Michael, could you draw what you are describing here? I would think that the neutral position for all the arms are 90 degrees (relative to each other) and they move each direction from there maybe 45 degrees (60 degrees max) or so for a total of 90 degrees of sweep. Is this what you mean?
Bevan
I’ll try come up with a graphic, but in the interest of time try to describe the setup better:
In my airplane, the roll servo is mounted to the left side of the main torque tube at the very front. The servo itself is found under the left side, front floorboard, in front of the wing spar and front stick, with the output arm mounted approximately the 5:00 o’clock position (neutral). The arm on the torque tube is also attached below the pivot point at the 6:00 o’clock position. The length of the attaching pushrod is approximately 14-16 inches.
As originally rigged, (viewed from the aft, looking forward) full left aileron would drag the pushrod to the right, towards the center of the aircraft. Of course, the output arm on the servo would follow and move from the 5 o’clock position towards 3:00 o’clock. As an unlikely set of circumstances, the main torque tube hit the primary stop
at the same exact time that the servo arm hit 3:00 o’clock and lined up the servo pivot, rod end and pushrod all in a straight line (center). This masked the issue because when moved normally, gravity and basic geometry would not let the arm move further than a direct line, but
rapid movement would generate enough inertia to allow the servo to go just past 3:00 o’clock, hit its stop, and lock over center.
Lengthening the pushrod moved the output arm on the servo back towards 6:00 o’clock in neutral which ensured the aileron torque tube hit the primary stop long before the servo could go over center. Now, the servo only hits about 4:00 o’clock at max travel, and no amount of inertia, slop or flexing will let the arm get anywhere near the 3:00 o'clock, over center condition.
Clearly, the geometry on this system is less than optimal and the servo travel to aileron movement is not going to be perfectly linear, but at least it is safe and I have full control deflection available.