CHAPTER 20 ■ COUPLERThe minimum length of axle that should be installed in a coupler is about 2.5 LEGO units long
(a 5 LEGO unit axle cut in half ). Anything less than that either isn’t long enough to connect to a LEGO piece
or has too little of the axle supported within the coupler’s metal tubing. Properly supported, even a 12 LEGO
unit axle can be attached to a coupler.
Sandwich’s coupler has a 3 LEGO unit cross axle. Actually, the coupler was made from a 6 LEGO unit
cross axle cut in half because that size of axle is a more common part. If you decide to cut an axle in half
(use the rotary tool cut-off wheel accessory), be sure to place the cut end into the coupler and leave the
official tapered end sticking out. The taper makes it easier to slide on a wheel.
Axles longer than 3 or 4 LEGO units tend to stick out farther than necessary for a wheel. That length is
usually reserved for axles intended to reach wheels or gears in a frame (see Figure 20-15). Placing a wheel at
the end of a long unsupported axle runs the risk of bowing or snapping the plastic axle.
Obtaining LEGO Cross Axles
Because of their usefulness, LEGO includes cross axles in most kits. If you don’t already have some extra
cross axles in your LEGO collection, you can obtain them easily from auction sites or BrickLink.
Figure 20-14. Three example lengths of LEGO cross axles beside a 4 LEGO unit brick (top) for comparison
purposes
Figure 20-15. A 6 LEGO unit cross axle installed in a coupler for connecting a wheel inside of a frame