Philippe Hurbain has created a pneumatic LEGO wheel. This wheel has no electronics and is controlled by two hand pumps, also made from LEGO. There are very detailed construction details available on his site that were created using LeoCAD and some LeoCAD plugins.

“The principle is simple:

* a piston is pressurized and contract.
* this contraction causes an arm to pull out the wheel. This arm pushes on ground and make the wheel tilt and advance.
* is also flips the pneumatic switch that controls the contraction of the next piston and expansion of the previous one. ”

Watch the videos:
Rolling video
Laying on its side video
Close up video
Pump video

See page 2 for more pictures