Want to build first combustion cannon

[vng21092]

Is PVC strong enough to safely handle the expansion of the gas/fuel when ignited? Also, can the chamber be the same size pipe as the barrel as long as the volume of the chamber is larger/equal to the barrel volume?

[jackssmirkingrevenge]

Is PVC strong enough to safely handle the expansion of the gas/fuel when ignited?

If made sensibly, yes. Avoid thin walled pipe and fittings and make sure your components are correctly joined.

Also, can the chamber be the same size pipe as the barrel as long as the volume of the chamber is larger/equal to the barrel volume?

Yup, it doesn't even need to be equal - even half the barrel volume will do.

This is with the chamber volume at around 60% of the barrel volume:

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Make sure you fuel it correctly, I recommend syringes: http://www.spudfiles.com/how-to-databas ... 22301.html

[vng21092]

If 60 percent of the barrel volume is ok, then whats the point of some people going to 150 percent? (1.5:1) Just for power? And does primer really make that much of a difference? Can I just use PVC cement by itself? Also, because the gas/fuels can come from different sources, I'd assume they have different values when referring to combustion/expansion volume, how would I know how much to use with each fuel? I'm planning on using propane, is there like a method to find out?

[jackssmirkingrevenge]

If 60 percent of the barrel volume is ok, then whats the point of some people going to 150 percent? (1.5:1) Just for power?

That and no love for efficiency

And does primer really make that much of a difference? Can I just use PVC cement by itself?

You can try, but don't come cryin' when the thing asplodes in yer face.

Also, because the gas/fuels can come from different sources, I'd assume they have different values when referring to combustion/expansion volume, how would I know how much to use with each fuel? I'm planning on using propane, is there like a method to find out?

C'est tout dans le wiki: http://www.spudfiles.com/spud_wiki/inde ... n_Spudguns

[vng21092]

You can try, but don't come cryin' when the thing asplodes in yer face.

... Would that really happen? I'm concerned now... I thought primer just softens the PVC so the cement would bond it better, would the joint be THAT much stronger with primer? O_o

[jackssmirkingrevenge]

Why take the risk? Follow the manufacturer's instructions

[vng21092]

only problem is... I already built the chamber without the primer, it's relatively small, 1 1/4'' x 6'', does the small size help at all? Smaller sized pipes are suppose to handle higher pressures right?

[jackssmirkingrevenge]

I'm not saying it will explode, but an unprimed joint is weaker than a primed one. You might want to try it out from behind cover for the first could of times, with heavy projectiles to force pressure.