Tandem-drive Bogie With Three Speeds
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ARECENT development by the Eaton Manufacturing Co., U.S.A., has been a tandem-drive bogie with three speeds, an arrangement evolved from their existing two-speed bogies. The bogie consists of two two-speed axles with a "power divider" inter-axle differential, and the layout is such that the driver can shift both axles to high or to low, or one axle to high and the other to low to give an intermediate range.
Thus, a bogie having axles with ratios of 4.56 and 6.21 to 1 would have an intermediate-range ratio of 5.38 to 1. When changing into the intermediate ratio the rearmost axle goes into lo* ratio whilst the leading axle stays in high ratio. The differential between the two axles accommodates the differences in axle ratio. Changes are carried out under air pressure with solenoid-actuated valves.