Rack Railway - Switches

Switches

Rack railway switches are as varied as rack railway technologies, for optional rack lines such as the Zentralbahn in Switzerland and the West Coast Wilderness Railway in Tasmania it is convenient to only use switches on sections flat enough for adhesion (for example, on a pass summit). Other systems which rely on the rack for driving (with the conventional rail wheels undriven) such as the Dolderbahn in Zurich, Štrbské Pleso in Slovakia and the Schynige Platte rack railway instead must switch the rack rail. The Dolderbahn switch works by bending all three rails, an operation that is performed every trip as the two trains pass in the middle.

The geometry of the rack system has a large impact on the construction of turnouts. If the rack is elevated above the running rails, there is no need to interrupt the running rails to allow passage of the driving pinions of the engines. Strub explicitly documented this in his U.S. patent. Strub used a complex set of bell-cranks and push-rods linking the throw-rod for the points to the two throw-rods for the moving rack sections. One break in the rack was required to select between the two routes, and a second break was required where the rack rails cross the running rails. Turnouts for the Morgan Rack system were similar, with the rack elevated above the running rails. Most of the Morgan turnout patents included movable rack sections to avoid breaks in the rack, but because all Morgan locomotives had two linked drive pinions, there was no need for a continuous rack. So long as the breaks in the rack were shorter than the distance between the drive pinions on the locomotive, the rack rail could be interrupted wherever there was need to cross over a running rail.

Turnouts are far more complex when the rack is at or below the level of the running rails. Marsh's first rack patent shows such an arrangement, and the original Mount Washington Cog Railroad he built had no turnouts. It was not until 1941 that a turnout was constructed on this line. The new turnouts installed on the Mount Washington line in 200? are essentially transfer tables.