Parts list:

To build your on-board air system you will need to gather a few things before you get started.
You will need an old A/C compressor, electric wire, some 3/8" ID air hose (300 PSI works well), 1/2" hose clamps, 1/8" or 1/4" thick steel pipe (can be 6" or 8" OD) with 2 weld-on pipe caps, 1/4" air hose fittings, Teflon pipe thread tape, and an air pressure switch (can be found at most hardware stores).



Building your air tank:


Once you have gathered your pipe, you need to cut it to length. 10-12" of pipe should be plenty. Next, weld your pipe caps on your pipe. If you're not good at it or can't weld, take the pipe to a friend or a local metal shop who can.
Once you have it all welded together, drill 2 3/8" holes on the top of the tank. Next, you need to tap some 1/4" threads in those holes. Now flip the tank over and poke another 3/8" hole in the tank and tap some more 1/4" threads in the hole. The one on the bottom of the tank is your drain hole. You may want to weld a piece of square tubing with a 1/4" steel plate to the tank as a mounting foot. Now that you have your tank welded and tapped, paint it. When it's dry mount it to the frame where you have room for it.

I am using some 3/8" steel rope as a back up mount in case the bolts vibrate loose or a weld breaks.


Installation:



First you need to install your A/C compressor if you don't already have one mounted.
Next, using the old A/C lines and compressor fittings, put a "quick chuck" on the discharge side of the A/C pump. You might also want an air filter on the intake side (I'm using a coffee filter and a 2 stroke oil mix bottle as a temp thing till tomorrow). Between the "quick chuck" and the compressor, you need to install a 1/4" pipe "T". This is so you can run an air line to your air tank. Connect enough of the 3/8" ID air hose to the pipe "T" and run the other end over to your air tank. Do not forget to tie the air hose to the frame with cable ties or something like that. Next, you need to hook your air hose to your tank using one of the 1/4" fittings. Before you screw any of the fittings into the tank you need to wrap the Teflon pipe thread tape around the threads a few times. This will keep any air from leaking out around the threads. Clamp the air hose to the fittings using some hose clamps. Don't over tighten them. Now thread the air pressure switch onto the second fitting on the top of the tank. Remember to use the Teflon tape on this one too. Now put your drain valve (a small ball valve works great) in the bottom hole. More Teflon tape here. Now you need to hook the power to the pressure switch. Back at the compressor, cut the wires going into the front of it. Leave enough wire on the compressor side (3 or 4 inches). Connect the wire to the pressure switch (as shown in the instructions that came with the switch) first. Find a good place to run the wires to your compressor. Don't forget to tie these to the frame, too. Now hook the positive wire on the supply to the supply/line wire of the switch and the negative wire on the supply to the supply/line wire of the switch. Do the same with the other two wires. Also, there's a switch on the A/C condenser that shuts off the power to the A/C compressor if there's no pressure in the lines. The condenser is located right near your heater box. Just cut both wires that go to this switch and hook them together and wrap it with some electric tape or a butt connector.


Testing:

Now, if I'm not forgetting anything... It's time to test your system. Get a squeeze bottle with some water and dish soap mix. This is how you're going to test for leaks. Make sure you have the drain valve closed and fire up your compressor. Shut it off before the tank is completely filled. Go to each air connection with your squeeze bottle and squirt a little water soap mixture on the fittings. If you see bubbles around the fitting try tightening it. Then squirt some more water soap mix on it. If there's still air bubbles take that joint apart and make sure you have Teflon tape on the threads. If it's where a hose connects to a fitting retighten the hose clamp and call it good. It wont hurt anything if there's small leaks in your system.

Remember to drain your air tank and lubricate your pump every so often.

To lubricate your pump, just dump some air tool oil down the intake side of the pump while it's running. Don't worry about the oil in your tank or hoses. It wont hurt anything. Just make sure to drain the excess oil through the drain in your tank.