SpudFiles

I was wondering weather a 3" cleanout for a combustion cannon has to be pressure tested because I can't find them anywhere and weather 3" to 1.5" reducers have to be pressure rated if i buy them from a place that uses them on a vacuum pump
thanks
Dave

I used 4" cleanouts on my first two cannons. One failed after a long time, and it was probably because the threads got gummed up and wouldn't screw in more than about 2.5 turns anymore.

The best answer is probably this:

Combustion guns, burning aerosol spray or even metered propane, will produce a MAX of around 85 psi. Cleanout caps are not pressure rated and are not designed to take that pressure.
However, the hot, expanding gases of combustion will follow the path of least resistance - as long as it requires less energy to push the projectile down the barrel, than to blow off the cleanout cap, you should be fine.
There's no guarantee that it won't eventually fail, though.
Theoretically a smaller cleanout will be safer, since it has less surface area for forces to be exerted on.

Consider mounting a 1.5" - 2" ball valve on the back of your gun instead of a clean-out. This allows you to inject fuel (unless you're using metered propane), vent fumes between shots, etc... without having to unscrew a cleanout every time.

Generally accepted wizdom on this forum is, pressure rated parts are a MUST for pneumatics, and a very good idea (but not absolutely required) for combustions.
I've built all of my combustions out of non-pressure-rated ABS, and with the exceptions of a cleanout cap failure and a barrel separating from it's threaded adapter, I've never had any problems with them. In fact, I personally feel safer using ABS for a combustion than PVC, because if ABS does fail, it's much less likely to produce shrapnel. It's also more shock-tolerant (smack a piece of ABS and a piece of PVC with a hammer and you'll see what I mean).

Hope that helps you.

Peace,
Pete Zaria.

so if I have a 2" pvc ball valve going to a 2" chamber 1.5 foot long thaen going to a reducer to a 1" barrel

Would that work?

Dave

Yep, that'd work just fine - in fact, you don't even need a valve that big.

My combustion gun has a 4" x 20" chamber and a 1.5" x 7 ft barrel. I use a 1.5" ball valve to vent the chamber.

Going to 3" for your chamber will make it more powerful and easier to work with - you can get a fan in 3" pipe much easier than in 2", etc...

By the way, if you didnt know, most of us put a computer fan or a camping fan inside the chamber of our combustions to mix the fuel and air together properly, and to vent out the exhaust gases between shots.

Peace,
Pete Zaria.

I always fill cleanout plugs with something to add a bit of strength before I use them. Even hot glue will help, but something like bondo or epoxy is better.
Cleanout caps do fail more than any other dwv part that I've seen so far. Normally it isn't a big deal, but if you want to shoulder fire a combustion it's a good idea to re-enforce them with something.

I have found a ball valve where a 3" pipe sleaves over it and then on the other end, a 2" pipe goes into it. this would let me have a 3" chamber but still have a 2" all valve which would stop me from fussing around with couplers and stuff which is increadibly hard to get in the UK

This is the valvehttp://www.koi-fish.co.uk/acatalog/pond_valves.html it is called 2" / 3" Ball Valve

Tell me if this will work
Thanks
Dave

@Dave,

That thing looks very clever and conveniant but no pressure rating or even material is listed (doesn't tell us if its PVC, ABS, PET, nylon, or anything else...). I'd AT LEAST find out what it's made out of before I bought it. Call them maybe?

Peace,
Pete Zaria.

That valve is awesome! Yeah, it should work just fine.

do u think you could help me find a valve from the UK

Dave





I have found another 1 it is on the same link but it is called 1.5" / 50mm Ball Valve It is ABS and it is 1.5" which is what was you said I shoud have but now I need to find Reducers for it.

Wot do u think?

http://www.aquaflowuk.com/2_and_3_Ball_Valve/25/157

what do u think of this

http://www.aquaflowuk.com/2_and_3_Ball_Valve/25/157

what do u think of this

Dave,

Look on Pipestock

Michael

It pvc, it says solvent weld.

so wht do all of you think of the ball valve in my last post?

It says that it is solvent weld so it must be pvc.

just incase it is abs, I will get a solvent weld that will glue abs and pvc.

Dave

Edit: Will the koi ball valves hold upto the pressure?
they seem really thick to me.

noo don't get that type of glue its not meant for pressure.
The ball valve is not abs.
Its Pvc, don't worry.

OK
so i get the ball valve, glue it in with pvc cement

I get that

will this work?

4ft of 1.5" pvc (barrel) going to a coupler (1.5"-3") 1.5ft of 3" (chamber) Going to a 2" ball valve but a 3" pipe can slide over it, a bbq ignitor as the ignition, and the ball valve to open and spray in the fuel (rightguard) Which would mean that I don't have to mess around with dvw clean-outs