LEGO 4-wheel-drive that keeps all wheels vertically on the ground in rough terrain

31 december 2004. In this creation I tried to built a 4x4 drive that can keep all wheels vertically on the ground in rough terrain, while the distance between the steering axes and centers of the steering wheels is minimal. The inspiration came from a discussion about Tatra's in the technical forum of the dutch site: The following three pictures show the first result. The car exists of three parts: a structure for the front wheels, a cenral beam for the motors and the chassis of the car and a rear wheel construction. The shapes of the front a rear parts of the car, or in other words, the rotation of these parts relative to the chassis, are stable as long as the flat tires can feel some flat surface. One motor is used to drive a differential between the front and rear wheels. The second motor is used for steering. The steering construction is classical and adapts it self to the rotation of the front wheel construction relative to the chassis

The following three pictures should give more insight in the construction. They also show the differentials in the front and rear wheel constructions.

The last picture shows one of the results with the use of springs. So far this appeared to be the best solution for stabilizing with non flat tires. The same solution is applied to the rear wheel construction. The wheels do not have so much freedom as in the flat tire solution.

I have tried to make the structures more elgant by removing the top beam from every set of three rotating beams in the structures. This resulted however in very unstable behaviour of the structues and the car.