You'd be surprised what you can do with servos modified with encoders, setup with an industrial grade cascading control loop. First demo video below demonstrates threading a mechanical pencil lead in and out through the writing tip. Second video demonstrates a 187gram weight at the end of a 470mm long rod. Third video shows that the modification is now a quick fitting of some 3D printed parts to the servo motor axle and servo housing.

  https://www.youtube.com/watch?v=ECLrLupFW10
  https://www.youtube.com/watch?v=_4mrb2T706s
  https://www.youtube.com/watch?v=Ctb4s6fqnqo
  https://github.com/adamb314/ServoProject