This is my lego racecar [Link], my entry to Kwon’s NXT racing competition. I hope it wins!
This has front wheel steering, back wheel drive, and a ton of awesomeness. It uses one servo, one power functions M-motor, and an NXT.
The drive happens with a power functions m-motor, attached so its output faces the rear of the vehicle, and then the gearing transfers the gearing to the wheels. There is no gearing for speed, only direction. But the m-motor goes fast, and that’s sufficient. The craft is lightweight, no power functions battery boxes or multiple servos for extra functions it doesn’t need. The only unnecessary pieces are the ones that make up the bumper and the pieces for decoration. I got most of my plating from Atlantis sets, by the way. The M-motor doesn’t have precise control, since it doesn’t have a built in rotation sensor, but it doesn’t need it.
The steering mechanism is with a rack and pinion. The servo drives a large 40 tooth grey gear, which drives a 36 tooth double bevel. That drives a 4 prong “knob wheel” which drives another, therefore transferring the direction. Finally, the last gear drives the 12-tooth double bevel gear attached to the gear rack.