Editing Simple machine (section)

===Classification of machines===
The identification of simple machines arises from a desire for a systematic method to invent new machines. Therefore, an important concern is how simple machines are combined to make more complex machines. One approach is to attach simple machines in series to obtain compound machines.

However, a more successful strategy was identified by [[Franz Reuleaux]], who collected and studied over 800 elementary machines. He realized that a lever, pulley, and wheel and axle are in essence the same device: a body rotating about a hinge. Similarly, an inclined plane, wedge, and screw are a block sliding on a flat surface.<ref>Hartenberg, R.S. & J. Denavit (1964) [http://kmoddl.library.cornell.edu/bib.php?m=23 Kinematic synthesis of linkages], New York: McGraw-Hill, online link from [[Cornell University]].</ref>

This realization shows that it is the joints, or the connections that provide movement, that are the primary elements of a machine. Starting with four types of joints, the [[revolute joint]], [[prismatic joint|sliding joint]], [[Cam (mechanism)|cam joint]] and [[gear train|gear joint]], and related connections such as cables and belts, it is possible to understand a machine as an assembly of solid parts that connect these joints.<ref name="Uicker2003"/>