monorail history

About the LEGO® Monorail System

LEGO® first introduced the Monorail System back in 1987 with set #6990 Monorail Transport System. This was part of the Futuron Space theme. Since then, two more have been introduced, a Town Monorail and another Space Monorail.

All of the sets share the same essential elements, the track, the monorail motor unit and the monorail train chassis. The track is grey plastic, about 4 studs wide and has a single rail running down the middle with vertical teeth on either side. Underneath the motor is a small metal gear wheel that engages with the teeth on one side of the rail (which side depends on which way round the motor is placed on the track). This is how the monorail train pulls itself along the track. The motor unit has 4 tiny wheels under it that run along the flat part of the track.

Each monorail train is built on two identical chassis parts with the motor unit in between. A sort of ball and socket joint and swing arm connects the chassis to the motor allowing it to flex in all directions. At the other end of each chassis is a 4 wheel bogie that supports the train and just follows the monorail track.

There are 10 different track pieces:

  • Long straights, 32 studs long.
  • Short straights, 8 studs long.
  • 90° curves, 28 stud radius.
  • Left and right points, 32 studs long, with 45°, 28 stud radius turnouts.
  • Left and right 45° curves, 28 stud radius (for points).
  • Stop/reverse switch track, 16 studs long.
  • Up ramps and down ramps, 32 studs long.
The straights and 90° curves are self explanatory. The points require a little more explanation. Unlike train points that have pivoting rails, these points slide an appropriate section of track in to place. Set in one direction, a straight piece of track is used, set the other way a curved piece is used. They can be operated manually but the coolest feature is that if a train approaches points set against it, it pushes a lever and changes the points back in its favour! Special curves are supplied with points because the turnout has a special zigzap shape that only matches one end of these curves. 45° curves come in left and right hand versions, connecting a left hand curve to left hand points makes a 90° turnout equivalent to a standard 90° curve. Alternatively, connecting a right hand curve to left hand points makes a parallel siding, offset at 16 studs from the mainline.

An interesting fact about the points and 45° curves is that they are not exactly 45° arcs of a 28 stud radius circle, why is that? If you do the maths you find that 45° represents x,y offsets of 8.2010 and 19.7990 studs. Not very nice numbers, but they wouldn't be a problem if all you were allowed to do was make 90° curves since

(8.201,19.799)+(19.799,8.201) = (28.000, 28.000)
If you were to make a parallel siding with these numbers you would get
(8.201,19.799)+(8.201,19.799) = (16.402, 39.598)
But LEGO® have obviously thought about this a bit more because the points and 45° curves are not true arcs of a circle. The x,y offsets are actually (8.0, 20.0). So the above equations become:
(8.0,20.0) + (20.0,8.0) = (28.0, 28.0)
(8.0,20.0) + (8.0,20.0) = (16.0, 40.0)
Much nicer numbers! And fortunately LEGO® supply 8 stud short straights so that the 40.0 offset can be matched with one long straight and one short straight.

The stop/reverse switch tracks are used to control the train and are placed at stations or at a dead end. Turning a knob on the side of the switch track moves a pair of catch plates. With the catch plates centered, the motor is stopped, with them moved one way the motor goes in one direction, moved the other way it goes in the other direction. This works when the train is already stopped at the switch track but can also be set prior to the train arriving. So you can decide in advance whether you want the train to stop, reverse or continue through.

Up and down ramps can only be used joined together to form a 64 stud ramp that takes the monorail from one level to another level, 10 bricks higher. Thoughtfully, LEGO® provides supports that are exactly 10 bricks high, making it easy to build elevated sections of monorail track. Sets with ramps also come with a couple of shorter 5 high supports for the joint between the up and down ramp sections. A unique feature of these supports is that they have double height studs on them, making a very strong joint with the underside of the track. This means you can't attach plates to them but bricks are okay.

Monorail trains run on a 9V battery, either an alkaline or a rechargeable.