In 1900 Frederick Whyte developed a way of describing the many types of wheelarrangements of Steam locomotives, This became known as the Whyte Notation.Using Whyte’s system you first count the number of leading wheels, then the driving wheels and then the trailing wheels. Using Whyte’s notation a locomotive with two leading axles (4 wheels) in front, 3 driving axles (6 wheels) and one trailing axle (2 wheels) would be classified as a 4-6-2 a Pacific Class.
The Midland Railway used a power classification based on the power output ofa locomotives pulling or pushing force (Tractive Effort) at 50mph for passenger locomotives and 25mph for goods. This force is the tractive effort that can be indefinitely maintained and this is called the Continuous Tractive Effort. After therailway nationalisation in 1948, British Railways also adopted it. This system used a numbering system from 0-9 with 0 being the lowest power. Using thissystem however it was possible to have different classes of locomotive with thesame power classification. Power Class Minimum & Maximum Tractive Effort lbf Passenger locos 50mph Freight Locos 25mph
0 under 3360 from 1928 under 6385 from 19281 3360-4479 6385-80642 4480-5599 8065-97443 5600-6719 9745-114244 6720-7839 11425-131045 7840-8959 13105-147846 8960-10079 14785-164647 10080-11199 16465-181448 11200 & over 18145 & over9 Not allocated used by British Railways from 1954
Types of Locomotive
Tank Engines or a tank locomotive carries it’s water in on board water tanks insteadof carrying it in a tender pulled behind it. There were several different types of watertank configurations depending on there style and position. The type with two tanks,one each side of the boiler which originated in about 1840 were the most common.These were popular for shunting and shorter distance routes as hey could not carrylarge amounts needed for longer journeys. Locos that carry there water on board are called Tank engines.
Saddle Tank locomotives had there water tank wrapped around the top of the boiler.
Tender Locomotives as there name suggests pulled a Tender behind them which contained the fuel and water. Steam locomotives used a larger amount of water compared with fuel so needed to carry large quantities for long journeys.
Pannier Locomotives had two water tanks one on each side of the boiler but not resting on the runing plate. This type of locomotive had a much lower centre of gravity compared to the saddle tank arrangement.
These wheel classifications would be followed by suffix to denote the type of loco.The Side Tank Engine shown below would be a 0-6-0T Side Tank=T Saddle Tank=ST Pannier=PT Well Tank=WT
Understanding Steam locomotive classes can seem quite confusing, especially forsomeone new to the subject. Steam Locos come in many shapes, sizes and powerlevels. Different railways favoured different classes of Locomotive depending on thework needing to be done. Many had the same class of loco but built and redesignedby themselves to suit there own requirements. Batches of locos would be givennames, Jubilee Class, King Class or you might hear one referred to as a Gresley A1or A3 after one of there famous designers. All the designers from all of the railwaystried to make their designs the most efficient, fastest and most reliable.
F = Freight G = Goods Mt = Mixed Traffic P = passenger XP = Enhanced Passenger
Locos would be described as an 8F or a 7p etc depending on there power classand type of usage.