Engineering Wonders of the World
Volume I

BRITISH LOCOMOTIVES. SIX-COUPLED LOCOMOTIVES. For a long time it was thought that engines with six-coupled wheels would be rather slug- gish for really fast work, or would need heavy repairs if they accomplished it. But this pre- judice against “ tied legs,” to use an expressive term that was frequently applied, has proved to be unjustified, and it is quite common for six-coupled engines to perform notable high- speed runs. The main idea of the type is to enable the full available power to be utilized. Where a boiler is provided of dimensions large enough to justify the employment of ten wheels, the six-coupled bogie type makes two-thirds of the engine weight available for adhesion, where- as the “ Atlantic ” type limits the proportion to less than half. In the earlier examples the wheel dimensions were moderate, but those of most recent date have drivers from 6 feet to 6 feet 9 inches in diameter. For all-round work the six-coupled express locomotive has proved very satisfactory. The Great Western six-coupled engines are 197 among the most interesting, because of the remarkable work they do, including the non- stop journey between London and Plymouth. (225j miles), which is effected in 247 minutes, despite the stiff gradients on the Newton Abbot- Plymouth stretch. The “ Great Bear ” (see illustration on next page) is the last word in six-coupled expresses in this country, and the only representative of the “ Pacific ” type—bogie, six drivers, and two small trailing wheels. It is by far the weightiest British express locomotive. The boiler is a large example of the tapered design, with huge Belpaire fire-box and Swindon steam superheater. The engine gives a tractive effort of 29,430 lbs., and has hauled goods trains of upwards of 1,000 tons weight at high speed, besides working very heavy express passenger trains. An interesting feature of the engine is the employment of four high-pressure cylinders, with piston valves. The tender has two four- wheeled bogies—a departure from standard practice—and is fitted with an improved type of water pick-up. Fig. 8.—FOUR-CYLINDER SIX-COUPLED EXPRESS LOCOMOTIVE, LONDON AND SOUTH-WESTERN RAILWAY. ■T,h7,l;y 20 «Ming 2,727 square feet. Working The fire box h fitM 4; M B °rr °yllnders me boiler 8team- tIw Md. «bating the loading driving wheeZ e^„e Drummonds wster-tube,. Watahaert valve gear (see page 230). Very powerful and tai