Build A Net Gun

Step 3 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

Assembly

• 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.

Comments

[pingpongplaya911]

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?

[pingpongplaya911]

Never mind I got it.

[MafiaGerbil]

Hey, I think I am having the same problem you did. How did you get it in there?

[pingpongplaya911]

You have to pull it extremely hard. I believe I used a pair of pliers and lubricated it with water or something similar. You have to pull it so the notch of the valve comes on the outside of the cap. It may seem impossible, but it's not.

[ultravark]

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).

[ultravark]

Link didn't work:
http://www.spudtech.com/detail.asp?id=44

[crispyjones]

I stayed away from these for a few reasons. They are usually 1/8" NPT, so you need some adapters to get to anything nominally PVC sized, that adds cost. If you knock against something hard with a rubber tire valve it just bends, I think these will be more likely to snap some plastic off with them. One of my net guns died a similar death when it fell off a railing and the metal pressure gauge snapped off a chunk of the pressure chamber. Also, as long as you drill the correct size hole, the rubber ones are very secure.

In summary, I didn't use them, mainly, because I am cheap, and I think they might make the launcher less durable.

[funwithfire93]

what kind of epoxy should i use

[crispyjones]

I recommend 5-minute epoxy, the kind that comes in the side by side syringe dispenser.  You want something that can flow around the air fitting and in to the orifices of the sprinkler valve.

[mwyr]

Where did you use 5-min epoxy vs PVC primer/cement?

[crispyjones]

Only use 5 minute epoxy for certain parts of the trigger valve, detailed in step 4 Fig 7.  For all other PVC to PVC joints use PVC primer and cement.

[mwyr]

Got it, thanks.

[engineer8604]

could you build a second pressure chamber and instead of 90 use a tee and a valve

[crispyjones]

Certainly.  I intended the 90° bend to be a pistol grip, the net gun will function fine (perhaps better) without it.

[Kantor]

when i stick the valve into the cap should i add some epoxy around it or will it hole pressure

[crispyjones]

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.

[mazingbrainiac]

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

[crispyjones]

The pressure gauge does not come attached to the coupler. You need to drill a hole slightly smaller than the threads of the gauge, and then thread the gauge into the hole you drilled. I would use loctite or similar to make sure it stays in place. The valve stem is of the type used on passenger car rims, and it is used in the same way. Drill a hole in the PVC and pull it through, just as you would installing a valve stem in a car rim. I am not sure what a compressor valve stem looks like, so I can't really give you any tips on making that work.

[mazingbrainiac]

http://www.tcpglobal.com/images/amfcp21lg.jpg this is what i was refering to as a valve stem for an air compressor, which connects to one of those http://www.harborfreight.com/cpi/photos/96300-96399/96398.gif i was thinking of fastening the first one to the cap with a 1/4 nut on the other side. any gauges u suggest? thnx

[crispyjones]

The first thing you posted is what I call a 1/4" male quick connect, the threads are pipe thread and will only thread into other pipe thread fittings. You could use something like a 1/4" black pipe coupler on the inside to act as a nut. Additionally, your pressure chamber won't be sealed unless you install a small ball valve between the coupler and the pressure chamber. If you want to use quick connects, I would use this type, similar to your second picture but with male threads at the base. These are air tight so your pressure chamber would be sealed. You would need to build a male to male adapter to fill it.
There is a Harbor Freight close to my house, so I use this pressure gauge.

[mazingbrainiac]

hm, yes thnx the air compressor came with everything i need. but do u know what the pictures i showed u r actually called? the piece u found is what i was referign to, just hard to find a picture.

[jtlax]

you forgot to add 2" coupler to the materials list

[crispyjones]

Good catch, I've updated Step 1and Step 3. I hope it wasn't a long drive back to the home improvement store.