The pictures posted by Larry yesterday of 485 in the Salida turntable pit raise some questions about what really happened. Assuming the engine "walked" down the lead beside the roundhouse, it seems to me that the locomotive would have had to have considerable speed built up when it went over the edge of the pit in order to get all of the locomotive and half the tender into the pit. If the throttle were leaking badly enough to get up that much speed, it would have been unworkable in service and the boiler would have been killed for immediate repair.
A typical leaking throttle on a K36 leaks enough to make it difficult to get the vacuum breakers (snifter valves) to drop when parking the locomotive. With the snifters up (closed) and the cylinder cocks closed and the valve gear reasonably far off center toward forward or reverse, and no brakes on, steam leaking past the throttle could build up pressure in the superheater piping sufficient to cause the locomotive to move, but as the pistons began to move, the pressure would quickly drop, and the locomotive, assuming level track, would stop, at which time pressure would again build up and the locomotive might move again, etc., etc., and the engine could "walk" down the track. If that were the case with the 485 in Salida, I would have expected to see the locomotive with its pilot in the dirt of the pit floor and perhaps the rear third of the locomitve in the air, perched on the edge of the pit, with the front of the tender jacked up by the elevated drawbars at the rear of the locomotive.
Earl or Floppo or anyone else who's run the K36's, does that sound about right or am I missing something?