Mechanical drive; clutch and four-speed transmission. The Whitcomb Locomotive Company of Rochelle, IL built this 15-ton, model SRD industrial switching locomotive. It was a gasoline-mechanical engine, but it was later given an 87 HP, 3 cylinder, GM diesel engine. It has a clutch and manual transmission that has four speeds in both directions. This drives the rear axle wheels via a double chain drive, with the front ones powered by the side rods ("B" classification). Mechanically driven locomotives never got much bigger than this one, capable of slowly moving a few cars in an industrial plant. The clutch and transmission could not handle the weights or speeds of long trains, even as a railroad switch engine. The diesel-electric locomotive, with electrical transmission of its power was developed for those jobs. This engine is 19 feet long and has 80-inch drive wheels. The "dome" on top of the engine hood is the sandbox. All locomotives carry sand to drop on the railheads when needed for extra traction. This locomotive was used at the St. Louis City's Howard Bend Water Plant. It was purchased in 1978.