Step 3: Build The Pressure Chamber

Picture of Build The Pressure Chamber

The pressure chamber is assembled first. It should be allowed to cure a full 24 hours before applying pressure. PVC pipe assembly is simple and is covered in other instructables as well as on youtube. A brief refresher on solvent welding PVC pipe. Use in a well ventilated area, make sure both pieces to be assembled are clean and free of burs, prime both pieces, put glue on both pieces, assemble with a twisting motion and hold for 15 seconds. For brevity's sake, solvent welding will be referred to as "gluing" PVC. The video shows how all the parts are assembled, make sure you have youtube annotation turned on.

Pressure chamber supplies
1 1" MPT (Male Pipe Thread) to 1" slip street elbow
1 1" elbow
1 2" to 1" reducer bushing
1 2" cap
1 2" coupler
1 foot of 1" pipe
Minimum 9" length of 2" pipe
1 valve stem
PVC primer and cement
Drill and 7/16" bit (or 5/8" if you purchased the larger base valve stem)
optional 1 pressure gauge

  • Drill the correct size hole in the center of the 2" cap. 7/16" for the smaller (.453" base) valve stem, or 5/8" for the larger (.625" base) valve stem. Pull the valve stem through this hole.
  • Cut a length of 2" pipe at least 9" long. Keep in mind that the longer it is the more time it will take to fill up if you are using a manual air pump.
  • Glue the 2" to 1" reducing bushing into the 2" coupler
  • Glue the 2" cap with tire valve to one end of 2" pipe. Glue the coupler to the other end.
  • Glue a short piece of 1" pipe into the bushing, glue the 1" slip elbow onto that.
  • Cut a piece of 1" pipe for the pistol grip, something between 3" and 6" should work. Glue the 1" MPT street elbow to one end of pistol grip pipe.
  • Glue assembled pistol grip pipe into 1" slip elbow on pressure chamber. Ensure that the threaded fitting aligns with the axis of the pressure chamber and doesn't point off to the right or left.
  • Optional: Drill a hole of slightly smaller diameter than the fitting of the air valve, locate the hole 3/4" into the pipe side (NOT the bushing side) of the 2" coupler. Use the air valve to cut threads into the hole, then thread back in using thread locker on the fitting.

arty8173 years ago
Hello i want to say this is wicked allready half way done but you see crispyjones, I live in Australia and we don't use inches like where you live, america probably so i wanted to ask what egsact moddle of the valve stem 453" can you please convert the inches in the metric system and tell me what egsace moddle to buy? or can you send me another link of what valve stem you bought PLEASE PLEASE PLAESE thanks:)
ultravark4 years ago
Is there any reason that you couldn't replace the tire valve with a schrader valve like this?  It just seems to me that screwing in the schrader valve would be more secure than the snap fit of the tire valve. (Though this is my first pneumatic cannon project, so I could be missing something completely).
Link didn't work:
How did you manage to get your valve stem through the hole? The .453 stem just seems too big for the 7/16" hole I drilled. Mine says " .453" RIM HOLE 1-1/4" LONG". Is that any different than the stem you used?
what kind of epoxy should i use
could you build a second pressure chamber and instead of 90 use a tee and a valve
Kantor5 years ago
when i stick the valve into the cap should i add some epoxy around it or will it hole pressure
crispyjones (author)  Kantor5 years ago
As long as you drill the correct size hole for the tire valve you selected, it should hold pressure just fine.  No epoxy or other sealants are used when tire valves are installed in car rims.
how would one attach the pressure gauge? is it already in the coupler when u buy it? and would it b safe to use a valve stem for a large air compressor? and if not, what does the valve stem that u used connect to? thnx
jtlax6 years ago
you forgot to add 2" coupler to the materials list