SpudFiles

As far as I know I'm the first to think of this, but if it isn't well what would you search for?

The idea is the piston is about 1/4 inch to small for the pipe and upon firing the piston seals against an o ring when the combustion is done the spring pushes the piston back to its "open state" since the piston is too small it allows for venting while not operating any valves.

I realize becuase of the spring the piston won't be able to seal on the o ring so the o ring should go on the end of the 3-1.5 inch reducer.

Why do this, couldn't you use a ball valve?
I'm designing a combustion gun that can be filled vented and fired from a distance. I've seen some cannons that use check valves and a mattress inflater but I plan to use this away from an outlet and I already need batteries for operating the propane metering valves.


If you have any questions, comments or constructive criticisms feel free to share.

looks alright.

you should think of making a prototype (smaller scale so you don't end up wasting too much good pvc if it doesn't work).

but yeah, nice idea. I have the strangest feeling i've seen something like this before but i can't quite put my finger on it.

ah well, what ever. good work!

Looks like the piston and spring are going to just flop around in there. Do you have a fan inside drawing air in? Also how do I close the vent before fueling? And it looks like you are depending on combustion to close the vent only briefly then open again in its unpredictable floppy state.

Maybe I'm missing something...

Have you considered a reed valve?

Something like that used in a pulse jet.

http://www.airtoi.com/pulse.htm

A fan should be able to open it for venting, and it would close for fueling as soon as you shut the fan off.

A separate fan would be required for mixing.

starman wrote:Looks like the piston and spring are going to just flop around in there. Do you have a fan inside drawing air in? Also how do I close the vent before fueling? And it looks like you are depending on combustion to close the vent only briefly then open again in its unpredictable floppy state.

Maybe I'm missing something...

There will probably be a two guide wires so the piston goes back evenly. When I build the prototype I'll try it with a loose piston and one with some equalization holes. There will be a fan in there as well I just drew a cannon around it so you guys see where it fits in.

@gippeto
Why would I need two fans? I could just reverse the current so it blows out and can suck in.

Why would I need two fans? I could just reverse the current so it blows out and can suck in.

A PC fan will not work if you reverse the polarity.
Most burshless motors wont. And you need brushless motors to prevent sparking.

use the reed valve of a crosser