Q: What do you get when you combine a bored geek, Internet access, and a trip to home depot?
A: A pneumatic projectile launcher
The main purpose of this little project is to create a launcher to get wire antennas high up in trees. Launch it with a projectile tied to a piece of fishing line, and then use the line to pull up a wire antenna. The barrel is easily changed though, so it can also be used as the classic spudgun, tennis ball launcher, or anything else.
The standard potato launcher uses something like hairspray to create an explosion behind the potato. Despite the fun playing with explosive chemicals, this is very hard to control. The pressure can vary anywhere between 30-70 PSI depending on what fuel you use, how much of it, and a few other factors. Controlling whether the projectile launches over the tree or over 3 trees and the cabin can be difficult.
Using a compressed air chamber pumped up with a bike pump, you can fine tune the pressure. Plus, in theory you could go to over 100 PSI quite easily, but due to safety reasons and a few weak points in this design I’ll probably keep it below 50. The main weak point is that the chamber is ABS but the only fittings I could find are PVC, so I had to find some special PVC/ABS general purpose cement which isn’t rated for high pressure. Of course, ABS pipe isn’t actually rated for high pressure either, but I have a feeling the fittings would be the first thing to fail on this. The materials used are below,
- 3″ endcap
- 2′ of 3″ pipe for the air chamber (150 cubic inches of air)
- Fittings that convert that down to a 1″ threaded male connector (pain to find, hence why I used PVC/ABS combo)
- 1″ sprinkler valve (manual or electronic with solenoid control)
- 1″ male threaded to 1″ female adapter
- 3′ of 1″ pipe for the barrel
The air chamber,
Easily interchangeable barrel,
I think a longer barrel might actually work better, I’ll have to do some experiments with it. The projectile I used is a 3″ piece of 3/4″ PVC with endcaps on both sides.
The result? The following video was using a 30 FPS video camera and the projectile traveled over 10 feet in 2 frames. If you do the conversions, it was traveling over 100 MPH when leaving the barrel.
I know this isn’t as computer related as my usual blog posts, but just wait till I get a few roving potato tanks patrolling my yard. Beware of guard robots and flying potatoes.