SpudFiles

Thanks PeteS, I didn't realize what you meant about having a flat sealing face I guess. I guess I though the union sealed on the outer flat ring rather than the inner angled face, for whatever reason. My union does have the bronze ring and every other feature you described.
It sounds like I'll be using foil for the lifespan of this launcher! I did design it with a future piston valve in mind, so maybe this summer I'll have enough time to get that worked out. Then burst discs will never be an issue.

noname wrote:It sounds like I'll be using foil for the lifespan of this launcher! I did design it with a future piston valve in mind, so maybe this summer I'll have enough time to get that worked out. Then burst discs will never be an issue.

You might find someone where you live who would chuck the pieces up in a lathe and give it flat sealing faces. I might do it for you for free, but shipping both ways would be a bit expensive and a hassle. So even for free the shipping might make it kind of pricey. I am guessing it would double or triple the cost of the union.

Using foil isn't the end of the world. You might even find a free or cheap local source for heavier foil in the form of pie pans or roasting pans, maybe used ones.

Building it up as a piston hybrid would be a fun project. That or just build another one with a piston valve.

These hybrids are really fun.

Hey Pete... I'm dying to build a piston hybrid. Obviously I'm set up for b disc on my current gun. But I'm sure ill have a few questions when i get started on the piston gun. Just giving u the heads up. Thanks

I'll help where I can, but I am still fairly new to all this myself.

Burst discs are fine for now, I just bought a 200 square foot roll of heavy duty foil, so that should be enough for about 200 16/20 layer burst discs. A piston valve is definitely going to take a lot of tinkering, so I'll need plenty of time to get that worked out.
For now, I'm satisfied! Hopefully going shooting tomorrow!

Excellent. Have fun with it. Oh and 16-20 layer burst disks? Wow. I am curious what kind of pressure that many layers take to burst for that diameter?

If you get damage pics, action pics, or vids please post.

Damn noname!!! What Pete said!! What pressure u firing at. Actually what size union u using. Believe it or not i found that after i ground my 1" steel Union down flat and cut a gasket for it, it seals much better than my pvc testing union with the built in o ring. I don't have to torque down on it at all to seal. I use around 6 layers of heavy duty foil for a 4x mix

I have no idea what pressure it takes for the discs to burst but I didn't think 16-20 was that many layers to be honest! Now you guys have me curious about what pressure it takes... It's a 1 1/2" union and the burst disc diameter is about 1.8" so I figured that's a lot of surface area, it wouldn't hold back as much pressure.

I got curious after reading this and tried some kitchen foil. I had never tried it and was surprised how thin it is and how little pressure it held.

Bottom line... I now see why you might need a lot of layers. The craft foil I use is about 5 times as thick.

BTW, another option I have used are those heat seal aluminized mylar bags. They are pretty heavy duty but do not blow out as cleanly as the craft foil or coke can aluminum which look laser cut when blown out.

The layer number is highly dependent on the exposed surface diameter too don't forget!

When I use standard aluminum foil in my hybrid @ 10X+ I regularly use at least 60-80 layers.

Yep, bigger diameter hybrid means I should be using a bunch of layers; I thought ~20 would be a good starting point. I got a big roll of foil, the only annoying part is tracing and cutting circles. If I had a cookie cutter thing for foil that would be awesome.

Get good shear style scissors and you can easily cut all 60-80 layers at once. Just be careful of the layers slipping on eachother.

If you can get a couple of bits of steel the same size as the discs should be, you can fold over your 80 layers, clamp it in a vice and cut around it, then trim with a Stanley knife. It's tedious, but it'll be perfect every time.

Ok then. Bigger dia in ur union. I thought u were using a 3/4 for some reason. I was using a 2" pvc in my normal combi gun and that required quite a few layers. there is a material pressure burst info page in the hybrid cannon info section of spudfiles. Its pretty informative!!

So I went to go shoot today off the side of the road in the middle of nowhere. My igniter sounded really weak, which was odd. I fueled up the cannon to a 2x mix to start off, but it wouldn't ignite. I depressurized and pumped all the propane out and looked in the chamber at the spark gap. It's really weak and looks tiny; I can't tell exactly but it doesn't look good!
My friends were disappointed, I was pissed off at how much work I put in tweaking the gun my last week of winter break so that it wouldn't require any work when I got to school. So we got a couple shots off as a pneumatic, but no fun hybrid shots.
I don't have a car so I've been storing the cannon in my friend's trunk until we have a good chance to go shoot. I'm pretty sure the cause of my problems is because of my ghetto ignition. I think the wire must have pressed up against the chamber and either run the battery out, fry the stun gun, or fry the ignition wire. As of now, all I can do is buy a new battery and hope that works, otherwise I have to find someone with a bench vise and a couple wrenches to find out what's wrong with my spark plug.