Hi all,
I used a water-based valve laping compound to open up the brass/bronze
bushing to allow the steel torque tube to rotate freely.
I had already assembled the fuselage halves together when John Hurst dropped
by on his trip from Arlington to Oshkosh and told me my control pressures
for operating the tailplane were way too high. Right away I knew he was
right but I dreaded the thought of tearing into the tailplane mechanisms.
I'm 6' 4" and have been so very careful in construction that I'd not yet had
to crawl into the back of the fuselage.
I disassembled the torque tube enough that I could rotate the drive plates
within the brass/bronze bushing. I used a water-based valve-lapping
compound so as not to contaminate the area for painting problems later. I
hand-twisted the drive plates with the lapping compound grinding down the
brass/bronze busing. It took about 10 minutes or so per side. Periodically
I cleaned out the area, applied lubrication and tested the friction so as
not to grind too much. It worked splendidly. The drive plates move like
silk within the bushing.
Using compressed air to blow water into the opening between the torque tube
and the brass/bronze bushing cleaned out the lapping compound.
I used a silicon based, penetrating oil, (Silikroil) to lubricate the
busing. Then added an expensive bicycle grease (Phil Wood grease) which is
weather resistant, doesn't evaporate for a decade or more and is able to
withstand extremes in temperature..
I used a fish scale to determine that the starting force to begin movement
of the tailplane is a pull of only 1.5 ounces. The sliding force, once the
whole mechanism gets going, is 0.5 ounces. The stick stops and holds it's
postion when the force is ended.
I'm thankful John dropped by. I have a better airplane because of him.
The whole disassembly, grinding, cleaning, lubricating, re-assembly
(including getting the tailplane movement limits exact) took a day...way
less than I had imagined it would.
Rob Neils
Spokane, Washington
A162 Europa tri-gear motorglider
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