Model Hot Air Pumping Engine

By Staff
1 / 2
1/4 Scale Rider Ericsson engine.
2 / 2
1/4 Scale improved Ericsson engine.

7574 So. 74 Street Franklin, WI 53132

1/4 Scale Rider Ericsson Pumping
-The castings for the Rider Ericsson hot air pumping
engine are of aluminum alloy and are sold by Meyers Model Engine
Works, 15929 Five Point Road, Perrysburg, Ohio 43551.

For those of you who, like me, purchased the castings several
years ago from Norbert Keeley, you might want to contact Mr.
Meyers, as the furnace and furnace door are now beautiful castings.
This is a great improvement over fabricating these parts from sheet
and bar stock, and these parts can be purchased separately. I had
the castings since 1978 and built both of these engines
simultaneously during the past year.

The Rider Ericsson castings were a dream to machine and
assemble. There is ample stock for machining and the parts fit
together well. Although prints do come with the castings, the
complete construction article, including the drawings, was printed
in the October, November and December issues of Live Steam
Magazine. These articles contain more drawings than do the prints,
along with the helpful text, so I chose to work from these

In my engine, I used ball bearings for the crankshaft, instead
of the needle bearings that are specified. Use shielded (not
sealed) ball bearings of 3/8‘ shaft size
and 7/8‘ O.D. and soak them in solvent to
remove all the grease. Then replace the grease with a light
oil-either by soaking, or with an aerosol. This will make the
bearings very free rolling. Also, I used ‘Oilite’ bushings
on every moving part, including the sliding fits like displacer rod
and pump rod. To seal the water pump flange to the cylinder on both
engines, I cut an O-ring groove in the pump flange. This took a
1/16′ cross section x ?’ I.D. O-ring.

While building this engine, I had the benefit of knowing several
people who have built the engine before me and I adopted their
changes that have improved the operation of this type of hot air
engine. The first change was to use steel for a displacer cylinder,
not copper as called for in the prints. Copper conducts the heat
right up into the cold end of the cylinder- just where you
don’t want it. I turned the steel tubing down to
.026′-.030′ wall thickness for the entire length of the
displacer cylinder. A piece of .020′-.031′ thick copper was
silver soldered to the bottom of the cylinder. Here the thin copper
puts the heat right where it is wanted.

The displacer cylinder is made from a pumice stone sanding block
that is called ‘Sand-No-Mor Abrasive Block’. This is
available at hardware stores. This block is drilled for the
displacer rod and the block is glued to the rod with ‘Permatex
No. 1’.

The cylinder with the steel liner shrunk in place was taken to a
local honing shop and professionally honed within .0005′ bore
and straightness. This assured me of a straight bore-very important
on a hot air engine.

The teflon piston packing has caused problems for several
people. Instead, use graphited string packing. For cylinder
lubrication, use silicone lubricant. It will not build up a carbon
deposit in the bottom of the displacer cylinder like oil will.

The furnace stack for each engine is made from 1′ copper
tubing, with a copper elbow. I modified the burner to use a 1988
technology propane torch. Both engines run after about 10 seconds
of low heat. The engine was brush painted with an automotive
synthetic enamel, over three sanded coats of thickened automotive
primer. This color scheme was copied from an engine that still had
original paint. Other color schemes that could be used are all
black or a dark green color with a black furnace. As with many
engine builders, the colors were changed during the years of engine
production. Sort of a ‘new image’, probably to try to
increase sales. This engine runs fine and pumps a good stream of

1/4 Scale American Machine Co.,
Improved Ericsson Pumping Engine
-The American hot air
pumping engine makes a very nice model when finished, but there are
some problems with the castings and prints that first have to be
dealt with. These castings are of cast iron. There have been hard
spots in the castings that always seem to fall right where a hole
has to be drilled. My understanding is that hard castings will be
replaced. The patterns and drawings were made by the late Brad
Eisner and are now being sold by Power Model Supply Company, Rt. 1,
Box 177, N.W. Cor. Hwy. 67 & Long Road, DeSoto, MO 63020.

The biggest problem with the engine is the many mistakes in the
drawings. I have prepared a list of print corrections and this list
is now being enclosed by Power Model Supply with each casting kit.
However, if you purchased your castings from Eisner and you do not
have the print corrections, I will send them to anyone who sends me
a regular size SASE.

For the crankshaft bearings, I used an SKF computer drive, thin
section ball bearing (#WEA-406-2Z-RT-5G68R). This gives a really
free rolling shaft, compared to the bushings called for in the
print. Also, I used ‘Oilite’ bushings on every moving part.
To slow down the amount of wear, I changed all the
1/8‘ diameter pins to 3/16’ diameter.
This is the size that is called for on the Rider Ericsson

The machining of the beam is critical and also difficult because
of its odd shape. One way to hold it would be to mount it securely
to a piece of cold rolled steel plate that has been machined
square. Drill and tap all the holes before removing the beam from
the plate.

The brass tube can be held into the water pump casting very
easily with ‘Loctite Retaining Compound’. Use
3/8 inch O.D. x 1/32 inch wall brass

As with the other engine, the bore was professionally honed. Use
graphited string for the power piston packing, and make the
displacer cylinder and displacer piston as described above, not
like on Eisner’s prints. Also, use the same burner as used on
the Rider Ericsson engine, not the one shown in the Eisner

The engine could be either painted all black, or in the orange
and black color scheme that is on my engine. Brad Eisner’s
8′ engine had original paint and was in this color scheme. The
builder’s plate that is supplied with the kit is fastened to
the top of the cylinder, behind the pump rod. This is also a very
good running engine, and quite powerful, due to the inertia in the
cast iron flywheel.

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