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Original Year
 1979
# of pieces
 401
Categories
 Other: Motorcycles
Dimensions
 37(L)x26(W)x21(H)
Features
 Steering, 1 cylinder engine
Other Views

857/8857 Motorcycle
iso revolve
Click the image to download the LDraw file of this model.
Model by Mark Chittenden
Set 857 was released under the "Technical Set" series in 1979 in Europe.  It finally made it to the US in 1980 with the number 8857 as an "Expert Builder"set, the first set which used the now standard 4 digit identification number.  This motorcycle featured a steerable fork and a chain driven 1 cylinder engine.  Traditional studded construction is used almost exclusively with the exception of the frame.

Despite the fact that many LEGO® motorcycles have been released over the years, this one is unique in many ways.  The parts list consists almost entirely of standard bricks, plates, and slopes.  The fenders, especially the rear, have compound curvature, yet were made entirely of plates.  All of the exterior design details were made in this way.  The frame, however, was built from pinned beams, which allowed the unusual angles which could never have been produced with studded construction.  This set is also unusual in that the primary functionality, the engine, is completely hidden when the model is completed.

Future motorcycles would usually use unique, narrow wheels, but this set used the same wheels as the auto chassis.  It also marked a couple of firsts.  The 16 tooth gear was used for the first time here, as was the chain link.  Realistic motorcycle functionality really required a chain, so here the engine is driven off the rear wheel via a chain.

Features
Steering
The front fork can be steered using the handle bars.  The fork simply pivots around an axle passed through a set of plates (with holes) on the frame.

Because of the sidecar, this motorcycle can not lean, so the turning radius is quite large.

 steering
Click for an animation of the steering in motion.
Engine
The engine is driven by the rear wheel through a chain.  The chain has a new 16 tooth gear at either end.  Motion is geared down through a set of 24 and 8 tooth gears.  The final gear set is a pair of 16 tooth gears which does not change the ratio, so the final ratio is 3:1 between the engine and the wheel.

The engine uses the offset axle holes of the 24 tooth gears to make a crankshaft.  Connectors placed end to end and clocked 90° form rods which connect to a specialized 2x2 square piston.  The "cylinder" is actually square. 

The mechanics of this engine are completely hidden below the fuel tank when the model is completed, so you can't see the engine in motion.  Even with the tank removed, the frame blocks most of the cylinder.

On the left side, you will also note a shift lever which is spring loaded with a rubber band.  It doesn't do anything, but it is a nice touch.  It only shifts down!
 engine    engine
Click for an animation of the engine in motion.
Sidecar
The sidecar does not have any technical function, but it looks cool!  I suppose, at the very least, it acts like a kickstand to hold the motorcycle up.

The sidecar is made entirely from bricks, plates, and slopes.  The only Technic element is the axle and the beam which supports it.
 sidecar
Wheels and Tires
This set uses three foam 24x43 tires and wheels, the biggest foam tire that LEGO® made.
 Wheels
 

Other Views
Side View
side view
 Side View
side view
Front View
front view
Top View
top view
Computer Render
Render

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