Southern valve gear was briefly popular on

steam locomotives A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material (usually coal, oil or, rarely, wood) to heat water in the locomot ...

in the United States. It combines elements of the

Walschaerts The Walschaerts valve gear is a type of valve gear used to regulate the flow of steam to the pistons in steam locomotives, invented by Belgian railway engineer Egide Walschaerts in 1844. The gear is sometimes named without the final "s", since ...

and Baker patterns.

History

Southern valve gear was devised by locomotive designers on the Southern Railway and used on many locomotives on that line. The first patent was issued to Wm. Sherman Brown in 1906. He continued work and another patent was issued July 23, 1912. The gear was first tested on Mikado 586 in February, 1913 at Southern Knoxville Shops. It was specified for some

USRA standard The USRA standard locomotives and railroad cars were designed by the United States Railroad Administration, the nationalized rail system of the United States during World War I. 1,856 steam locomotives and over 100,000 railroad cars were built ...

locomotive designs, though many locomotives constructed to these patterns used Walschaerts or Baker valve gear instead. The Southern valve gear was used on many Southern Railway locomotives, including survivors

630 Year 630 ( DCXXX) was a common year starting on Monday (link will display the full calendar) of the Julian calendar. The denomination 630 for this year has been used since the early medieval period, when the Anno Domini calendar era became the ...

and

722 Year 722 ( DCCXXII) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar. The denomination 722 for this year has been used since the early medieval period, when the Anno Domini calendar era became ...

. It was also used on East Broad Top numbers 16-18, which survive today.

Operation

Unlike the Walschaerts and Baker systems, the Southern valve gear dispensed with the combination lever which transmitted some of the crosshead motion to the valves. As with those systems it used a return crank on a driver (instead of the eccentrics used by the

Stephenson valve gear The Stephenson valve gear or Stephenson link or shifting link is a simple design of valve gear that was widely used throughout the world for various kinds of steam engines. It is named after Robert Stephenson but was invented by his employees. ...

). The return crank attached to the eccentric rod, which hung from a pivot close to the far end of the eccentric rod. This pivot attached to the end of the radius hanger, the other end of which attached to a link block which slid back and forth in a track curved in the same manner as the expansion link of a Walschaerts gear. In this system, however, the track was fixed in place; sliding the link block back and forth controlled reversing and cutoff. At the end of the eccentric rod, close to the radius hanger, the rod connected to the transmission yoke. The upper end of this rod connected to a bellcrank, which translated the up and down motion of the transmission yoke into back and forth motion of the valves. The mechanism is a little less obvious than that of the other types, but control is fundamentally like that of the Baker system. In this case the controlling factor is the angle between the radius hanger and the transmission yoke; when they are parallel, there is little up-down motion of the transmission yoke and the engine is centered. As link block moves back and forth, the angle of the radius hanger changes, and the up and down motion of the transmission yoke in response to the back and forth motion of the eccentric rod is increased or decreased.

References

The Traveling Engineers’ Association: Examination Questions and Answers
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Project Gutenberg

External links

* includes a description and illustrations of the Southern valve gear {{steam engine configurations Locomotive valve gear