Spud gun science expiriment

[metalmeltr]

My teacher may be offering extra credit for performing and documenting a science experiment to share with the class. My first thought was potato guns. I planed to test popular fuels and see which is most powerful. Instead of coming up with a consistent projectile and setting up plywood targets I want a simpler Mythbusters inspired approach. The cannon would be hung by hinged suports and have a marker attached to the gun, the marker would be placed up aginst a piece of plywood with a replaceable paper surface. When the cannon is test fired the gun's recoil will push the cannon back drawing a line on the paper. After finding the most powerful fuel I will shoot at several sheets of plywood for demonstration purposes. I intend to use a burst disc basic combustion cannon for this experiment. I plan to test the following fuels
ether
hairspray
carburetor cleaner
Fuel X(polyolefin adhesion promoter)
Propane
MAPP

With the burst disk in place will I need to use a projectile or will the gun recoil with the burst disc?
After I do the expiriment I will be sure to post the results.

[Technician1002]

The mass of the expelled air will cause a recoil. It will be less then the recoil with a heavy projectile.

[metalmeltr]

As long as the gun will recoil that is all that matters, acuallly less recoil may be better because the hinged suports would only have 90 degrees of travel, I may put a spring on the suport to provide resistance if nesasary.

[theBOOM]

Use, no barrel, but beware that a burst disc combustion without a barrel WILL be loud, so warn the people or use proper ear plugs or something.

Just make a 1 inch combustion gun, get a union, make an "epoxy sparkplug" and tap in a quick disconnect and make an external MAPP meter for the gun, shouldn't be too hard.

Btw, since it's gonna be small, make the "hinges" loose, so that the gone gets more recoil.

EDIT. it is gonna be small right? Maybe give us some more info of the cannon you want to build

[Gun Freak]

Or you could make it simpler and use a pneumatic and test which pressure will have the most recoil
How are you going to meter the fuels like hairspray to make sure there is an even amount of all?

[theBOOM]

Gunfreak, if he decides to go pneumatic, he'd have to bring a pump or some type of air resevoir to fill the gun, too much of a hassle IMO.

I say he makes an external fuel meter, take about 3 loaded meters and just demonstrate a couple of shots infront of the class.

[Gun Freak]

Nah pneumatic would be way easier, but we all know the lower pressure shot would have more recoil haha jk

[theBOOM]

I don't know I think combustiones look cooler than pneumatics when it comes to firing, the muzzle flash really gets people going, it'll probably entertain the class more than a pneumatic. Just my opinion though.

[Gun Freak]

the pneumatic was a joke... he should go with the combustion for sure.

[metalmeltr]

I doubt I will be taking the gun to school. The experiment would be done at home and record though video and photos. I want to build a full size gun with a 2" x 5' barrel and 4" diameter chamber, I have yet to calculate the chamber length. aresols will just be sprayed in for a certain length of time(2 seconds?).

[theBOOM]

I think you should def. meter it just to make it look more scientific I guess, it's not hard at all, and you can show your teacher how you made the calculations and all... Put a heavy projectile on the barrel and you'll have some massive recoil.