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The Construction of Cranes and Other Lifting Machinery
Edward Charles Robert Marks
No preview available - 2018
armature arranged axles barrel shaft beam bearings bevel boiler bolts bottom bracket brake wheel cage carried cast-iron centre constructed controlled crab sides crane post cylinder derrick diameter direction disc driven drum electric elevation employed end carriages engine fixed flanges frame friction wheel full load girders guide pulleys handle hoisting horizontal hydraulic illustrated at fig iron jack jib crane jib head lever leverage lifting chain lifting machinery lifting mechanism lifting the load line shaft link chain lower machine makers mechanical advantage Messrs minute motion shaft motor operated ordinary overhead travelling pawl pinion pitch plates pulley block pulling purchase radius rail track rails ratchet revolutions per minute revolving rods roller path screw shown in fig slewing specification speed spur gearing spur wheel steam crane stress supported teeth tie rod tons travelling crane traversing vertical weight whilst winch wire rope worm gearing worm wheel wrought-iron
Page 104 - The pulley on an engine shaft is 5 feet in diameter, and it makes 100 revolutions per minute. The motion is transmitted from this pulley to the main shaft by a belt running on a pulley, and the difference in tension between the tight and slack sides of the belt is 1 15 Ibs.
Page 221 - In the furnaces referred to below the formu'ro given are applicable if the steel used has a tensile strength of not less than 26 nor more than 30 tons per square inch. If the material of furnaces has a less tensile strength than 26 tons per square inch, then for each ton per square inch which the minimum tensile strength falls below 26, the coefficient is to be correspondingly decreased by ?$ part.
Page 202 - ... system described above, lifting can be continued at full speed and the load brought to rest instantly by pulling over the handle, the only revolving parts which have to be brought to rest being the barrel and brake drum, which have comparatively small inertia and do not revolve at an excessive speed. The great gain in speed is in lowering, which can be performed at a vastly greater speed than is possible by a reversible motor, there being a perfectly free run out under the control of the foot...
Page 38 - To be strictly accurate, therefore, the force must be considered as acting at the centre of the rope ; hence the diameter of the rope must be added to the diameter of the wheel. There are various forms of the wheel and axle. In the common windlass, motion is given to the axle by means of a winch, which is a lever like the handle of a grind-stone. The windlass used in digging wells, has usually four projecting levers or arms. The wheel used in steering a vessel is furnished...
Page 139 - ... of a testing machine might be altogether unfitted for the manufacture of a chain which has to resist suddenly-applied stresses and shocks. The " proof strain " generally adopted for chain is what is known as British Admiralty proof, and is about one-half the ultimate strength, or twice the working strength of the chain. It has been contended that the system under which a chain is tested with a load double that it will have to carry in practical work is a very bad one, but, if there is a weak...
Page 201 - ... motor. The hand lever actuating the lifting controller, also actuates an electric solenoid which controls the lifting friction coil clutch, the arrangement being such that on moving the lifting handle forward from the off position, current is switched on to the solenoid, the clutch is put into gear, and the lifting motor started simultaneously ; after the clutch is in gear a further movement of the lever cuts out resistance and speeds up the motor. Provision is also made of a mechanical connection...
Page 183 - If, from any cause during working operations the current should fail, the brake magnet would instantly release the brake, and allow it to take charge of and sustain the load.
Page 202 - ... a perfectly free run out under the control of the foot brake, and what is of equal importance, lowering can be commenced instantly without perceptible pause from lifting at full speed ; the lifting armature can continue to revolve with slackening speed during the period of lowering, and then comes to rest quietly without shock. As a matter of practice it is found that a load can be lowered 60 ft. before the armature has ceased to revolve. Capstans. — It is unnecessary to deal fully with capstans...