logo
Original Year
1981
# of pieces
379
Categories
Cars and Trucks: Tow Trucks
Dimensions
28(L)x12(W)x16(H)
Features
Steering, Winch, Hoist,
Wheel Lift
Other Views

8846 Tow Truck

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


Set 8846 was released in 1981 but was never available in the USA.  It features rack and pinion steering, a ratcheting rear boom hoist, a ratcheting and pivoting wheel lift, and a winch.  Construction is primarily studded with the windscreen made up of old hinges rather than the new toothed elements.

This model packs a lot of functionality into a small package.  The ratcheting wheel lift supports heavy vehicles very well, and the twin winches really give this model a wide variety of vehicle pulling options.

This is the smallest of the tow trucks which LEGO would release, but is surprisingly functional for its size and easily competes with the others.

Features

Steering
The front wheels can be steered using an overhead control.  This is the first model to have such an overhead control, and would come to be known among fans as a "Hand of God" control for obvious reasons.  This allows the model to be easily "driven" around the room by the builder.  The steering wheel in the cabin also rotates from a belt and follows along with the steering.  The belt is not tight enough to actually control the steering from this position.

The overhead control drives an axle connected to a pair of 14 tooth bevel gears.  The second axle drives a rack via an 8 tooth pinion gear.  The steering mechanism itself uses the new control arms and toothed links as shown in the computer image.

steering   steering 
Click for an animation of the steering in motion.
Wheel Lift
The primary function of the tow truck is a wheel lift used for lifting the vehicle under tow.  It is sized for vehicles with similar sized wheels and spacing as the tow truck.

A crank on the left side of the vehicle drives through 3 sets of 8 and 24 tooth gears (as seen in the computer image) for a total gear reduction of 27:1.  Crown gears are used to convert torque around perpendicular axes.  The first stage pinion also mates with a pawl which supports the wheel lift and prevents it from backdriving.  The final stage raises the lift directly.

The end of the wheel lift can pivot on the lift arm which allows it to align with the vehicle in tow when cornering.

The lift is constructed almost entirely of the new toothed connectors and axles,  which seems to be an ideal use for them.
wheel lift     lift
Click for an animation of the wheel lift in motion.
Click for an animation of the wheel lift rotating.
Boom Hoist
A boom hoist on the rear of the truck can pull a vehicle from a ditch using a cable and hook.  A crank on the right side on the vehicle ratchets on a pawl and drives the cable drum through a set of 8 and 24 tooth gears.

The angle of the boom is fixed. 
boom
Click for an animation of the boom hoist in motion.
Winch
The forward end of the vehicle has a winch which is controlled via a clever hidden mechanism.  A spare tire on the hood can be rotated and drives a set of 24 tooth gears (see computer image).  The crown gear drives a pinion which, in turn, drives another crown gear on the cable drum.  The final two sets of gears cancel out and result in a ratio of 1:1.
winch     winch
Click for an animation of the winch in motion.
Differential
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.

In the case of this model, the differential is unnecessary because the ring gear does not drive anything, but it is still a nice detail.
diff

Wheels and Tires

This set uses four rubber 17x43 tires and standard old gray wheels.
Wheels
 


Other Views

Side View
side view
Top View
top view
Back View
back view
Towing
This truck tows 8845 beautifully.
tow
Computer Render
render

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