This document provides instructions for building a motor sled for children based on the design of snowmobiles used in Arctic regions. The sled is powered by a small gasoline engine turning a drive wheel via a chain drive system. Detailed diagrams and instructions are given for constructing the sled frame, mounting the engine, making parts like the radiator and starter, and finishing details. The finished motor sled can reach speeds up to 10 miles per hour and provide children with thrills of Arctic travel close to home.

1. MOTOR SLED
A Junior version of the snowmobile
for the small fry Arctic explorer.
BY AI.FRED BROSSEAU
IN THE far northern stretches of
Canada, not far from the Arctic Circle,
the U. S. and Canadian Armies recently
completed a test of motorized equipment
called "Operation Musk Ox." The gas
powered sled described in this article
works on the same principle as the snow-mobiles
used in this operation and while
its ten mile an hour speed doesn't equal
the army's equipment, it will still give
your boy all the thrills of Arctic traveling
without going any further away than
down the street and back.
While this isn't the sort of project that
can be completed in a few evenings spent
in the home workshop, for the man who
is experienced with metal working and
who has a lathe and drill press, the sled
should be fairly easy to construct in a
reasonable period of time. The detailed

2. drawings of the principal parts shown are
clear and easy to follow. Large-scale work-ing
drawings are also available from the
MI Reader Blueprint Service and will be
of considerable assistance in building
the sled.
The power plant in the original model
shown in the photos consisted of a 1/3 to
1/2 horsepower, water-cooled Forster C W
model gasoline engine, driving a wide
toothed wheel through a reduction gear
and chain drive. However, an optional
installation could be made with a McCoy
or Hornet air-cooled engine of the same
horsepower. This would eliminate the
auto heater radiator which is required to
cool the Forster job. With either installa-tion,
the 20-1 ratio between the engine
and wheel develops enough torque at the
drivewheel to move the average size
youngster. The usual difficulty in starting
the two cycle engine is overcome by gear-ing
the kick starter down 5 to 1 so that a
quick push really turns it over and the
heavy flywheel keeps her going.
To start the ball rolling on the con-struction,
make the sled itself of either
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3. Engine installed. Drive wheel is
raised or lowered with lever.
birch or maple, following
the drawings for the details.
A pair of cheap 4 ft. skis
cut to the required length
will save you a lot of time
as they are already grooved
for the runners.
The next step is mount-ing
the engine. The base is
made of 1/8" CRS steel with
the sides welded at right
angles and everything kept as square as
possible. Follow this up by making the
small and large ball bearing housings
(4 and 21), insert the bearings and then
fit them to the sides. Use a piece of tissue
between the gears to locate the bearings,
drill through the housings and tap the
sides for screws. The shaft extender
parts (11) used to extend the crankshaft
of the engine and to provide a means for
locking the flywheel and the pinion gear,
are then turned and threaded true. Com-plete
these operations in the lathe before
you cut the parts off. The pinion (12) is
pushed on to the intake side of the
crankshaft, the flywheel on the other
end and the shaft extenders pushed
through the bearings and screwed up
tight. Follow this by making the motor
bolts (16) and then drill 4 No. 36 holes
in the base, tap 6-32 to match the mount-ing
holes on the engine. The bolts are
screwed into the base and locked with
one nut while the engine is adjusted
very carefully between the two other
nuts and then locked down tight. The
reduction shaft (5) which turns the
drivewheel, operates the water pump
and starts the motor, is made from 3/8"

4. drill rod, polished with emery cloth in
the lathe or drill press so that the bear-ings
will just slide on. The large gear
and the sprocket are pinned to the
shaft with No. 4 taper pins.
The chassis (38) is then cut from 1/8
in. thick angle iron and welded. The
engine base is bolted to it with 5-1/4 in.
stove bolts and lock washers. The next
operation is to make the wheel frame
(39) from 5/16" CRS steel. Follow this
by constructing the drive wheel (35)
according to the details in the drawing.
The radiator (28) required to cool
the Forster engine can be made from
the core of a used car heater. After
testing it for leaks, the intake and out-let
tubes are unsoldered and the core
made into the radiator, following the
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5. HEADLIGHT-drawings.
An aluminum plate (40) is used
to fasten it to the end of the plate sup-ports
for the engine.
The next parts to be made and installed
are the carburetor float assembly (31) and
the gas tank (27). The wheel frame is then
fitted to the reduction shaft and the drive
wheel mounted in place. An aluminum
hood keeps the snow out of the mecha-nism.
After the hood is in place, cut the
drive chain to the correct length and con-nect
the small sprocket and drive wheel,
riveting over the removable link if
necessary.
The starter assembly (9) is made from
1/4 " CRS and the rachet wheel locked
to the shaft with an Allen set screw in a
3/16" hole drilled 1/8" deep. Following
this, the choke (13) is made from 1/16"
brass, slid over the intake and clamped
tight. The water pump (19) is then con-structed
and put aside to be mounted
against the side of the motor hood after
it is installed. Use two screws tapped into
the body of the pump to do this. The last
part of the mechanism to be made and
installed is the wheel lever (26). In opera-tion,
the forward position is for starting
or idling, the rear position engages the
drive wheel for running.
The sides of the motor hood consist of
a welded frame covered with aluminum,
bent to shape as shown in the drawing.
At this point, the water pump previously
mentioned is installed and rubber tubes
connected to the radiator and engine
block. Before the hood is completed, the
two dry cells for the ignition should be
mounted on one of the sides, using the
aluminum battery clamp shown.
The back of the hood is a piece of
curved aluminum with an opening cut in
it for the dashboard. This piece is screwed
to the sides and the entire hood bolted
to the chassis. The extensions at the front
of the sides fit into the radiator shell. The
dashboard itself is made from aluminum,
drilled and slotted for the toggle switches,
panel light, throttle and brake levers.
The brake operates by simply cutting the
ignition and using the drag of the wheel
to stop the sled. After the dash and igni-tion
wiring are completed, the board is
fastened to the back of the hood, using
four 6-32 screws. Next, make the top of
the hood and hinge it to the radiator shell.
The seat for the junior explorer should
be made following the details in the draw-ings.
Use two 14 in. thumb screws in
slotted holes to make it adjustable. To
finish the sled, paint the top of the hood
and running gear one color and use a
contrasting color on the sides.
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