Model: L02 Positive Return Cam
This positive return cam mechanism is a practical application of curves of constant width as shown in models B2,B3,B4. The curved equilateral triangle has been called by several mathematicians, a Reuleaux Triangle, because Reuleaux was the first to present an extensive discussion and analysis of these curves in his 1875 book on Theoretical Kinematics. However this particular cam can be found in an 1820's steam engine in the Science Museum in London. It was used to control the entrance and exit of steam into the cylinder chamber. The "Reuleaux Triangle" cam moves a valve and has a pause or dwell in the motion. It is likely that this device was discovered by several inventors perhaps as early as the time of the first Watt engines in the late 18th century. However ingenious this mechanism, it has all but been forgotten by engineers in the early 21st century. In this mechanism, the parallel guides are at an incline that changes the phase of the dwell period. See discussion in B2.

Francis Moon 2003-05-29

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