Instructables

Rapid fuelling potato cannon mounted on Kubota tractor

Featured
Picture of Rapid fuelling potato cannon mounted on Kubota tractor
This potato cannon has a unique one-way valve system that lets the fuel (propellent) into the combustion chamber and prevents the explosive gases from escaping out through the valve.  The cannon can be refuelled and fired in a couple of seconds.  We decided to mount the cannon on the bucket (front end loader) of our Kubota BX25 tractor.  With the bucket as a shield, we get a big safety advantage, and we also get a nice tank-like experience when manoeuvring the cannon in position to strike the target (see video below).

The cannon is fired with a remote electronic ignitor connected with wires to the spark plug in the cannon combustion chamber. The ignitor is secured to the tractor engine hood with a couple of rare earth magnets.  The ignitor is an inexpensive unit available at hardware stores and is normally used to ignite gas barbecues.    The wooden cannon cradle is mounted to the bucket with two C-clamps making it quick to install and remove.  We mounted a GoPro Hero2 camera on the cannon barrel to record the potato firing action from that perspective.
 
Remove these adsRemove these ads by Signing Up

Step 1: Study what is out there paying attention to the safety aspects of this kind of project



We checked out potato cannons on the web and based the fundamental design on what we learned there.  We ended up going with ABS plastic pipes and associated fittings for the cannon.  The combustion chamber has an inside diameter of 3 inches and is about 24 inches long.  The cannon barrel is 1-1/2 inches by 36 inches.  A reduction coupling connects the two pipes together.  The other end of the combustion chamber is fitted with a female coupler and a removable (threaded) clean-out plug. Hair spray seems to be the propellent of choice so that's what we experimented with first.

The YouTube video, below, shows the cannon in action and also presents some of the construction details.  The Instructable step by step instructions below are quite detailed to help the builder have a greater chance of success.

A second video giving more construction information can be viewed here: http://youtu.be/T7r6I8M4AG4  

Be aware that this kind of device can be very dangerous - it would be smart to read and view plenty of  background material before construction and testing.

J,R,D, Ltd6 months ago

This is a great design! The only thing I would change short of a autoloading feature(not sure how that would be done anyway) would be to flip the C clamps around just in case the bucket is lowered all the way.

batonas2 years ago
Hi, I have made few combustion cannons myself and I know that it the biggest problem with those is venting, it takes some time because you have to uncap it and and vent it by hand, for my cannon I've made another valve just to vent it with an 2L inflatables pump, I used ball valve but one way valve would be better, so my question is - how long does it takes to fully load after a shot? P.S. if anyone have some questions about combustion cannons feel free to ask :)
nlinventor (author)  batonas2 years ago
batonas - Hi, this was our first potato cannon and Max (star of the show in the video) had just a 5 day visit. He got to do some tractor driving and help me make the potato cannon. With that limit on time we didn't get a chance to do a lot of testing - BUT I know what you are getting to re venting. Although we enjoyed the construction and testing of the design we were rather disappointed in the overall results because of many misfires. Max wanted me to try taking of the cap and give it a try but I didn't really get around to that before he had to leave. My thought on a possible solution would be to have a can of compressed air to inject in to the fuel port and to see if that would do the job. I haven't tested this so it is only speculation right now. What do you think? Do you think that would work?
compressed air would definitely do the job, but can would not last long and it cost so I prefer inflatables pump (rechargeable one would be convenient) and one way valve.
P.S. make a fuel meter for your cannon, hairspray is the worse you could use, here's a link
http://specialized-weapons.wonderhowto.com/how-to/build-propane-meter-for-use-combustion-launcher-210166/

To fix the compressed air not lasting long one could always mount one of these in the bucket: http://www.harborfreight.com/5-gallon-portable-air-tank-65594.html And then you would have plenty of air.

I thought abs was not pressure rated though, pvc is, but pvc has poor thermal breakdown point.

NEITHER are okay. Only use metal piping unless it is a combustion cannon. Then use polyvinyl chloride. It must be pressure rated.

frighteningly ingenious... Im glad to have seen it but i wish i would have thought of it.
Does anybody know if I should use abs or pvc for a potato gun using hairspray?
nlinventor (author)  Spenceravery1 year ago
We used ABS. Other use PVC - seems like both are ok but check further to be sure.
DeeFarm1 year ago
Hi, I write for Farm Show magazine (www.farmshow.com) and would like to interview you for an article. Email me at dee_goerge@yahoo.com.
Thanks!
msh13531 year ago
bravo "nlinventor"
that's greet
nlinventor (author)  msh13531 year ago
Thanks :)
papagordie1 year ago
Well done with some creative ideas.
nlinventor (author)  papagordie1 year ago
Thanks papagordie :)
PS1182 years ago
Very nice, indeed!

The only thing left is an auto-loading mechanism and you've got a potato TANK!
nlinventor (author)  PS1182 years ago
PS118 - Thanks, maybe you or some other instructables creator will handle the auto-loading part.
I think the loading itsself could be accomplished by the same time-tested mechanism used in Gatling Guns, if not for one major problem. What's really holding us back in this science is the non-uniform shape of the potatoes.

What the future demands is some kind of form or mold to grow a consistent caliber of russet.

That, or perhaps if we could somehow harness and employ tater tot technology...

LOLz :D
Where I lived as a kid, we had a potato and onion farm nearby. They standardized the sizes of potatoes all of the time, through a simple set of metal grates while processing them.
Are you allowed to make a punch press to cut the potato into a clean cylindrical shape prior to loading? If you can make a potato cannon I am sure you can build a simple biscuit cutter (band saw blade in the round?) onto the front of the cannon, and make a "tamper" with a spike on the end, to ram the potato into the cannon, cutting off the excess in the process.
- oh, forgot to say, we used to just ram the potatoes ONTO the barrel, versus trying to make them fit inside the barrel. Makes a nice cork!
well, of course this is not as sci-fi, but you could pre cut your tuber ammo with a short piece of the barrel pipe.
nlinventor (author)  PS1182 years ago
Well they make square tomatoes so you never know.
nlinventor (author) 2 years ago
Foxtrot70 - Thanks! The electromagnetic gun sounds interesting :)
Foxtrot702 years ago
Excellent Instructable!!! Great position for the video cam for shooting, I'll bet Max is the first kid in the neighborhood to have a potatoe cannon one like this! Your next generation should be an "electro-magnetic rail gun - ring launcher", with it you can punch holes through 1/2" plywood.
mikeasaurus2 years ago
This is the potato cannon Instructable I have been waiting to see. Thank you.
nlinventor (author)  mikeasaurus2 years ago
mikeasaurus - Thanks, but check out all comments, such as from batonas, because the idea is still underdevelopment with respect to venting or purging the combustion chamber. I don't expect to get back at our cannon until perhaps next spring or summer to do more testing.