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A portcullis (from Old French porte coleice 'sliding gate') is a heavy, vertically closing gate typically found in medieval fortifications. [1] A portcullis gate is constructed of a latticed grille , made of wood or metal or both, which slides down grooves inset within each jamb of the gateway.
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The gate does not swing on a conventional hinge. Instead, it is fastened to cylinders that loosely encircle a tall post. The bump gate's self-closing mechanism utilizes one or two cables from the gate's upper crossbar, terminated high on the post. When the gate swings open, the swivel action as the cables wind around the post raises the gate ...
A treadwheel crane (Latin: magna rota) is a wooden, human powered hoisting and lowering device. It was primarily used during the Roman period and the Middle Ages in the building of castles and cathedrals. The often heavy charge is lifted as the individual inside the treadwheel crane walks.
The wheel raises boats by 24 metres (79 ft), but the Union Canal is still 11 metres (36 ft) higher than the aqueduct which meets the wheel. Boats must also pass through a pair of locks between the top of the wheel and the Union Canal. The Falkirk Wheel is the only rotating boat lift of its kind in the world, and one of two working boat lifts in ...
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In this case, the drive sheave is directly attached to the end of the motor. Gearless traction elevators can reach speeds of up to 20 m/s (4,000 ft/min), A brake is mounted between the motor and gearbox or between the motor and drive sheave or at the end of the drive sheave to hold the elevator stationary at a floor.
In 1956, the Chinatown Improvement Committee, appointed by Mayor George Christopher, made the archway its top priority; [11]: 148–151 the proposal initially included two gates: one at Grant and Bush for Chinatown, and another at Pacific and Kearny for the Barbary Coast red-light district. [13] Two design drawings were shown in December 1956. [14]