Pitch servo installation in RV-7A -- old problem, new solution?

[roee]

As others have noted on various forums, the TruTrak pitch servo installation in the RV-7A results in the push rod having a pretty substantial sideways angle. I'm told this is ok. But I'm also finding that even still, I'm having to add spacers between the push rod and the servo arm as well as the bell crank, to prevent the push rod from rubbing on the bell crank. I understand TruTrak recommends against adding spacers at the servo arm due to added stress on the servo. So...

I have another solution to propose, and I'd like to solicit some feedback, especially from TrutrakTech (Lucas?). My proposed solution is to connect the push rod on the opposite side (i.e. the left side) of the servo arm and the elevator bell crank. With no spacers on the servo side, and just one washer serving as a spacer on the bell crank side, the geometry actually works out very nicely, except that the push rod just barely rubs on the servo mounting bracket at the top of the flange where it's diagonally cut. (I'll venture a guess that this was actually the intent when the bracket was designed, but it just wasn't quite enough clearance.) I think I can make it work by trimming just a bit more from the mounting bracket, maybe 1/8 inch deeper, at that diagonal-cut area of the flange. I think that would provide ample clearance for the push rod, and shouldn't significantly affect the strength of the mounting bracket. Any thoughts?

Thanks,
-Roee

Proposed solution:
http://www.kalinskyconsulting.com/rvproj/images/20090713_1.jpg

[TrutrakTech]

*Please disregard the installed location of the washers in the pictures below, they have no relevance to the issue at hand. These pictures were posted to illustrate the side of installation of the pushrod relative to the bellcrank. Thanks!*

Roee,

The beauty of experimentals is you get to do your own thing. I don't particularly see a problem with the way you've connected it, but I have attached pictures of how it's done with our drawing. You shouldn't have any trouble with clearance. Did you put the 2 #10 washers underneath the rod end bearing between the bell crank and the rod end? That should be sufficient to space the rod out and keep it from rubbing. The alignment will be OK.

I wish I had some better pictures to display as these aren't ideal shots, but it's all we have available at the moment. Our RV9 is in Florida so I can't snap any pictures of it's installation. Thanks!

http://i28.tinypic.com/2zplbtv.jpg

http://i28.tinypic.com/10mrehw.jpg

http://i29.tinypic.com/qs5ls1.jpg

[roee]

Thanks Lucas. The photos you posted look like they're of an RV-6, right? I'd be curious to see your RV-9. The RV-7 and 9 are similar to the 6 in the general arrangement of the structures, but the dimensions are slightly different. I have tried it your way on my RV-7A, but I was finding (as others have) that a few more washers were needed, including a couple of washers on the servo side, to make sure nothing would rub or bind. I read elsewhere that you (I don't know if you personally, but someone at TruTrak) recommended against adding spacers or washers on the servo side due to increased stress on the servo. Is that indeed a concern, or not so much with only a couple of washers?

I can see that your arrangement can be made to work if a sufficient number of washers are used, if that's ok after all. And other arrangements can be made to work as well. I'm just trying to make an educated decision on which arrangement to go with, and make sure that I don't violate any important constraints, hence the question. Thanks for the info.

-Roee