my monster cannon

[The High Plainsman]

i have mentioned it already on here, but i figured it was time to make a thread about it.

i am planning to make a gigantic compressed air cannon using one 18' 4" diameter sch 40 barrel, two 10' 6" diameter sch 40 tanks, and two 3" piston valves (this hasnt been decided for sure yet, but i like the idea).

has anyone here built one this size before? and if so, is there any advice/warnings you have before i commit a good deal of time and money to the project?

assuming i do actually build this, i will post pictures of the progress in this thread (there is still a chance that it will fall through).

[boilingleadbath]

I'm of the understanding that large cannons like that tend to have issues with torque in the barrel-chamber connector.
You might think about asking DR (sorry, I don't remember his contact information) this question, or asking at spudtech. They are more geared towards this type of tecnical discussion.

[The High Plainsman]

i will be sure to use something to firmly connect the barrel to the tanks at several points, probably plywood forms on the inside, and i can get access to a banding machine (like they use for stacks of wood) to pull it together nice and tight.

thanks for the advice though.

[shadowwalker]

Definately better make some rediculous support for that. My 4' chamber of 4" and a supah+ valve kicks enough when dry firing to concern me, I haven't been able to test heavy stuff yet.

Also, moving that is going to suck, but maybe you have the room and won't need to.

[The High Plainsman]

yeah, it is going to be built around 4-6 pieces of 3/4 inch plywood shaped to the tanks and barrel and it will be screwed to 2x4 runners that go the length of the tanks that can have a sheet of plywood attached to the bottom so that sandbags can be put on it to prevent energy loss due to recoil. ive got moving it taken care of as well (hopefully, i will be able to disassemble the whole thing down to about 4 major pieces, plus the wood, and all of them can be moved in my partner in crime's truck).

[DonTheLegend]

Even though recoil will steal power, it might be a good idea to incorporate some kind of stand that will move on slides to keep the gun from tearing itself apart. And considering the size of the gun, the power lost to recoil will probably not even be noticeable. I am in the process of making a recoil stand for my cannon (dual 6" x 48" chambers, 4" piston valves, and a 3" x 8' barrel)

[The High Plainsman]

that, i will keep in mind.


the idea i had about it was to get about 800 pounds of sandbags to put all around this thing to keep it from destroying itself (and also to help contain shrapnel in the event of a failure). if anyone has tried this with a big gun, i would like to hear how it worked before i try it on mine.

[aussiecyclist]

i've recently made a large piston cannon.

6" chamber 70" long
3.2" barrell 130" long (60" of that is inside of the chamber)

it has some HUGE recoil

shoots wine bottles full of water over 300meters (900ft)

shoots "rockets" over 450meters (1300ft)
these rockets are a piece of 1" PVC 30" long
atop these rockets are a small coke bottle filled with sand( around 600grams)
the rear of the rocket fits the barrel snug with the top of a big coke bottle sawn off.

the rear of the cannon screws off so that i can make any mods to the piston if needed (generally just more lube)

the large piston has had no problems as yet and i've certianity been putting it trough it paces

large pistson shouldnt have probs unless contrtucted incorectly