I grew up with earthmovers and I have operated excavators for many years. My favorite machine is the hydraulic excavator. However, I changed jobs so I don't operate excavators anymore. Unfortunate, because I still regularly get itchy hands when I see these machines running. Unfortunately, buying a real excavator is not an option for me. Now there are remote controlled excavators for sale that run on model-hydraulics, but they cost a fortune. So there was only one thing to do, build one myself!
First i looked on the Internet if there were more people that had this idea. Sure enough, after some searching I found several videos and pictures of working RC excavators that did not cost thousands of dollars. They were converted excavator models from "Bruder". Yes, childrens toys, but I must say that these models are very detailed. So i bought one and got to work.
This excavator works with hacked servos, that can spin indefinitely. These servos are connected to wooddrillbit thats running in an aluminum tube, with a steel pin in it which engages in the drill. This makes the turning movement from the servos to a Linair movement for the cylinders.