Brian,
Not an uncommon feature of this loco. The usual problem: handling of the chassis can easily result in one or both connecting rods receiving a little bend inward toward the wheels. It doesn't need much and they can then catch on the second axle crankpin. Other foulings of rods are possible, but this is the most common. The nest time it stops make a careful inspection before handling the loco. Gently bending the rods so that they all miss each other at all rotational positions and side to side displacements of the wheels is the cure.
Less optomistically, if the loco has been run a great deal there may be significant wear in a number of locations. The coupling rod holes on the crankpins may have worn sloppy enough that one or more can slip partway over a screw head and lock on for example, or even comes right off the crankpin screw. If a penetrating lubricant has been used on the chassis the insulating bushes in the wheels one side can deteriorate, and the wheels go out quarter. But these are less likely.
Not an uncommon feature of this loco. The usual problem: handling of the chassis can easily result in one or both connecting rods receiving a little bend inward toward the wheels. It doesn't need much and they can then catch on the second axle crankpin. Other foulings of rods are possible, but this is the most common. The nest time it stops make a careful inspection before handling the loco. Gently bending the rods so that they all miss each other at all rotational positions and side to side displacements of the wheels is the cure.
Less optomistically, if the loco has been run a great deal there may be significant wear in a number of locations. The coupling rod holes on the crankpins may have worn sloppy enough that one or more can slip partway over a screw head and lock on for example, or even comes right off the crankpin screw. If a penetrating lubricant has been used on the chassis the insulating bushes in the wheels one side can deteriorate, and the wheels go out quarter. But these are less likely.
