The Corsair82: 82% F4U-1A Corsair

I want the main landing gear to operate just like the real Corsair main gear system. I took pictures of real Corsair gear, studied the Corsair maintenance manual, and studied a set of plans I was given. The plans were drawn by Lou Maniero. He attempted to build a Corsair replica back in the mid 1980's.

All of the information I had wasn't enough to help me understand how it worked. I built several mock ups before I understood the system enough to make it work. The following series briefly outlines the steps I took to accomplish my landing gear goals.

The gear in this sequence will never be installed in the aircraft. It is just the prototype.

Main Gear Pic 01
Using Lou Maniero's plans I built the linkages for the main gear retract system. I used light aluminum parts at first.
Main Gear Pic 02
This shows the "drag links" being built.
Main Gear Pic 03
I built a strut using PVC pipe and the collars in which the strut rotates are made of wood. At this point, I still don't know how it works.
Main Gear Pic 04
At the top of the strut is a cone made of resin. It has a steel tube in it. At the top of the tube is a pin which holds a threaded pipe in place. The pin allows the pipe to articulate. This is the part that makes the gear rotate as the gear is retracted.
Main Gear Pic 05
The parts are assembled on a test stand. The white female threaded pipe is mounted in the leading edge of the wing. It does not move as the gear retracts. This is the key to the rotation. The part is aligned at a certain angle. That angle determines how many degrees the gear rotates.
Main Gear Pic 06
I will use a Beech Bonanza main gear strut for the Corsair82 main gear. These struts were sent to me by Brian Bartter.
Main Gear Pic 07
I had to turn the strut on my lathe to clean it up.
Main Gear Pic 08
I am now building a powered prototype for the gear. The parts have to be strong enough to operate, but not yet aircraft quality. This is the part that will hold the pivoting threaded pipe. Kind of a strange parts combination, but I have to use what works in order to develop the parts I need.
Main Gear Pic 09
I've now assembled the gear using parts that will hold up to the stresses of retraction. The original parts, the wood and PVC, broke every time I tried to make the system work, even though I was actuating them by hand. The collars (the two white parts on the strut) in this picture are made of very high density plastic. I was able to machine and thread these parts. The strut turns inside these collars as it retracts.
Main Gear Pic 10
I've now attached a pneumatic cylinder and an electric valve to actuate the system.
Main Gear Pic 11
Actuating the system broke the female threaded pipe. I also found that the male threaded pipe was binding. Instead of using threaded parts, like the real Corsair, I machined a smooth replacement part that consists of a pipe and collar. This gives more contact surface area to distribute the stress.
Main Gear Pic 12
The new part is mounted. The inner pipe is pushed in from the back. It has a collar welded to it's rear side which keeps it in place (see previous picture). A collar held in place with set screws keeps it in place from the front. This part rotates very smoothly, now.
Main Gear Pic 13
The whole assembly mounted on the test stand.
Main Gear Pic 14
The next four show the retraction sequence.
Main Gear Pic 15
Here is the second picture in the retraction sequence.
Main Gear Pic 16
Here is the third picture in the retraction sequence.
Note the rotation of the wheel. In this case the right strut on the airplane. Each wheel rotates 87 degrees as it retracts. They also rotate in different directions. Each rotates towards it's respective wingtip.
Main Gear Pic 17
"Up and locked". The way this gear operates is really cool. The key to making it work was to assemble it in the up position, as shown here. I didn't know that at first, which caused a lot of parts to fail. The placement of the collar, which is about at the center of the strut, is the most important step. It must be placed and locked in place in the up position, while allowing the strut to rotate inside of it. This sets the geometry for the whole system to operate correctly.
Click on any photo to see an expanded version.

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