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acceleration allowed amount amperes angle armature arrangement barrel bearings bending brake breaking calculated carriage carried centre chapter circuit coil column compression connected constant continuous controller crab crane curve diagram diameter direction draw driven drum efficiency electric equal equation factor feet per minute follows foot force friction full load gear girders given gives hoisting hook horizontal inches increase length lever lifting load losses lowering machine magnet material maximum means motion motor necessary obtained parallel passes period pitch position pressure proportions pull radius represents resistance rise roller rope running shaft shown in Fig shows side speed square inch steel steps stop strength stress strut surface Table taken teeth temperature tension tons tooth torque tower travelling traversing turns vertical weight wheel wind wire
Page 303 - ... It consists of a controller with magnetic blow-out, and with overload release gear. The controller is worked by a pedal projecting above the capstan case by about 4 inches. This pedal is removed when the capstan is out of use. The pedal is connected to a dashpot which prevents the controller being operated too rapidly when a driver is starting the capstan, but, at the same time, by means of valves in the plunger, allows the controller to return rapidly to the off position. The return to the off...
Page 301 - ... engaged with a steel pinion. The latter is keyed on the same shaft as a brass worm-wheel. The driving worm is cut from a blank forged solid with its shaft, and is coupled direct to the motor spindle. The worm and wheel work in an oil bath. The motor runs at 1,000 revolutions per minute, and is completely enclosed. In construction and design it is similar to the crane motors, but is shunt-wound to avoid large variations in speed of the capstan head. Upon the motor shaft there is fixed an automatic...
Page 10 - ... current in opposition to that supplied to it, thus automatically controlling the speed of lowering. Even with a shunt-motor, however, there is a possibility of the speed becoming excessive in lowering, unless the controller is specially designed to prevent it. When starting the motor, whether hoisting or lowering, resistance must be inserted in series with the armature and gradually cut out as the speed rises, until the full voltage is obtained across the brushes. For lowering, an additional...