Original Year
# of pieces
Farm Equipment: Tractors
(with plow)
Steering, Lifting plow, Differential,
PTO, 2 Cylinder Engine
Other Views

8859 Harvester

iso revolve
Click the image to download the LDraw file of this model.
Model by Jerome Boulanger

Set 8859 was released in 1981 as an "Expert Builder" set.  It features rack and pinion steering, a reciprocating 2 cylinder engine, a rear differential gear, a PTO, and lifting rear implements including a plow.  Both studded building techniques and pinned construction are used throughout.  It is somewhat ironic that the USA name for this set is "Harvester" considering that the included implement is a plow which is for planting, not harvesting.

This tractor is considerably bigger than the one it replaces (851), and has increased functionality.  The differential, engine, and PTO are all integrated and driven from the rear wheels.  Unlike the previous tractor, the body is framed primarily in beams rather than built up out of plates and bricks.


The front wheels can be steered using a wheel in the cabin..

The wheel drives a 16 tooth spur gear used as a pinion through a universal joint.  The pinion drives the steering rack.  The steering mechanism itself uses the new control arms and toothed links as shown in the computer image.  The connection between the steering rack and arms is very elongated in this model due to the height of the model above the wheels.

steering    steering 
Click for an animation of the steering in motion.
This set features a front mounted 2-cylinder inline engine.  The engine uses the offset axle holes of the 24 tooth gears to make a crankshaft.  Connectors placed end to end and clocked 90 degrees form rods which connect to 2 specialized 2x2 square pistons.  The "cylinders" are actually square. 

The engine is connected to the rear wheels via a large number of gears as can be seen in the computer image.  2 sets of 24 and 8 tooth gears cancel out their respective gear ratios, making the final ratio a function only of the differential set, 2:1.

The engine is hidden under a hood which is hinged and has an attached rod to hold it open.
engine    engine    
     Click for an animation of the engine in motion.
Implement Lift
The implements can be lifted with a 4 bar linkage connected to a ratcheting lever next to the cabin via a set of translating racks.  The translating racks interface with a 90 degree crank arm built from the new toothed elements.  The implements remain parallel to the ground as they are lifted.  A beam on one side interfaces with a 16 tooth gear and acts as a ratchet pawl to keep the implement from descending under its own weight.
Click for an animation of the lift in motion.
The plow features a series of 4 offset tines which are spring loaded with rubber bands.  These can be lowered below ground level to create furrows.

Instructions for a number of other implements are included with this set including a seeder, a tiller, and a thresher.  Some of these require parts from a supplemental set to build.
Click for an animation of the plow in motion.
The rear axle uses a differential gear.  It incorporates a built in 28 tooth ring gear which can work either as a bevel or a spur, similar to the 24 tooth crown gear.  It is made to house 3 of the new 14 tooth bevel gears.  One is on each axle, and one planet gear in the middle allows the axles to turn at different rates.

The differential drives a Power Take-Off (PTO) at the rear of the vehicle.  This PTO does not drive anything in the basic model, but various attachments could be added.
Click for an animation of the differential in motion.

Wheels and Tires

This set uses four foam 24x43 tires and wheels, the biggest foam tire that LEGO made.

Other Views

Side View
side view
Top View
top view
Back View
back view
Front View
front view
Computer Render

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