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Shaft
Solid shafts. As a machine component a shaft is commonly a cylindrical bar that supports and rotates with devices for receiving and delivering rotary motion and torque .The crankshaft of a reciprocating engine receive its rotary motion from each of the cranks, via the pistons and connecting roads the slider-crank mechanisms , and delivers it by means of couplings, gears, chains or belts to the transmission, camshaft, pumps, and other devices. The camshafts, driven by a gear or chain from the crankshaft, has only one receiver or input, but each cam on the shaft delivers rotary motion to the valve-actuating mechanisms.
An axle is usually defined as a stationary cylindrical member on which wheels and pulleys can rotate, but the rotating shafts that drive the rear wheels of an automobile are also called axles, no doubt a carryover from hor-and-buggy days. It is common practice to speak short shafts on machines as spindles, especially tool-carrying or work-carrying shafts on machine tools.
In the days when all machines in a shop were driven by one large electric motor or prime mover, it was necessary to have long line shafts running length of the shop and supplying power, by belt, to shorter c
outer
shafts, jack shafts, or head shafts. The line
shafts were asmbled form parate lengths of shafting clampled together by rigid couplings. Although it is usually more convenient to drive each machine with a parate electric motor, and the prent-day trend is in this direction, there are still some oil engine receives its rotary motion from each of the cranks, via the pistons and connecting roads the slider-crank mechanisms , and delivers it by means of couplings, gears, chains or belts to the transmission, camshaft, pumps, and other devices. The camshafts, driven by a gear or chain from the crankshaft, has only one receiver or input, but each cam on the shaft delivers rotary motion to the valve-actuating mechanisms.
An axle is usually defined as a stationary cylindrical member on which wheels and pulleys can rotate, but the rotating shafts that drive the rear wheels of an automobile are also called axles, no doubt a carryover from hor-and-buggy days. It is common practice to speak short shafts on machines as spindles, especially tool-carrying or work-carrying shafts on machine tools.
In the days when all machines in a shop were driven by one large electric motor or prime mover, it was necessary to have long line shafts running length of the shop and supplying power, by belt, to s
horter coutershafts, jackshafts, or headshafts. The line shafts were asmbled form parate lengths of shafting clampled together by rigid couplings.
Although it is usually more convenient to drive each machine with a parate electric motor, and the prent-day trend is in this direction, there are still some situation in which a group drive is more economical.
A single-throw crankshaft that could be ud in a single-cylinder reciprocating engine or pump is shown in Figure 21. The journals A and
B rotate in the main bearings,
C is the crankpin that fits in a bearing on the end of the connecting rod and moves on a circle of radius R about the main bearings, while
D and
E are the cheeks or webs.
The throw R is one half the stroks of the piston, which is connected, by the wrist pin, to the other end
of the connecting rod and guided so as to move on a straight path passing throw the axis XX. On a multiple-cylinder engine the crankshaft has multiple throws---eight for a straight eight and for a V-8---arranged in a suitable angular relationship.
Stress and strains. In operation, shafts are subjected to a shearing stress, who magnitude depends on the torque and the dimensions of the cross ction. This stress is a measure of resistance that the shaft material offers to the applied torque. All shafts that transmit a torque are subjected to torsional shearing stress.
In addition to the shearing stress, twisted shafts are also subjected to shearing distortions. The distorted state is usually defined by the angle of tw
