Gas Engine Magazine

Water Pumping Aermotor Engine

By Staff

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

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

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 2×8 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

  • Published on Aug 15, 2013
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