Replacing broken landing gear
Posted: Sun Jan 15, 2012 11:15 pmObviously restorers have to deal with missing landing gear when restoring some of the Dinky aircraft. The brittleness of the metal of the oldest ones can make this particularly challenging. After some fussing around, I found that the "total commitment" approach was best. Cut everything away, and start all over again with machined aluminum parts.
The two projects I will present here are the Gladiator (I did four of them) and an Autogyro. In all cases, the subject Dinky had little or no landing gear left. Two of the Gladiators, and the Autogyro were also very brittle with cracks, AKA "fatigue". Though metallurgically speaking that's not really what it is - it's not like the Dinky has been stressed thousands of times to near it's ultimate capacity! I think it's more akin to intergranular corrosion.
I fix the fatigue with a good dousing in thin cyanoacrylate, and before it can set, I place the Dinky in a vacuum chamber, and remove all the air. The glue bubbles. When the air is returned, the bubbled glue is then driven deep into every crack by the returning air pressure. I then evacuate again right away, and leave it for a while. The glue seems to set quite well this way. Some dressing of excess glue is often required, but the results are pleasing. Once painted, you can't really tell, and I think that the vulnerability to the environment is forever ended.
Getting back to the landing gear, and starting with the Autogyro, tolerating a loss of authentic appearance, it was easier to just fill the center of the fuselage with the block glued in the middle. This made the landing gear part all one piece, and very robust. It was obviously necessary to pattern from a good Autogyro. The following photos show the progression:
Then on to the Gladiator. With the other damage fixed, it was time to make up new gear legs. I measured a good Gladiator to dimension the repair part. It was interesting to observe that the original gear legs are not exactly symmetrical left to right - difference minor, not an issue! It was easier to gang six repair landing gear, as once the milling machine is set up, you may as well do a bunch! I drilled two holes to accommodate pins, which would correspond to pin holes I drilled in the fuselage, which I'll get to later. The following photos show the progression.
With the gear legs made, it's on to machining a slot and two pin holes in the bottom of the fuselage, to receive the repair part. The fuselage was impossible to hold in a vice, so I had to machine a paired and pinned aluminum clamping block. This would hold the Gladiator firmly by the engine cowl, and fuselage behind the wings. Everywhere else had lots of clearance so as to not damage flying surfaces. This block made holding the Gladiator for machining just fine.
A slot was cut across the bottom of the fuselage, so as to cut away all the old landing gear. and allow the two pin holes to be drilled. This slot just caught half of the propeller pin hole, but was behind the actual pin. It corresponded exactly to the thickness of the aluminum parts I had machined.
Once done, glue in place, and finish. It was necessary to lathe turn a bunch of new wheels.
The finished product...
The two projects I will present here are the Gladiator (I did four of them) and an Autogyro. In all cases, the subject Dinky had little or no landing gear left. Two of the Gladiators, and the Autogyro were also very brittle with cracks, AKA "fatigue". Though metallurgically speaking that's not really what it is - it's not like the Dinky has been stressed thousands of times to near it's ultimate capacity! I think it's more akin to intergranular corrosion.
I fix the fatigue with a good dousing in thin cyanoacrylate, and before it can set, I place the Dinky in a vacuum chamber, and remove all the air. The glue bubbles. When the air is returned, the bubbled glue is then driven deep into every crack by the returning air pressure. I then evacuate again right away, and leave it for a while. The glue seems to set quite well this way. Some dressing of excess glue is often required, but the results are pleasing. Once painted, you can't really tell, and I think that the vulnerability to the environment is forever ended.
Getting back to the landing gear, and starting with the Autogyro, tolerating a loss of authentic appearance, it was easier to just fill the center of the fuselage with the block glued in the middle. This made the landing gear part all one piece, and very robust. It was obviously necessary to pattern from a good Autogyro. The following photos show the progression:
Then on to the Gladiator. With the other damage fixed, it was time to make up new gear legs. I measured a good Gladiator to dimension the repair part. It was interesting to observe that the original gear legs are not exactly symmetrical left to right - difference minor, not an issue! It was easier to gang six repair landing gear, as once the milling machine is set up, you may as well do a bunch! I drilled two holes to accommodate pins, which would correspond to pin holes I drilled in the fuselage, which I'll get to later. The following photos show the progression.
With the gear legs made, it's on to machining a slot and two pin holes in the bottom of the fuselage, to receive the repair part. The fuselage was impossible to hold in a vice, so I had to machine a paired and pinned aluminum clamping block. This would hold the Gladiator firmly by the engine cowl, and fuselage behind the wings. Everywhere else had lots of clearance so as to not damage flying surfaces. This block made holding the Gladiator for machining just fine.
A slot was cut across the bottom of the fuselage, so as to cut away all the old landing gear. and allow the two pin holes to be drilled. This slot just caught half of the propeller pin hole, but was behind the actual pin. It corresponded exactly to the thickness of the aluminum parts I had machined.
Once done, glue in place, and finish. It was necessary to lathe turn a bunch of new wheels.
The finished product...
