So I was reading about pvc air rams, and decided to try and build my first one. I started by copying someone else and using the 1 1/4 schedule 40 tube with a 1" inner tube sliding inside it. It worked but I wasnt over all impressed. I started thinking how a screen door cylinder works and came up with this pvc air ram.


The concept is to have a dowel inside a tube that is pushed by air that moves a rod up and down.

I used a 1 1/4" schedule 40 pvc tube about 3' long as the case of my ram, with two glue on caps.

The top cap has the center drilled out to a 9/16" hole, the rod will travel through this.


The bottom cap eventually was drilled out in the center to 7/16" and then tapped with a NPT 1/4-18 (for standard air compressor fitting)


The most important part was the center plunger or dowel, I started with a 1/2" oak dowel, a 3" stud that is wood threaded on one end and 3/16" machine threaded on the other (commonly used for the knob on kitchen cutting boards), 1" schedule 40 pvc, 2 large thick washers the same O.D. as the 1" pvc, and 3 3/16 nuts.




Its very important that the washers stay tight, if the washers move it will rub on the inside wall of the outer tube and stop the plunger from moving.

Also the tubes MUST be cut perfectly square, or the washers will have uneven pressure and fail. I used a tubing cuter to make all my cuts.


Now the rod needs to be pre-drilled, its VERY IMPORTANT to drill the rod perfectly in the center or it will jam at full extension. Tighten the plunger into the rod as far as it will go.


I found that a larger plunger at full extension was a better way to go, It supports the prop better at full extension.

I had to get a 3/16" coupler, and some longer 3/16" thread rod, I ended up with a 5" plunger. Cut the extra thread off flush with the last double nut on the plunger so it doesn't jam on the air fitting at the base of the ram.

Glue the top drilled cap on, DON'T GET GLUE IN THE RAM!

You can dry fit the bottom cap on and test the ram, fine tune, and then glue the bottom cap when ram is fully functional.




PS. Do not tap the Side of the Tube for your air fitting (above), When the plunger retracts the washer hits the fitting and eventually knocks them off center, jamming the rod.

I assume with the proper valve switch you could add another air fitting to the top and "force" the ram down too.

All said and done I give this a 8.5 out of ten, If money was no object I would put more concentration into the plunger.

Here's a video with the ram running as 40 psi on a remote switch.