Water Pumping Aermotor Engine

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


Dave Irey's 8-cycle Aermotor does what it was made to do thanks to Dave's homemade water-pumping display.

Photo By Dave Irey

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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.

The pump mounting

The 3-inch pipe couplings were put in the lathe and a 3/16-inch wide, 1/8-inch deep groove was cut in the middle of each one to receive a 3/16-inch round rod bent to form a U-bolt. The U-bolt was threaded in 1-1/2-inch, 3/16-inch by 24-inch thread. These two couplings were slid on the pump tube and secured with PVC epoxy, as regular PVC pipe glue sets up too fast. This special epoxy for PVC pipe has a five-minute slide/align and set up time.

From oak wood I cut two pieces 1-1/2-inch thick, 8-1/4-inch long and 3 inches wide. In these I cut a half circle 2 inches deep. These will be mounts for the pump and go onto the just-made and glued pipe couplings on the pump tube. The U bolts go into and around the grooves cut in the PVC pipe couplings and through the wood. I countersunk where the nuts and flat washers will go, as the wood pieces will fit tightly against the vertical pump bolster mountings. With the pump mounts made and installed, two wood bolster mounts were made to fit on the front T-frame of the engine. These are made of wood about 25 inches long, 2 inches thick and 4-1/4 inches wide. They will bolt on to the front T-frame of the engine and will be fastened with 5/16-inch carriage bolts. During all design and fabrication a 3/8-inch piece of plywood was holding them square and vertically aligned. I decided to leave this piece of plywood on the bolsters as it has taken quite a bit of knocking about and held up well.

Four brackets that receive the pump mountings were fabricated out of 3/16-inch-thick steel 1-1/4 inches wide and 8-1/2 inches high. I made these four pieces by heating them with a torch and bending them into shape. I did one first, and when I got it right I copied it three more times. The parts resemble a lower case “h” with the left rear leg cut off. These steel pieces are bolted to the wooden bolsters with 1/4-inch by 3-1/2-inch lag bolts.

The pump linkage

The Aermotor 8-cycle engine is a pump jack and gas engine in one package. A 1920 sales brochure shows the setup using a cast iron pump. My setup using plastic parts requires a 1-inch square steel vertical guide post as the 5/16-inch brass rod is not strong enough to handle the lateral thrusting motion. This 1-inch square steel post is 44 inches long and has two 1-1/2-inch by 2-inch ears welded on to it. One is at the bottom, the other is 9 inches up, and both are drilled for 3/16-inch wood screws to fasten it to the oak pump mounts. I made the trunnion bearing and yoke out of 1-inch steel round rod, bored it to fit the 3/4-inch steel cross pin and made it a loose fit. The sliding sleeve part is two pieces of angle iron 3-1/2 inches long welded together to form a loose-fitting sliding sleeve. A 3/4-inch steel horizontal cross pin 2 inches long is welded to this sliding sleeve. The 3/4-inch bearings have a 1-inch wide, 1/8-inch thick, 6-inch-long steel piece welded to both of them. These will bolt to the top actuated arm, making a flexible universal joint. Still working from the 1920 Aermotor sales catalog, I made a top actuated cross arm from a piece of 1/4-inch thick steel 1-1/4 inches wide and 43 inches long. This arm is stationary on one end and moves the water pump up and down on the other. This gives the pump a 12-inch stroke and will move about 1-1/2 quarts of water per stroke. To calculate the pump stroke and pivot pin location I made a cardboard pattern and wood stick 5 feet long (shown below) and by moving the stick to various positions was able to calculate the length I needed to make the wooden arms with steel ends.

The upright arms

I bought a 10-foot piece of 16-gauge 1-1/2-inch square tubing and some 1-1/2-inch wide, 3/16-inch thick flat steel. The tubing was cut at a very long angle. These will receive 1-1/4-inch square oak pieces 23 inches on the front movable arm and 34 inches long for the rear stationary arm. A piece of the 1-1/2-inch flat steel stock was arc welded onto the angle cut 1-1/2-inch square tube end to close the open end. Then a 2-inch-long piece of the 1-1/2-inch flat steel stock was arc welded to it to make the pivot point and the arm the right length. Each arm has a different connection on each end: The driven arm is 31-1/2 inches long and the stationary arm is 35-1/2 inches long overall length.

Top arm

The top steel actuated arm is 50 inches long with the universal joint yoke on it. It was drilled for two steel 5/16-inch steel pins, which are the pivots that upright arms go into, and this makes for a quick setup and take down. The bottom pivot for the stationary arm is a 5/16-inch bolt drilled through both the steel 1-1/2-inch tube and the oak wood. It is drilled through the 2x8 that runs under the engine, rearward from the front tee, and a 5/16-inch bolt 5 inches long is the lower pivot point and allows the arm to fold down flat. The driven arm off the main gear also folds down flat for transporting.

The 5-gallon recycle pail 

I thought the recycle pail would be simple, but not so. The pail is round and tapered, so I had to cut double curved/tapered 2-inch plastic washers to fit so my fittings would seal up tight and be at a 90-degree angle from ground level. This was kind of a slow trial and error process that required a galvanized threaded fitting to go inside to help tighten and seal it all up. At a recent antique power show, we had set up our original Aermotor pumping engine along a walkway. One of the regular walkers said, “I didn’t know that there was a wellhead here.”

Because of the long winter, I wasn’t able to get the engine/pump out of my basement workshop soon enough to get it running and tuned. When I do, I will write a short final story about it.

Read More: Aermotor Redux Part 1 of 2.  

Contact Dave Irey at 6348 Mildred Ave., Edina, MN 55439 • (952) 943-8357