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The crane's hook is kept level by automatically paying out enough extra cable to compensate for this. This is also a purely mechanical linkage, arranged by the reeving of the hoist cables to the jib over a number of pulleys at the crane's apex above the cab, so that luffing the jib upwards allows more free cable and lowers the hook to compensate.
The difference in radii can be made very small, making the mechanical advantage of this pulley system very large. [4] [5] In the extreme case of zero difference in radii, MA becomes infinite, thus no force (besides friction) is needed to move the chain, but moving the chain will no longer lift the load.
A Doppelmayr tricable gondola lift in Sölden, Austria Operation and maintenance of tricable gondola lift Penkenbahn in Mayrhofen, Austria. The tricable gondola lift, also known as the 3S gondola lift, is a cable car system that was developed by the Swiss company Von Roll transport systems in Thun to unite the benefits of a gondola lift with those of a reversible cable car system. '3S' is an ...
Such systems operate between 4,000 to 5,800 psi (28,000 to 40,000 kPa). The North American market developed low pressure / high volume systems, which allowed operators to share the hoist's hydraulic system with other hydraulically powered devices. These systems typically operate with a larger gear pump and larger hydraulic reservoir. Operating ...
Hoist atop an elevator. A hoist is a device used for lifting or lowering a load by means of a drum or lift-wheel around which rope or chain wraps. It may be manually operated, electrically or pneumatically driven and may use chain, fiber or wire rope as its lifting medium.
A drum hoist (steel wire rope visible) and motor. In underground mining a hoist or winder [1] is used to raise and lower conveyances within the mine shaft.Modern hoists are normally powered using electric motors, historically with direct current drives utilizing Ward Leonard control machines and later solid-state converters (), although modern large hoists use alternating current drives that ...
An elevator (American English) or lift (Commonwealth English) is a machine that vertically transports people or freight between levels. They are typically powered by electric motors that drive traction cables and counterweight systems such as a hoist, although some pump hydraulic fluid to raise a cylindrical piston like a jack.
A hoist controller is the controller for a hoist. The term is used primarily in the context of electrically operated hoists, but it is apparent that the control systems of many 20th century steam hoists also incorporated controllers of significant complexity. Consider the control system of the Quincy Mine No. 2 Hoist. [1]