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Lift and dump capacities of hydraulic hooklift hoists typically range from 8,000 to 68,000 lb (3,630 to 30,800 kg). Generally a hoist is capable of lifting (off the ground) and dumping (onto the ground) the same maximum capacity, although there can be exceptions where short wheel bases are involved.
The first of these systems used mechanical clutches between luffing and hoist drums, giving simplicity and a "near level" result. [5] Later systems have used modern electronic controls and quickly reversible motors with good slow-speed control to the hoist winch motors, so as to give a positioning accuracy of inches.
In air-cooled piston engine aircraft, spoilers may be needed to avoid shock cooling the engines. In a descent without spoilers, air speed is increased and the engine will be at low power, producing less heat than normal. The engine may cool too rapidly, resulting in stuck valves, cracked cylinders or other problems.
A hydraulic cylinder is the actuator or "motor" side of this system. The "generator" side of the hydraulic system is the hydraulic pump which delivers a fixed or regulated flow of oil to the hydraulic cylinder, to move the piston. There are three types of pump widely used: hydraulic hand pump, hydraulic air pump, and hydraulic electric pump.
The cylinder areas, motor displacements and mechanical torque arms must be designed to match load pressure in order to bring down the power losses. Pump pressure always equals the maximum load pressure when several functions are run simultaneously and the power input to the pump equals the (max. load pressure + Δ p LS ) x sum of flow.
In the example above of the dump truck, the weight of the dump body, now raised at an angle of 60 degrees but empty of the load, must be enough to force the unpressurized hydraulic fluid out of the cylinder and cause it to retract to the fully collapsed position. [6] Spider lift set up outside a building.
Hydraulic winch systems can use accumulators and passive heave compensation to form a semi-active system with both an active and a passive component. In such systems the active part will take over when the passive system is too slow or inaccurate to meet the target of the AHC control system.
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 (), however modern large hoists use alternating current drives that ...
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