Does anyone still consider using servos as gearboxes for small tank models? They are compact, powerful and easy to modify for such use.
The gear trains are robust enough for smaller models. all you really need to do if you want to use them as a gear drive is bypass the control board
and control the motor directly. If you want to use them as a controlled gearbox with a built in esc you need to bypass the feedback pot. You also need to eliminate the
limiter that usually prevents the servo mechanism from turning 360 degrees. There used to be articles all over the web including RCU on how to do this.

This technique apparently has fallen out of favor but it would seem perfect for such an app and servos are available in just about any size and power level you'd need
as well as being reasonably priced.

Jerry