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This is actually a rebuilt, repainted, updated version of my Complete Advanced Combustion plans here - http://www.spudfiles.com/forums/complet ... t4512.html .
~250ci chamber, shown with a 4' 1.5" barrel (I know, huge C:B ratio, I designed it with a longer barrel in mind).
All DWV, Cellular-Core ABS pipe bought from Home Depot dirt cheap. I've pressure tested sections of this pipe to 125psi overnight with no failures and I feel very safe using it for a combustion gun. I wouldn't want to use it in a situation where it would see pressures over 60-70 psi for extended periods of time, but for this application, I think it's even better than PVC; if it does fail, it shouldn't throw off any shrapnel.
Simple propane meter - no regulator, just a torch head, some hose, two ball valves, some brass fittings, and a pressure gauge. Works perfectly. Two shots at 65psi on cold days, two shots at 70psi on warm days, perfect mix.
Spark strip made from copper clad circuit board - check out here - http://img257.imageshack.us/img257/1552 ... ont9jy.jpg . Currently using a BBQ sparker (rear handle) because my camera flash circuit died. Building a better ignition circuit, that's why it's "almost done" and not "completely finished". The BBQ sparker jumps all 5 gaps on the spark strip without a problem, though.
1.5" ball valve for venting, and an 80mm coolermaster computer case fan powered by two 9v batteries and a push on/off switch in the front handle.
Breech loading using a simple pass-though fitting method and threaded adapters.
The original design for this gun was heavily influenced by Gort's famous Blue Flame, and a few others here on SpudFiles.
The method for attaching the vent valve/reducer assembly to the chamber, I think, is unique. I tapped in six threaded helical inserts into the chamber wall from the inside, using some superglue on the threads. I then drilled six holes, lining them up perfectly of course, in the 4"-2" reducer. Six large bolts are then installed in the holes to seal the chamber. It takes a few minutes with a rubber mallet to tap the assembly onto or off of the chamber; I've had to open it up twice to adjust things, but last time I tweaked it, I epoxied everything in place so it should never need to be adjusted again.
The voltage for the fan and spark strip are passed through these bolts (wires soldered to the helical inserts inside) so that no holes in the chamber are required for wires. The only holes in the chamber are for the propane meter, and the bolts, and all the holes are where pipe and a fitting overlap.
I know ABS is black to start with, but I gave the whole gun two coats of Rustolium for Plastic black spray paint (the valve was white, and I liked the shiny finish). It's wearing off the barrel where it rubs against the barrel support, but that was kind of expected.
On to the pics....
Propane meter closeup:
Vent assembly closeup:
"Bottom" side of gun:
"Back" side of gun:
The rear handle is temporary, until I build the new ignition circuit (which will be a camera flash with relay and motorcycle ignition coil, and will be put into the painted, unattached handle in the middle).
Looking into the vent valve, you can see the shiny label on the CoolerMaster fan.
The fan is simply sandwitched between the 4"-2" reducer and those bolts. It can't move at all, the blades spin freely, and it's placed just right. Can't beat it.
Damage shot against an empty 1 gallon olive oil can - projectile was a decent size rock with a rag for wadding, from about 15 ft away.
I've gotten hang times around 30 seconds with medium-size rocks. I'm looking for some SDR21 pipe locally so I can play with golf balls (I have a huge sack of dinged up ones....). I'd order online, except I want a 10 foot stick of it . Once I get some SDR21 I'll borrow a chrono from a friend and find out how fast it'll get golf balls going.
This gun has also successfully skipped a potato over 300 yards across the surface of a small lake. That impressed the hell out of me.
Best damage shot ever was a large rock, using a potato as wadding, clear through both sides of a broken propane BBQ grill. I'm not exaggerating.
Also left on my to-do list is a nicer looking front barrel support. The current one works excellently but looks ghetto. Any ideas?
I'll be updating the old "Plans" to reflect the new changes soon. Hope you enjoy, and I hope this is useful to the n00bs. Feel free to ask questions.
Very nice Pete, I like it
"Some say his pet elephant is pink, and that he has no understanding of "PG rated forum". All we know is, he's called JSR. "
Pizza! Nice cannon dude, very clean, excellent paint job, and gotta love those handles! Oh, you can get 10' of 1.5" sdr 21 at Tractor Supply Co. for like 4 bucks. I really like this cannon. Excellent work.
CO2 tank hybrid: Gotta fix the meter
Cane gun: Needs a pilot/fill setup
1.5" piston valve gun: Almost done
Thanks for the comments, guys.
I'll check and see if there's a "Tractor Supply Co." within driving distance of here. I also found one plumbing shop about an hour away which has it, but wants $30-something for a 10' stick, and that wouldn't include the 2"sch80 to sleeve it with obviously....
With my previous cannons (combustion and pneumatic, although I've only done one pneu), they felt kind of pieced-together when you were holding it, as if it would break if you dropped it. In fact, frequently, on my old cannons, something would come mis-aligned and would have to be fixed before it would operate again.
One of my objectives for this gun was to make everything feel solid, and build it to be able to survive a short drop onto the ground without needing adjustment before it could be fired again. I succeeded here, although the barrel support could be better. Any ideas on that?
FYI, the zip ties around the very front reducer by the ball valve are where I attach the shoulder strap, which I didn't include in the pics. I also have a 6 foot, 2" barrel, which can't be muzzle loaded (no room for a pass-through), but is a lot of fun to goof around with.
You know, I was going to use camlocks but decided not to because it was going to be over $30 for a male and female 1.5", and it would also make interchangeable barrels more difficult.
Any suggestions on that barrel support, guys?
Yes, you can try saddle tees or even reducing tees.
One tee slips over the chamber and one over the barrel with a pipe connecting the two as a support. The barrel's tee acts like a guide so it's free to slide out for breech loading.
If you choose to use a regular reducing tee, you'll need to bore out the "step" in there that keeps the pipe from going too deep into the socket. If you have a lathe then it's no problem. Otherwise find the appropriate hole saw and do your best to bore it out. For the barrel's tee, bore it real good or you might have a problem getting the pipe to slide well through it. Sprinkler.com has a good selection of reducing tees BTW.
Here's a list of hole saw diameters I found. The ones labeled with pipe entrance are what you need depending on the pipe size.
3/4", 3/8" pipe entrance
7/8", 3/4" pipe tap, 1/2 pipe entrance
1-1/8", 1" pipe tap, 3/4" pipe entrance
1-3/8", 1" pipe entrance
1-1/2", 1-1/4 pipe tap
1-3/4", 1-1/2" pipe tap, 1-1/4" pipe entrance
2", 1-1/2 pipe entrance
2-1/4", 2" pipe entrance
2-1/2", 2" pipe entrance
2-5/8", 2-1/2" pipe tap
3", 2-1/2" pipe entrance
3-1/4", 3" pipe tap
3-5/8", 3" pipe entrance
3-3/4", 3-1/2 pipe tap
4-1/8", 3-1/2" pipe entrance
4-1/2", 4" pipe entrance
4-3/4", 4-1/2" pipe tap
I've always been a fan of that breech loading method. It eliminates all the fudging around with rubber seals and o-rings and such. Good luck and once again good work!
Looks pretty good, although you could have simplified the breech loading one hell of a lot by simply cementing male threads on the chamber and female threads on the barrel.
Oh, and just wondering, how much does a 4" x 2" Sch 40 DWV ABS bell reducer cost you?
Admittedly your breech loader would require one less part, but is it really any less complicated? It's still a screw-on, screw-off breech loader.... Thanks for the tip though, if I build another combustion I'll make sure to do it that way.
The DWV ABS 4" - 2" reducers are around $6 I believe.
Total project cost for this cannon including the pipe and fittings, valve, meter fittings, gauge, copper clad circuit board for the spark strip, bbq sparker, paint, and a few propane tanks came to about $130. Kind of expensive, I know, but I did "waste" a few parts throughout the design evolution. I could probably build one scratch for under $100.
I'm going to build a 1/2 scale model of this cannon to give to a friend for Christmas, so maybe I'll play with that design a bit more. I intend to make a "mini" version of this design, though.
Thanks for the input. I might try the saddle T for a barrel support.
I was just asking about the reducer to see how much ACE rips people off. Home Depot doesn't have the reducer, OSH doesn't have it either, but Ace does, for a shocking $11.76!
I like your gun alot, the damage it does is awesome.
When you say you get 30 sec hang time, was that timed by a watch or counted, one elephant, two elephant etc, if you are getting 30 sec hang time i wonder what range you could expect. The rate of acceleration due to gravity is 9.8m/s/s which means to me that for a hang time of that duration you would have to achieve an altitude of around or over 1000 feet- i have been led to believe that this is a near impossibility with a combustion cannon.
Anyway not to take away from you efforts
I would really love to see a mini version of this, what is it's name BTW?
Happy spuddin (or rocking as the case may be!)
America, the greatest gangster of all time. With 200 million odd foot soldiers at it's whim and call.
When you fill your car with refined oil remember that it has been paid for with blood and guts, some from your own countrymen, most not.
It was counted, not timed with a stopwatch, but I'll repeat the experiment for you soon There are a lot of variables though, like the size and weight of the rock, friction of the wadding, length of the barrel, etc... so I'll either try to find a standardized ammo, or weigh the rock before launching. An altitude of 1000 feet does sound optimistic at best (though probably not impossible with a long enough barrel).
I do know for a fact it will skip a potato over 300 yards though, because my friend lives on a private lake which is almost exactly 300 yards across, and we've successfully skipped spuds all the way across. Also put a rock clear through both sides of a broken, slightly rusty Coleman propane BBQ grill.
Haven't named it. It's the seventh "revision" of my propane-powered combustion guns. Any ideas?
Yep, the mini version should be fun - going to build it for a good friend around Christmas if time allows.
Aesthetics are an important part of an "advanced combustion" - gotta scare women and children, and make your beer-drinking-football-watching friends say "holy $hit". Thanks for the compliment
One of the many perks of investing money in a hobby which will probably never return our investment in any material form, it just makes you feel good.
Thats a really nice cannon Pete... correction, its a f*ckin nice cannon.
Been a while since I've seen you put anything up here cannon wise, but I'm glad you did.
Stanford Class of 2012
"In the end our society will be defined not only by what we create, but what we refuse to destroy"- John Sawhill
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