Self-propelling refers to the ability of a device or machine to move by its own force or momentum. A common feature in construction, forestry, mining, and agricultural equipment, the self-propelling feature marked the beginning of most machines in their early invention phase.
This introduction of this feature was beneficial because it allowed a task to be completed with the need for little or no mechanical or steam power. As equipment became more modernized, and movement could be supplied by such systems as hydraulics, pneumatics, winches, and mechanics, the self-propelling component of machinery only intensified within the manufacturer industry. This is because of its resourcefulness, reliability, and the energy-saving costs associated with it.
Below are some examples of equipment that have utilized the self-propelling feature, a list inclusive of early and modern types of equipments and the manufacturers who developed them.
Rollers were amongst the earliest self-propelling machines because of the nature of their shape. Able to roll on slopes and steeper hills, the roller became a form of construction and agricultural equipment long before it was powered by steam in the 18th century. Its self-propelling ability made it useful for a variety of tasks. It was used to tow heavy military equipment and to pull other heavy farm and construction materials. The self-propelling component is still relevant to rollers today, although some are powered in some way as well.
Bomag was one of the manufacturers that took advantage of this feature when it launched out its initial line of rollers. Bomag's self-propelling tandem roller was a heavy-duty piece of equipment used for large compaction applications.
Log loaders, machines used for loading and unloading timber in logging applications, were also self-propelling machines. The Decker self-propelling loader, produced by Clyde Iron Works Co. in the early 1900s, propelled itself with the use of chain drives that moved it forward on rail lines. As evident from this machine, early rail-mounted machinery could produce movement of its own accord.
Motor graders made their start as self-propelled machines as well and many manufacturers such as Caterpillar, Fordson, and McCormick Deering produced self-propelling motor graders, made operable by tractor-mounted modifications.
In fact, tractors made a majority of equipment self-propelling. Combines, machines used to reap and thresh in a single operation, were also mounted on tractors for increased mobility. After combines were invented, they were paired with tractors for the first time in Australia in 1938. Since then, manufacturers such as International Harvester, Massey-Harris, and John Deere have incorporated harvester combines with tractors, fully utilizing the self-propelling feature.
In the 19th century, shovels and excavators were designed to include the self-propelling feature. The Otis Shovel, invented by William Otis and constructed in 1836, used one bucket on its arm to penetrate and lift earth. It had a power thrust that could manipulate the radius of the cut of the soil. Like many excavators today, it could slew (swing), crowd, and hoist. Over time, the rail-mounted excavators were made more mobile by mounting them on tractors and trucks.
The self-propelling feature acted as a catalyst for the evolution of many types of machinery, and it is still beneficial to manufacturers today.