This is all i needed for it:
2 nails or spark plug
1 meter of PVC pipe, most diameters will work, i recomend under 90 and over 30 unless you have a pacific projectile in mind
wires, about one meter will be enough
high pressure pipe glue or epoxy glue
Projectile (i used news paper tape and rocks)
Explosive gas ( i used deodorant and then switched to a butane refil bottle, most arosols will work, DO NOT USE PETROL as it is to powerful for a PVC pipe)
spark generator, i used the one from my barbecue or you could pull apart a gas lighter
Tripod with clamp (i used my telescope stand as it fit perfectly, but the stand is optional if you wish to hold the cannon, just make sure it doesnt explode and splinter into you)
Drill and bits
How to build:
Step 1: Build your spark Plug
Dill two holes of about two centimeters apart into your pipe about 10-15 centimeters from the back of the pipe, use a drill bit slightly smaller than your nails so they fit in snug. Now Hammer your nails in so the tips are very close, enough for a spark to ark across. Now solder/ twist your wires onto the nails. After thats complete glue your wires in air tight with the epoxy or pipe glue. Now connect your sparking devise to the wires and test that every time you spark you can see an ark from nail to nail. Once its consistent your ready for the next step. I have though of two alternatives to the ignition method i just described: a) Use a spark plug instead of nails b) glue and entire gas lighter into the back of the pipe so when you pull the trigger the flame ignites the fuel in the pipe.
Step 2: Glue the back on the pipe
This step is fairly simple, paste your glue on the pipe and the inside of the PVC pipe end and push them together to block off the back end of the pipe. Make sure it is the same end of your sparker. Now wait for it to dry ...
Step 3: Making your projectile
I made mine projectile out of rocks wrapped up in news paper then held together with boxing tape. Your may wish to use scrunched up foil, vegetables or if your using the right sized barrel the traditional spud! (thats a what some people call potatoes in Australia in case you didnt know) As i will say later you can experiment with different projectiles. Make sure your projectile fits snug as if it doesn't the gases will just pass it and only push it a small distance.
Step 3: Set it up!
If your using your barbecue sparker then attach your wires to that, if your using other ignition methods set up those. Now set your cannon into your tripod/ clamp it down. Now get your fuel and spray about three or less one second bursts into the pipe (experiment with fuel quantities) and jam your projectile into the barrel about 30cm down or less. Its now set up!
Step 5: KA-BOOM
Set off your ignition mechanism and watch your projectile fire into the air and, if fired at night, you'll see an incredible blue muzzle flash. Just make sure you dont try to hit people with it :-P Now you can experiment with different ammo and see which one works best.
You may notice that it can be quite loud and is great for annoying neighbors, if you do not have that intention you will need to use a lighter projectile such as scrunched up foil. You can also Put on a show and at night, fill up your cannon heaps, even use a small amount of petrol, and explode it without petrol. it will make a quiet wwwuummpp sound and create and AWESOME blue muzzle flash that is worth seeing. In the video you'll see a 1 kg projectile fire about 100meters (sorry about the video quality, it was caught on a phone)
This can be quite dangerous if misused and i will except no responsibility for what you do with it, so do not do anything stupid (durr) and make sure you check theres no defects as i will take no responsibility for accidents.
It would be appreciated if you vote for me in the maker bot challenge, it would be really cool, useful and productive for me to assemble and use the MakerBot. And no, i didn't build this just for the challenge. Thank You for reading and watching
PS: The laugh at the end of the vid isn't mine :-)