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Electric BUHOR - Frame, Elevator and Rudder

Started off building the frame as described for
the original glow .40 version. The first
departure from the original was to fabricate a
motor mount for the electric motor.  





At this point I was thinking about how the CG
would compare with the glow version. The
electric motor is mounted farther forward than a
glow engine (which would mount directly to the
forward ends of the frame), and of course, needs
a battery pack to be carried on board. On the
other hand, there's no fuel tank changing weight
-- and trim? -- during each flight as fuel is
used up.

After a lot of thought on the matter -- in other
words, lots of guesstimates linked together with
hazy logic -- I decided to just mount everything
by eye and tweak the CG later.
The motor mount is made from 1/4 inch plywood
with two matched pieces of aluminum angle (same
as frame) machine screwed to either side.
There's a space between the two pieces of ply to
allow for the motor shaft which protrudes beyond
the back of the motor case. You can see the
motor here, Turnigy 35-42, selected to (I hope)
approximate the power of a .40 glow engine.





Used a steel square to install the motor mount
as straight as possible. Drilled the screw
holes in place through the aluminum frame and
the plywood while trying to maintain everything
in alignment by hand. In hindsight, I'd
recommend clamping everything in place to drill
rather than trying to hold all the pieces in
place with your fingers.





Here you can see how the motor mount goes
together, including the open slot for the back
end of the motor shaft.





Mounted the servos with cable ties run through
holes drilled in the aluminum frame. Padded
them with scrap pieces of plastic foam and
strapped them down firmly. I used only two
servos -- rudder & elevator -- with an ESC for
the motor. The original BUHOR plans call for an
aileron servo in the wing, but I decided to
leave that out in the hope of having one less
thing to think about while learning to fly. Got
the idea from an ultra-light pilot who flies a
plane with no ailerons by trimming the elevator
and then controlling rise and decent with the
throttle only. We'll see how this works out.





Here are the two servos mounted. Control rods
are made from cooking skewers and bent paper
clips. Skewers were cut to approximate length,
paper clips were wrapped around skewers and tied
with nylon string, their ends bent to fit the
control horns and then glued to skewers with a
hot glue gun. Control horns are Venetian blind
hold-down tabs that come pre-drilled with three
holes exactly where we want them. The two holes
on the base serve for mounting and the hole at
the tip gets the end of the paper clip which is
bent to stay in place. I found this skewer &
paper clip idea on the web a long time ago. Not
sure who originated it.
Note that machine screws and nuts with PVC
backing pieces are used on all control horns
instead of sheet metal screws specified in the
original BUHOR plans. Also, I put a drop of
Super Glue on all bolts to help keep nuts in place.
Overkill?





Wrapped the receiver batteries & RCVR in more
plastic packing foam and strapped them to frame
like the servos. Could've saved weight with a
BEC, but went with the separate dedicated
RCVR/servo battery pack for safety. I was
worried about accidentally running the motor too
long and depleting the main battery pack, which,
with a BEC, would leave me without rudder or
elevator control to (I hope!) bring it down
safely. I wired everything together, powered up
the RCVR and XMTR, and everything seems to work
OK.

Note the glowing LEDs on the XMTR & RCVR.

It's Alive!



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