By Jeff Conner

This 25 hp Bates & Edmonds 17kw model electric plant is in 1:8 scale. The unusual looking OHV engines used eccentrics and pull rods rather than cams and push rods. This valve arrangement was known as the ‘alligator link’ valve motion. The full size engines used two built-in adjusting features to time the valves. These same features could not be duplicated in the model at this scale, but other provisions were incorporated to make timing manageable.

The eccentric and valve depressor lever over-travel on the model requires compromises in valve lift, and duration each influencing the other. Confusing at first, but there is an orderly method that works. Fortunately, slow speed engine valve timing and valve lift isn’t that critical and the engine does well at slow speeds.

The prototype B&E engine was found at the Coolspring Power Museum. It was surveyed and photographed and Doug Kelley did the engine build drawings. The model was fabricated from aluminum, brass and steel bar stock. Bore x stroke is 1.00” x 1.18”.

The model has a wet sump using splash lubrication as did the real B&E engines. The compression ratio is about 5.5:1, and it runs smoothly at 550 RPM with, or without, load. The crankshaft is a 360⁰ type (two up, two down) with counterweights and ball bearing mains. The S/S ignition is a single coil waste fire type.

The fuel system is a modified 3mm self-compensating RC carburetor using propane fuel. The model features follow the prototype fairly closely, but a few exceptions were necessary at this scale.

A 1918 dated piece of B&E electric plant literature shows Garwood Electric Co. DC generators were used by Bates & Edmonds on their full range of 5.5 to 27kw DC electric plants. DC electric plants were popular in that era in rural and grand hotels attracting guests wanting to experience the modern marvel of electric illumination.

The direct connected Garwood model generator was fabricated using a rewound 12 pole alternator stator core. It uses permanent magnets for excitation and provides a regulated 12vdc output. The generator output is 3 amps at 12vdc at a speed of 500 RPM. It is capable of higher output with a larger regulator, but the current rating and regulator suits this engine/generator combination nicely. The generator is a 2-bearing type. It hums a bit due to the magnets and slow speed, but does a good job.

The modular switchboard, metering, and radiator idea was seen in another model builders work. It worked out very well here, and incorporates a lot in a small footprint. The cooling system uses a computer radiator, expansion tank, and generator powered thermostatically controlled fan which is rarely needed at light load.

I have a couple friends that have similar taste in vintage engines and model building. We pick an old slow speed stationary engine to model based on uniqueness and looks, or whatever catches our fancy. It is usually my job to find a prototype, photograph it, survey it, and research available information. A good friend with engineering and drafting skills sits at his vintage drafting board and makes up the drawings. Then we go about building our own versions of the same engine. I usually build my models with generators attached since I worked in the engine power generation business for 30 years.