Donkey engine

Steam donkey, or donkey engine, is the common nickname for a steam-powered winch, or logging engine, widely used in past logging operations, though not limited to logging. They were also found in the mining, maritime, and nearly any other industry that needed a powered winch.

Steam donkeys acquired their name from their origin in sailing ships, where the "donkey" engine was typically a small secondary engine used to load and unload cargo and raise the larger sails with small crews, or to power pumps. They were classified by their cylinder type – simplex (single-acting cylinder) or duplex (a compound engine); by their connection to the winches (or "drums") – triple-drum, double-drum, etc.; and by their different uses: high-lead yarder, ground-lead yarder, loader, snubber, incline hoist, etc. A good deal of the cable-logging terminology derived from 19th-century merchant sailing, as much of the early technology originated from that industry.

A logging engine comprised at least one powered winch around which was wound hemp rope or (later) steel cable. They were usually fitted with a boiler and usually equipped with skids, or sleds made from logs, to aid them during transit from one "setting" to the next. The larger steam donkeys often had a "donkey house" (a makeshift shelter for the crew) built either on the skids or as a separate structure. Usually, a water tank, and sometimes a fuel oil tank, was mounted on the back of the sled. In rare cases, steam donkeys were also mounted on wheels. Later steam donkeys were built with multiple horizontally mounted drums/spools, on which were wound heavy steel cable instead of the original rope.

This describes the use of a steam donkey for logging operations. In the simplest setup, a "line horse" would carry the cable out to a log in the woods. The cable would be attached, and, on signal, the steam donkey's operator (engineer) would open the regulator, allowing the steam donkey to drag, or "skid", the log towards it. The log was taken either to a mill or to a "landing" where the log would be transferred for onward shipment by rail, road or river (either loaded onto boats or floated directly in the water). Later, a "haulback" drum was added, where a smaller cable could be routed around the "setting" and connected to the end of the heavier "mainline" to replace the line horse.

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