Twin elevator servos

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1

Hi All,

My current fixed-wing project uses one servo for each separate elevator half. Due to the airplane-servo geometry, elevator servos should be contra-rotating, since left & right elevator servos and linkages are installed mirror-image of each other.

Because of this, one servo is on the “elevator” Rx channel and the other on “Aux 1”, and the Spektrum DX8 radio mixes them accordingly. But what to do with the Ardupilot input/output on the second, “Aux1” channel? As of now, I see only two ways out:

  1. Reverse the geometry on one of the servos (i.e, link the elevator on the other side of the servo) thus having both servos running in the same direction, and then just “Y” them together (which I’d rather not do because this would involve different linkage lengths & geometry, possibly disrupting elevator travel sync);

or

  1. Have both elevator outputs “Y-ed” at the APM elevator output, and then insert a servo reverser before one of the servos.

One advantage to either approach is that I’d free the “Aux1” channel that is currently used for the second elevator half.

Is there another, simpler way of doing this? Am I missing something?

Thanks,
Bruno

2

[quote=“BrunoBL”]Hi All,

My current fixed-wing project uses one servo for each separate elevator half. Due to the airplane-servo geometry, elevator servos should be contra-rotating, since left & right elevator servos and linkages are installed mirror-image of each other.

Because of this, one servo is on the “elevator” Rx channel and the other on “Aux 1”, and the Spektrum DX8 radio mixes them accordingly. But what to do with the Ardupilot input/output on the second, “Aux1” channel? As of now, I see only two ways out:

  1. Reverse the geometry on one of the servos (i.e, link the elevator on the other side of the servo) thus having both servos running in the same direction, and then just “Y” them together (which I’d rather not do because this would involve different linkage lengths & geometry, possibly disrupting elevator travel sync);

or

  1. Have both elevator outputs “Y-ed” at the APM elevator output, and then insert a servo reverser before one of the servos.

One advantage to either approach is that I’d free the “Aux1” channel that is currently used for the second elevator half.

Is there another, simpler way of doing this? Am I missing something?

Thanks,
Bruno[/quote]

Put the other elevator half on a channel above 4 and set RC#_FUNCTION to 19 (elevator), and set RC#_REV to -1. I think that should work.

3

Thanks jschall,

Will look into that. Good idea.

Bruno

4

Hi,

Did this solution work? I’m also looking for a similar setup.

Thanks!

5

that method will work, but you need to be careful to set the MIN, MAX and TRIM values correctly for the extra output
Cheers, Tridge