Model Sideshaft Engine

By Staff
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7574 So. 74 St., Franklin, WI 53132

This is a photo of the model hit and miss sideshaft engine that
I built by modifying the engine castings sold by Ted Young into a
sideshaft design. I changed the standard type flywheel governor, as
shown on the prints, into a vertical flyball governor. The engine
runs very well, and the governor keeps it at 400 RPM, firing about
8-10 revolutions. This engine has a 1.250′ bore, and a
1.750′ stroke, with a compression ratio of 8.5:1. The castings
were very nice to machine, and the drawings were clear and correct.
The basic engine, sold by Ted Young, is a well designed casting kit
that will run slow because of the heavy flywheels. While not a
model of any particular engine, it closely resembles the shape of
Lauson, Badger, and Christensen engines.

Some changes that I made on this engine can be incorporated into
any small gas engine. These are as follows:

I used an O-ring for a head seal, as I do on all my engines.
This makes a great pressure-tight seal, and provides a
metal-to-metal fit between the head and cylinder.

All bearings, except two, are purchased Oilite sintered bronze
bushings, with the main bearings being the flanged type Oilite
bushings because the flange provides the thrust surface for the
crank. The two exceptions are the connecting rod bearings. These
are standard purchased bronze bearings. Oilite bearings should not
be used here, due to the shock load on the bearings from each
explosion in the cylinder. All applicable bearings were split in
half with a .010′ thick Dremel slitting saw, held in the
milling machine chuck. When the bearing was installed in the
engine, the kerf gap was filled with strips of plastic shim
stock.

CARBURETOR MODIFICATIONS

Never grease a sintered bronze bushing, as the grease fills the
pores and prevents the impregnated oil from coming out of the
bronze, defeating the purpose of this type of bearing. If you wish,
you can feed oil into the bushing. The sideshaft and governor shaft
also both run in Oilite sintered bronze bushings.

The lever on the sideshaft bracket, next to the large governor
gear, advances and retards the spark. This part is the same as used
on the Wyvern engine. The upper lever mounted to the head is the
speed control. It is connected to the governor with a spring that
changes the tension on the governor balls.

The carburetor was modified to a spray pipe design to give
better gas vaporization. This change can be incorporated into any
model engine. The drawing shows the revised carb.

The spiral skew gears with a 2:1 ratio were made by a local gear
shop. Now gears like this can be purchased from at least two model
suppliers.

The governor gears are stock gears from Boston Gear Company. The
governor balls are .375′ bronze balls.

Building the engine was a fun project. It is an interesting
engine to watch run, and I figured that the only way that I would
ever own a sideshaft engine of any kind was to build one.

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