Without some kind of ignition the spud gun is nothing more then a useless piece of pluming. On this page I will describe the ignition systems that I use for firing the spudgun.

The simple one
I have used this type of ignition for all the spud guns that I have build. It’s reliable, easy to get, easy to replace, and it’s cheap, it’s a lighter. Here’s a picture of it:
 

On all spud guns I have build a screw able cap that I can remove for spaying fuel into the combustion chamber, and for ventilation after firing the gun. In this cap I have drilled a hole in which the lighter fits tightly.

The advanced one
This ignition system is used for firing my tennis ball cannon. Why do I build it when I have a simple and reliable fringing mechanism at hand? The answer is: safety. I’m building this system so I will be able to detonate the cannon from a save distance. I need the save distance when I start experimenting with highly flammable fuels.

The ignition system will consist of:

• an old automotive ignition coil;
• a sparkplug;
• a condenser;
• a switch;
• a few meters of wire;
• and a 12V battery.

The old ignition coil I got out of my old car.

The first version I build did not include a condenser, but included a few other items:

• a relay;
• two 12V batteries
• and a sparkplug cable.

The only thing I got from this first attempt was a clicking sound from the relay that I used. Great! The relay works, so what! So I decided to remove the relay from the setup, which also meant that I only needed just one battery.

The second attempt resulted in completely nothing! Hmmmm... I did not use a condenser. A car does, let’s try using a condenser in the setup.

The third attempt resulted in sparking sparkplug. That’s probably why they call them sparkplugs. Anyway, I build the sparkplug into another screw able PVC cap. After hooking up the ignition system I went outside to test the cannon. After a dozen attempts not a single shot was fired. Conclusion: the spark is to weak, back to the drawing-board. A few googles later I decided to remove the high resistance sparkplug cable.

Instead of the sparkplug cable I used a thick low resistance copper cable. Still I found the spark to be weak. Next I decided to move the sparkplug electrodes further apart, and managed to get a bigger more powerful spark. Back outside I went for another test run. The results where very satisfying, out of 4 attempts the cannon fired 4 times without hesitation. Click here if you would like to see the ignition system in action.

Below you will find the schematics for hooking up the ignition system.

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