Model Hot Air Pumping Engine


Rider Ericsson engine

1/4 Scale Rider Ericsson engine.

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7574 So. 74 Street Franklin, WI 53132

1/4 Scale Rider Ericsson Pumping Engine-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 articles.

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 water.

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 engine.

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 tubing.

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 prints.

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.