View Full Version : TruTrak Servo friction?

01-27-2006, 01:31 AM
Hello everybody,

I have just picked up an aileron servo from TruTrak on my trip to the USA this week.

I got it out of the box and turned the arm by hand. It feels like there is some friction, not "smooth" friction, but it feels like it is turning in small steps, when it is disengaged. I checked the TruTrak web site and found that there is, what they call, 1,2 inch/lbs "residual torque". Is this a lot? Or is it so little that you can not feel it when flying the plane? What I am more concerned about, is the fact that you can feel it moving in small increments ("notches" or small steps).

Looking forward to some input from people that are already flying with these kind of servo?s.


Al Kritzman
01-27-2006, 05:47 AM
What you discribe is normal for the Trutrak servo. It is a stepper motor that you are back driving. When it is installed you can feel the steps on the ground if you try but you has a big machanical advantage with the stick. In the air with airloads on the controls you will never notice the steps.

Alan Kritzman
Cedar Rapids, IA
300 hrs on the airplane, 150 on the trutrak.

01-28-2006, 03:55 AM

With "Mechanical advantage", doe you mean that the stick will feel more solid and the plane will be easier to fly? (more stable?)


Bob Axsom
01-30-2006, 09:37 AM
I flew my RV-6A for around 100 hours before I decided to put the TruTrak roll and pitch servos in (associated with Pictorial Pilot and Altrak). I can't tell it is there when I fly the plane manually (which is most of the time). The stepper motor backdrive stepping sensation is exactly what you should expect stepper motors do as you break magnetic flux lines as you rotate the shaft.

Bob Axsom