James Thompson Marshall (1854, Glanford Brigg, Lincolnshire [1] - 1931, Knaresborough, Yorkshire [2] ) was an English railway and mechanical engineer known for inventing the 'Marshall valve gear' for steam locomotive use. James Marshall began his engineering career at the Leeds-based Steam Plough Company, and later moved to the city's Boyne Engine Works.
J. T. Marshall invented and patented several different valve gears but these should not be confused with the "Marshall valve gear" patented by Marshall, Sons & Co. in 1879. At least one of J. T. Marshall's valve gears was a rotary type and the only known application was to the Austrian BBÖ Class 114 locomotive.
The better-known J. T. Marshall gear was a modified Walschaerts valve gear which was first applied to a Great Northern Railway mineral locomotive, no. 743, in 1901 [3] and received a glowing report. [4] Next, it was tried on GNR Class C2 No. 1520 in March 1903. There was no external change visible on the locomotive as a result of this modification. When the valve gear was in use, the motion was derived from two eccentrics, one of which gave lap and lead movement by swinging the link backwards and forwards on its suspension bracket. The other eccentric was set at 90 degrees to the crank and rocked the link by means of a bell crank on the hanging link pin. The position of the radius rod die pin in the link determined the direction of movement and the cutoff. Showing little advantage over the normal Stephenson link valve gear, it was removed from the C2 'Atlantic' in April 1907 to ease maintenance. [5]
A modified version of the gear (for outside drive) was tried on SECR N class no. 1850 in 1933-4 but, again, it was not a great success. [6]
Marshall died in 1931.
A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be transformed, by a connecting rod and crank, into rotational force for work. The term "steam engine" is most commonly applied to reciprocating engines as just described, although some authorities have also referred to the steam turbine and devices such as Hero's aeolipile as "steam engines". The essential feature of steam engines is that they are external combustion engines, where the working fluid is separated from the combustion products. The ideal thermodynamic cycle used to analyze this process is called the Rankine cycle. In general usage, the term steam engine can refer to either complete steam plants, such as railway steam locomotives and portable engines, or may refer to the piston or turbine machinery alone, as in the beam engine and stationary steam engine.
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