Aileron Bell Crank Assembly

Dan assembled the aileron bell cranks.  The bushing holes in the angle brackets were matched drilled, in the drill press, a little under and reamed to final size.  In case you don’t know bronze bushing are designed to be press fit onto bores but this casues the inner diameter to collapses a tiny bit.  We could just start the bronze bushing in by hand until it stopped.  We then checked the fit of the rotating steel bushing.  Dan polished the outside of teh steel bushing on the Scotchbrite wheel.  We thought it was good so used the arbor press to insert the bronze bushings.  There is a peice of phenolic to space the angle brackets.  We had to use a shim of paper on either side of the phenolic to get the rught feel.  (I would really prefer ball bearings  but given the limited motion of the bell branks this seems like a good design, but we both wanted a good smooth feel the rotation.)

For some reason our aluminum angle has a big inside radius so the head of the angle clamp bolt and the nut did not sit flat.  We machine a little spot face so they sit properly.  We will sand this area really smooth.

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Aileron Bell Crank Parts

We have been working on the Aileron Bell Crank parts.  Used the scan/print spray glue method for the parts that had make to print size on them.  After the root rib trim episode we looked at the how these parts are assembled.  For example the U channel parts are stiffeners on the rib behind the bell crank assembly.  The length should be accurate but it is position so there is clearance between the end and the skins.  So there is no need to be right on the 1/64 dimension, which might save a little time for making four parts.

Aileron Bell Crank Parts
Aileron Bell Crank Parts

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New Aft Root Ribs

Dan cranked out two new aft ribs and since we knew they we for the root positions he did not have to make the front and back flanges.  He trimmed them a little longer so we would have plenty of edge distance from the first row of rivets:

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Positioning the root ribs with the others:

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Put the aft wing skin on to see how it fit, Looking Good

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Too Short Aft Root Ribs

After we trimmed the aft root ribs per the dimensions on the plans and got them positioned with clamps it looked really good.  (We were working on the left wing aft root rib.)  When Dan match drilled through the bracket to the rib the hole at the edge of the rib the hole was really close to the edge, a little too close.  Really fustrating.  All the dimensions seemed right on.  We think that perhaps the holes in the bracket were a 1/32″ off and the rib position was a 1/32″ off and the tilt of the root rib doesn’t help either.  Perhaps all these little dimensions add up to the hole being off.  Dan claculated the theoritical drawing distances and there is only an 1/8″ from the hole to the edge.  Reviewing the plans there is no reason why the rib couldn’t be a little longer on both ends to give adequate edge distance.  The rib just overlaps the attach brackets.  So we discussed a doubler but decided to remake the ribs and trim them a little longer.  One advantage of scratch building is that remaking parts is not imtimidating.

This was an interesting episode, if we had looked ahead in the plans we might have noticed the rib trim dimension was not critical and could be changed.  However it would take a lot of time to research every part dimension to see what it’s function is.

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Wing Root Ribs

Dan & I worked on the wing root ribs.  These start are standard ribs but trimmed shorter so you can rivet them to some aluminum angle mounted on the spars.   We read on a few websites that on the front rib one can cut out the material between the lightening holes.  This makes reaching into the wong easier for rigging.  One can see a picture of this in the Sonex website under Support – Instruction Sheets – Wing Installation/Removal Instructions .  You can see the oval in the forward root rib.  We made the root rib gussets, they are different than the rib gussets.

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Left Wing Rib Gussets

Dan match drilled the gussets on the left wing ribs.  One wants to make sure the gusset flange is mated tights against the rib flange when match drilling the rivet holes with the rib.  You don’t want a gap between the gusset flnage and the rib flange when you go to rivet the assembly to the spar.

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