servo disengage only with electrical power?

[Taigajoe]

Hello,

I got these days my ordered servo SV32 and was very astonished that the arm moves not freely.

I looked at the documentations and cannot find out more.

My question is: Does the servo needs electrical power to disengage?

If the answer is "Yes" then is my next question: What is happening at electrical power failure during the flight? Does that mean I have to break the "shear screw" at electrical power failure to steer the plane manual?

Until now I used a Trio AP and the servo is disengaged if power is off.

Thanks!

Regards,

Taigajoe

 

[dynonsupport]

We designed our servo without a clutch, which is one less mechanism to fail. The trade-off here is a little bit of residual drag. But, this should be very minimal, and certainly shouldn't impede the arm from moving. Installed, it should be a little bit noticable on the ground, and practically not noticable in the air with the air loads acting on the aircraft.

Should power fail, the servo will turn off and will spin freely. Only in the event of a gross mechanical failure (we have never heard of one) that causes the servo to seize would you need to break the shear screw by overpowering it. We haven't heard of a case of this sort of failure though.

 

[Taigajoe]

Thanks for your response!

 

[jabirujim]

I am considering the Dynon AP and servo system for My Samba  http://www.urbanair.cz/web/pages.php?id=samba_xxl&lang=en . I already have the D100 and D120. My controlls are very light both on the ground and in flight. I have been trying to find out exactly what force is required to overcome the "friction" of the servo when the AP is disengaged an can't find it.  

Can you advise what forces are required to overcome the Servo Friction on both the SV 32 and 42 with the standard and long arm at the 3 positions.

Thanks,
Jim

 

[dynonsupport]

The SV-32 has 0.8 in/lb of residual torque (friction)
The SV-42 has 1.2 in/lb of residual torque.

Both of these are about 2% of the max torque the servo can put out. We have yet to ever hear of a customer that can feel the servos in flight.

The torques above are listed at the shaft. You can do simple math to figure out the linear force required at the arm length you will use. You need to choose the arm position for proper throw, not based on torques.

 

[Brantel]

You will never notice the servo in flight when not engaged. You can feel it on the ground but not in the air.

 

[jabirujim]

Thanks folks for the Prompt replies. I will do the maths once I have measured the throws required.

This will probably become a small project for the Winter.

Jim

 

[DBRV10]

If you have a jabiru and think your controls are light, you will most likely not even notice the servo's on the ground or in the air.

I set up 2 x A/P's in Vans RV8's recently and the same question was asked as the RV really is light in controls. They were both surprised that there was no change once airborne.

DB