Page 32-05 Revisited: Control Stick Bushings

After installing the stabilator cables (post to follow) I spent some time moving the stick around and watching the stab move.  I could definitely feel play in the stick.  If I held one stick full forward, I could move the other stick about 1/16th inch at the top.  After trying to convince myself that "It

doesn't matter, I'll never even notice it while flying," I decided I couldn't accept it.  In my head I'm hearing the experienced builders whispering to me.  They're saying "Perfection is the enemy of flying your airplane."  I ignored the whispers.

In the picture at left, I have unbolted the stick and pushed out the bushing.  The bushing gets clamped tightly between the ears on the cross shaft, and relative motion occurs between the ID of the steel tube passing through the stick and the OD of the bushing.  For fore-and-aft motion of the stick (controlling pitch) I could feel the play, for lateral motion (roll) I could feel no play.  The problem arose when I originally reamed the ID of the steel tube.  The OD of the bushing from the factory was 0.375 inches (plus a bit) and wouldn't come close to passing through ID of the tube.  I lightly reamed the ID (using the red neck reamer shown -- a bolt with the head cut off and an axial slot which anchored a strip of #200 sandpaper).  I was able to borrow an actual 0.375 reamer and it passed easily through the tube.  Slightly

larger reamers were apparently, based on their prices, diamond coated and I couldn't afford to buy one for two passes through the tube followed by retirement to the reamer drawer in my toolbox.  The odd thing was that the bushing would pass 80% of the way through the tube starting from either end.  I decided the only way this could happen was if the ID of the steel tube was correct but the tube was very slightly bent in an axial direction.  Here's where I made the mistake: I reamed it a bit more until the bushing would go all the way through, then assembled everything.  This got me the end-to-end play when moving the stick fore and aft.

After determining that I couldn't stand the play, I had slightly oversized bushings made (thanks Joe), then carefully sanded the OD of the bushing into a slight hour glass shape (OD smaller in the middle).  Pilot's side is perfect, co-pilot's side still has slight play (I'll never fly from that side!).  The red neck lathe is shown (bushing held on a bolt which was chucked into my drill).