Logging railroads often had rough, temporary track, steep grades and sharp curves. Conventional steam locomotives, long and heavy with large driving wheels, would derail on the crooked track and lose traction on inclines. Specialized locomotives were required. Three principal designs were used in the United States: the Shay, Climax and Heisler. The Cass Scenic Railroad has examples of all three.

While details differ, the basic concept of all three types is similar. The pistons rotate a crankshaft, powering a long, jointed drive shaft that turns the wheels through reduction gears. Unlike conventional rod locomotives, all the wheels of geared locomotives are drivers, arranged in short-wheelbase, swivel trucks. Slow and steady, all their weight used for traction, geared locomotives produce far more useful power on hills than conventional locomotives of similar weight. Because of their flexible trucks, they negotiate poor quality track that would stop a rod engine cold.

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The SHAY was built by the Lima Locomotive Works of Lima, Ohio from 1880 to 1945. There were over 2,700 Shays constructed ranging in size from about 10 tons to well over 150 tons. Today, there are about 85 left. Cass has examples of 70, 80, 90, and 150-ton models. The Shay’s vertical cylinders (shaded in the diagrams), and drive shaft are on the right side of the locomotive and transmit power through gears on the wheels. In order to balance the drive machinery, the Shay boiler is off-set to the left of center on the frame.

 

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The CLIMAX was built by the Climax Manufacturing Company of Corry, Pennsylvania from 1884 to 1928. There were about 1,100 constructed, of which fewer than 20 still exist. There were some of 90 to 100-tons and a number around 10-tons; most were 30 to 70-tons. Cass has one 70-ton Climax. The Climax has two parallel cylinders, one on each side of the boiler. The transverse crankshaft is geared to the drive shaft running down the center of the locomotive. Unlike the Shay, the wheels are powered through gears on the axles and the boiler and the drive machinery are centered on the locomotive’s frame.

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The HEISLER was built by the Heisler Locomotive Works of Erie, Pennsylvania from 1892 to 1941. There were about 850 built and approximately 32 survive. The size range was from about 15 tons up to 90-tons. A Heisler has one cylinder on each side of the boiler, slanted inward at a 45-degree angle, powering a longitudinal crankshaft. Like the Climax, the drive shaft is on the center line of the locomotive and the boiler and the drive machinery are centered on the frame. Unlike the Shay and Climax, the drive shaft is geared to only the inner axle of each truck; the outer axle is coupled by wheel cranks and side rods.

The centrally located drive shafts of the Climax and Heisler give them greater flexibility than the Shay. However, the Shay is easier to maintain with its machinery all in the open, a major factor in the Shay’s popularity.