Nose Gear Doors


With 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 easy).


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!


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Professional Photography by Les Bidrawn    |    © 2010