Pivoting Special Duty Truck

Every LEGO® train fan knows the LEGO® train motors only have four wheels. So, to make an SD engine, a wheelset needs to be added to the LEGO® motor. However, adding a wheelset to a LEGO® motor causes another problem, the radius of the curved LEGO® track is too small for three wheelsets, when the wheelsets are separated by three studs, to go through a turn. (Three wheelsets adjacent to one another can roll through a curve without a problem.) For three nonadjacent wheelsets to successfully negotiate a curve, one wheelset must be able to move. There are two methods which allow one of the wheelsets to move: a sliding wheelset or a steerable (pivoting) wheelset can be used. The sliding wheelset works best for a design that uses three unpowered wheelsets. The steerable wheelset works best when an extra wheelset is added to a motor.

This steerable wheelset uses two 2x2 turn tables to connect the wheelset to the motor.

Follow the links below for step by step directions. The directions were created using MLCad which is a specialized drawing program written by Michael Lachman. At the moment, there are no specialized programs for drawing LEGO® on a Macintosh, but there is a Macintosh version of the program LDLite! MacLDLite is an LDRAW file viewer. If you choose to download MacLDLite please read the note at the bottom of this page. (LDRAW is a program written by James Jessiman for drawing with LEGO® bricks. His efforts inspired a great many people to develop tools for drawing with LEGO® bricks.)

Here is the LDRAW file.
If you are only interested in the actual connection between the motor and the wheelset just look at steps 3, 4, and 5 for the bottom connection and 11, 12, and 13 for the top connection.

Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Step 8
Step 9
Step 10
Step 11
Step 12
Step 13
Step 14
Step 15
Step 16

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If you download MacLDLite do not run it right away. Make certain that you create a folder called LDRAW, and make certain that you add the "P" and the "PARTS" folders to the LDRAW folder before you launch MacLDLite for the first time (The MacLDLite page has a link to a site from which you can download the "P" and "PARTS" folders). Launch MacLDLite by double clicking the file you wish to view; otherwise, you will be prompted to enter the path to the file. The first time you launch MacLDLite it will prompt you to find the LDRAW folder. Use the dialogue box to navigate to the correct folder and select it. If you chose the wrong folder you will have to delete the preferences file, found the the "Preferences" folder inside the "System" folder, to get a second chance to select the correct LDRAW folder.