The Corsair82: 82% F4U-1A Corsair

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The arms are in place and the whole thing is assembled on a test stand. I built what I call the "Cage". It is a steel frame that contains the whole assembly. This component will allow the whole assembly to be installed or removed from the wing all at once. It is also designed to take all of the stress from the retraction/extension process.
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Notice the nice hydraulic cylinder I found at an old warehouse.
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Rear view.
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Front view. The "Cage" shows up well in this picture.
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A problem arose at this point in time. The gear would not retract the final 3.
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The over center link was the first thing I identified as the cause. It was fine in this position. It needed to be longer in the retracted position. My changing the geometry from that of the real Corsair caused this.
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The fix was simple, but it took me a long time to come up with. One day a guy called me about building composite telescopes. When I got off the phone with him the idea hit me like a pie in the face. I simply made the link telescopic. This photo show it in the closed position.
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Here is the link in the open position, when the gear is retracted.
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The next problem was the size and stroke of the hydraulic cylinder. I need a cylinder with a closed length of 13' maximum and a 10" stroke. The one I used at first was too long and had too short of a stroke. This picture shows how much space is added to the length of the cylinder by the mount and the front seal. All of the cylinders available had about 5" more cylinder than stroke.
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With Al Wise's help I designed a new cylinder. The seal is very short and only adds about an inch past the fluid input point.
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The mount is even with the seat point of the piston. The fluid is input from the end. Al did a great job. It ended up 12" closed and has a 10.5" stroke. That gives me a little room to play with.
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The installed cylinder.
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Here is a close up of my universal.
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Here is a close up of the real thing.
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It ends up the thing was binding as the gear approached it's full up position. It worked well without the lower strut. I guess the weight of the wheel and brakes at that long moment arm was imposing too much stress on the universal. A slight twist was all it took to help it along, so I figured it wouldn't be too hard to fix. Wrong!
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I redesigned the universal to have less surface area to bind. I cut the old joint off the top part of the strut and receiver part of the mounting.
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I welded a universal joint that goes on an impact wrench.
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This ended up binding at the point where the retaining pin goes through. It actually bent the pin.
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I tried the opposite approach. I made the universal more massive.
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You can see there is more surface area to spread the stress over.
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The assembled parts before installation in the ninety degree position.
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The zero degree position.
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The parts installed.
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Before testing the new universal, I decided to move the point at which the hydraulic cylinder attached to the strut. By lowering it a bit, I figured I would give it more leverage. I couldn't actually move it, so I built a bracket that would simulate moving it.
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I made the bracket long enough to allow me to try multiple points.
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An inch was all it took to make it work. It is amazing how much leverage changed with that small amount of movement.
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The spring for the over center lock has been installed. Every change creates a new problem. The spring was getting caught in the folding arms of the gear.
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I installed the spring over the telescopic links.
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It works! Now the gear slams into position. The rope stops damage to the strut where it hits the test stand. There will be a limiting component in the actual system.
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This is a collection of all of the parts I built and discarded before I got it right. There were more, but I reused a lot of parts and some went in the trash. The "Cage" shown in this picture didn't survive the initial testing. The face plate bent and actually broke free of it due to the binding in the universal.


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