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6mm hybrid design

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Unread postAuthor: spanerman » Thu Sep 06, 2007 3:28 pm

are you sure you can get a burst disc to seal in those fitttings? it may be worth buting a 1/4 union or similar..
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 06, 2007 4:55 pm

Probably because of the dangers of autoignition and/or detonation that they pose.


Well said, I've seen a pneumatic rifle that was filled with oxygen instead of compressed air which then detonated, there wasn't a lot of it left.

What mix will you take it to?


I'd like to hit mach 1, I'll start at 3x and build up from there.

are you sure you can get a burst disc to seal in those fitttings?


Yeah, a couple of o-rings/rubber washers and it'll be fine.

The front barrel/breech assembly is curing, in a few hours i'll seal the schrader in place then I'll give it a full 24 hours to cure before trying it out.
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Unread postAuthor: DYI » Thu Sep 06, 2007 6:11 pm

Wow, filling a pneumatic rifle with oxygen... He's lucky he didn't get a Darwin award. Oxygen wouldn't even be a very great gas for a pneumatic, since oxygen is denser than nitrogen. I wouldn't even want to use air in a high pressure pneumatic, too dangerous in my opinion. I did have a chance to get a 100-1500 psi output nitrogen regulator, but decided against it because of cost, and the fact that parts rated for that kind of pressure aren't exactly cheap.

I decided on the more practical (and cheaper) 50-500psi output regulator, which is now sitting in my room. All I need now are some hydraulic quick connects (arriving on the weekend), and the Type 16 nitrogen tank (arriving in 2 weeks), and the 500 psi cloud will begin.

A hybrid chamber made out of epoxy, that has to be a first. Mach 1 could be difficult though, what kind of projectile do you plan on using? Lets hope that the epoxy will be up to it.
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 06, 2007 6:15 pm

Wow, filling a pneumatic rifle with oxygen... He's lucky he didn't get a Darwin award.


This is what was left:

left side

right side

The owner is lucky to be alive.


A hybrid chamber made out of epoxy, that has to be a first. Mach 1 could be difficult though, what kind of projectile do you plan on using? Lets hope that the epoxy will be up to it.


I'm sure it will, if not, you'll see me on the news and you can write letters to the station telling them how angry you are at my stupidity ;)

Hans Brix? Oh no!

*ahem*

I think 0.12 gram BBs will be the projectile of choice for velocity figures, we'll see.

Here's the work in progress, what do you guys think of the spark gap (before I seal it all up)?
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Unread postAuthor: thespeedycicada » Thu Sep 06, 2007 6:23 pm

thats beautiful i love it and the spark gap is genius.
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 06, 2007 6:29 pm

thespeedycicada wrote:thats beautiful i love it and the spark gap is genius.


...but is it too much/to little to ignite a hybrid mix with a piezo?
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Unread postAuthor: DYI » Thu Sep 06, 2007 7:22 pm

That air rifle got owned. Seems like solid proof that detonations really are what they're cracked up to be.

The chamber looks good. at a 3x mix, the piezo should be capable of a spark at least 1/12"-1/6". How much is all this epoxy costing you? It's usually used for patching leaks, but building entire pipes out of it must use a substantial volume of the stuff.
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Unread postAuthor: noname » Thu Sep 06, 2007 7:57 pm

I'd HIGHLY advise against using a PVC chamber, especially with one that's walls are only 1/8" thick. Use a steel chamber, and save yourself the worry of it blowing up.
Also, hitting supersonic with a 3x mix and that small of a chamber is probably not going to happen. Your chamber is about 3 times the diameter of your barrel and mine is 4 times the diameter. I shoot at 6x mixtures with a 20 foot barrel and people still won't believe it shoots Mach 1.
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Unread postAuthor: mopherman » Thu Sep 06, 2007 8:18 pm

noname wrote:I'd HIGHLY advise against using a PVC chamber, especially with one that's walls are only 1/8" thick. Use a steel chamber, and save yourself the worry of it blowing up.
Also, hitting supersonic with a 3x mix and that small of a chamber is probably not going to happen. Your chamber is about 3 times the diameter of your barrel and mine is 4 times the diameter. I shoot at 6x mixtures with a 20 foot barrel and people still won't believe it shoots Mach 1.

he could always sleeve it inside some of that brass tubeing that hes so fond of. :D
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Unread postAuthor: Novacastrian » Thu Sep 06, 2007 9:21 pm

I'd go a tiny bit smaller with your gap JSR, as you won't be able to adjust it after you glue it up. Probly like a 1.5 mm gap (if you want to go above 3X)
Great to see that you are making other things apart from pumpys :)
Good luck mate.
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 06, 2007 11:19 pm

DYI wrote:How much is all this epoxy costing you? It's usually used for patching leaks, but building entire pipes out of it must use a substantial volume of the stuff.


I bought 4.5kg over 3 years ago for a little over $100, there's a about 1/6th of it left.

I'd HIGHLY advise against using a PVC chamber, especially with one that's walls are only 1/8" thick. Use a steel chamber, and save yourself the worry of it blowing up.


This is just for starters, if going any higher all will be substantially sleeved.

Also, hitting supersonic with a 3x mix and that small of a chamber is probably not going to happen. Your chamber is about 3 times the diameter of your barrel and mine is 4 times the diameter. I shoot at 6x mixtures with a 20 foot barrel and people still won't believe it shoots Mach 1.


The Mach one target is one i'd like to reach eventually, for this project the aim is more to see what sort of power a small hybrid cartridge would have and if it was worth trying out as getting carts machined isn't going to be cheap.

I'd go a tiny bit smaller with your gap JSR, as you won't be able to adjust it after you glue it up. Probly like a 1.5 mm gap (if you want to go above 3X)
Great to see that you are making other things apart from pumpys


As it is it's about 1.5mm. Technically I can adjust it slightly by using a dowel or a hook to bend the wire through the front fitting but I would have absolutely no way of gauging the difference.

I love compressed air but sometimes you need to go a little different :)

Time to seal it up, testing in 24 hours or so.
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Unread postAuthor: Novacastrian » Fri Sep 07, 2007 4:18 am

Be sure to wear your goggles!! :D
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Unread postAuthor: jackssmirkingrevenge » Fri Sep 07, 2007 4:43 am

Novacastrian wrote:Be sure to wear your goggles!! :D


oops :D
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Unread postAuthor: FeLeX » Fri Sep 07, 2007 7:04 am

I still think unpressurized oxy-propane mixture should be tried just to see what kind of power it can reach.
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Unread postAuthor: Novacastrian » Sat Sep 08, 2007 6:11 pm

C'mon JSR, is it tested yet?
Not to be pushy or anything! :D
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