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Although Stephenson’s valve gear consists of two simple eccentrics connected by a curved link its main application between the locomotive’s frames precludes visual study in motion.

This video runs in Windows Media, the more recent versions of which allow the option of continuous performance.  Please await loading.


Courtesy Peter Manning and Allan Wallace

The video model is taken from Beyer-Peacock’s order 890; 2-2-2 locomotives for NSW.  It is an early example of misusing a launch-type link and although centrally suspended appears not to incorporate correction. As valve travels increased this approach would become unsustainable.


The following videos have been constructed to view Stephenson’s and Walschaerts’ gears in motion through 360 degrees and later versions of Windows Media will allow continuous rotation.

The STEPHENSON link motion is the GWR set applied to the two outside cylinder locomotives of several Classes and is one of the finest of such applications.

Unlike Stephenson’s gear WALSCHAERTS’ is usually an outside application and may appear more familiar.  This example is a BR Class 4.