[imtringued]

>Now days there are tons of cheap robot arms that have a servo motor for each joint, because servos are cheap and complex mechanics are not.

Servo motors aren't cheap at all. Encoders aren't cheap either, in what universe do you live? The RC toys don't count by the way, because the cheap RC servos are terrible.

A fly ball governer? Is this some kind of joke? How are you going to operate it in any orientation other than upright? Why would you even want to?

There are probably ways to build a control loop with discrete electronics components that is cheaper than a mechanical system like that. Heck, it is probably cheaper to build an entire CPU with discrete components and then program that.

The reason nobody knows this crap is because it is useless. Your pseudo nostalgia for an age that existed before your time is ridiculous.