the size of the landing gear completely filling the wheel well, and the
curvature of the fuselage, there seemed no way to make the gear
work. I had actually contemplated building them
"static", at the suggestion of a few people, but that was just
freaking unacceptable. After all, one of the design goals was for
all the subsystems to actually function.
Anyway, this latest episode
of obsessive behavior lasted 5 days, but we got them functioning
beautifully! I started by making the door panel liners (I often
get motivated to a section by doing a meticulous detail, so I am too
invested in a section to quit). The raised sections are cut from
2.5mm Plastistruct half-dowels. Then they are paired up, and the
ends sanded round in a lathe. Styrene cement bonds them to
the panel (I am really liking working with styrene, it's almost too
One of the problems was
that preliminary measurements showed that it was impossible for any
straight linkage rod to actuate the 3rd door! Any linkage I could
come up with had to be 10mm longer when the gear were up than when the
gear were down! I solved this by building an RC Car (Mini Z) shock
absorber "Inside-Out". By placing the spring inside, the
shaft (A Blade 400 pitch rod was the right length) can extend by 12mm
when pulled. The spring on the outside is just for appearance, it
does not do anything, it all happens on the inside.
Gearbox Hobbies gleefully
filled my order for "One each of every freaking little shock
absorber for cars, and every threaded shaft you have in the
store". Actually, John, Jack, Sparky, and Peter are a great
help and get me odd parts from airsoft guns, cars, planes, and boats to
make my scale ravings come to fruition. The ball ends are chunks of a
T-Rex 450 washout arm (also a handy part for these endeavors, I have
"consumed" about half a dozen of these puppies already
throughout this project).
With the 3rd door
assembled, it works like a charm. The door has a ledge that serves
as a foundation for the other 2 doors, and rests on it's own stops (the
white styrene bars in the wheel well). Their 2.5mm thickness was
all the clearance I had, and one of them even had to be notched!
It seems like forever ago
that I built the gear door retraction mechanisms into the nose piece just for this day!
I beefed up the rods to look like hydraulic actuators, and attached them
to the forward gear doors using those handy washout arm chunks (again).
Here is a view
"straight into" the wheel well. You can see how the rod
is a bit longer than when the gear is down, this holds the door shut
against the stops quite nicely.
Finally, here is a shot
with the doors closed. The small dots on the front of the bay
doors are N52 neodymium magnets, to keep the doors from vibrating ajar
with the mechanics running, or with servo power disengaged.
And here you can see them
in action! The sun was low when I shot this, so there is some
glare. A bit difficult shooting from the bottom, but gear door
always work perfectly when the heli is inverted, the real test is how
everything works when upright!