"Don Bruder" wrote in message
news
In article ,
Adam Smith wrote:

I wonder what they use in those potato and pumpkin cannons?

The only one I ever saw used a 2" iron pipe with a cap on the end tapped
for a spark plug. Some butane was sprayed into the pipe from a lighter
refill canister, which mixed with the air of course, then the potato was
jammed in almost to the bottom to compress the mix. Then, a 9V battery
was applied to an ignition coil hooked to the spark plug. Next time I
saw the potato it was hundreds of feet in the air. I didn't do this
myself BTW, and I didn't want to be anywere near it when it was
fired--I'm not crazy. I saw this experiment at an
all-engineering-students frat house back in my college days.

Bah... You make it sound like all spud-guns are an accident waiting to
happen.

Well, they are... But mainly if you can't AIM.

Best one I ever encountered was made out of nothing but PVC pipe and a
flint sparker out of an old coleman lantern. Barrel was 1.5" pipe about
3 feet long, with a fiarly long taper cut on the inside edge of the
muzzle end to make a pretty decent "knife edge" for cutting out good
tight-fitting chunks of potato. The "breech" was made out of a 4x8 inch
"cleanout" section with a screw-in cover, and the barrel was threaded
into a 4-inch to 1.5 inch cover/cap that fit the cleanout tube. Punched
through the side of the breech was the sparker. Firing sequence: Unscrew
breech plug, spray a 5-7 second shot of rite-gard, final-net hairspray,
or similar into it and slap the cap on. Grab big tater, and punch down
onto muzzle end, cutting out a tight-fitting chunk of spud, punch
spud-slug down with a carefully measured chunk of broom handle for
compression, point, and spin the sparker. T-whunk! Tater gone bye-bye!
At a rather impressive rate of speed.


Ours had a 4 or 6 inch PVC barrel, a 1 1/2 inch busing inside, then a
cleanout plug at the end. Also used the flint igniter. Fuel was starting
fluid or pentane. The 4 incher would shoot a well packed snowball quite
nicely.

Always wanted to refine it for a more rapid fire and a larger barrel flame
at night...