This Instructable will show you how to build a cheap air ram for holiday props, robotics or whatever else you want to do with em! You could just go out and get a screen door closer, but for the price of two and a few extra steps, you can make around 10 of them a foot long ! If needed, you can change the length of the cylinder as well as the diameter of the pipe used. Here I am using 1/2“ pvc. If you want to use larger pipe, you will have to do some trial fitting at the hardware store for a piston and seal. Let’s get to it!

Step 1: Materials and Tools

1/2“ sch 40 pvc pipe

1/2“ end caps (2)

1/4“ steel/aluminum round rod

1/4“ 20 nuts (2)

Air fitting

Plastic bottle cap

5/8 o.d. 5/16 i.d. rubber grommet

5/8x1/4x3/8 nylon spacer

Pvc cement

3/8 drill

17/64 drill

1/4 20 die

Drill/drill press

Sand paper or belt sander

Step 2: End Caps

Drill a 3/8 hole in the center of one 1/2 end cap and a 17/64 hole in the other.

Thread in the air fitting into the cap with the lager hole and put this one on the 1/2 pipe.

On the pipe, you may need to bevel the inside edge of the opening to make inserting the piston easier.

Step 3: Piston

Take the nylon spacer and see if it fits easily into the 1/2 pipe. If not, lightly sand it down so it slides very easy in the pipe. A belt sander is handy for this!

Take the bottle cap and cut a washer the same size as the nylon spacer with a 17/64 hole in the center.

Step 4: Push Rod

Take the 1/4 rod and the 1/4 20 die and thread the rod far enough to screw on both nuts, the nylon spacer, grommet and plastic washer.

Put on the end cap (open end facing threads), a nut, the spacer, grommet, washer followed by the last nut.

Lube everything up and slide the piston in the cylinder body and slide on the end cap. You can glue this cap on but you may need to take the ram apart to maintain or replace the grommet. This side does not hold pressure but it does stop the piston so a stop on the arm it moves is a must.

Step 5: Notes

On the end of the push rod that’s sticking out, you can heat, flatten and drill a hole in it to mount it. Or you could thread it and put a ball end on.

Before you put the piston in, drop a screw into the cylinder head first that’s long enough to stop the piston from popping out of the pipe and into the end cap and prevent damage to the grommet.

For a return, hook a return spring on the mechanism the ram will move. A stop on the mech is a good idea as well to keep the piston from going too far and blowing off the end cap or to keep the grommet in the cylinder body, preventing damage.