Maintenance alert - Van's mixture bell crank

[scsmith]

For those of you that use the Van's mixture bell crank and bracket, I found a wear problem after only 30 hrs.

The bell crank is made with a center tube that has a pressed in bronze bushing. This bushing turns on a AN4 bolt that passes through the bracket. You set the bolt tightness to maintain free motion of the bell crank, and use a castle nut and cotter pin.

After only 30 hrs, I found that pivot holes in the bracket were wearing oval from the bolt turning and/or pressure.

So, I reamed out the bushing in the bell crank to 11/32, and faced off .005 off the end. Then, I made a second bushing that was a nice slip fit into the bell crank and was .005 longer than the bell crank tube/bushing. This allows me to tighten the pivot bolt down tight against the ends of the inner bushing, and use a metal lock nut. The bell crank turns freely and the pivot bolt can't move to wear the bracket.

It should have been made this way in the first place. Check yours to see if you are getting a lot of slop in the bell crank pivot from the bolt wearing out the bracket.

[hgerhardt]

I noticed that too, in the first few hours of Phase 1, even. I didn't go to the extreme you did, but I've been using teflon tape (the sticky kind, like Van's sells for the flaps) on the bracket for the bellcrank ends to ride on. I use several layers (maybe .020" thickness) to create a cushion of sorts and that stops the movement. Tighten the nut just enough to get a bit of squish in the tape. I replace the tape at condition inspection annually. Works well.

Heinrich Gerhardt
RV-6, 303 hours