Introduced in the early 1900s, the internationally used Whyte Notation (representing the number of leading/driving/trailing wheels, via a numbers and dashes system) classifies what?
Whyte notation Whyte notation The Whyte notation for classifying steam locomotives by wheel arrangement was devised by Frederick Methvan Whyte, and came into use in the early twentieth century following a December 1900 editorial in "American Engineer and Railroad Journal". The notation counts the number of leading wheels, then the number of driving wheels, and finally the number of trailing wheels, groups of numbers being separated by dashes. Other classification schemes, like UIC classification and the French, Turkish and Swiss systems for steam locomotives, count axles rather than wheels. In the notation a locomotive with two leading axles (four wheels) in front,
Driving wheel locomotives with side rods, including most steam and jackshaft locomotives, the driving wheels have weights to balance the weight of the coupling and connecting rods. The crescent-shaped balance weight is clearly visible in the picture on the right. In the Whyte notation, driving wheels are designated by the middle number or numbers in the set. The UIC classification system counts the number of axles rather than the number of wheels and driving wheels are designated by letters rather than numbers. The suffix 'o' is used to indicate independently powered axles. The number of driving wheels on locomotives varied quite a