How to Build a Potato Gun
										or
Fun with Vegetable Artillery
by: Bungalow Bill
with help from: Uncle Jack
thanks: Walsh and Packard Hardware

	Ok, this file is for all of you who are bored on a Sunday afternoon in 
the fall, with no place to go and nothing to do. You want to have some 
fun? Build a potato gun, and your happiness will be complete. Here's the 
scoop.

	Using PVC pipe and epoxy, and a little ingenuity, I have created one of 
the coolest ways to have fun legally that I have yet seen. A potato gun 
will cost you about $15 to $20 to make, but they last a long time and as 
I say, are great fun. Basically, you are constructing a pressure chamber, 
with a potato as the safety valve. You stick a potato in one end, and 
spray some hair spray in the other. Apply ignition and pow! 300 foot 
shot!

	Go to your local hardware store, and buy the following:

			3' of 1.5" diameter PVC pipe
			1' of 3" diameter PVC pipe
			connector parts to connect 3" to 1.5"
			3" screw end
			PVC epoxy
			flint spark lantern lighter
			extra flints
			super hold hair spray

	The connector parts are two pieces that fit together, one with a 3" 
diameter, and one the fits into the 3" piece with a hole for the 1.5" 
pipe. You epoxy these two pieces together, and then epoxy the 3" pipe to 
one side, and the 1.5" pipe to the other. The screw end fits over the 
other end of the 3" piece of pipe, and has a cap that screws on. The 
flint spark lighter is a small metal rod, about 2" long, with a knob on 
one end. When you flick the knob, it makes a spark at the other end.

	Using the PVC epoxy, assemble the screw end and the connector pieces. 
Swab on enough epoxy all the way around one piece, and then slide the 
other over it, quickly. It dries solid in about 5 minutes or less. Twist 
the two pieces after you get them together, until you can't twist them 
anymore. Then set them aside.

	Using a file or a grinder (preferred), taper one end of the 1.5" pipe, 
so that it is sharp. It needs to be able to cut the potato as you insert 
it in the gun, so make it fairly sharp. I actually used a wood plane on 
my first gun, which did the job pretty well.

	By now the pipe pieces should have dried enough. First, epoxy the screw 
assembly to one end of the 3" length of pipe. Examine the flint ignitor. 
It should be sort of L shaped. At the bottom end of the L, you will see 
that there is a sort of screw cap there. Unscrew it carefully, and remove 
it. There should be a long spring attached. Now pop out the tiny flint 
which is inside there, and set these aside, being careful not to lose 
them. At the top end of the L, there is a small screw. Unscrew it, and 
then remove the twisting knob from that end. Be careful not to drop the 
spark wheel from the other end.

	Now drill a hole in the 3" pipe, towards the back where the screw end 
is. The hole is for the ignitor, and it needs to be far enough back so 
that you can change the flint without removing the whole ignitor 
assembly. There should be two nuts on the ignitor. Remove one, and slide 
the assembly through the hole, and then replace it. Get the two nuts 
tight on either side, so that the ignitor doesn't slide around. Now 
replace the knob, the screw, and the flint and cap. Check the ignitor to 
make sure it's working, if not, fix it. Now epoxy the conector piece for 
the 3" - 1.5" pieces onto the 3" piece. Twist the two pieces until they 
are solid. Now epoxy the 1.5" length of pipe into the connector. You're 
done!

	The gun will fire all kinds of things, I've used potatoes, apples, 
bananas, and some other things. Potatoes work the best and are also 
cheap, but if you have an apple or pear tree, those will work fine too. 
Push the potato over the tapered end of the barrel, so that it cuts and 
makes a nice seal. You can throw away the excess, or stuff it in there 
along with the potato for added effect. Use a dowel or just a straight 
stick and push the potato down to where the 1.5" pipe meets the 3".

	After some testing, I have concluded that super hold hair spray works 
the best. As with the projectile, you can use any sort of aerosol 
product, but hair spray is the cheapest. Super hold has the added element 
of isobutane, which gives the extra punch for a 300 foot shot. Remove the 
cap from the end of the gun, and spray in some hair spray, about 3 
seconds worth. A fine balance is needed between too much spray and not 
enough. Also, you must factor in the noise. Less spray equals more of a 
report. Quickly cap the end, not too tight. Aim carefully, and flick the 
ignitor. The gun should go off with a good report, and the potato should 
fire off. There is no kickback, so don't hesitate to steady the gun 
against your hip, but do bear in mind that if you don't allow enough time 
for the epoxy to dry, a piece might fly off.

	PVC pipe is rated for 150 to 200 psi pressure. Testing with a pressure 
guage has shown that the hair spray ignition only produces about 10 psi, 
so the danger of pipe explosion is minimal. The only thing to keep in 
mind is not to point the gun at anyone, because at 75 feet per second 
muzzle velocity, a potato can be pretty painful, although not leathal.

	If you want to experiment with your own gun designs, I recomend trying 
out smaller lengths of pipe. A shorter barrel, however, will result in a 
less accurate shot. More or less hair spray will alter the range of your 
shot. I don't recomend using other explosives as propellant, due to the 
possibility of pipe explosion. My friend used Car-Start in his gun, and 
got great shots, but the ignition pressure was 115psi, which is much more 
dangerous than what you get with hair spray.

	Potato guns have been determined as legal by several judges, because 
they do not qualify as a gun or a bomb. Hence, you should be able to use 
them without much trouble from the law. I do recomend using them in open 
areas, such as school football fields, as opposed to your back yard. The 
noise tends to bother the neighbors after a few shots. Other than that, 
have fun, and email me if you have any questions.