Mechanisms
The job of a mechanism is to transform the force and motion supplied by the user at the input, to the force and motion needed to do a task elsewhere.
Some things that mechanisms have in common:
They need a human to operate them
They are designed to do a job
Most have properties that can be traced back to ancient times
Let’s look at some early developments in human technology and see how it is still relevant today.
Slides p5-p9
The Mystery Box
Input and output are general terms that can be used with any system. A special language is used in describing the most basic type of mechanism, the lever. The input is called the effort and the output is called the load. As with the terms input and output both the effort and the load could describe either a force or a location.
In addition to the effort and the load points every lever has a pivot that allows the rest of the device to rotate. Notice how rotation about the pivot causes the paths of motion to be arcs instead of straight lines. In the language of levers, the pivot is usually called the fulcrum. Several important characteristics of lever operations depend on the arrangement of three elements: fulcrum, effort, and load . There are three different configurations of these elements in levers. Based on these arrangements levers are categorized.
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A special lever called the bell crank was developed to transmit input motion into output motion through a right angle.

Linkage Puzzles