Hey guys,

You've all got really good points and valid concerns. I worried about the same things when I first came up with the idea, but the system proved to be even better than I hoped.

Mechanical advantage was a necessity in the old days, when servos were weak. As servos improved and Quique showed us what can be done with 60 degrees of throw, the need for advantage went out the window. If your servo requires mechanical advantage to move your surface, you probably need to upgrade your servos. Plus, remember that a linkage becomes less efficient as you move away from center, whereas Direct drive maintains 100% efficiency at all points of motion. However much torque you have at the servo shaft, you get more of it to the control with direct drive.

Resolution is the next issue. You are all absolutely correct about gaining resolution with a reduction linkage - in theory. If you use leverage to reduce your motion by 1/2, you should double your resolution. But, this logic neglects the deficiencies inherent to a linkage setup. Linkages have a small amount of play. If they had no play in the joints, they would bind - and any play is a loss of resolution. Add to this the deflection you get from the rubber servo mounting grommets, the deflection from servo arm twist, the deflection from the control horn...well, let's just say you are loosing much more resolution from your linkage than you realize. Increasing the amount of leverage just increases the forces imposed on the linkage, and that makes all of the deflections worse.

When you add it all up, you lose all of the theoretical resolution you thought you were getting from your linkage - and then some! Direct drive does not suffer from any of these resolution robbing problems.

Hope this helps...John