Good question regarding backward running. As some of you may recall, the former SP 2472 damaged a driver axle bearing during a long backup move as part of a Gilroy Garlic train operation. The axle journal, and the crown brass that rests on it, overheated due to inadequate lubrication, badly scoring both.

The problem was with the lead-in taper in the crown brass. Most of the bearing portion of the brass is cylindrical, with clearance on the order of several thousandths of an inch between it and the axle. But there also needs to be a lead-in taper, such that lubricant picked up by the axle from the grease cake or oil bath, as the case may be, will be fed into the bearing surface. It turned out, the 2472 had the taper only on the side of the crown brass needed for moving forward. Thus, it had inadequate lubrication during a backward move.

For those of you not familiar with journal axle bearings, they are only a half-bearing designed for taking vertical load in one direction only, which of course is downward on the axle. The bottom side of the axle journal passes through a "cellar" where it picks up lubricant.

In the case of the 2472, repair consisted of lightly machining and polishing the axle journal surface to clean up the damage, and I believe they needed to make a new crown brass.