Here is a great video about how one guy built his own 1:32 scale radio controlled excavator. I think it might be a plastic model which would make things a lot easier, the biggest problem with my Hitachi zaxis 210 is the weight of the excavator arm.

He clearly shows you how he built his rams from some servos. He has removed the potentiometer and the control circuitry to leave him with a motor and a strong metal gearbox. To this he attaches what appears to be a wood drill bit to use as a threaded rod and mounts the entire thing in a body which resembles an excavator ram.

The result is a lovely excavator with smooth control, you can see it working at the end of the video. If you have any questions, ideas or comments please visit the RC Tractors Forum and let us know.