How snug is just right?

I'm working on the aileron bellcrank in the RV9A (WD-421). The bellcrank rotates around the brass bushing. But how lose or tight should the fit between the two be. Right now I have to push the bushing into the bellcrank on top of my table. If this is too tight, what is the proper way to make the bushing diameter smaller or the bellcrank larger.
Thanks Russel
RV9A QB wings

Are you sure?

rkochcyxh said:

I'm working on the aileron bellcrank in the RV9A (WD-421). The bellcrank rotates around the brass bushing. But how lose or tight should the fit between the two be. Right now I have to push the bushing into the bellcrank on top of my table. If this is too tight, what is the proper way to make the bushing diameter smaller or the bellcrank larger.
Thanks Russel
RV9A QB wings

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Are you sure the crank rotates around the bushing? It might be the whole assembly rotates around the bolt.

Just asking.

NOTHING ever rotates on the bolt, only the bushing. I had this come up when I was building my nine. When the bellscrank is welded together the weld may intrude into the tube the bushing fits into. It was recommended by Vans to ream out the hole using a drill bit or reamer(I don't remember the exact size but it should just be the same as the inner diameter of the bellcrank tube). Make sure the bushing extends out approx. 1/64" on each end of the crank so the the crank doesn't bind up on the brackets. Lastly, make sure to grease the bushing before final install.

I agree with Jorge - check the bellcrank tube for imperfections, including the powder coat on the ends. I deburred the ends of the tube slightly, and also filed them flatter to get rid of the powder coat on the ends and allow the crank to rotate cleanly on the bushing.

When trimming the bushing to length, get close and then chuck it into your drill press (using hand pressure only - don't tighten with the chuck key or you might distort the brass or leave marks) and slowly lower it onto a flat file as it turns. This will give you a nice square and clean end on the brass bushing. You can also systematically and slowly decrease the length of the bushing until it is just right.

I trimmed my bushing to about 1/64 or less on the ends. There should be enough gap that you can feel the bellcrank move parallel to the bushing, but only very slightly.

cheers,
greg

I've debured the ends of the housing and when I slide the bushing in, it makes it half way and it's still lose. Then it binds. It doesn't matter what end I start from. What is the best way to ream out the bellhousing?
Russel Koch
RV9A QB wings

I've debured the ends of the housing and when I slide the bushing in, it makes it half way and it's still lose. Then it binds. It doesn't matter what end I start from. What is the best way to ream out the bellcrank?
Russel Koch
RV9A QB wings