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Old 11-10-2016, 09:08 PM
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czechsix czechsix is offline
 
Join Date: Mar 2006
Location: Spring Hill, KS
Posts: 365
Default Bearing fit in new Aileron Brackets (SB 16-03-28)

I received the parts for the replacement inboard aileron bracket today (decided to go ahead and do the mod now before riveting on the bottom skins). In the old bracket the bearing was a press fit, but with the new bracket the bearing has some noticeable free play...the machined recess in each half of the bracket is perhaps a couple hundredths of an inch larger than the outside diameter of the bearing. You can just drop the bearing in and actually slide it around a bit. Has anyone else found the same thing with your SB 16-03-28 parts?

My concern is that if there's even the slightest amount of movement of the bearing housing vs the aluminum bracket, it's eventually going to cause wear that will require replacement of the bracket and bearing. It will probably be less prone to movement after the two halves of the bracket are riveted together, but since there aren't rivets all the way around the circumference of the bearing I'm not confident that the clamping force will be sufficient to guarantee no movement will occur under the cyclical loads that it will experience with aileron movement. A good interference fit like the original design would make me feel a whole lot better...
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  #2  
Old 11-10-2016, 09:12 PM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
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A good observation. In addition to potential wear, the free-play could also reduce the flutter margin. Probably not with the minute slop on initial assembly. But add a bit of wear on top of that and ???

One possible approach would be to pot the bearing in place, with filled epoxy. Something like JB Weld. Be sure not to get any in the bearing. Wax is good for that.
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  #3  
Old 11-10-2016, 10:05 PM
Jake14 Jake14 is offline
 
Join Date: May 2014
Location: Seattle
Posts: 323
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I did the same on my QB wings while the lower skin was still off. Didn't notice any slop, but wasn't looking for it either. Just now checked them by putting a screwdriver through the hole and applying considerable force; they seem very snug. I'll definitely put it on my checklist at annual time...
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