The Antenna Launcher 1.0

21 05 2009

Q: What do you get when you combine a bored geek, Internet access, and a trip to home depot?

launch

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,

DSCN0789Valve,

DSCN0791Easily interchangeable barrel,

DSCN0790

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.

DSCN0787

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.

http://www.youtube.com/watch?v=Mb7QRQ-EEus

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.

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7 responses

21 05 2009
Kristian the Conqueror

Barely 3 weeks since finals ended an you’re already building pneumatic spud guns… Good god man, relax a little. Or get a job.

However since I’m taking the time to post here, I’ll make a small suggestion; try and see if you can get a barrel for your gun that’s threaded along the inside for it’s full length. That or see if you can improvise somehow your own rifling. I am thoroughly of the opinion that your range will be increased unless you’re using some model of sabot (which beings to mind another idea for projectiles…)

23 05 2009
worldwise001

He’s getting a job. Well it’s more of an internship.

8 10 2009
Allied Antennas

cool project. Any updates?

9 10 2009
pherricoxide

I attached a cheap $10 fishing real with hose clamps and used it successfully at field day. Other than that I haven’t made any improvements since it seems to work well enough the way it is.

31 08 2010
Everest Base Camp Trek

Fantastic site. A bunch of beneficial information here. I’m posting it to a few friends!

12 07 2013
Bruce Lunde

Do you electronically fire the solenoid?

16 07 2013
pherricoxide

In this version I didn’t, but later a 9V battery and a push button got strapped to it to do exactly that.

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