Crack Repair, Gear Leg Attach Socket
 

Any experience, advice or comments on repairing a crack in the gear leg attach socket (RV-3, O-320, Dynafocal mount)?



Thanks...Joe

This is not going to be an easy fix
 

Joe,

This crack can be repaired, but it's going to involve a lot of work to repair it properly.

I would recommend you buy a new engine mount if you have more $$ than time.

If you repair it, or have it repaired I would recommend adding an overlay of some 4140 sheet to help avoid future cracking. And I might add a gusset also.

I would do both sides while you have the mount off.

That's my take on it!

Mark

Get a copy of AC43.13-1B/2A.

You're probably going to have to remove the weld in the vicinity of the crack and re-weld most of the cluster. A gusset(s) between the 2 tubes descending from the engine and tied into the gear socket might not be a bad idea either, but I'm no engineer.

If you elect a weld repair, you'll need full penetration and a very clean surface inside and out. You'll also need to maintain roundness of the socket ID, no easy trick. I'd bet Van's gear lag sockets are reamed after welding.

Cleaning is straightforward. I'd pull the mount off the airplane and media blast. To aid penetration you might "V" the crack slightly, but a Tig usually makes penetration effortless. To end up with a smooth ID and help maintain roundness, you might try machining a solid brass plug to match the ID of the socket. The weld will not fuse with the brass. The coefficient of thermal expansion for brass is slightly higher than for steel. Insert the brass plug and torch preheat the plug and steel evenly to about 500F before welding. I'm pretty sure the brass plug will knock out after it cools, but I can't guarantee it.

Does it have a steel ring insert in the upper end of the socket, with the ID of the ring matched to the gear leg diameter? If so, does the crack extend through the ring? If the crack doesn't extend through the ring, it becomes an easy repair; just Tig the outer tube for penetration. You might still use the plug, but the weld wouldn't touch it.