Editing Constant-velocity joint (section)

== History ==
[[Image:Universal joint.gif|right|frame|Animation of a [[universal joint]] ]]
The predecessor to the constant-velocity joint was the [[universal joint]] (also called a ''Cardan joint'') which was invented by [[Gerolamo Cardano]] in the 16th century. A short-coming of the universal joint is that the rotational speed of the output shaft fluctuates despite the rotational speed of the input shaft being constant. This fluctuation causes unwanted vibration in the system and increases as the angle between the two shafts increases. A constant-velocity joint does not have this fluctuation in output speed and therefore does not possess this unwanted vibration. Also, although universal joints are simple to produce and can withstand large forces,  universal joints often become "notchy" and difficult to rotate as the angle of operation increases.

The first type of constant-velocity joint was the ''Double Hooke's (Double Cardan) Joint'' which was invented by [[Robert Hooke]] in the 17th century. This design uses two universal joints connected by a shaft and offset by 90 degrees thereby cancelling out the speed variations inherent in each individual joint. 

Many other types of constant-velocity joints have been invented since then.
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