EDIT: sorry, I mean 50mm long, not 80

This is just weird. I can't get ignition with my little spud gun.

The chamber is a 1" iron pipe. I am using a camera flash for ignition, after having tried piezos without success. The spark from my camera is very solid.

I am using butane, but I have also tried a mix of combustible gases.

Any ...

I'm using propane.

Yeah, doesn't work.

There are better ways of doing it, but this is just so much simpler.

I just need to make the grooves for the plug, and the only downside is that I might have to wait a few seconds. It takes the glowplug about a second to get to full heat.

I will go ahead and try it out. I'll report any results ...

No, the spark gap was small.

I don't mind the delay, as long as it actually fires consistently.

I am having trouble igniting the gas with piezos. They are really unreliable and frustrating. (is this normal?)

I have been thinking of using a tiny glow plug from an RC boat, by scewing it into the back of my chamber's pipe cap.

When attached to the power source, the coil of the glow plug starts ...

That could be a cause of the damage to your fan,as the flame front pressure wave moves towards the barrel,in short.Your fan has pressure build up on one side and damaging it.

How to fix this?Move the ignition point to in front of the fan and have the fan as far back in your chamber as you can ...

Yes, the ignition was about 1cm behind the fan.

You really could have put a longer barrel on this to gain more power.
Whats with the quick connect on the back, venting? That piezo will only last about 2 seconds- how about using a bbq piezo and moving the spark gap to the middle of the chamber.
I wouldn't say it is the least elegant cannon ...

You just used a proper flimsy fan, maybe breaking the corners off to make it fit made some hairline cracks.
I seriously doubt it. The plastic was incredibly tough. And I didn't break pieces off it, I carefully sawed the extra flaps off the corners (which had nothing to do with the places at which ...

It cost less than 25 euros to make, and took about 30 mins to build (and 12 hours for the glue to dry). It works, and it's pretty fun. Needs a new chamber fan though.

Have you guys ever had trouble with chamber fans breaking? After a few shots a corner segment of my fan broke off.

http://img208.imageshack.us/img208/8775/kuva004rt9.jpg

Is this normal? Do you guys use metallic fans or something? And how do you guys mount the fan in place? I shaved the corners ...

My chamber fan's frame broke at two places...

Oh wow, I should really pay more attention... I've been using polypropylene all along. Great stuff, apparently, and cold resistant, which is great up here in Finland