You are not going to be able to launch that potato without
something to ignite your propellent. You need a ignitor
to fire off your fule. This page deals with the common
ways of setting fire to your propellent.
These are some of the most common types :
This might be the most simple method but it is also the least efficiant. To use this, simply drill a hole in the side of your combustion chamber and ignite the fuel by inserting a lit match in the hole. Drawbacks to useing this method are that part of the explosion will vent out throught the hole and reduce your range. You may also risk burning your fingers using this method. If you don't wan't to burn your fingers with a match, you may use an ultility lighter like this one
Safer than the match method, this method reduces your chance of burning your fingers but it is still not efficient because you also have to have a hole in the chamber.
There is also a delay between ignition and fireing. Fuses are hard to find but you can cut some off fireworks
You can get this at a sporting goods storethat sells lanterns. This thing is just a piece of flint and a steel wheel on a stick with a knob that allows you to strike the flint by rotating the wheel . Install it by drilling a hole in the side of chamber the size of the shaft. Follow the instructions on the package on how to put install it as you would normally install it in a lantern. To ignite, give the knob a twist. This ignition method is inexpensive and it is also efficient because the shaft seals the hole.
It also throws burning flint everywhere so it is very good in ignition of the propellent.
This is a lighter that has a long nozzle and are commonly called "Ultility Lighters".You may purchase these at a supermarket or a sporting goods store or just get a old one from someone. It doesen't matter there is still lighter fluid in it or not because the flint is what ignites the fuel To install, drill a hole in the side of the chamber the size of the lighter nozzle and glue it in with epoxy glue. The end of the lighter should extend halfway in to the chamber. Make sure it is secured firmly or it may blow out later.To fire, just press the trigger and BANG!
If you have a gas bbq, this is that red button that you hit to start the grill. It works by generating high voltages by strikeing a quartz crystal which powers a spark electrode inside the grill. This is the most common method of fireing potato guns. Wire the ignitor to a car sparkplug. (see picture)
Now drill a hole in the side of the gun the size of the threaded part of the sparkplug. Screw the spark plug in firmly. Ignitors can be taken off bbqs or
you can get repalcement ignitors at a hardware store or at Barbeques Galore. After the spark plug is installed, you'll have to tape
any loose wires and the ignitor to the gun. Position the ignitor someplace where you can press it easily.