lego helicopter-demonstrator. We think that the idea of demonstrating the working of a helicopter with a balance can be extended to other movements of a helicopter as well. We are currently doing experiments with an improved control and a new balance to demontrate lift, landing and cyclic control. This month, september 2002, I discovered a very beautifull model by Ross Crawford that shows all the controls! Why haven't I seen his model earlier ? .

Lego simulation of car-movement after a crash. I think it is easier to make a software model that predicts the following movement than a LEGO-car-model  for the following movement. The speed was 60 Km /hour. During a very short time the driver had to steer and brake simultaneously. The brake for the left front wheel was disabled. After this time both brake and steer were left out of control by the driver. Click image to see an introduction.

Challenges I haven't dealt with yet.
Lego cars with automated gearing. The idea is to use the resisting force that slows down the car or even blocks the motor for switching gears. A very nice demonstration model is constructed by Jeff Jahr
Continuous variable transmission. Explanations and one solution is given by Rob Stehlik
Omnidirectional wheel. Mark Warren pointed me to Acroname's omnidirectional wheel. Their Palm Pilot Robot Kit (PPRK) uses these wheels as part of a Killough platform. This might provide another way to create wheels for Lego® holonomic platforms.