SpudFiles

I just test fired some of what I consider crazy powerful potato cannons. They may be wimpy compared to some of the stuff folks here have built, but... One is a coaxial with a 3" chamber and a 1.5" barrel and the other is also coaxial, but with a 2" chamber and a 1" barrel. Both have 5' long barrels and full length chambers. Both are barrel sealing piston valve designs.

The 1" one was fired at 215 psi which is under the rating of the tubing (280 psi rated), but is well over the rating of the pilot valve (1" Orbit jar top). The 1.5" was fired at 180 psi which is also well under the rated capacity of the tubing (260 psi) and still over the rating for the orbit jar top.

I think the Orbit jar top pilot valves could fail at these pressures, but they reportedly tend to just blow out the diaphragms rather than explode. The 1" launcher did 511 mph (750 fps) and the 1.5" one did 555 mph (814 fps). The 1.5" one is starting to be too scary to fire in my test setup at that pressure. I think I am done testing it until I can test outdoors with some shielding or from a safe distance. Heck I am done with testing the other one indoors as well.

Fun stuff for this rainy day though.

Big bores shouldn't really be tested indoors, my former bedroom and test range was liberally ventilated with holes and fragments... if you're going to do it regularly, designate an appropriate area

Also, beware abusing the pressure rating of plastic components. Failure is unlikely within reasonable limits will at the very least be hard on your ears if it occurs.

jackssmirkingrevenge wrote:Big bores shouldn't really be tested indoors, my former bedroom and test range was liberally ventilated with holes and fragments... if you're going to do it regularly, designate an appropriate area

My designated area is at least in the basement