Flap Motor Fit?

[ravenstar]

Finally reached the point of installing the flap motor in 12iS build. After carefully measuring and setting the length of the push rods and testing the movement I thought it'd be easy enough to just drop the motor in and attach the bolts to either end. But, no! Fully retracted the motor is almost a full inch short of the crank assembly's forward stop. The motor has a 2 inch travel, and I measured the travel on the crank assembly at approximately 2 1/4" which makes sense. I rechecked the measurements on the push rod as best I could without fully disassembling the flaperon mixer and it seems to be as I remember it very close to the 11 29/32" specified. I figure I'd need to take a good 5/16" off the pushrod to get the crank and motor to align, but just to meet the spec I had to screw the bearings in almost as far as I could with the jam nuts in place. I might get 1 or 2 turns between the two ends which isn't nearly enough. This just doesn't make sense to me. How can it be so far off? (All the control movement is smooth and seems normal. There are no binding parts to suggest something isn't placed properly.)

Van's suggested rechecking the measurements, and then if they're ok to check the final flap movement and travel after assembly. But it's obvious to me it's not going to have the full range and I sure don't want to get the plane fully assembled and have to take it all apart again. Neither the problem nor the advice make any sense to me. What were other people's experience? It seems like the supplied pushrod is about a half inch too long since there's no margin to adjust the bearings.

 

[Rv-12David]

Please post some pictures. Maybe someone can spot a reason for your problem.
My flap motor fit as advertised with no drama. I do remember that the both rod ends needed to be tightened right down to the last thread into the WD-1216 I order to 11 29/32” final length.

 

[ravenstar]

Well, that's unfortunate for me. Something certainly is wrong with my assembly. I disassembled the push rod to double check my measurements. The first photo shows the distance from the flap crank to the center of the pivot bolt in the flaperon mixer where the push rod is attached. The photo is distorted, but the crank is positioned so that the push rod is perpendicular to it as described in figure 4 on page 32-07. The 12" mark is aligned with the edge of the crank, and the distance is actually a little shy of the 11-29/32" called for. (I believe the discrepancy is due to the distortion of the image. It checked out on the bench before I installed it.) A longer push rod isn't going to help, though.



The second image shows the push rod removed from the mixer. I checked to make sure I could not shorten the pushrod further. There's only a fraction of a turn available on each end, so this is as short as I can make it.



The third and fourth images show the position of the crank when it's connected to the flaperon and fully forward relative to the end of the flap motor fully retracted. In this position, the pivot arms holding the mixer are against their forward stop. The pushrod is loosely attached to the mixer, and the flap motor loosely attached for the purposes of the picture because as I mentioned I had removed them.

 

[ravenstar]

I've got it. It's not going to be fun to fix, but at least I understand what has happened. I reversed the F-01242-L and F-01242-R which positions them and the motor way too far forward. Thanks for the photo, that was the hint I needed!

 

[Rv-12David]

Ah that would explain it. I’ve done similar and found when looking at someone else’s pictures thinking they have something in a different place than me. Of course to find I’m the one in the wrong place.

Glad you’ve found the problem.