tich

Can you offer some advice please. Last night I was flying my midwest super stinker- a 14 pound aerobatic aircraft with two futaba 3152 servos on the elevators. After a snap roll one of the futaba servo arms, supplied with the servo, failed at the hub. Was I unlucky or should I be using an alternatative horn to the one supplied with the servo? I was able to land the plane, after a fashion as one elevator was displace to about 20-30 degrees down from normal. Hence I was able to spot the problem- if the plane had crashed I would not have been able to determine the cause as I would have assumed the arm had been damaged in the crash..

Bax

My Feedback: (11)

Very likely, the pushrod didn't move in a straight line, but caused a bit of flex on the servo arm. Over time, this would fatigue the servo arm to the point where it would fail. You cannot have a pushrod move in such a manner that the servo arm is given a slight twist as it's working. If that can't be avoided, you may need to use one of the ball-end type of links to allow the pushrod to move around a bit.

tich

I used a ball link and the plane had very low flight time -perhaps an hour or so. However the ball link could certainly impart a twisting moment on the arm. The failure definitely occurred during a snap maneuver. I am perfectly happy with the servo apart from this arm issue. Other sources suggest that a stiffer arm is the way to go on larger, heavier models such as this and I will try this.