This robotic crane was my first robot arm that was actually quite functional. It could move anywhere on its treads, and the arm had several degrees of freedom, including a wrist that turns. Orginally, I designed this with the RCX (that’s why there are no NXT motors on board), which controlled Power Function receivers with its IR transmitter. Later on I switched to the NXT, which in turn controlled the on board Power Functions with a Mindsensors PF Mate. A pneumatic compressor and a switch are located on the underside of the arm. They manipulate the robot’s claws.