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Servo load feedback?

Old 03-12-2009, 11:59 PM
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Default Servo load feedback?

I wasn't sure where to ask this. Couldn't really find anything about it.

First, the destination: I'm starting work on a F6F-3 Hellcat. I've designed my own slotted fowler flaps, and I'd like to find a way to keep the flap servos from being over-torqued.

Now the question: Is there a way to measure the current draw for a given servo (torque), and readjusting the servo to match the torque.

I would like to be able to safeguard against dropping flaps at too high a velocity and ripping them off the plane. If I could limit the position of a servo by the torque being applied against it (like a gyro, but with torque as the input rather than motion), then if I dropped the flaps at too high a velocity, they would automatically retract until the position fell bellow the torque limit.

Any thoughts?

If this should be in a different forum, just say.
Old 03-13-2009, 01:26 AM
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Default RE: Servo load feedback?

Don't know if this will help. Hitec's new digital servos have an overload protection which is programmable. As far as i know the scheme works on sensing current drawn and you can set the max torque you would like delivered via programming. This wouldn't allow for the flap to auto retract , but would save burning a servo out. There was a mob called SM Services in the U.K. which did electronics for a large scale B52 jet which may have had similar issues. Check RCMF UK forums and i'm sure you will find a link.
Cheers and good luck , Leon.
Old 03-13-2009, 03:02 PM
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Default RE: Servo load feedback?

All full scale aircraft have a maximum flap and gear operating speed. Flight speeds have to be reduced from max to use them. Models are the same.

You're not going to alter the torque of a servo. What it's rated at is the max you will get out of it. Best to figure that a flap will require a servo that can handle a high load due to aerodynamic loads placed upon the flap. The linkage willl need to be excellent and high in strength and rigidity.

Measuring current draw is easy. On the ground with an H-9 volt and amp meter. In the air with an Eagle Tree telemetry system. The price of the Eagle Tree is the hard part.

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