Portable steam engine

A portable engine is an engine, either a steam engine or an internal combustion engine, that sits in one place while operating (providing power to machinery), but (unlike a stationary engine) is and thus can be easily moved from one work site to another. Mounted on wheels or skids, it is either towed to the work site or moves there via self-propulsion.

Portable engines were in common use in industrialised countries from the early 19th through early 20th centuries, during an era when mechanical power transmission was widespread. Before that, most power generation and transmission were by animal, water, wind, or human; after that, a combination of electrification (including rural electrification) and modern vehicles and equipment (such as tractors, trucks, cars, engine-generators, and machines with their engines built in) displaced most use of portable engines. In developing countries today, portable engines still have some use (typically in the form of modern small engines mounted on boards), although the technologies mentioned above increasingly limit their demand there as well. In industrialised countries they are no longer used for commercial purposes, but preserved examples can often be seen at steam fairs driving appropriate equipment for demonstration purposes.

Portable engines during their were typically towed to their work sites by draft horses or oxen, or, in the latter part of that era, motive power including self-propulsion or towing by traction engines, steam tractors, other tractors, or trucks. They were used to drive agricultural machinery (such as threshing machines), milling machinery (such as gristmills, sawmills, and ore mills), pumps and fans (such as in mines and oil wells), and factory line shafts (for machine tools, power hammers, presses, and other machines).

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