check valve, or you could install a battery powered blower.

Use a propane meter.

I'm pretty bad at explaining things, and I'm not all that into combustions, but you should be able to answer most of your questions by reading the stickies and posts at the Spudtech.com forums.

This would make a pretty cool small rifle, with a remote propane tank.

[willielax101]

I found that spraying a little hairspray works best for me. but even if it doesnt take 25 min its like a nerf musket . All it can do is shoot 70 ft and has an assload of a reload time. Be careful with that thing it can explode and that isnt fun.

[LastManAlive]

For combustion tanks, use hairspray or blackpowder. But by far not butane, it doesn't work like hairspray. I find AquaNet level 3 WITH fragrance to work the best over suave etc.

[fobpawwor]

Haha, nice. Ya it has to have the fragrences. Do bigger tanks really work? Because Ive found it more efficient with smaller tanks.

[The Inventor Guy]

For combustion tanks, use hairspray or blackpowder. But by far not butane, it doesn't work like hairspray. I find AquaNet level 3 WITH fragrance to work the best over suave etc.

Nice one, dickless.
Hairspray pretty much IS Butane. It's the butane in the hairspray that does the burning.

I would suggest NOT Blackpowder because it burns way too hot for this kind of use. If you are going to use combustion, which I have nothing against, then use either Propane or Butane.
Propane is a very clean and efficent fuel. When 1 part of Propane is mixed with 5 parts of oxygen, it burns and shoots great. The reason why it is a clean fuel, is because it's by-products are Carbon Dioxide and Hydrogen Monoxide. CO2 and Water. Propane is the gas in your house like hot water, oven and stove. It's also in the barbecue gas bottles you buy at the servo or hardware store. Or most other places. (this is also what the Tippmann C3 uses)
Butane is a good option because it's easy to find as it's in just about every cosmetic and fragrant aerosol. Body sprays, hair sprays - well, just about everything anyway.

Once again, I would solely advise AGAINST the use of Blackpowder is this kind of use - it's just way too hot.
Propane or butane all the way. And also, you need to make sure you're getting enough oxygen into the chamber. Perhaps you could try this: Spray some of the fuel in to a bike pump tube, then place the piston rod back into the tube and press it down - this, theoretically, should push out the fuel and enough oxygen for combustion. In case you didn't catch it, I mean attaching the pump tube to the chamber, so you pump the fuel/air into the chamber, and I don't mean like a hybrid.

-Tidge.

-Tidge.

[WratH]

You could probably get away with a small shot of ether, too. If it doesn't fire the first time, open the cap and wave it around for a bit then put the cap back on and try to fire again.

[Petrie]

thanks alot you all have been real helpful especially the inventor guy.

[notorious oxide]

I have made 4 mini combustion guns which i have used deodorant as fuel for. Their chamber sizes are (in order of construction date) 25mm pvc x 8", 32mm pvc x 12", 40mm pvc x 8", and 25mm pvc x 4". I used 2 quick presses of lynx africa (works better for me over many other flavors of lynx)for all of them and the 4" uses 1 quick press and a small wave in the air. The 4" is the only one i have made for shooting darts, never got around to range testing but for its size it was great. The rest all use 6.5mm x 700mm barrels. I have tried using butane and propane but i found them way too inconsistent, which would require a lot of getting used to or an injection system. I hope my babbling helped a bit.

Edited by notorious_oxide, 03 May 2006 - 02:54 AM.