Servo motor recommendation sought

Well, for cheap I would say to either use brushless DC (BLDC) motors made for RC cars or just any cheap brushed DC motors. I know there is code for driving the hobby BLDC motors through an ESC. The ESC is the Electronic Speed Control and accepts the same signals as the analog servos you are using now. So you already have some of the code. You will need encoders too for position feedback. That's what makes the DC motor a servo. The servos you are using now just use a potentiometer for position feedback. CUI makes some pretty good and inexpensive encoders. Just search for the CUI AMT20 series encoders at

These encoders have switchable resolutions, which is plenty handy. I have used these encoders on machine tools and they worked just fine. Eric

The problem with the cheaper analogue type servos is that the actuator position is determined by an analogue pot. connected to the output shaft. For a variety of reasons hysteresis has to be provided to prevent the actuator output 'hunting', with a result that in your type of application you will get quite large positional errors, and a low number of actual possible actuator output positions. Have a look at the Dynamixel MX series - these are quite expensive -

on one control bus. Actuator positional information is derived from a high resolution magnetic angle sensor giving 10 or even 12 bits resolution over 360 degrees. They are also solid, repeatable positions not subject to analogue drift due to time, temperature and ageing parameters.