A roasting jack is a machine which rotates meat roasting on a spit.[1] It can also be called a turnspit, although this name can also refer to a human turning the spit, or a turnspit dog.[2] Cooking meat on a spit dates back at least to the 1st century BC, but at first spits were turned by human power. In Britain, starting in the Tudor period, dog-powered turnspits were used; the dog ran in a treadmill linked to the spit by belts and pulleys. Other forms of roasting jacks included the steam jack, driven by steam, the smoke jack, driven by hot gas rising from the fire,[3]and the bottle jack or clock jack, driven by weights or springs.
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A steam-powered roasting jack, in the form of a rudimentary steam turbine attached to a spit, was described by the Ottoman engineer Taqi al-Din in his Al-Turuq al-samiyya fi al-alat al-ruhaniyya (The Sublime Methods of Spiritual Machines), in 1551.[4] A steam-powered turnspit was also briefly mentioned by John Wilkins in his book Mathematical Magick (1648.)[5] A steam-driven jack was patented by the American clockmaker John Bailey II in 1792,[6] and steam jacks were later commercially available in the United States.[7]
Leonardo da Vinci sketched a smoke-jack with four vanes. Smoke-jacks were also illustrated in Vittorio Zonca's book of machines (1607).[8] A later description appears in 1648, in John Wilkins's book Mathematical Magick.[9] The 1826 A Treatise of Mechanics describes a smoke-jack:
Smoke-jack is an engine used for the same purpose as the common jack; and is so called from its being moved by means of the smoke, or rarefied air, ascending the chimney, and striking against the sails of the horizontal wheel which being inclined to the horizon, is moved about the axis of the wheel AB (plate XXI. fig 1.), together with the pinion C, which carries the wheels D and E; and E carries the chain F, which turns the spit. The wheel AB should be placed in the narrow part of the chimney, where the motion of the smoke is swiftest, and where also the greatest part of it must strike upon the sails. --The force of this machine depends on the draught of the chimney, and the strength of the fire.
Smoke-jacks are sometimes moved by means of spiral flyers coiling about a vertical axle; and at other times by a vertical wheel with sails like the float-boards of a mill: but the above is the more customary construction.[10]
A bottle-jack was a clockwork motor in a brass shell, shaped like a bottle.[11]