Looking through the email archives, the alignment of the front and
rear tufnol bearings/bushings with the aileron torque tube appears to
be a critical step in preventing control stiffness.
There are no specific guidelines about this on the manual. I am mostly
concerned about thermal expansion since the cockpit can see 70C
difference from summer to winter. The torque tube is about 24" long
and looks like zinc plated steel. For 70C, the thermal expansion will
be about 22 mils. So I am thinking I need to insert 12mil shims on
either side of the tufnol bearing before bonding the fork and the
bushing, and then removing it after cure.
Then there is also the question of tufnol expansion due to moisture.
There is a chart on tufnol.com on how much tolerance should be allowed
for water absorption. This is for prolonged immersion so it can be
considered a worst case scenario. For the 1/2" bearing, this
translates to about 0.8mm, or about 32mils.
So putting both factors together, I am thinking of inserting 25mil
shims on both side of the tufnol, for a total of 50mil play. Does this
sound right?
All of this could turn out to be a moot point if the flex in the
cockpit module is a greater factor.
Comments are welcome.
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