Salamanca was also the first rack and pinion locomotive, using John Blenkinsop's patented design for rack propulsion. A single rack ran outside the narrow gauge tracks and was engaged by a large cog wheel on the left side of the locomotive. The cog wheel was driven by twin cylinders embedded into the top of the centre-flue boiler. The class was described as having two 8"×20" cylinders, driving the wheels through cranks. The piston crossheads slid in guides, rather than being controlled by a parallel motion linkage like the majority of early locomotives. The engines saw up to twenty years of service.[3]
It appears in the first painting of a steam locomotive, a watercolour by George Walker (1781–1856) published in his The Costume of Yorkshire.[4]
Four such locomotives were built for the railway. Salamanca was destroyed six years later, when its boiler exploded. According to George Stephenson, giving evidence to a committee of Parliament, the driver had tampered with the boiler's safety valve.[5]
Salamanca is probably the locomotive referred to in the September 1814 edition of Annals of Philosophy: "Some time ago a steam-engine was mounted upon wheels at Leeds, and made to move along a rail road by means of a rack wheel, dragging after it a number of waggons loaded with coals." The item continues to mention a rack locomotive about a mile north of Newcastle (Blücher at Killingworth) and one without a rack wheel (probably Puffing Billy at Wylam).[6]
A model of the locomotive, built by Murray in 1811, is part of the collection held at Leeds Industrial Museum. It is the world's oldest model locomotive.[7]
References
^Hamilton Ellis (1968). The Pictorial Encyclopedia of Railways. The Hamlyn Publishing Group. p. 20.
^McCann, Mick (2010). How Leeds Changed the World: Encyclopaedia Leeds. Leeds: Armey Press. p. 227. ISBN0-9554699-3-7.
^Nabarro, Gerald (1972). Steam Nostalgia: Locomotive and Railway Preservation in Great Britain. London: Routledge and Kegan Paul. p. 139. ISBN0-7100-7391-7.
^Thomson, Thomas, ed. (1814). Annals of Philosophy. Vol. IV. Robert Baldwin. p. 232. Retrieved 16 December 2014.