Wednesday, November 18, 2009

Good conductor, bad conductor

Weyerhaeuser Timber Company White River Branch #1 is a diesel-electric locomotive built in 1951 during the transition from steam to diesel. It is an important object in the Museum’s collection for the era in which it was built, because it represents local King County history (Enumclaw area), because of its connection with the forest industry, because of its builder (Fairbanks Morse) and because it worked together with White River Lumber caboose 001 that is also in the Museum’s collection. And, well, just because (yes, Spike disliked that reason too!)

Diesel-electric refers to the power transmission. A diesel engine turns an electric generator and relays control how much electricity is sent to electric traction motors that are mounted on each axle. It is a very efficient design and similar to the concept used in hybrid cars, except there is no storage battery.

Locomotive 1 is operationally complete and for nearly 20 years regularly pulled trains on the interpretive railway. Unfortunately, electrical problems developed a few years ago and the locomotive has been out of service ever since. Unfortunately, electrical problems concomitant with managing old locomotives because wires and components that are nearly 60 years old tend to be bad electrical conductors when they should be good, and good electrical conductors when they should be insulators. (In this context, conductor is not the boss of the train, it refers to the electrical properties of something. If something is a good conductor, electricity will probably flow easily through it.)

Locomotive 1 is slated to go on long term exhibit in the new Train Shed when that structure is completed later next year. In preparing for that exhibit, the Museum’s staff has been attempting to address known issues including stuck fuel injectors (Fairbanks Morse Engine sent out a crew to fix this problem) and electrical problems. For the 1, electrical problems appear to be confined to two traction motors that have an unusual buildup of carbon dust. In that situation, we would call that carbon a very bad good conductor: it allows the high voltage intended to power the electric traction motor to leak into areas where it is not supposed to. If an attempt were made to operate those electric motors, the result would be a very bright flash and a lot of molten copper, and that would almost certainly make future operation unlikely.

Over the past several months, various cleaning techniques have been applied to the locomotive 1’s traction motors. It is too soon to tell if the locomotive will be able to operate with any regularity, but some of the results are promising enough that a new set of carbon brushes – an essential component in a direct current traction motor – has been installed.

We have a lot more information to share about locomotive 1 – and even an exciting announcement or two – so watch for more posts in the coming weeks and months.

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