SpudFiles

I have been mulling around with an idea for a combustion cartridge. My inspiration came from JSR's design, but I didn't quite like his ring idea. Instead, I came up with a design that incorporates a spark strip-like design.

In the front of the cartridge is a piece of aluminum tape to act as a burst disk and make sure the gas won't escape. This design does not provide a location to fill the gas in the chamber for I am unsure where to place it (a good location suggestion would be appreciated).

My question (short of will it work) is: if I have the two connections on the screw heads, will the electricity travel through both gaps, or just the closest one?

EDIT: I realized that because these are wired in parallel, this design won't work. I have remade my design, as seen below.

Thank you for any help you can give.

The fill location will depend entirely on the breech design on your cannon. I would be inclined to mount it in the rear and move the exterior spark gap contact to somewhere on the outer diameter of the "chamber".

Can I assume the blue box represents your projectile?

Yes, spark gaps must run in series with each other if driven by the same spark source. Therefore the first (top) drawing is correct. I would just delete the bottom drawing to help avoid confusion.

You probably don't need any type of a fill port for the propane.

1. Take a cartridge.
2. From the front of the open shell inject the correct amount of fuel into the back using a small ID piece of hose attached to a syringe or meter.
3. Drop the ammo in the top of the shell.
4. Seal the top of the shell with tape or something similar.

Propane doesn't diffuse all that fast. You should be able to work with the open shell for at least several seconds before the fuel can escape. Inject the fuel into the bottom of the shell and it'll stay there for more than long enough to get the round and seal in place.

I fill up my PB combustion with the chamber wide open, It works fine.

Looks like a good design. Im exited for the results!

If you really want a fill port you might be able to just drill a very small hole (perhaps 1/16" D or smaller) and inject the fuel with a needle. Cover the hole with a piece of tape. The tape wouldn't have to be all that strong to withstand the force of firing.

jimmy101 wrote:If you really want a fill port you might be able to just drill a very small hole (perhaps 1/16" D or smaller) and inject the fuel with a needle. Cover the hole with a piece of tape. The tape wouldn't have to be all that strong to withstand the force of firing.

You could always tap a small hole, 8-32 threads I think they are, and screw a computer case thumb screw in there to close it up. Just twist the screw out to refuel then back on to close.

starman wrote: You could always tap a small hole, 8-32 threads I think they are, and screw a computer case thumb screw in there to close it up. Just twist the screw out to refuel then back on to close.

I think this would work the best. Either that or I just take a brass plug to fill up a hole.

Also, in regards to the picture versions. My version 2 of the design was so bad, I decided to omit it all together.

mega_swordman wrote:Also, in regards to the picture versions. My version 2 of the design was so bad, I decided to omit it all together.

Good man...

Agreed with the above in that you can fill through the mouth of the cartridge and cap it with the projectile, that's what I did with mine.

Also, why the flow restriction?

Also, why the flow restriction?

Probably to make sure the projectile does not fall down in the chamber.
This could be achieved with a simple bolt though.

psycix wrote:

Also, why the flow restriction?

Probably to make sure the projectile does not fall down in the chamber.
This could be achieved with a simple bolt though.

Correct. And that does sound much more practical now that I think about it

I apologize in advance for the double post, but I felt as though this would make more sense if I gave it its own message.

I have finalized the combustion cartridge idea. Your advice was good and I implemented it within the new design. Also, I am going to "borrow" some ideas in this project. Namely, the spark strip from starman's "Tripe Thunder". Also, I decided against just spraying in the front because I wanted to have it be a bit more exact. Instead, the back has a brass plug that will be threaded into another "borrowed" idea, homedepotpro's propane meter.

Hopefully, construction of this project will commence soon. Thanks again.

mega_swordman wrote:Instead, the back has a brass plug that will be threaded into another "borrowed" idea, homedepotpro's propane meter.

If you're going to use HomeDepotPro's injector, why don't you install a female quick connect to receive it instead of the brass plug? It self seals and is super easy to connect...

I like your decisions here.... 8) Of course I am a little biased...

Some points you might want to consider:

- Given that combustions need a roughly 1:1 ratio, cartridge the same diameter as barrel = very short barrel or very long cartridge

- Too many studs jutting out of the cartridge body, not conducive to smooth feeding if indeed you plan a feeding mechanism

- The bolt stopping the projectile doesn't need to extend across the whole diameter of the cartridge

- Using a syringe, adding fuel through the mouth of the cartridge is a perfectly good way to fill it.