The need for wood for a wide range of uses grew rapidly in North America in the second half of the 19th century as new regions were developed and settled. This also increased the amount of felled wood that had to be transported from its place of origin to the sawmills. The transport of logs by horses or on rivers had proven its worth, but the transport volumes could not be increased indefinitely. The solution was rail transport.
However, since each logging area could only be used for a limited period of time and the trees needed many years to grow back at this point, another problem arose: the construction of railway tracks was time-consuming and costly, which opposed use over a limited period of time. The solution were provisionally laid rail tracks, partly made of prefabricated sections, which were placed on the forest floor without a ballast bedding. This resulted in an uneven track with steep inclines and sometimes tight curves. Even when crossing smaller rivers, the construction of bridges was sometimes not worthwhile, so that the rails were sometimes even laid directly into the river bed, as long as the water depth was not too great.
It was now important to find suitable locomotives for these routes. At best, small, two-axle tank locomotives were suitable for the uneven ground with tight curves. However, these were soon no longer strong enough and larger locomotives with multiple axles had a more or less rigid frame, which prevented them from being used on such routes. With the cars in North America it has long been customary to bed them on two bogies due to the fact that the tracks in many places were laid with less care than in Europe. Therefore, various types of steam locomotives were soon developed, which also rested on bogies. New approaches were also taken to power transmission, as the usual cylinders located near the ground were susceptible to water and dirt. This led to the well-known, typically North American designs such as the Shay, the Climax and the Heisler. What they all had in common was that they were available in significantly different sizes, but all sizes shared the same basic structure.
The first type, which was the most successful of the three with around 2,770 built until 1945, went back to the sawmill owner Ephraim Shay. In search of a suitable locomotive for his company, he created the first locomotive of this type in the winter of 1873/1874. It was based on a flat car, on which he placed a vertical boiler, which supplied two vertical cylinders mounted on one side. All four axles were driven via drive shafts and bevel gears. After some improvements, he turned his design to the Lima Machine Works in Lima, Ohio, which delivered the first locomotive in 1880. In the following year, Shay transferred all rights to Lima, enabling the company to achieve strong growth.
The first Shay locomotives looked similar to the prototype until they switched to a horizontal long boiler and the locomotives came closer to the appearance of conventional steam locomotives. Now there was a clearly recognizable front and rear end and the cylinders and drive gear were always mounted on the right-hand side. In order to balance the weight, the boiler was moved slightly to the left. After the first copies had two cylinders, almost all larger models were later built with three cylinders for smoother running. Despite the good running smoothness, no Shay reached more than 20 mph, but a very high traction compared to its weight.
Appearing only a few years later and with a total of a little more than 1,000 units, the locomotive of the Climax type was not quite as successful. There were similar designs by different men, some of whom were also involved in legal disputes. However, the idea is generally credited to Charles D. Scott, who approached the Climax Manufacturing Company of Corry, Pennsylvania to implement it. The two cylinders of the Climax were basically arranged on both sides as in conventional steam locomotives, but they were usually much higher and drove a jackshaft. This in turn transmitted the power to the bogies via a driveshaft mounted centrally under the locomotive. The axle differentials still used in the first drafts proved to be counterproductive and were soon no longer installed. What was special about the Climax locomotives was that most of the locomotives had a two-speed gearbox. Baldwin also made geared locomotives that were very similar to the Climax locomotives.
The third of the three most successful types of geared locomotives from the USA came from Charles Heisler and shared the central driveshaft with the Climax. Here, however, the cylinders were arranged in a V-shape directly behind the first bogie, similar to a V-engine. While the drive shaft on the Climax drove each individual wheel set directly, on the Heisler it only drove one axle per bogie directly. The second axle in each case was driven via coupling rods which were visible from the outside. The first Heisler locomotives were built in 1891 by the Dunkirk Engineering Company in the city of the same name in New York State. Larger numbers began to appear in 1894 at the Stearns Manufacturing Company in Erie, Pennsylvania, which renamed itself the Heisler Locomotive Works in 1907. A total of around 850 copies were made by 1941. The Heisler is often said to have been the fastest of the three types.