Co-Bo

Co-Bo or Co′Bo′ is a wheel arrangement in the UIC classification system for railway locomotives. It features two uncoupled bogies. The "Co" bogie has three driven axles and the "Bo" bogie has two.

The British Rail Class 28 is the first (and only) UK locomotive with a Co-Bo wheel arrangement.

A similar wheel arrangement, with five axles across two bogies, is also used in Japan for the Class DE10, DE11, and DE15 locomotives. As these are diesel-hydraulic locomotives, they are of C-B arrangement, not Co-Bo. A hydrodynamic transmission on the locomotive frame is driven by the prime mover, then drive to each bogie is taken by cardan shafts. The axles of each bogie are all driven, and all geared together, rather than having traction motors.

Some Engerth steam locomotives were built to the Fink system, with the four trailing wheels driven by a crankshaft and connecting rods, thus making them 0-6-4-0Ts instead of 0-6-4Ts.

BoCo is a fictional Co-Bo locomotive, a British Rail Class 28. The locomotive appeared in the Thomas the Tank Engine book Main Line Engines.

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