====== Fourth wheel ======
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The **fourth wheel** is part of the [[wheel train]] of a [[watch movement]]. It is labeled "Z5" in the illustration at right.

It is named for its position (fourth) in the wheel sequence of the [[going train]]. It is also sometimes called the **seconds wheel**, though this is easily confused with another gear, the [[second wheel]].

The fourth wheel moves the seconds hand in watches with a subsidiary ("[[small seconds|small]]") seconds dial and has the corresponding gear ratio.

===== See also =====
  * [[Wheel train]]


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