Editing Belt tensioner

<gallery>
Image:Belt-tensioner 1.jpg|Two views of...
Image:Belt tensioner 2.jpg|...a SBF tensioner.
</gallery>

==Overview==
A '''belt tensioner''' is used to create a generally constant tension on a [[belt]] as it changes in length due to normal wear, or due to changes in span lengths as a result of span speed differences, wherein the belt is driven by a single drive pulley from the output shaft of the engine and wherein the belt rotates driven pulleys, each operating an automotive accessory. 

==How it works==
The belt tensioner includes either a flat-wound spring or a helical spring, a spring casing and an arm. One end of the spring is attached to the spring casing and the other end of the spring is attached to the arm. The arm pivots with respect to the spring casing when the spring exerts torque. The spring casing is attached to the engine, and an idler pulley is attached to the arm. The spring is preloaded by twisting the arm relative to the spring casing. The idler pulley on the arm is then placed against the belt. As the belt span lengthens, the torque from the preloaded spring continues to cause the idler pulley of the arm to apply pressure against the belt, keeping the belt in tension.


===Sources=== 
*[http://www.wipo.int/patentscope/search/en/WO2006052552 BELT TENSIONER AND METHOD FOR MAKING A BELT-TENSIONER ARM AND A SPRING CASE] from Patentscope.
=Overview=
Around the world there are some differences in the words used to describe things in the automotive field.

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