Nomenclature of Steam Locomotives
A steam locomotive is normally
identified by the arrangement of its wheels. This locomotive generally has two
types of wheels.
Driving wheels These
wheels are coupled with each other and are directly connected with the
pistons. The higher the diameter of the driving wheels, the greater the
tractive power, but the lower the speed.
Idle wheels These wheels distribute
the load of the locomotive on the track.
A locomotive is normally
designated by a three-digit code. The first digit indicates the number of idle
wheels in the front, the middle digit indicates the number of driving wheels,
and the last digit denotes the number of idle wheels that come after the
driving wheels. A locomotive with a nomenclature of 4-6-2 indicates four idle
wheels in the front, six driving wheels, and two idle wheels after the driving
wheels (Fig. 24.1).
It may be noted here that the
middle digit indicating the driving or coupled wheels is the most important of
all. The hauling capacity of the locomotive is decided by the number of driving