PVC Air Cannon

Step 3 Modify the end cap

This is the trickiest step in the whole build. First, you need to cut out the valve part of the old bike tire. Try to make it square, but its no big deal if its not. Make sure to leave a lot of the surrounding rubber though.

Next, drill a hole about the size of the stem of the valve into the center of the end cap. A 5/16" bit worked well for me, but check for yourself before you drill. The important thing is that there's a really snug fit when the stem goes through the end cap. Remember, there's going to be 100+ psi of pressure there.

Once you have a nice snug hole for the valve to go into, put some super glue on the rubber surrounding the valve, and stick the valve into the end cap. Smooth out the rubber so there is a tight and smooth seal against the PVC.

Comments

[hammer39]

No glue needed. When you pull a tire valve through the hole it seals because of its shape. Look at a car tire, You can see how it seals.

[Circuit7]

Its better to be safe than sorry though. That thing somehow slips (not likely) then there is no way to get that thing out without destroying your gun.

[jderksen1]

I found that the thread-in valves you get off motorcycle rims work good. You drill the hole, tap a thread in it and put a washing and nut on the inside. You can also put some silicon around it to seal it a little tighter as well. I find doing this acts as a more permanent fitting.

[hammer39]

Just use a valve stem for car tires. You can get it at Auto Zone or wal-mart. Drill the proper size hole, and pull the valve through. No glue needed.

[GianniMora]

you would have to glue it some how or else there will be an air leak... is suggest JB weld