"Knock it Off"
LG Setup
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by John Ernst
Nov 16, 2004
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I HATE bending wire!. It doesn't make a difference
if it's a prop hook, cabane strut reinforcement,
tailwheel assembly, or landing gear stiffener...
I hate it. I've never been able to get my finished
product to take on the nice clean profile that's
drawn on the plan. It's never symmetrical, never
lays flat, never has the correct bend angle. Can
you tell I have a problem?
So, I'm always looking for other ways to attach
landing gear.
When I was working on my Sopwith Triplane, Mike
Taylor suggested using magnets to secure a removable
cowl - allowing easy access to the electric motor.
What a great idea! It worked like a charm - three
magnets held the cowl in place, and with a slight
twist the cowl broke free of the surprisingly strong
bond.
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I'm currently working on a Nakajima Ki-27 "Nate"
for the Diels "Pacific Theater of Operations"
Cook-Up on the FFCU
site. This airplane has a fixed gear
setup with sculpted wheelpants. There are 4 different
LG options on the plan, each calling for a bent
wire framework - except for one. Guess which one
I chose? |
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The wireless setup has an extended 'tongue' from
the LG leg that inserts into a slot in the wing
made by two wing riblets. Although this would
be a secure connection, I felt that a rough landing
(not that it would ever happen!) could make the
LG legs snap off and damage the wing. My little
modification uses magnets to secure the LG, creating
a 'knock-off' set up that will give way before
damage occurs. This also allows removal of the
LG entirely for flight, if I wish.
The magnets I used are from a company called "FORCEFIELD".
They are 1/8" diameter, by 1/16" thick,
and surprisingly strong. Here's the link:
http://www.wondermagnets.com/cgi-bin/edatcat/WMSstore.pl
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start with, the LG legs are built up of several
layers of 1/16" sheet, and then sanded
to a streamlined shape. |
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Each leg is covered with an outer 'skin' to
cover the wheel. |
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The 'tongue' I mentioned earlier can be seen
in the photo below. I had to remove the tongue
and sand the top of the LG leg smooth to create
a base to insert the magnets.
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On the wing, the 1/16" slot for the LG tongue
had to be widened and filled with sheet balsa -
also to create a base for the magnets. In hindsight,
I should have made the width of the wing base at
least 3/32" - not 1/8," which is the same
width as the magnets. When drilling the holes for
the magnets, the wood just split apart. Luckily,
it was sandwiched between the two riblets.
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So, I located two holes for the magnets in the wing,
and inserted a pair of magnets into each hole, allowing
only one of the two to penetrate into the balsa
sheet. By inserting the pair, it helped insure that
the magnetic polarity was correct. I used thick
Cya to attach the magnets. This setup isn't pretty,
but it works. You can see the second magnet sticking
up above the surface of the sheetwood. |
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After this was dry, I colored the tops of the exposed
magnets with a red "Sharpie" marker (because
the ink doesn't stick to the metal), lined up my
LG leg in the correct location, and placed the LG
leg over the magnets to transfer the red dot to
the leg. The photo shows the dots enhanced, but
you get the idea. all you need to do is get the
holes lined up. |
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| Drill
the holes in the LG leg, insert the magnet - making
sure you keep the polarity correct. I added glue
into the holes, then placed the leg over top of
the magnets that were sticking up above the wing
surface, and popped the leg in place. I then separated
the LG from the wing to allow the glue to dry. |
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In the two photos below you can see the completed
attachment setup.
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The hardest part of the whole procedure was sanding
the wing / LG Leg attachment to the correct angle
so the legs are perpendicular to the ground because
of the wing dihedral.
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Finally, the LG leg is rough shaped and prepared
for final sanding.
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I'm pleasantly surprised at how well this setup
appears to work. The LG is very strong front to
back, although somewhat less strong, or wobbly,
from side to side. That is to be expected with
the magnets set up in tandem as I have done. If
they were to be set in a triangular pattern it
would be even stronger, but there begins to be
a weight penalty. I also believe it would be over-kill.
The object for me was to make a 'break-away' LG
set up, and if you make the connection too rigid,
you've defeated the purpose.
If anyone has any questions or comments, I can
be reached at...
jjernst@verizon.net
Good luck - give it a try!
john ernst
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