SpudFiles

Today i just finished building my big ass metal pistol. It looked like something out of a sci fi movie, plus it weigh around 3lbs......

I would post a picture but i lost my camera so i will have to looked for it.


I am having some trouble tho, i already got the spark to jump in the metal chamber just fine with a flyback cable but i hit a really weird problem.

My gun is built in the following order.

1in cap, 5in 1in pipe, 1in to 3/4in reducer, 2in 3/4in pipe, 3/4in 1/2in reducer, 2in 1/2in pipe, 1/2in to 1/4in reducer, 6in 1/4 barrel.

It is a really long pistol at around 2 feet.

Here is the problem

It doesn't have any power at all, it barley shot a spit ball 10 feet. (It sounds like a poof)

I have tried all types of fuel from propane, butane, hairspray and others but none seem to have any effect.

Is it a problem with my chamber or is it my sparker(Its a lighter sparker behind a trigger that makes a small spark 3mm)

Any ideas why this isnt working????????????????????

Wait, did you really mean that the barrel is only 6" long? Because if it is, you're not going to get any power out of it without several thousand psi.

Try it at 30x. If you survive, you'll notice that power has improved to the point that it's almost as powerful as a small pellet gun.

Well DYI is completely right
make the barrel something like 24in long and I guarrentee it will work

No problem, i can get the barrel up to 24in but i will have to buy 3 more 6in 1/4in pipes and 2x1/4in couples but other than that it should be fine.

I was almost at the point of mixing oxygen in with the mix because this is a metal chamber that can take a lot more punishment that pvc but that could be dangerous.

You can't get larger nipples? Most lengths of steel pipe are threaded on both ends. It would be much cheaper, practical, and more effective is the barrel is one piece.

Also, 1 in is a pretty small diameter chamber. I've noticed that when you decrease the diameter, the power seems to go with it.

But increasing the barrel length should at least give it some decent range.

Because the smaller the diameter, the less flow there is to the barrel.

Blitz wrote:Because the smaller the diameter, the less flow there is to the valve.

What valve? Did you mean flow through the barrel?

Blitz wrote:Because the smaller the diameter, the less flow there is to the valve.

WRONG!
Its combustion matey!

The smaller the chamber diameter, the longer it has to be for a specified volume.
The longer the chamber is, the more the flamefront has to travel, thus the more ineffective your combustion will occur.
The optimal chamber shape is a spere with the ignition in the middle or in cillindric shapes, about the same diameter as length.

Gah, yes I meant barrel. Edited.

psycix wrote:Assuming a single ignition point, the optimal chamber shape is a spere with the ignition in the middle or in cillindric shapes, about the same diameter as length.

I fixed your post.

Did you try different size spark gaps along with different amounts of fuel?

D_Hall wrote:

psycix wrote:Assuming a single ignition point, the optimal chamber shape is a spere with the ignition in the middle or in cillindric shapes, about the same diameter as length.

I fixed your post.

Agree! Thanks