British steam locomotives versus the rest

or

Were British engines impotent?

The basic precept of the steam locomotive, namely a glorified kettle on wheels, had been established right from Richard Trevithick's Penydarren locomotive of 1804. Thereafter numerous technical improvements were made, and engines naturally became larger, heavier and faster as the demands made upon them increased. Nevertheless, the basic principle of using a fire to boil water, raise high-pressure steam and mechanically impart motion, has never been significantly altered in the history of steam locomotion. Such challenges as steam turbines, either with mechanical or electric drive, have been few in number and short-lived. The main challenge to steam on the railways has been the electric motor and the internal combustion (diesel) engine, which, as we all know, had all but vanquished commercial steam traction by the end of the 20th Century.

Having said that all steam locomotives are fundamentally the same, various traditions emerged in different parts of the world. Steam locomotion began in Britain, and British steam locomotives were always distinctive. In particular:

• their width and height and boiler diameter was constrained by the restrictive British loading gauge;

• distances were generally short and passenger trains were light, rapid and frequent, so brute strength to move heavy trains was seldom a major requirement;

• the British railway network was developed early and lines were laid out to satisfy the motive power of the day, which meant that gradients were generally very modest when compared with the challenging hills found in some other countries;

• relatively short travel distances and the use of water troughs meant that tenders could be kept small (the provision of a large tender can make any locomotive look more imposing!); and

• a particular British industrial aesthetic persuaded locomotive designers to keep their engines looking tidy, with a notable absence of external plumbing and accessories.

In Continental Europe travel distances were often greater, trains were heavier, gradients steeper and the loading gauge was more generous, so needless to say steam power in some countries (notably France, Germany, Spain, Austria, Norway, Czechoslovakia and Russia) developed in the early and mid-20th Century to satisfy these requirements. Nevertheless, the differences were not generally overwhelming, and the tractive effort and performance of - say - a German 01 class 4-6-2 was very comparable to their British equivalents of the time. However, particular note may be made here of the French tradition, which produced some of Europe's largest locomotives, including an enormous family of technically very complex 4-cylinder compound Pacifics, as well as noteworthy classes of 4-8-2s and outstanding but singular examples of a 4-6-4 and a 4-8-4. Interestingly, if British steam locomotive development had been left in the hands of the Big Four companies, there might have been some innovations comparable to those found in France. For example, the LMS was reputed to be considering a 4-8-4 passenger locomotive, but such fancies were dispelled by nationalisation and the advent of the utilitarian British Railways' Standard steam fleet and the subsequent switch to diesel and electric traction.

Other factors which made continental European steam power look more impressive than comparable British engines included the preference for external plumbing (some Europeans found the prettiness of British engines positively effeminate!). Moreover, a taller loading gauge enabled boilers to be mounted higher above the frames and/or boiler mountings, such as chimneys and domes, to stand higher. It may be added that the low platforms used at most European stations automatically made most locomotives look about a metre higher than their British counterparts!

In North America the factors that made many European engines actually or apparently larger than their British counterparts were further exaggerated. Distances could be enormous and in some areas gradients could be severe and continuous for many miles. Trains were less frequent than in Europe, and correspondingly heavier, and freight haulage was also more significant, especially on the transcontinental east-west routes where an absence of waterways placed greater reliance on rail transport. Accordingly, the steam locomotive developed to its fullest extent in North America. Modern passenger power tended to use the 4-8-2 and 4-8-4 wheel arrangements, whilst freight locomotives graduated through 2-10-2 to 2-10-4 and
4-12-2 rigid frame configurations, whilst articulated locomotives were developed of enormous size and strength, boasting such wheel arrangements as 2-6-6-6, 4-6-6-4 and 4-8-8-4.

Most other parts of the world variously followed the traditions of Britain, Europe or America to a greater or lesser degree. Although it is commonplace to consider most foreign steam locomotives as huge, many were, in fact surprisingly modest in size, especially where narrow gauges and/or light track restricted overall dimensions.

And were British engines impotent? It cannot be denied that they had neither the need nor the opportunity to attain the dimensions or strength found in North America or parts of Europe, whilst their elegant appearance looked less macho than counterparts in some other countries.

Nonetheless, many British locomotives were very creditable performers, and it was the British A4 Pacific #4492 Mallard which won and still holds the authenticated speed record for steam traction at 126mph (203km/h), whilst some of the largest locomotives remaining in use within recent years were British-designed Beyer-Garrett articulated machines, as used in East and South Africa.

Statistical data

Statistics of some 20th Century passenger and mixed-traffic steam loco designs are appended. Note that tractive effort is merely an indication of power, and represents the maximum force at any given time at the rim of the locomotive's driving wheels while working itself and its train: it always exactly balances the net resistance forces met by the train. Tractive effort is not by itself a measure of power. It is a theoretical figure to indicate how hard a loco can pull when 85% of full boiler pressure is applied on the piston diameter. This applies for two-cylinder locomotives: for those with more than two cylinders the valve diameter is multiplied by half the number of cylinders, but the formula does not work for compound locomotives with both high and low pressure cylinders. Other factors in the equation include the leverage implicit in the ratio between the distance from the axle to the crank-pin and the distance from the axle to the rail

Note that in the table values are given in metric measures. To obtain tractive effort in pound-force, factor each entry by 2.2046, and to obtain figures in ISO kilonewtons (kN) factor by 0.00980665.

T.V. Runnacles

Hong Kong Railway Society

March 1998

Click here for Comparative statistics of some 20th Century steam passenger and mixed-traffic locomotives

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