SpudFiles

Well have fun.. .not too much though

looking forward to seeing results!

Won't the "glow plug" melt the surrounding epoxy?

Maybe carbonize it in time, but if the wire is thin enough it should be able to absorb the heat briefly without damage. otherwise he'll have to go with alumina or asbestos composite or something
JSR,

Have you tested a propane/air mix to see how hot the glow plug has to be to ignite the mix?

Remember too, that higher density air will sink heat out of the wire more quickly, causing a slow warm-up and lower max temperature. Even if a 1x mix ignites instantly, you may have a slight delay with a 10x.

As to fueling accurately,
Just flood the the chamber with propane and go for 23x

Great work Jack, I've been following this thread... still no working ones but it is still cool. Anyway, where do you get all your schraders and why do you have so much of them?

i joined ze nazi party - zey're cool daddy-oh!

edit: oh dear, I'm posting LINKS under the influence now - but good syntax I see

Well have fun.. .not too much though

Clearly

Won't the "glow plug" melt the surrounding epoxy?

Techncially it only gets hot between where it's touching the cartridge body and the schrader.

Fnord, hadn't considered these points to be honest, guess we'll find out soon!

where do you get all your schraders and why do you have so much of them?

ebay, and since I use a lot I buy them 25 at a time

edit 2: after some testing, fail! I believe the problem is the ignitor, as it didn't even ignite a mix at atmospheric pressure. Back to the piezo then, I'll let you know when it's worth watching this space

edit 3: I drilled out the check valve from the previous prototype and replaced it with a schrader, we'll see how that goes.

Ouch, one more failiure..
I will pray for the next attempt! You just have to have limited patience with a project and this would certainly be pushing it for me :p

I wish you good luck. I wanna see a working cartrige!

Well, finally, SUCCESS!!!!

This prototype is basically this with the nozzle check valve replaced with a schrader, and here it is at 6x - the video doesn't really show how loud it is!

[youtube][/youtube]

And here it is a 1000 frames per second, I think I'll try with less lighting to show the flash...

[youtube][/youtube]

the video doesn't really show how loud it is!

Classic after the first successful hybrid!

This is so nice!
Do you have any possibillity to put a barrel on it? I would like to see the chrony results of this thing.

Not more my stunned mind can come up with other then congratts!

so it uses a nichrome wire or a piezo??

SpudFarm wrote:This is so nice!
Do you have any possibillity to put a barrel on it? I would like to see the chrony results of this thing.

Thanks, really happy with it

So, I've proved that by compensating for the pump volume it's possible to meter mixes in a small chamber. However it seems silly to have such a fat cartridge for a tiny calibre, so I'm thinking of scaling things up a little - same cartidge body, but 3-4 inches long, and for 3/8" bearings. Something like the "Gong" pistol from Appleseed would look good as a finished project



Fuelling is still a bit touch and go, so increasing the cartridge volume would make it more reliable.

so it uses a nichrome wire or a piezo?

This is with a piezo, I'm going with CpTn_lAw's data here that it should be ok up to 8x mix with should be enough for my purposes.

That first video put a scary smile on my face

al-xg wrote:That first video put a scary smile on my face

Not 'alf the size it put on mine

Working on a heavier version as we speak

Do you think the larger version will have enough power to cycle an action?

If I managed to do it with a combustion, I'm sure a hybrid's chances are even better. I'm going with a 3.5" long cartridge so there will be plenty of volume.

I was thinking that the straight walled design of the cartridge might lend itself to an action similar to an M1 carbine.