Southern 0-8-0 Locomotives in Great_Britain

Class Z (Locobase 3187)

Like the W class 0-6-0s, these were developed by REL Maunsell. Rather than main-line freight work, however, these were shunting (switching engines or yard goats in US parlance). The two outside cylinders drove on the third axle, while the inside cylinder cranked on the second.

The requirement, says the Southern E-Group's website at [] (visited November 2002), was "for a locomotive which was capable of delivering a lot of power after lengthy periods of idling, to do so without excessive blowing off and slipping [note the high Factor of Adhesion], being quiet in operation and to be able to negotiate tight curves."

All of these requirements the Zs met -- "responsive, powerful ...practically immune to slipping with a very quiet beat". They conquered tight curves with lateral play in the 1st and 4th driving axle although the closely spaced wheelbase produced considerable overhang front and rear.

[] (viewed 30 Jan 2005), in a discussion of JS Cocks's Southern Railway Locomotives to 1938, adds Holcroft's comment that the 3-cylinder layout helped heavy shunting [switching] locomotives in several ways. In particular, the 3 cylinders' 6 beats per wheel revolution smoothed out the power and continued to move "almost imperceptibly under circumstances where an equivalent two-cylinder engine would have stalled."

Ten more planned for 1931 were cancelled because of the decline in traffic caused by the worldwide depression. Three operated under War Department direction in Scotland in World War II and the class later acted as helpers on the 2.7% ruling grade from Exeter St. Davids to Exeter Central. They were retired in 1962.