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Propane Meter and Propane Injection

Propane is an excellent fuel for spudguns.  It is clean, safe and very cheap!  A blue cylinder for torches costs about $3.  Camping propane can be bought in the green Coleman cylinders for around $5-6 for 2 cylinders.  Either will work with this setup.  Hopefully these plans will help with the construction.

Type 1:

This is a little different style of propane meter than what everyone else uses.  The advantage is that you can use this on any gun you make, just adjust the PSI of propane in the meter for each individual gun.  All the launcher needs to use this meter is a schrader valve.

Here is a parts list:

  1. propane torch head (the cheap ones) cut below the bend with a pipe cutter.  This connects it to the propane tank. 
  2. a 7/16" compression to 1/4" male pipe fitting.  This connects to the brass pipe you just cut on the torch head (these are extremely hard to find, but I bought mine at
  3. 1/4" Tee
  4. out one side of tee: 100 PSI Pressure gauge with 1/4" male pipe thread (MPT) (100psi for more accuracy)
  5. going out of the other side of the tee is a 1/4" MPT close nipple
  6. a 1/4" ball valve
  7. a 1/4" nipple ( I think it was 1" or 1 1/2" long)
  8. 1/4" tee
  9. out one side of tee: 1/4" close nipple
  10. tire valve filling tool (air chuck?)
  11. out the other side of tee: 1/4" close nipple
  12. 1/4" to 3/8" adapter
  13. 3/8" to 1/2" adapter
  14. 1/2" to 3/4"  bell adapter
  15. 6" 3/4" pipe nipple
  16. 3/4" pipe cap
  17. lots of Teflon tape on all threaded parts.

I used brass on most of mine, but I would suggest using galvanized pipe, because it is much stronger, I had one mishap when my niece knocked mine off my dresser and broke it.  It broke at the 1/4 inch nipple (the one I thought was either 1" or 1 1/2" long).  But anyway that is the part list, one good thing about this propane meter is that you can use it on multiple guns.  The last thing you need is a valve stem with 1/4" pipe thread on the other end, and a pipe tap to tap your chamber (I bought mine at , but you should be able to find them at most hardware stores).  One last thing, how to use it: with the ball valve closed let about 30 PSI into the small section, then close the gate valve on the torch, open the ball valve, and this small charge will seal the air chuck valve part.  Then open the gate valve and fill the meter to the desired pressure, mine is 37psi, but will vary with the gun.  Close the ball valve then press the air chuck onto the valve stem on your chamber.  It sounds like a long procedure, but it is really simple and fast, only takes a few seconds to do.

As a side note you could put a small regulator somewhere before the ball valve to make the propane be the same pressure all the time without having to look at the pressure gauge.

Type 2:

This is the type of meter that most people use.  

Details coming soon....


For info on how much propane to use (as in PSI), and an extremely useful fuel calculator see Latke's site on my links page.  Also see SpudTool for info.


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