Let's Make Robots!

actuation

Hobby Servo and then...how are large robotic arms actuated?

I'm working on several robotic arms as a hobby.  I've used Hitec robot servos to good results, but I'd like to construct an arm that is strong: capable of lifting 10+ lbs from a 24" arm.   Obviously, hobby servos aren't going to work.

What kinds of servos (are they stepper motors?) are used in larger scale robots?