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VISUAL VOCABULARY / 06

Mechanism Atlas

Compare how the same input rotation becomes reciprocating or linear motion.

Original schematic model; not a load, friction or safety engineering simulation.

Rotation into movement

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Slider-crank

Slider-crank

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45°

Appearance and name

Slider-crank

How it works
A rotating crank and connecting rod drive a slider back and forth.
Difference
Unlike a rack, the slider returns once per revolution.
When to use
Piston-style reciprocating motion.
Limitations
Motion depends on crank and rod geometry.

Build instruction

Slider-crank. A rotating crank and connecting rod drive a slider back and forth. Piston-style reciprocating motion. Motion depends on crank and rod geometry.

Eccentric disc cam

How it works
An eccentric rotating disc lifts and lowers a contacting follower.
Difference
Unlike a connecting rod, follower position depends on the cam profile.
When to use
Periodic vertical displacement.
Limitations
Ideal maintained contact; no spring or wear.

Build instruction

Eccentric disc cam. An eccentric rotating disc lifts and lowers a contacting follower. Periodic vertical displacement. Ideal maintained contact; no spring or wear.

Rack and pinion

How it works
A rotating pinion translates a meshed rack.
Difference
Unlike the two reciprocating mechanisms, continued rotation keeps moving the rack.
When to use
Converting rotary input to linear feed.
Limitations
Schematic tooth mesh; no backlash or friction.

Build instruction

Rack and pinion. A rotating pinion translates a meshed rack. Converting rotary input to linear feed. Schematic tooth mesh; no backlash or friction.

Coverage

CoverageNot included
Slider-crankScotch yoke / four-bar
Eccentric disc camCam dwell profiles
Rack and pinionLead screw

References

Encyclopaedia Britannica — crank mechanism · Cam mechanism

Photo Atlas · Diagram Atlas