SpudFiles

good luck! Eager to see the results of this experiment.

I'll be needing it! Well, after preliminary testing, as I sort of expected the one-way valve didn't seal, so I need a better solution. Time to take a part a lighter

I also noted that with the "valveless" type, there's no way to extract the projectile in case of misfire without destroying the seal.

jackssmirkingrevenge wrote:I also noted that with the "valveless" type, there's no way to extract the projectile in case of misfire without destroying the seal.

Um... Push projectile in, let cartridge vent, refuel?

Time to take a part a lighter

One word, Jack.

Ragnarok wrote:

jackssmirkingrevenge wrote:I also noted that with the "valveless" type, there's no way to extract the projectile in case of misfire without destroying the seal.

Um... Push projectile in, let cartridge vent, refuel?

If you push the projectile in then how would you get it back in the seal?

Time to take a part a lighter

One word, Jack.[/quote]
Hahaha I was thinking the same thing

thats how this design works gun freak, he turns the cartridge upside down while filling, as he removes the syringe the pressure forces the bb into the seal, its like one way valve, only the projectile makes the seal.

But then is the projectile in the chamber while it is fueling?

Gun Freak wrote:But then is the projectile in the chamber while it is fueling?

Yes.

SWOOSHHHH. Ok I'm clear now

bah, semantics

Gentlemen, I can report progress WE HAS IGNITION!

Unfortunately, not enough pressure was generated to pop the BB out of the seal, but at least I managed to successfully ignite a hybrid mixture in a chamber volume of less than 1mL!

[youtube][/youtube]

You can just see the glow starting at around 8 seconds, also the cartridge body got very warm, which I take as proof that the mix ignited but was contained in the cartridge.

Needs some work but this is certainly very encouraging

For the sake of completeness, this was my (unfocussed...) firing setup with a standard ignitor, I pressurised it with a 10mL syringe with around 0.5mL of butane.

looks very promising jsr, and I love the simplicity of design, is this the fill valve one or the completely valveless one?

Congratts!

What approx mix was that? Make a setup that alows you to reach 10-20x and this should get really interesting.

Good luck.

Edit: If you have such a thing as a window or something in your batcave you can just put the stuff you are filming in the light from the window to get better light.

This is the "valveless" one, unfortunately in order to enable a good seal for the syringe I had to make it quite long, so the BB has quite some distance to travel before popping out. Also, the seal has a 6mm o/d and is in a 6mm i/d tube, so it can't really expand easily to let the BB through.

I rebuilt the "valved" version with a different type of one way valve, I'll see how well that works. If it holds pressure it will at least allow me to load the BB so that the seal just barely holds it, giving it a much better chance of actually firing.

SpudFarm wrote:What approx mix was that? Make a setup that alows you to reach 10-20x and this should get really interesting.

Technically I started with 11mL of fuel/air mix compressed to just under 1mL, in a very simplistic world that's about 10x mix...

Hmm, should I try with a 50mL syringe

If you have such a thing as a window or something in your batcave you can just put the stuff you are filming in the light from the window to get better light.

I filmed it in darkness purposely in order to make the glow visible

Maybe to solve the large distance of travel needed you could use a larger diameter tip on the syringe and have its own seperate seal that the bb can travel through easily, this could double as a good breach seal when these cartridges are actually used.

That could also be a good solution. I definitely want to go with a bigger cartridge body, like for example the 3/8" tubing I used for the original prototype in this thread, or keep the 6mm tube and go down to 3mm calibre instead of 4.5mm for these prototypes. I would also have to adapt the syringe nozzle to fit into a larger diameter seal but that would be no big deal.

The important thing is that I've hit upon a way to reliably fuel and pressurise small volumes, which gives me the confidence to put a lot more work into perfecting this idea, as this was the primary snag I had hit upon.

I dont think going down in calibre would be a very good idea, because the surface area and force go down exponentially, so you would need very high mixes, and a pretty finicky detent/seal. I would find a easily and cheaply available material, maybe 1/2" copper pipe, and base cartridges on that. Although ofcourse as you get bigger cartridges you need bigger "syringes" or suitable replacement. Perhaps you could devise a sort of 2 stage pump for pressurizing premixed fuel, because you wouldnt want to store it at high mixes in large volumes.