Looking at making a spud gun with the kid but realize that aerosol propellant is A) finickyB) inefficientSo I am looking at two design modifications. The first is swapping out the spray with low-yield homemade gun powder. It makes the gun smaller for the guy, the air/propellant ratio can be ignored, and it sends that potato flying. Only drawback is the kick, but he can always set it on the ground like a mortar. The second modification, though more dangerous, is replacing the potato with a cheap aerosol can and having a trigger with a nail in the bottom to puncture the can and send it flying with air pressure rather than an explosion. Would either of these two work?
>>2226393Consider acetylene. Just need calcium carbide and water. Might blow off your hand though.
>>2226393Do compressed air with electronic solenoid if you're concerned of efficiency. You'll need to use some steel if you're doing gunpowder and launching aerosol cans is a less efficient than a few sprays of said aerosol.You can use a small 12 volt sealed lead acid battery and one of those cheapo car compressors. High pressure release valve on the tank would make it safer. Fill with air until you hear the valve hissing.
>>2226396Hard no on that one, chief. Looking to excite, not traumatize.>>2226398I see the point about the cans. The air compressor does sound tempting, but side lessons in chemistry sound good, too. Supposing I do go the gunpowder route, would just the ignition chamber need to be metal, or would the whole barrel have to be to withstand the heat? Changing out PVC for metal piping shouldn't be too much hassle, but thinking of weight, material strength, and corrosion.
>>2226416I think gunpowder is just as dangerous as acetylene, if not more so, provided you measure out your reagents precisely. Pretty sure you can get a more consistent charge than with aerosol. Still get a chemistry lesson too. Flash powder and nitrocellulose might be serviceable propellants too, and are easily made, but might be a bit much for something with your kid. If you want to go pneumatic, one way to go is foregoing a regular valve and using a single-use rupture disc.
Using anything but metered air, with your PVC reservoir and intermediary piping rated higher than your ABS control valve bursting pressure is a fool's errand waiting for disaster. 110 psi in the reservoir and before valve piping gets you well within the safety margin of the 125 PSI burst pressure of the ABS sprinkler valve you modify for instant activation. WHEN the valve fails, by cracking and then splitting, you'll know when it's time to replace components before the whole of your cannon detonates and grenades the PVC and KILLS YOU.Tl, Dr: sch 40 PVC+ABS sprinkler valve=you living long enough to realize your fun toy works under water and can shoot a C cell through 2x 3/4" sheets of plywood
>>2226393>The first is swapping out the spray with low-yield homemade gun powder.That's called a cannon. They've proven themselves quite viable historically.
>>2226451Those use a hefty amount. I was initially thinking a pinch.
Why not propane or butane?
>>2226463>I was initially thinking a pinchYou really have no understanding of powder charges, do you? You should go pneumatic.
>>2226398Compressed air works great for yogurt cups. Cups are conveniently sold in similar diameters to piping.
>>2226393the problem with aerosol is the if you overfill the chamber you displace the oxygen, and then it can't burn. if you want to fix that install a bike valve so you can pump in air. Now fill the chamber with as much aerosol as you want, seal it up, and pump in some air. this will be much more efficient and powerful, and it's an easy modification.
>>2228550this will also teach the kid about fuel/air mixtures, and it'll be easy to optimize the gun.
>>2226393Just replace your bullets with chunks of potato, everything else will work the same.
>>2226396My pop made me one out of an old engine block and I used acetylene. I launched caulk tubes completely out of my sight.
You want ABS with a metered propane injection setup. You find the volume of the combustion chamber then calculate how much propane is needed then make a pipe with that volume. Fill pipe with propane then connect it with ball valve to combustion chamber.Google it, there are calculators that figure this out for you.Please no use pvc as pressure vessel.
Gasoline in a small spray bottle. A couple quick squirts and you have instant fuel injection, and nothing gumming up your launcher like hair spray.