JOHN DEERE AR MODEL

By Staff
article image

102-20 Country Hill Drive Kitchener, Ontario, Canada N2E 1R7

In the spring of 1984 a lifelong ambition was realized when I
finished the little John Deere AR pictured here.

A start in determining the scale of the model was made by the
tires available, and the size of my lathe. 1:5 seemed the best,
making the length 25′, width 13′, and height 11′ to the
radiator cap. This scale also allowed a 1′ bore, for which
commercial rings were available. The stroke is 1′ valves,
3/8 diameter, and the plugs have x 32
thread.

All parts on this model are machined from the solid. No castings
were made. The majority of structural parts are aluminum alloy,
with cast iron pistons and wet sleeves. The valves are stainless
steel. The aluminum rods have hardened wrist pins which work well,
but the aluminum big end bearings running on the free machining
steel crankshaft have to be watched carefully.

Progress is very slow in this type of job, but much time was
saved by using gears from typewriters, etc. where possible. Some of
those such as the steering gear and worm were purchased from Boston
Gear.

An oil pump is incorporated giving force feed to the big end and
main bearings. The thermo-siphon cooling system holds about 5
ounces, circulating through 54 1/8
brass tubes in the radiator. The ignition is battery and coil, as
it is impossible to scale down a magneto to this size.

The transmission has two speeds forward, with reverse, operated
by the hand clutch with a 2
1/8”disk. Brakes are external
contracting on the differential shaft.

Apart from much satisfaction listing to the little guy run, the
experience I have gained gives me an appreciation of why John Deere
eventually went to a double throat carburetor on their 2 cylinder
engines. It seems that I will have to change the induction and
carburetion also, if it is to work properly at idle.

Many thanks for helpful advice and encouragement go to friends,
Mr. George Barrett and Mr. L.C. Mason, in particular. The
latter’s work may be known by modellers from his books and
articles in Model Engineer.

I would be happy to hear from anyone wishing further
information^

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