tech e blog

***I also prefer lantern igniters to the grill style electric ones. however, it is much more efficient and safer to put the igniter in the middle of the screw on cap, as opposed to drilling a hole in the side of the combustion chamber. this way you don't compromise the structural integrity of the chamber, and you get a more complete burn and compression wave. besides, if the igniter fails, now you just have to buy a new cap. ***make sure to use primer and cement on both parts of the glue bond, not just cement on one side as shown in the video. ***grind or sand the outside edge of the muzzle, making a sharp edge pointed towards the center. this will cut your ammo to size, making sure it is a proper snug fit in the chamber.

1. First make sure constructing this type of potato gun is legal in your state. I know TX constructing a device that uses a flamable propellant to launch an object is illegal. Now the air powered one I have is very much legal. 2. After you do put it all together let it set for at least 2 hours, I've had some close calls with not letting the PVC cement set all the way. 3. For the female cap end keep some silicone spray handy, chances are if you are going to be using hairspray or something like that it will cause the threads to get really gummy and will be nearly impossible to open without a wrench. 4. Fuel mixture is by far the most important part of this gun, you don't want too much because then there won't be enough oxygen in the chamber to ignite the substance. Too little, and the potato will just kind of fall out the end of the tube, haha. I've found that carburetor cleaner (contains ether) to be one of the best propellants. Very flammable so be careful, when I first started I was putting way too much in, then I realized you barely even need to spray this stuff in there. Makes an impressive boom though. If you want to make a freakin' large cannon(got ours shooting like 300 yrds easily). Use 2'Ft of 4"inch and 4'ft of 2"inch with a 4"-to-2" adapter.

You really should make proper glue joints...not as shown in the video. Use primer/cleaner first, and then apply glue to both mating surfaces before sticking them together. And don't use the cheap drain pipe stuff, either! The heavier, non-cellular white PVC has a much higher burst strength. If you use the cellular ABS and badly glued joints, you may find yourself with worse than Lego's shattered dreams...