All Steel Over-Under

[motorfixer1]

I finished my all steel combustion launcher and thought I would showcase for all to see.
Chamber- 4" exhaust tube and elbow at chamber end is a 2" mandrel bent piece.
Ignition- Shureshot AR-15 Kit with two handed firing for safety. Dual gaps totaling .250"
Electronics- Two 6V R/C receiver packs wired in series, LM317 voltage regulator to power ignition. I want to add a 555 ic for fan timer later as I have already constructed the circuit on a breadboard.
Fueling- 8"X3/8 meter pipe with one touch valve. External filling station with compact regulator. Fills meter through schrader at bottom of one-touch valve. Mapp gas or Propane capable.
Barrel- 5" of 1.5" sch. 10 steel pipe honed and internally polished. (not pictured) 2" cam lock detatchment.
Misc- 10 cfm chamber fan mounted to chamber service plate with 1" ball valve for sealing from atmosphere. The chamber and all interface ports pressure tested to 115 psi. All interface bushings epoxy sealed with VPI to remove voids. I have only test fired burst discs as of yet (alum foil). I will test fire this weekend if I get time! Otherwise what you see is what you get, any questions feel free to ask. I hope to post some pics with the barrel mounted and from farther away as soon as the weather gets warmer. Sorry for the close quarters.

[Gun Freak]

Wow that thing is amazing!
Very nice job. It looks like it would make a nice hybrid! I'm not too fimiliar with the chamber material though, but I believed it was used on a pneumatic launcher that was run on 250 psi...

[saefroch]

That's an amazing build for an advanced combustion. If you put that level of work into an atmospheric combustion, you should build a hybrid. They're not really all that much more complex.

[Lockednloaded]

Great work, lots of fun accessories. To turn this up a notch and hybridize it, all you would need is a fill valve. you've got a meter, a burst disk holder, and a strong chamber already.

[motorfixer1]

Thanks for the positive comments everyone. I am not sure of the strength of the chamber tubing so I don't think I will be going hybrid with this one. I have plans for a hybrid in the making, maybe next winter or something.

[Gaderelguitarist]

Very nice. How heavy is this sob?

I have a combustion with a dual vertical grip setup like this as well, though it's mostly pvc.

[Moonbogg]

Thats nice! You just joined the all metal, blue colored combustion cannon club. It now has two members.

[motorfixer1]

Gaderelguitarist wrote:

Very nice. How heavy is this sob?

I just weighed it 15.2 lbs w/o the barrel. Much heavier than pvc launchers? I Don't know.

[Gaderelguitarist]

Yes it is much heavier. With the barrel I think mine is a max of 10 pounds. It has an UHMW chamber and a plywood grip set with a 5' pvc barrel.

I would imagine the barrel would add another 5-10 pounds, making this one very solid cannon. Any plans to cover the electronics with something?

[Technician1002]

I have a spare R22 Freon tank I'm looking into turning into a first combustion. 3 gallon chamber with a 260 PSI working pressure rating. Thinking of having a soda can barrel.

[motorfixer1]

I finally got to test fire yesterday as a completed cannon and this unit would not fire. When I was test firing, I was filling the chamber through the vent port with my handheld torch, closing the valve, and then firing. I did not have the meter installed as of yet.
This is when I find a serious mistake in my math that calculated what size the meter pipe was to be! By my calculations I thought that the 8"X3/8" pipe was the right size, WRONG. Too lean!
Meter should be 3/4" pipe 8" long which looks like:
326.5 C.I. chamber
4.26 C.I. meter chamber
54 psi charge in meter (for MAPP gas)
When 3/8" pipe was used looks like:
326.5 C.I. chamber
1.52 C.I. meter chamber
152 psi charge in meter (for MAPP gas) My regulator only goes to 65 psi!!
Does this sound right to anyone else?
I'm not sure if I should include the volume of the elbow and the reducer at the front of the chamber in these calculations or not. I did include it in these calculations and will try a larger meter and see what happens.

[Gaderelguitarist]

I'm not generally one to look at the math behind these things, but it sounds like you may be putting too much fuel in there. At least thats generally the problem most people have with fueling

[metalmeltr]

I have a spare R22 Freon tank I'm looking into turning into a first combustion. 3 gallon chamber with a 260 PSI working pressure rating. Thinking of having a soda can barrel.

I have similar plans for a 20lb. propane tank>

[TwitchTheAussie]

Thats a pretty bada$$ cannon you got going on man