is a geared locomotive. Most were and are still single speed, but some did employ a variable-ratio gearbox and multiple ratios. Types of geared locomotive The vast majority of geared locomotives in the world were built to one of three distinct designs, whether licensed and official, or clones built after the expiration of key patents. Of the types, the Shay locomotive was the most numerous and best known. The overwhelming majority operated on the North American continent, but with a number in use in various parts of South America and a fair number in Australia and New Zealand, including home-developed types. These were not the first locomotives to use geared transmission. Richard Trevithick's Coalbookdale Locomotive used a large gear instead of side rods to link the crankshaft to the driving axles, with a net 1:1 gear ratio. The early Grasshopper (1832), Crab (1837) and Mud Digger (1842) locomotives built for the Baltimore and Ohio Railroad used gear ratios on the order of 2:1 so that each turn of the crankshaft caused about two turns of the driving axles. This allowed use of relatively small driving wheels without sacrificing speed. The Shay locomotive The Shay locomotive features an offset boiler with a multiple-cylinder engine affixed to it on the opposite side, driving a longitudinal shaft geared to the axles via bevel gears (see also Ephraim Shay, inventor). The Climax locomotive The Class B Climax locomotive has two inclined cylinders driving a transverse crankshaft, geared to a longitudinal driveshaft placed centrally on the locomotive and driving the powered trucks via internal gearing. There was also an earlier Class A Climax with a vertically mounted marine-type steam engine, working through a similar drive-line, via a two-speed gearbox. The Heisler locomotive The Heisler locomotive has a 'Vee-Twin' style steam engine, one cylinder each side of the boiler, affixed to a centrally located longitudinal driveshaft, again geared to the wheels. Other Types Besides the three main designs mentioned, there were other designs and clones: The Sentinel Waggon Works built numerous geared shunting locomotives to several designs mainly with vertical water-tube boilers and high-speed, enclosed, poppet-valve engines. These combined high-pressure boilers with high-reduction gearing to provide high torque at low speeds. The Willamette locomotive was an improved-upon clone of the Shay locomotive produced in limited number by Willamette Iron & Steel (better known for their steam donkey engines) after key patents expired. West coast logging customers