After getting my excavator set a few weeks ago and building the models, I started building something I've always wanted to build... A remote controlled mobile arm. After about 2-3 weeks of building and fine tuning I finished. I came up with the name ROTA (Remotely Operated Technic Arm) The programming took an additional day, shortly after I took some videos and put them together so here is the video explaining all the mechanisms:
The base is a basic skid-steer base that I strengthened as I built the arm.
The 2 NXT motors are geared down 1:667 and control the driving function. I reinforced the treads due to a slight amount of bending when the arm (weighing around 5 lbs) would try to lift something heavy. The base took the shortest amount of time to build only around 45 minutes with an additional 15-20 minutes fixing all the flaws.
The arm was really fun to build but it also gave me the most trouble.
I used 3 linear actuators, two for the whole arm and one for the bend in the middle. You can see the gearing (4th picture) for the two actuators that lift the whole arm. I did not use any gearing for the bend in the middle (5th picture). I originally was going to use two actuators too lift the middle bend but instead I used only one because I needed the other one for the hand. The arm took me about 2-3 hours too build and perfect.
The hand also gave me a lot of trouble.