SpudFiles

i was wondering if anyone knew if there was a certein c:b ratio that the barrel is too small and the chamber too big that it destroys the cannon?

idk why i just kinda thought of it.

Even if you made a chamber without a barrel (but still having a barrel opening) you still wouldn't manage to destroy it... Still, i suppose it is conceivable that a completely sealed chamber would rupture, so I guess what you should be asking is for a chamber volume:barrel diameter ratio.

i think what he is saying is is it possible to have, say, a 8" chamber, and a hypodermic needle for the barrel, even if the barrel was 200 feet long.

jackssmirkingrevenge wrote:Even if you made a chamber without a barrel (but still having a barrel opening) you still wouldn't manage to destroy it... Still, i suppose it is conceivable that a completely sealed chamber would rupture, so I guess what you should be asking is for a chamber volume:barrel diameter ratio.

yea basicly, liek what is the ratio that just gets bye without exploding.

It's generally accepted that a decently rated chamber could take the force of a fully contained propane combustion, and possibly MAPP gas as well.

So in short: With a good cannon, there is no maximum ratio.

Well, you could make a chamber that wouldn't hold up to the pressure. Since the volume of a cylinder increases much faster than the inner surface area when you increase the size of the chamber, the pressure exerted by the force of the combustion on each square inch increases. I'm not sure how quickly, but you could reach a size when the pressure became too great.

Maximum theoretical pressure is independent of chamber size. If your pipe is rated to 100 psi or greater, you shouldn't need to worry.

wasn't worryin just wanted to knwo lol, but thanks, randome stuff come and goes in my head :happy2:

paaiyan wrote:Well, you could make a chamber that wouldn't hold up to the pressure. Since the volume of a cylinder increases much faster than the inner surface area when you increase the size of the chamber, the pressure exerted by the force of the combustion on each square inch increases. I'm not sure how quickly, but you could reach a size when the pressure became too great.

Paaiyan...
I thought you were in college? Where do you come up with such dumbass statements?

The peak adiabatic pressure in a combustion chamber is independent of the volume of the chamber. (Like freefall said)

The peak combustion pressure of stoichiometric propane in air is about 120 PSIG. In the real world, the peak pressure is less due to heat loss and other affects.

Doesn't matter if the chamber is 2in³ or 2,000,000in ³, the peak pressure is the same (again, neglecting heat loss).

I don't think you need to be this harsh on paaiyan

It wasn't that stupid a statement - the surface area of a container and the volume is a non-linear relationship. And higher diameter pipes have lower pressure ratings.

Ok, it's an incorrect conclusion, but it's logical - none the same.

It's the same as the gravity issue. Historically, heavier objects were thought to fall faster, and lighter ones slower. You could feel a bigger force pulling down on a heavy object, and the harder you pulled on something, the faster it moved... so it was logical (but wrong. However they didn't have the benefit of Newton's 2nd law).

It doesn't make our ancestors stupid, just not in full possession of the facts.

I feel like a complete moron now. I know exactly what I did, but I have no earthly idea why I did it. I was doing some homework at the time and mixed some things up, I declare my earlier statement to be null and void, as well as stupid beyond words, please ignore it.

It's okay paaiyan, we still adore that hamster in your avatar with a pancake on its head.
Back to the topic on hand, since its only a pressure spike, you can have a chamber with no holes or anything and still contain it.

GGAAHH!! Is a bunny. Not a hamster.