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high mix hybrid ideas and questions.

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: DYI » Wed Jan 27, 2010 6:18 pm

POLAND_SPUD wrote:well yea but that's doesn't sound very practical, right ?

this thing is going to be expensive, loud and powerful so it's best to make him aware of all this... also this thing is going to attract a lot of attention if fired close to habituated areas


Once again, practical?
Practical is a relative quantity, and it scales as the inverse square of affordable and feasible to build.

Turning a few thousandths off a 2" aluminum or steel bar and drilling a hole in the back to stabilize it doesn't take very long. Aerodynamic darts are obviously another matter, but they're not a 5 minute job for any bore.

Driving a bulldozer into someone's house will attract a lot of attention too, and ranks very close on the crazy scale to firing a 150kJ gun in a populated area.

One thing to look out for is that the internal diameter of most tube is not a guaranteed quantity, and can be off by as much as a millimetre for the larger tubes. If he gets lucky on the internal diameter of the barrel, it'll be perfect for firing 2" ball bearings and 2" rods. If not, then any projectiles will need to be turned (or perhaps cast).

POLAND_SPUD wrote:or a small shed, right ? :D


From experience with my 100kJ gun, I assure you that unless the small shed was well stocked with sandbags and concrete blocks, it wouldn't be much of a contest. :roll:
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Unread postAuthor: Jeeperforlife » Thu Jan 28, 2010 12:11 am

Moonbogg wrote:Looks good. Why do you have tubes around the studs? If you aren't careful, the tubes will absorb all your torque, and then the end caps might not be tight enough, or evenly tightened.

EDIT: I guess what i'm saying is, just make sure they float and aren't compressed.


I am not sure what you mean by the tubes will absorb the torque. The reason I put the tubes full length is so there is no way they could pull off the chamber. I know I could turn up the welder and burn them in so that they could not pull away. But I was trying to keep the heat down on the chamber, they will still be stich welded. I did not think it could hurt any thing. Am I wrong?

I do realize that Larda did not use a spark plug. I just meant the plug that was insulated for the wire going into the chamber. I did some looking today and have a rough idea I am going to try for the ignition going into the chamber. One question I have is did his wire just heat up or did it burn? I assumed it burnt and melted. I am open to any and all ideas on the ignition system.

Here is the Gauge I have planned.
http://www.mcmaster.com/#3943k132/=5kcziw

For a shut off valve I was thinking of a all stainless needle valve also.

I do realize this is not practical. Although I do remember something about using a spud gun to clean out drains. Maybe I can contract out to the city to clean out sewers. :idea:

I do think it is worth mentioning the majority of the time I will be using this at 50X or so. The main round would be a 2" round rod sharpened and a 2" OD pipe welded to the back so it has a hollow base when at high mixes. It would weigh a few pounds. I could use this for the barrel.
http://www.speedymetals.com/ps-3508-204-2-12-od-x-188-wall-dom-steel-tube.aspx
That way I could be able to run 2" OD rounds with out problem.

I have got a system worked out for recoil so I don't think it will be a problem.

As far as range and stopping the rounds there is 20 acres I have to play with. Beyond that Is a sharp hill going up for them to dig in to.

DYI-
I am glad you chimed in. Do you still have your large hybrid? What did you learn from it I could use? What kind of gauge did you use?

I am still a ways off from building it. I just wanted to know what everybody thought.
Thanks for the Ideas,
Marcus

P.S. jeepkahn,
I currently own a 05 TJL on 33s it is my DD, My wife has a 08 patriot, and a 92 XJ on 36" H1 tires and bead locks for our toy.
It is funny a gun that costs $1,000 sounds like a lot but you can't even lift a Jeep and put tires on it for that. That is why my wife likes this hobby it is cheaper than most.
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Unread postAuthor: Moonbogg » Thu Jan 28, 2010 12:39 am

If you weld the tubes in place, then you just lost the point of having bolts. You will be relying on the strength of the welded tubes and not the studs.
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Unread postAuthor: DYI » Thu Jan 28, 2010 3:16 pm

When you talk about the tubes "pulling away from the chamber", what exactly is the concern? Are they just to make everything easier to line up when you attach the front and back plates? Moonbogg's just reminding you that the tubes will need to be a little bit shorter than the chamber, so that you can tighten the endplates down fully.

That gauge will be fine for the air, accurate to +/- 1X. What do you plan to use for the propane? Without a crazy accurate gauge, you'll need at least two. More if you want to be able to operate at any mix between 1X and 200X.

Larda used a melting wire that had to be replaced after every shot. I can't think of anything that would prevent you from using a nichrome glow wire.

Like everything else I owned, the OPP stole my 100kJ hybrid. I didn't get to do much testing with it, because the lathe was out for repairs at the time I built it. I only had it for three months, and only fired three shots, one of which was to clear out a very stubborn jammed round. Big guns are essentially just small guns, but bigger :lol:

Difficult to assemble, unwieldy to transport, time consuming to use, just what you'd expect. They've got a lot of kick, make a big noise, and launch whatever you throw down the barrel through most targets you can carry without help.

I used a 0-30psi gauge for propane, and a 0-300psi gauge for oxygen and buffer gas (nitrogen, in this case) injection, both of them +/-1%.

Mine was a real PITA, but that's because I was too busy to build a proper stand for it. Burst discs were 256 layers of aluminum foil, and I got one or two out of a 100' roll of foil. Just don't go into this project with the impression that it won't be a long day's work to get a couple shots out of it.
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Unread postAuthor: Jeeperforlife » Fri Jan 29, 2010 12:27 am

Moonbogg wrote:If you weld the tubes in place, then you just lost the point of having bolts. You will be relying on the strength of the welded tubes and not the studs.


The tubes won't be welded to the end caps. The studs are still the only thing holding the caps on. I was planning on leaving the tubes a spaced a little back behind the chamber so it would have plenty of room. Also I will have the thickness of the gasket or the thinkness of the burst disk.

DYI wrote:Like everything else I owned, the OPP stole my 100kJ hybrid. I didn't get to do much testing with it, because the lathe was out for repairs at the time I built it. I only had it for three months, and only fired three shots, one of which was to clear out a very stubborn jammed round.


That sucks, It is good to see you back. It was several of your projects that really got me interested in this hobby.

I realize this is quite a feat. I have a plan for a stand that will make reloading easier and faster by making everything well supported and air tools for disassembly and reassembly. For burst disks I am planning on using aluminum flashing that is .0092" (.33 MM). It is cheap and I can cut 20 or so in less than a minute using a hole saw in the drill press. I will try to build a prototype for the ignition in the next few days, It wont be exact But it will be close. I have found out that the tax refund I was expecting did not come through as I hoped. This will delay the project but not kill it.

Marcus
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