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25 Nov 2022

25-03: Bearing Bracket Misalignment Issue

Page 25-03 has you prepare the bearing bracket parts F-01450-L & R into pairs. They are identical when you receive them, however you have to countersink them on the outboard sides such that you end up with a couple of pairs of the brackets, matched to each other. They then have a COM-3-5 bearing installed and they are double flush riveted together before being installed on the Cover Ribs, which are then installed onto the forward centre bulkhead using bolts and rivets.


So, all was going well. I managed to get all the countersinks in the correct locations on the correct side of the parts. The parts were clecod together and the edges filed and deburred so they match together as a couple of pairs of parts. 

I then cleco'd the parts together with the bearing in place. One pair of parts went together fine, however the other one was very misaligned; to the point where i was unable to get a rivet into the holes. I believe that when the parts are manufactured, they machine out the bearing recesses into a large sheet of many bearing bracket parts. Then then take the sheet to the punch and stamp out the brackets themselves with all the rivet holes. I imagine there is a very large sheet of many brackets done at once. I think that perhaps, in the drawing, one bearing recess is drawn slightly out of kilter in relation to the holes. Other people have reported they have no problems with these parts at all - and one pair of my brackets is fine. 

Here you can see how the once perfectly aligned edges are no longer aligned once the bearing is put in place.


With no bearing in place, the edges are aligned perfectly

Here you can just see a sliver of blue inside the bearing recess hole. I drew some sharpie on one part and the blue shows that when the holes are lined up, the bearing recesses on one side of the parts doesn't match the other side. One side has been machined out of kilter in relation to the rivet holes.


This shows how far out of kilter the rivet holes get when the bearing is in place. I was not able to get a rivet in these holes, and if i reamed them out the other side would have been significantly oval.

With the screws in place, and the bearing installed, the rivet holes are all out of alignment. 

In any case, i sent and email to Van's about the problem, and posted about the problem on the RV-14 Forum on Van's Airforce. 

Support came back and offered to replace the parts. So i put this section on hold and moved onto Section 26. A month later... the new parts arrived. 

The new parts arrived and i immediately went out to the shed to see if they had the same issue:




As you can see, the new parts had no misalignment, which supports my theory that at least one bearing recess drawn in the set of parts is out of whack, while the rest of the parts are ok. 

So i moved on with the section, and countersunk the new parts, deburred and filed the edges to match as a new pair and then primed them. 


Once these were dry, i was able to double flush rivet them together using the squeezer and finally rivet them to their cover ribs. The bearings on both are free and loose. 

I double flush riveted these together with the screws in position. The plans call for -7 length rivets, but as per the wiki, these are too long. -6 length worked perfectly. 

-7 rivets would have been too long here. 



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