Roll servo bracket fit

[rvg8tor]

I started the install of the roll servo on my RV-8A today and after taking the lower bell crank bracket off to install the Dynon bracket I discovered the holes are off.  The hole that the bell crank bushing bolt goes through should be in the middle of the tow holes that attach the bracket to the wing spar.  My bracket is off just slightly.  I can put it all to together just fine, but if left his way the bell crank bushing will start to ware unevenly and develop some slop.  I wonder if I am an isolated case or if other might have this issue.  I would be easy to miss, you might end up with the bell crank bushing waring out prematurely after  a few hundred hours.

The attached picture shows what I mean.  I bolted the two brackets together through the bell crank bushing bolt hole.  I then set it on graph paper with the center axis of the stock bracket highlighted in orange.  You can see the miss alignment, I confirmed this by holding the Dynon bracket up to the full size bell crank drawing on DWG 15A (top view).  The holes that attach the bracket to the spar are fine, it is the bell crank bushing bolt hole that is not centered between the spar attach holes.

I am posting this so others might check their brackets as well, I bought mine a few months ago so maybe mine is an isolated one.

Cheers
Mike

 

[rvg8tor]

New bracket arrived!

Amazing, I received my new bracket from Dynon this morning and I only talked with them yesterday, UPS Saturday delivery, more service than I expected.

The new bracket and the old are the same, just slightly off.  This tells me that all of the brackets have the same issue.  I guess it is not an issue yet since all of the testers have been flying with the Dynon bracket.  If it becomes an issue it will show after several hundred hours if at all.

I think the play between the bell crank; the bushing and the bolt will allow for the 1/16" the bushing hole is off.  I added some more pictures to my log (link to entry below) to show what I am seeing, trust me I measured this several ways and come up with the same thing.

I am curious, if someone else has the roll servo bracket for an RV-7 or 8 (they should be the same) compare it to DWG 15A and tell me if you don't see the same difference.

http://www.mykitlog.com/users/display_log.php?user=rvg8tor&project=403&category=0&log=79702&row=1

Cheers

 

[rvator51]

Hi Mike,

I have two thoughts on your bracket.

1) Maybe its the Vans bracket that is off slightly, so that's why they dont match.

2) I would make one of the brackets over myself to make them both match. I wouldn't take a chance on having any problems with any part of this linkage. It's too flight critical to not have it perfect. Just my opinion.

Regards,
Tom Velvick
RV-4

 

[Ken_Kopp]

Just today I installed the same dynon roll servo bracket in my right RV8 wing along with all stock bellcrank hardware and push-pull rods. Everything dropped into place and aligned effortlessly. There is no binding or misalignment with any of the bolts. If the hole in the dynon bracket is off by such a slight amount I don't see that as a problem as it would so slightly cause the bellcrank to rotate off a true vertical axis which is easily withing the tolerances of the push-pull rod bearings. Without the servo arm connected the aileron travels its full range of motion without an discernable friction.

I also filed the brass bushing to the mininum 1/64" clearance called out in the plans to eliminate the vertical play evident with the bushing in stock condition.

My two cents...

Ken

 

[rvg8tor]

Just today I installed the same Dynon roll servo bracket in my right RV8 wing along with all stock bellcrank hardware and push-pull rods. Everything dropped into place and aligned effortlessly.  There is no binding or misalignment with any of the bolts.  If the hole in the dynon bracket is off by such a slight amount I don't see that as a problem as it would so slightly cause the bellcrank to rotate off a true vertical axis which is easily withing the tolerances of the push-pull rod bearings.  Without the servo arm connected the aileron travels its full range of motion without an discernable friction.

I also filed the brass bushing to the mininum 1/64" clearance called out in the plans to eliminate the vertical play evident with the bushing in stock condition.

My two cents...

Ken

Ken,

I installed the bracket as well, and it does operate just fine, but it does not eliminate the fact that the bracket is off.  Is it a problem maybe not, but only time with the slightly off bell crank will tell.  I am hoping after I have a chance to talk with Dynon they will try to modify the manufacture of the bracket to match the plans dimensions.

I know my Van's bracket is correct because it matches the full size drawing exactly.  And if you actually measure the bracket the bushing hole is in the middle of the two spar holes, something that is not true with the Dynon bracket.  The current bracket has worked just fine for those that are flying with them but it does not change the fact that the Dynon bracket does not match the dimensions of the stock bracket.  

I guess I am just anal, which is why I looked so closely at the bracket in the first place, it might also be why I build so slowly!

Cheers