The question that faces many of us in the old engine hobby is: What can we have our engines doing besides just idling? Most of us have probably been amazed from time to time at the creative engineering we have observed at engine shows. This is in addition to the factory designed pumps, grain shellers, wood saws, light plants, etc.
Here in the north, where the show season is short, we have a lot of time to attempt to be creative. During the winter of 2005/2006, my attempt to put an engine to use resulted in this Massey-Harris-powered AC generator.
This engine was made by Cushman to be sold in Canada as a Massey-Harris. It is identical to a Cushman Cub. I bought it from an antique dealer in Quebec, Canada, as a non-running unit in the late summer of 2005. The work needed to get it running involved a thorough fuel system cleaning with acetone, as the old gas had turned to rusty gum. Two other small problems were setting the ignition timing from an extremely advanced position (causing it to kick back even with the timing lever fully retarded), and fixing a broken speed adjusting screw (which held the governor on wide open throttle). That was all that was required to get it running. It appears to have nearly all of its original green paint and all of the silk-screened Massey-Harris lettering with scrolled pinstripes on the front of the block. The addition of a new muffler (with no modifications to the engine exhaust port) from a Kohler-powered John Deere lawn tractor makes for a quiet-running unit.
The 115-volt, 2-kilowatt AC generator was originally belted to a single-cylinder Wisconsin air-cooled engine that was not running. The tag on the generator says, "Montgomery Ward Powerlite." Vintage is unknown, but probably 1950s.
Both engine and generator had V-belt pulleys attached when acquired, so the question was: How could a 2 HP throttle-governed engine that is rated to run at 750 RPM operate an AC generator that attains standard output voltage at 3,600 RPM? We all know the answer to that: Given enough time and money, most anything can be accomplished!
Once the correct pulley diameters were figured out, I had planned to just change the engine pulley to keep the cost down and the project as simple as possible. But a mechanic friend happened to be around while I was laying out the project and he thought out loud about the procedure. He said, "Why don't you make a line shaft between them to increase the 'cool factor' and have more action visible?" After the math was refigured so the original pulleys could be used as is, the line shaft idea was developed.
The line shaft was made from 3/4-inch cold-rolled round rod with a standard 3/16-inch keyway cut 4 inches in from each end. (Both ends could therefore have pulleys on them.) The pillow blocks and bearings were purchased locally. The zerk-type grease fittings were replaced with our familiar turndown style grease cups for a vintage look to the line shaft. The line shaft was placed in such a position that the belts are the same size, both adjustable through slots in the pillow block mountings and the bracket on the generator.
The cart was made from some donated oak. I purchased 8-inch diameter cast iron wheels, riding on 3/4-inch diameter axles. Bolsters were fabricated from 1/4-by-3-inch flat steel with a steerable front axle, and 1/2-inch round rod for the handle. The generator is bolted through the wood right to the rear axle for static grounding.
Upon initial startup and testing, it was found that by setting engine speed to 650 RPM, the generator operates at its required 3,600 RPM, with output at 120 volts AC.
To answer the question about what size pulleys you are looking at, the engine has a 6-inch diameter pulley driving a 3-inch pulley on the line shaft. The 11-inch pulley on the inside of the line shaft drives a 4-inch pulley on the generator. The line shaft pulley sizes were derived using the formula printed in an original Hercules Gas Engine Operating Instructions that came with each new Hercules engine purchased. The end results were verified with a mechanical tachometer that contacts the center of the shaft.
My mechanic friend was present at the inaugural run. He said it had the "cool factor."
Contact Bob Naske at: 2059 State Highway 29, Johnstown, NY 12095; firstname.lastname@example.org