Using a few machined pieces, and some off the shelf gears, could I build a drivetrain for a robot without having to buy one of those complete servo actuators? Why would I do this? I think they are 2/3 the price. You can either spend $5400 for ready to go actuators, or $3800 for something 95% as good. I think this is good if your robot is a "living document". Check my math on this, and let me know what you think.