want to couple 2 servos in parallel

You can feed the same signal to two servos, they will move in parallel.

The problem with linking 2 servos directly mechanically is that there
is no guarantee that both servos will have the exact same speed,
response, movement envelope, be trimmed the same, etc. they are going
to fight each other and you will waste power and energy. (and strain
the servos needlessly)

I think if you couple them through a differential, that would solve the
problem, effectively taking the average of both servos movement,
mechanically. But you will have to invert the signal going to one of
the servos (there are cables you can buy that do that). With this
arrangement, you will get a free bonus: rotation of the arm. So you
will have double the power for flexing, and be able to rotate the arm.

bruno

pogo wrote:

     A mechanical differential will work.  Tearing apart the
servos and running both motors from the same controller
will work, maybe.  Using real servomotors with encoders
and forcing synchonization in software will work.

     All those solutions will cost more than getting a
bigger R/C servo.

                John Nagle

bschwand wrote: