Restoring of corroded brake shield

Suomeksi

The restoration of a hard corroded part of the landing gear in a earlier blog post raised a debate. Since the commenting with a photo is not possible, I decided to write a short blog post about the question.

In the photo are two original parts of VL Myrsky. The left hand side part is oxidized and corroded but the right hand side part is in rather good condition. The objects in question are parts of landing gears but neither rims nor brake drums. They are part of the brake system of VL Myrsky. They are brake shields.

According to the service instructions of VL Myrsky II (page 25) brake system is functioning as follows: "The wheels of the main landing gears are equipped with hydraulic brakes. The brakes are according to the expansion tube system, where the pressure of the hydraulic liquid expanses the rubber tube in the brake shield. It pushes friction surfaces (brake shoes) against the brake drum and result is braking."

The round brake shield is made from magnesium cast. During the long storage period in a garage, a chemical reaction has started and led to a rich oxidation. Due to the oxidation the magnesium casts have some corroded spots. If they were made from aluminium they would suffer the future use. But they are made from magnesium and therefore a restoration was needed.

The best method to restore was strenghtening by cement. The cement used was made from non-shrink epoxy resin. After the cementation the brake shield was lathed to the original size. The brake shield on the board is waiting for painting.