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Road Freight Type B-B

by Omer Lavallee   One of the new expressions in diesel-age terminology is the "second generation" locomotive represented in this issue by MLW-built road freight unit No. 4239, resplendent in the new CP Rail "action red" livery.   At the risk of oversimplification it might be said, that second generation units are those designed to replace original diesel road, roadswitcher and switching locomotives that had, in their turn, replaced steam locomotives between 10 and 25 years ago. While second generation diesels

may often be recognized by their "low nose" profile affording good visibility from the cab, and by a tendency toward higher horsepower ratings per unit than their predecessors, this is not a hard and fast rule. Rather, the changes are those not visible to the casual observer, such as in the design and capacity of the diesel engine itself, the locomotive's "prime mover", and in the use of static controls, such as transistors and diodes, instead of moveable equipment of the relay type.   Some of the recently-added units are not, in fact, completely new. Many of them, including CP Rail's 4200 series, utilize components salvaged from

older locomotives such as traction motors.   Nonetheless, the low-nosed, long carbody road freight locomotive, mounted on four or six wheeled trucks, have become a recognized railway motive power "look" of the 1960s, and CP Rail has kept up with the trend by maintaining a fleet of 150 such locomotives, ranging in power from 2,250 to 3,000 horsepower per unit. These ratings may be contrasted with the 1,500 and 1,600 horsepower units generally prevalent on our lines nearly 20 years ago.