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How does a slider-crank mechanism convert piston motion into crankshaft rotation?
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Six simple machines for transforming energy into work.
A slider-crank mechanism converts reciprocating straight-line motion into rotary motion through a series of connected parts that rotate freely at their respective bearings.1
The process functions as follows:
- Piston Movement: Pressureāsuch as that produced by an explosion in a gasoline engineāforces the piston (part 4) to slide back and forth within the cylinder.1
- Transmission: The piston is connected to a connecting rod (part 3) at the wristpin bearing (C). This rod, in turn, connects to the crankshaft (part 2) at the crankpin bearing (B).1
- Rotation: As the piston moves, the connecting rod transmits this force to the crankpin. Because the crankshaft is anchored at the main bearing (A), the linear motion of the piston forces the crankpin to follow a circular path, thereby inducing rotation in the crankshaft.1
To maintain continuous motion, a flywheel is typically attached to the crankshaft to provide the necessary energy for the piston's return stroke.1