We are going to jump
ahead quite a bit, as I did not take photos of about 3 months of
sanding, patching bubbles, sanding again, sanding more, and then really
sanding. Did I mention sanding? Oh, then there was more
sanding... I would work on this for 5 hours per day, and after two
weeks of work, people would visit my garage and say: "Gee, you haven't
done any work on your helicopter!"
For those of you who
don't already know, a Fenestron is a shrouded tail rotor of a
helicopter that is essentially a ducted fan. The housing is integral
with the tail skin, and, like the conventional tail rotor it
replaces, is intended to counteract the torque of the main rotor.
Anyway, this is where
Bryan came to the rescue. I needed to couple the Vario gearbox
for the Fenestron fan to the standard Align Torque Tube. Bryan made
a number of custom parts for this assembly, we replaced the Pitch
ring with one that fit the original Vario part. This requires two
shoulders on the ring, one for the bearing, and one for the nut to
seat. This was made pretty much "caliper to lathe", so there was no
diagram. The actuator arm was made to replace the Vario one, and fit
the bellcrank. The mounting plate for the bellcrank support arm is
just a square of aluminum, drilled to fit the end of the gearbox,
with a relief to prevent rotation, and a mounting hole.
Align boom is larger than the Vario, so a thin sleeve must be made
to make up the difference in diameter . A shoulder on the sleeve
prevents it from sliding up the Align boom. The Vario gearbox
connector 49/56 is disassembled (remove the pin and slide off the
articulating connector) and reassembled with a machined part that
has been made to accept the Align Torque tube.