SpudFiles

I want to fire my combustion cannon without loading it so it is safe to use in a small area.
I was wondering if anyone who has done something similar recommends that I use wadding (paper towels or something) to ensure it works properly. Is there any risk of paper wading catching fire?

Well if you want to try a dry-fire I suggest you use some kind of wadding, otherwise the fuel tends to flow out the barrel and just go pfft. Paper wadding not reccomended, but that just depends on what your fuel is. I suggest using on old dishrag or somethign similar. It's less likely to catch fire and if it gets scorched it's no big deal.

i use wood plugs with a plastic bag to slow it down when i fire in my backyard

You can use a burst disc to hold the fuel in...

noname wrote:You can use a burst disc to hold the fuel in...

That's not really an option for some cannons.

wet toilet paper makes a nice seal

I'm too lazy to use a burst dist right now, but that is a great idea because my cannon's barrel just so happens to have one of those sch 80 unions on it.
I ran my cannons specifications through a calculator, and the estimated propane combustion pressure peaks around 120-130 psi. I don't need a very strong burst disk at all, I would actually prefer it to fail at a low pressure since all I need it for is holding fuel.
Does anyone out there have recommendations for burst disk materials that will give out between 10-30 psi

lol, um, i dont want to do math now, but i calculated for my combustion there will be like .578 psi of propane in the chamber, so i would use like a piece of computer paper, or wax paper

Wax paper seems like it should work great.
Burst disks in a combustion launcher, the thought never occurred to me even when I have the correct type of union for mounting one. Thanks for all the suggestions guys.

just wondering, why is there a union on your combustion launcher?

So I can remove/exchange the barrel.

A burst disc can go in the male/female threaded joint of a detachable barrel, that's what I use. It won't get a perfect seal, but it's enough to hold in the fuel.

I didn't use a male adapter/ female adapter combo like normal. I used an actual union, the three piece kind made out of SCH 80 PVC.
I tested use of a burst disk made of wax paper about a half hour ago, and it worked great! It was loud. All this burst disk talk has made me want to make a hybrid, but I've put too much money into cannons in the past few weeks. I gotta stop myself.

glad to hear it worked
um, im in the same predicament, i need a job

If you still want to use a wadding a moist hand towel works great, or one of those foam water ball toy do too.