ORIGINAL: 3D Joy
Servo arm lenght is not so much of a factor.
You'd better see it this way : If the servo moves 60 degrees each way and the control surface moves 60 degrees each way, you are getting pretty close to the limits of resolution and holding torque.
The above assertion it true but there are caveats which displace the assertion.
There are other factors in play, in this case the primary factor which would dictate 60=60 is the control arm length of the elevator or surface in question. Generally speaking we do not see a 1:1 ratio in this area, in fact it’s undesirable. We'd prefer to see an uneven ratio that would promote mechanical advantage. If the servo arm length is equal to the control arm length we see 1:1 ratio if the servo arm is 1.25" and the control arm is 1.5" we realize mechanical advantage at the cost of surface deflection. This small concept plays a factor in the FORCE passed to the surface from the servo, in this example FORCE will be greater than that provided by the servo.
188in-oz servo with a 1.25" arm coupled to 1.5" control arm will net 225ozs of FORCE to the surface, TORQUE remains constant. Mechanical advantage is in play...
This maybe an unrealistic with this specific model as the control arm maybe much shorter. 1.25"/188oz-in=150ozs Force, coupled to a 1" control arm you'll see 150ozs Force at the control surface, NO mechanical advantage.