Gas Engine Magazine

Reader’s Scale Engines

By Staff

I built this model engine in 1999 from a set of castings and
drawings Ted Young was offering at that time. It is a neat little
engine of 1-1/2-inch bore by 1-7/8-inch stroke with jump-spark
ignition. The cylinder and piston are both cast iron. I turned two
grooves for rings on the piston, but I found upon assembly that the
engine had such high compression (5.6:1) that I never have
installed rings.

I bored the cylinder as near parallel as I could and I honed it
with a brake cylinder hone. I then turned the piston to as near the
cylinder bore as I could and still just push the piston through the
bore. I used Comet cleanser as a lapping compound to get a close
fit that would leave just enough room to maintain a film of oil. I
have run the engine many times at shows and events in the last four
years, and the compression has not decreased.

For ignition, I use a 9.6-volt 900MAh Ni-Cad rechargeable
battery Radio Shack sells for radio-controlled cars. The battery is
mounted in the engine base. I can check its status by turning the
flywheel until the points are open. With the switch on, I place one
probe of a volt/ohm meter to the hot wire connection to the breaker
points and the other probe to any ground on the engine. I made two
little brass connectors that plug into the battery’s plastic
connector, and covered them with heat-shrink tubing

The spark coil is from a junked string-trimmer engine,
manufactured before the move to coils with a built-in solid-state
circuit (eliminating the points and condenser). There is no way I
know of to make coils with built-in solid-state circuits work on
our engines that use a battery ignition.

The base is made from pieces of I-inch by 4-inch oak glued
together using Elmer’s wood glue. This method of construction
makes it easier to make all the pocket cutouts for the battery,
wiring, gas tank, etc., before the individual pieces are glued
together. Handles across the ends of the base make it easy to lift
the model, and I’ve found the one on the front to be essential
when cranking with the flywheel against the engine’s high
compression.

Paul Brien , 4312 Lone Oak Road Nashville, TN 37215
paulbrien@aol.com

  • Published on Mar 1, 2004
© Copyright 2022. All Rights Reserved - Ogden Publications, Inc.