Slider Crank - How it works:
To understand the principle on which the Slider-Crank works we need to go back to the Drag-Link mechanism, posted below:
In the Fig. you can see that the Drag-Link mechanism ABCD consisting of Link 1,2,3 and 4 is the same as discussed in the previous post. This Grashof-Linkage acts as a Quick-Return mechanism, in addition to this we add another Link-5 and slider E which can be considered as the Link-6. This is a theoretical model by which, you can notice, the uniform rotation of Link-2 can be converted into a reciprocating motion through Link-5 so that the Link-6 moves back and forth in a straight line E"EE'. The ratio of α and β, i.e. the time taken to move forward and the time taken for the backward movement, is called the time ratio of the mechanism.
Taking the logic a step ahead we can use the hypothesise.... if the follower, in the mechanism, has an infinite length then what would happen.
In such a situation a point on the axis of the pair, joining the connecting link to the follower, would move back and forth in a straight line. You can visualize it by looking at the Fig. posted below.
For all practical purposes the follower is a rectangular block or a piston, constrained to move is a straight line by a guide or a cylinder respectively. The slider-crank is the most widely used in the automobile engine, a sectioned view of an auto engine is being posted for your ready reference.
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