Water Pumping Aermotor Engine

8-cycle Aermotor engine gets ready for show season with a homemade water-pumping display.

| October/November 2013

I collect and show gas engines at several power shows each year. I need a display that is interesting as well as fast and easy to set up. I chose to make a water- pumping display for my 8-cycle Aermotor engine using PVC pipe and fittings, and a 5-gallon pail as a recycle tank. I made one in the 1990s and its picture was in the February/March 2013 Gas Engine Magazine.

The pump

From my local hardware store, I purchased a 36-inch-long piece of 3-inch PVC pipe, a 3-inch tee reduction fitting with a 2-inch outlet in the middle, some 2-inch PVC pipe and miscellaneous fittings, a 1-1/4-inch sink drain part that makes a 90-degree bend at the end, a 1-1/4-inch extension coupling to couple this to the 3-inch tube of the pump and a 1-1/4-inch threaded PVC sink trap adaptor. I also bought some 1-foot-square 1/2-inch and 3/8-inch-thick flat black plastic as well as PVC epoxy glue and bathtub caulking.

I started by cutting my 3-by-36-inch long PVC pipe to 24-1/2 inches and then ran my cylinder hone through to clean up any imperfections. The PVC pipe can be longer if you want to make the pump taller. Next, I made the piston out of flat plastic, 1/2-inch thick, sawn out on the band saw. Then I drilled and tapped a 5/16-inch by 24-inch thread hole in the center of the rough-cut piston for the 5/16-inch round brass actuating rod. Then, using a 5/16-inch by 24-inch steel bolt with the hex head sawn off as a mandrel, I fastened the plastic piston to the bolt so I could chuck it in my 3-jaw lathe chuck. I turned it to fit the 3-inch PVC pipe, which has to be a good fit or else the water will leak by and cause poor flow at the outlet end. I made two of these. The second one will be a foot valve at the bottom of the 3-inch tube. I drilled four 5/8-inch holes in both valves for the water to flow through.

I made two valves 5/16-inch thick by 2-3/4-inch wide out of plastic to serve as check valves that float on top of the piston and on the bottom stationary 3-inch bottom valve. The bottom 1/2-by-3-inch valve has a V groove and shoulder turned in it for an O-ring so no water leaks by it. It uses the same 2-3/4-inch flat check valve, a 3-inch by 5/16-inch brass shaft threaded to 5/16-inch by 24-inch, which allows the valve to open and close and keeps it in place. I made the main pump shaft from a 5/16-inch brass round rod 24 inches long, threaded to 5/16-inch by 24-inch. I threaded 1-1/2-inch on only one end, and I will thread the other end when I determine how long it has to be. With the piston and flat check valve installed on the shaft, I made and soldered a brass sleeve stop to keep the check valve in place, allowing it to only raise 5/8-inch to flow water.

The bottom valve, or foot valve, is held in place by the tee fitting. The tee fitting just slides on and is drilled and tapped for three 1/4-inch by 20-inch by 3/4-inch bolts to keep it in place. It must be able to be taken apart if service is needed. The 3-inch top cap was put in the lathe and a 5/8-inch hole was drilled in the dome top for a brass guide bushing. This was a fitting from my “brass box” of fittings. I threaded the cap, screwed the fitting in with epoxy on the threads, and epoxied a nut and flat washer on the underside to secure it. The fitting was drilled 3/8-inch as the 5/16-inch round brass pump shaft is a loose fit.

The outlet tube

The 3-inch pumping tube needs a 1-1/4-inch outlet main pipe, 17 inches up from the bottom. I used a plastic sink trap adapter with a gasket/O-ring and nut, and then I had to drill a 1-7/8-inch hole in the 3-inch pipe before enlarging it just a little bit more for a snug fit. This outlet main pipe stuck too far into the 3-inch tube and had to be cleaned up so the piston can be removed from the top. I just marked it with pencil and cut it on the band saw before finishing the inside of it up with No. 50 sandpaper stapled to a large dowel. This plastic fitting has a shoulder on it, so I made two plastic block spacers with metal flat washers to hold it in place. Two 1/4-inch by 20-inch bolt holes were drilled and tapped into the tube, and epoxy for PVC pipe holds it securely together in place. 1-1/4-inch plastic sink trap pipe goes out from the trap adaptor 10 inches, and then I glued a 5-inch piece with an elbow on the end going out over the 5-gallon pail. The bottom fitting is 2-inch plastic pipe 9 inches long going from the 5-gallon pail to the tee fitting on the pump bottom. This connection is not glued or bolted, just slid on. The weight of the water keeps the 5-gallon pail in place and makes for a fast take down when packing up to go home. The same goes for the outlet fitting: just uncouple it from the pump. I store and transport these parts in the 5-gallon pail.