completely descriptive or adequate for all purposes. The most widely
mechanical engineer on the New York Central and Hudson Railroad. The
system is generally accepted in Great Britain and the British
Commonwealth and in North and South America.
The Whyte classification is based on the number of locomotive
wheels on the axles of each type of truck. Wheels or trucks are of
three types--leading (front), driving, and trailing (rear). Truck is
the term used to designate a wheeled assembly that supports a
locomotive or a car body. The Whyte system uses a series of digits
or numerals separated by hyphens to specify the number of wheels in
each type of locomotive truck. The first numeral denotes the number
of wheels in the leading truck, the next one or two represent the
number in the driving group, and the last specifies the number in the
The numerals always refer to the wheels from front
Digits are never omitted; if there are no leading or
trailing wheels, a zero is used.
All wheels on Army diesel-electric locomotives are drivers;
there are no leading or trailing wheels. The diesels have either two
sets of six-wheel trucks or two sets of four-wheel trucks.
Therefore, the digits 0-6-6-0 denote no leading or trailing wheels
and 2 sets of 3 driving axles with 2 wheels on each, or a total of 12
Likewise, an 0-4-4-0 locomotive would have no
leading or trailing wheels and two sets of two driving axles each, or
Figure 1.4 illustrates the Whyte
system of classifying diesel-electric locomotives.
Another system, commonly used in Europe and other parts of the
world, uses letters and figures to identify a diesel or electric
locomotive by its axles.
Letters are used for driving axles and
numbers for nondriving axles.
In this system, "A" stands for one
driving axle, "B" for two, "C" for three, and "D" for four. A small
"o" placed after the initial letter shows that each axle is
Thus, a single unit locomotive with two
individually powered two-axle trucks would be classified as a Bo-Bo.
One with three axle trucks in which the center axle is an idler would
be designated as an A1A-AlA.
to furnish primary power and electrical equipment to transmit
In the engine's