Hi Ehab,

Yes indeed the torque of the servo does not change. The torque available to move the SURFACE, however, definitely changes based on the linkage geometry (remember the Bobcat elevator thread ?!?).

The system that Ian is describing is basically the same as a system with a very long servo arm, attached to a very short horn on the surface. Of course then you need set the ATV to 25% to get the correct throw!!

Now we all know good practice is just the opposite....short servo arm, long control horn on the surface and ATVs set up to 120%....just the opposite of Ian's case.

As a rule, you want a linkage that provides for the maximum movement of the servo for the associated movement of the surface. We all sort of know intuitively that setting up a surface and then setting the ATV down to 25% is not a good idea.....this is the reason.

And yes the slop will increase in Ian's case as well. Just as a normal servo linkage increases torque, it decreases the effect of most kinds of slop, when slop is measured at the trailing edge of the surface.

As for an RDS, this is a better choice, as an RDS allows for better geometry (ie you get the torque mulitplication of the "standard" servo linkage, but slop is much tougher to control in an RDS installation as well).