Aside from massive Technic structures, I also enjoy building small (relative to a 12' crane) machines with driven wheels.

An age-old problem with LEGO bricks is how to construct a steerable wheel that is also driven (i.e. the front wheels of a 4wd vehicle). Making this out of LEGO bricks is not very easy. For one thing, it's nearly impossible to get the pivot point of the steering in-line with the contact point between the tire and the ground. LEGO bricks are just too large and the tires aren't deep enough. U-joints have to be used which makes the problem even worse. They are long (4-brick widths) and the resulting structure build around the u-joint becomes large.

The first LEGO-produced answer to the problem was found in the 8880 Super Car. The car had 4 wheel drive with 4 wheel steering. The only problem with this was that most of the parts used to make the actual suspension were very specialized and found only with this set.

For about 15 years now, I've been building steering/suspension assemblies out of common parts. Below you will find links to sub-pages featuring my ideas. They're not perfect, but they'll work.