Original Year
# of pieces
Cars & Trucks: 4x4's
Steering, differential,
V-6 engine
Other Views

8850 Rally Support Truck

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

This is one of 3 1990 models centered around a "Rally" theme.  This model is a 4x4 or sport utility vehicle.  A V-6 engine is located in the front and is made from the new engine parts introduced this year.  The engine is driven by the rear wheels through a differential.  The front wheels have rack and pinion steering.  The Technic figure also made a reappearance here after being absent for a year.  Construction is almost entirely of pinned beams.

Each of the Rally vehicles had a special numbered flag which matched the third digit of the set number, in this case "5".  This is one of the first sets to include an engine made of the new engine parts.  It is quite a large model and holds up very well compared with some of the much newer 4x4's.


The front wheels can be steered using a "hand of god"wheel at the top of the vehicle.  The wheel drives through a set of 24 tooth gears.  A pair of 8 tooth pinions then drive the gear rack.

The steering mechanism itself uses control arms and toothed links as shown in the computer image.
steering    steering
Click for an animation of the steering in motion.
The V-6 engine is located under the hood (even though there is no hood). 

The engine is made from the new cylindrical engine elements and is driven by the rear wheels through a differential.  The 28 tooth differential ring gear drives a 14 tooth bevel gear.  The drive shaft then runs forward to 3 16 tooth spur gears which transfer the rotation up to the engine.  The gear ratio is 1:2.   The final axle drives the crankshaft of the engine.  The crankshaft is offset 1/2 stud from center, giving the pistons a stroke of 1 stud.  Each pair of pistons shares a common crank pin.  Because the crank pins are each offset 180 degrees, the forward and back cylinders are synchronized.  This can be seen clearly in the animation.  This would make for a very rough engine!

The set of 24 and 8 tooth spur gears seen in the computer image drive a PTO (power take off) in the rear of the vehicle.  If the model is motorized, this axle is used to power the wheels and engine.
engine    engine
Click for an animation of the engine in motion.
This set uses a rear 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 14 tooth bevel gears.  One is on each axle, and one planet gear in the middle allows the axles to turn at different rates.  This addition results in very smooth turns for this model.
Click for an animation of the differential in motion.
Wheels and Tires
This set uses 4 of the 20x30 solid foam tires and wheels.

Other Views

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

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