Jenny Lind locomotive

David Joy, the Chief Draughtsman of E. B. Wilson and Company, was asked to visit Brighton railway works to make tracings of the drawings of a 2-2-2 locomotive designed by John Gray for the railway so that ten further examples could be built. However, before he had completed the task, Gray had been dismissed from his post of Locomotive Superintendent, and his successor Thomas Kirtley did not favour Gray's complicated horse-leg motion. As a result it was left to Joy and James Fenton, the works manager at E.B. Wilson, to adapt the design.[1] Joy had spent his formative years studying all the locomotives he came across, sketching them, making notes, and interrogating their owners and crews — and, if he could, getting rides on them. [2]

As is usual in engineering, there were a number of trade-offs to be made in steam locomotive design. There is a limit to the rate that steam can be delivered to the pistons; therefore, higher speed was obtained with larger driving wheels. These, however, limited the size of the boiler, since it needed to fit between them, particularly with the preoccupation of the time with a lower centre of gravity. The tendency had been to lengthen the boilers with supporting wheels front and rear. Thus, passenger engines, like the so-called Long Boiler locomotives, were usually of a 4-2-0 wheel arrangement.[3] However, too long a boiler also created instability. Some locomotives improved adhesion for heavier loads by coupling pairs of driving wheels, but there was a tendency for the wrought iron coupling rods to break especially at speed. Thus, four- and six-coupled locomotives were used for freight trains.

Joy and Fenton settled on a medium-sized boiler, 800 sq ft (74 m²) heated surface area, with a pressure of 120 lbf/in² (827 kPa) and concentrated on its steaming abilities. In this, James Fenton had particular expertise. The engine had 15-by-20-inch (380 mm × 510 mm) inside cylinders and 6-foot-0-inch-diameter (1.83 m) driving wheels. Gray's so-called "mixed" frame had an inside frame for the cylinders and driving wheels, with inside bearings, and an outside frame for the 4-foot-0-inch-diameter (1.22 m) leading and trailing wheels, using outside bearings. The inside frame stopped at the firebox, so that the latter was as wide as the wheels would allow. By this means he minimized the overhang at each end.

After strengthening of various members, the engine was three tons heavier than expected. However, it steamed freely and was economical on fuel. It was to this that its success was attributed, along with the increase in boiler pressure that had become possible over the years. However, credit must be given to Joy's suspension arrangements that made it extremely smooth-running and stable. The name "Jenny Lind" was given to the first one delivered to the LB&SCR.