Johnny

Hi Guys

I guess when that subject of what servo to use in your latest aircraft comes up, I guess some of us may go by the manufacturer's recommendations or maybe we just have a look at what other people are using. Maybe I am missing out on something here, but that is what I have done in the past, without any problems, but surely there must be some method of working out what servos with what power output we require. If any of you guys out there can throw some light on this subject, it would be very helpful or maybe we all copy of what the other guys have done. I don't know. Anyhow help please!

Johnny

WS

Do a search for ' hinge moment ' and you might find something. I think if surfaces are aerodynamically and mass balanced, there is theoretically no hinge moment. If there is a moment, then you will need to calculate the torque required and flutter becomes a concern. Otherwise, I think the speed of the servo is more important for most applications.

rmh

The servo speed ratings ar quite misleading- they are effectively no load ratings .
Under load they may be less effective than a slow device with better centre holding power.
Servo ratings are a lot of confusion for many -simply because looking at the max torque out put seems to suggest that the holding power is better on higher torque servos.
Not so -
The new digital servos apply much more current to the motor at a very small movement from center -
The result is that the surface can hold it's position against air loads - far better.

If you are looking for the "right servo " for a project - , you can easily be misled .
It is a good idea to check with those who really understand the loads you will actually be controlling- then select the appropriate device.

CurtD

My Feedback: (1)

Johnny, if you have Microsoft Excel, I have an excellent servo load calculator spreadsheet that I've used extensively. It has graphic representations of your setup and can tell you reasonably accurately what your servo loads will be, allowing you to choose the correct servo for the application. Let me know and I can send it to you via PM.

CurtD

HighPlains

My Feedback: (1)

Servo torque calculator at this web site:

http://www.morgantech.com/Servo%20To...0Caculator.htm

Johnny

Hi Curt

Thanks for the reply. Yes, I do have excel and would very much like to see a copy of your spreadsheet.

It will probably turn out that we used the right servos, but anyhow it will be nice to know that we are right. Many thanks

Johnny