For some time, I had assumed that I would just use 1/4" ID PM bronze flange bushings on my flap and aileron pivots. I never even did any benchmarking on what is used in the airplanes I have been looking at. And because I am using off wing pivots for flaps and ailerons, I was hoping the keep this stuff tight for aero drag reasons.
Two nights ago, I did a check on bushing contact stress, and realized that for the pivots that also carry the actuator load, they were overloaded! Gulp. I feel like a dope...
So, I checked into bushings and miniature ball bearings and needle bearings... Lots of stuff that can carry the load, but gee whiz, not very compact. Nor cheap. It even looks like if I just stuck with PM bronze and went to 3/8"ID, I would be OK.
Then I started thinking about the rest of the issues. Dive speed is 268 knots, and the clearances that bushings imply has me wondering if bushing clearance would get me into flutter issues. Perhaps bearings are the way to go..
So, what do the rest of us know about control surface hinges, slop in the system, and the need for bearings?
Billski
Two nights ago, I did a check on bushing contact stress, and realized that for the pivots that also carry the actuator load, they were overloaded! Gulp. I feel like a dope...
So, I checked into bushings and miniature ball bearings and needle bearings... Lots of stuff that can carry the load, but gee whiz, not very compact. Nor cheap. It even looks like if I just stuck with PM bronze and went to 3/8"ID, I would be OK.
Then I started thinking about the rest of the issues. Dive speed is 268 knots, and the clearances that bushings imply has me wondering if bushing clearance would get me into flutter issues. Perhaps bearings are the way to go..
So, what do the rest of us know about control surface hinges, slop in the system, and the need for bearings?
Billski
