mini hybrid win!

[Insomniac]

This isn't strictly on topic, so I apologise for the hijack, but your mini hybrid exploits were the inspiration behind what I just tried...

Basically, I have a tiny burst disk gun which I installed a spark gap on so that when I get some syringes and whatnot I can try my hand at a low mix mini hybrid (it's a small, thick glass reinforced plastic fitting, not metal). I was tooling around with it but coudln't even get it to ignite as a regular combustion as I have no way to correctly meter fuels at the moment, and it's a very small chamber (about 10 ml). So instead, I started bridging the spark gap with a bit of aluminium foil, and dumping a small (five or six camera caps) capacitor bank though it. Made cool sparks and whatnot, so I decided to pressurize it with air and put the burst disk on, to see what would happen (I was wondering if all of the aluminium would burn in the high pressure atmosphere).

So I pressurized to 200 PSI, dumped the capacitor bank though and POW! The burst disk failed and fired a bunch of sparks out of the barrel. Either a spark had hit the burst disk causing failure, or the momentary pressure spike from the arc in the tiny chamber had caused it to fail. Did it again and filmed it in high speed because it looked cool...

So, wondering what to do next, I decided to completely purge the chamber with butane to see if it altered the muzzle flash at all... sprayed some liquid butane into the chamber, to ensure that there was plenty there (there was a tiny bit of liquid at the bottom when I sealed it up), pressurized it, and touched the capacitor contacts to the electrodes... BANG! I had hearing protection of course, but I actually felt the blast from this one... and dad racing to my room to yell at me seemed to confirm my suspicions that it was considerably louder

Upon looking at the 1000fps footage, it looked like what happened was that the butane mix combusted almost instantly the moment it left the barrel, as it was only a little bit too rich to burn properly in the chamber... about a foot or so of flame out the front of the barrel only lasted for 2 frames or so, which probably explains the noise... Not sure what use this little 'invention' has, but it sure makes a hell of an impressive bang, without being picky on mix. Also works as a form of triggered burst disk without the gas, which is nice.

Anyway, back on topic....

[jackssmirkingrevenge]

Upon looking at the 1000fps footage, it looked like what happened was that the butane mix combusted almost instantly the moment it left the barrel, as it was only a little bit too rich to burn properly in the chamber... about a foot or so of flame out the front of the barrel only lasted for 2 frames or so, which probably explains the noise...

Are we going to get to see the footage?

Played around with this using a less restrictive seal. It won't ignite past 17x, and at that mix number the power is rather disappointing, it left a dent but didn't go through the long suffering UPS case, hmmm...

[al-xg]

I'd stick with the 9mL one, just use a single use suppressor, or tape some tissue paper to the suppressor muzzle. That even works on a paintball gun, but obviously isn't that practical on something that fires 17 times a second....

[jackssmirkingrevenge]

I'd stick with the 9mL one

The mini hybrid volume is actually 18mL, I might have gone too far on the other extreme with this one. It doesn't bode well for small sized cartridges though...

edit: maybe my expectations were too high, at 16x it will put a BB through both sides of a soup tin - not exactly weak for its size. I'll try and get some chrony data tomorrow.

[youtube][/youtube]

[jakethebeast]

for that small launcher, i think thats impressive damage

[Fnord]

Hybridpengun?

[jackssmirkingrevenge]

Hybridpengun?

Thought about it, but the complexity of fitting a piezo ignitor in a pen sized package that probably won't be more powerful than a HPA piston pengun doesn't really seem worth it...

[POLAND_SPUD]

It doesn't bode well for small sized cartridges though

cartridges make sense on firearms... what's the point of using them if you can fill the chamber with fuel, air and then vent it ?
The only advantage I can think of is cooling effect

[ilovefire]

It doesn't bode well for small sized cartridges though

cartridges make sense on firearms... what's the point of using them if you can fill the chamber with fuel, air and then vent it ?
The only advantage I can think of is cooling effect

what i like about the cartridge idea is that you can get multiple shots of relatively quickly without having a gun that is all big and bulky with tubes and fuel tanks and that kind of stuff all over it

[POLAND_SPUD]

yeah but you've got to have a mag large enough to fit as many cartridges as you want to get shots. so if you want to get more than 10-15 shots then the size and weight of cartridges might be greater than the size and weight of automated metering system...


also don't forget that you have to fill and load cartridges too
sure it doesn't have to be mounted on a gun but still you're somewhat limited by the size and weight of cartridges + you need a standalone metering station

[Insomniac]

True, but I'm sure over 95% of the guns people build here serve no true purpose... they are just little engineering challenges which are fun to use after they've been built. So the answer to 'Why make cartridges at all?' is 'Why not?'

And here's the footage of my little experiments last night... the first video is at 420 fps, aluminium foil over the spark gap, ~200 psi of air in the chamber (no projectile of course).

Second one is at 1000 fps, and has a chamber purged with butane then pressurized to ~200psi. I've slowed them both down to frame-by-frames as it happens too fast to see much at all when playing at normal speed.

Anyway, here's the footage:

[youtube][/youtube]

[Gun Freak]

Wow thats an awsome video Insomniac, I love the colors in the second part...

[ilovefire]

would i be right in saying that you used a clear burst disk?

[Lockednloaded]

Insomniac, why don't you use a projectile? it seems very powerful, good work on your hybridish gun thingy... Any pictures of it?

[Insomniac]

Ack, I was sure I replied to your post... it mustn't have gone through or I forgot to click post...

Anyway, yes, it is using a clear burst disk. How could you tell?

And I'm not bothering with a projectile as this really isn't optimized for it... I doubt the spark and the butane is doing anything for the power.... all the spark on it's own does is function as a way to easily trigger the disk. With the butane, I suppose it MAY be functioning as a hybrid, as a butane purged chamber at 200psi ought to have something like 7% propane/air... far from ideal, but I believe this is just within the limits of combustion. So I may actually have a hybrid on my hands, or I may not... as it will fire regardless of whether there is fuel inside or not, it's difficult to tell for sure. I don't have pictures of it as it's really nothing special.... a small poly-pipe nipple with an endcap and shrader, two nails for electrodes (surprisingly airtight), and a hose adapter with a short 8mm barrel epoxied in. The collet holding the hose adapter looks somewhat weak though, so I won't be surprise if it fails spectacularly. At least all the shrapnel ought to fly away from me if this happens.