my ESPEE MODELERS ARCHIVE
California's Railroad to the U.S. 1861 - 1996
|SP||AM-2||2-6-6-2||4200-4211||rebuilt from MM-2|
|SP||AM-2||4-6-6-2||3900-3911||rebuilt from MM-2|
|SP||AC-1||2-8-8-2||4000-4016||rebuilt from MC-1 and MC-2|
|SP||AC-2||2-8-8-2||4017-4028||rebuilt from MC-4|
|SP||AC-3||2-8-8-2||4029-4048||rebuilt from MC-6|
282 units built between 1909 and 1944.
MC = Mallet Consolidation
MM = Mallet Mogul
AM = Articulated Mogul
AC = Articulated Consolidation
Mallet comes from the designer of articulated compound locomotives one Anatole Mallet. To be a true Mallet locomotive, it must be articulated and be a compound, i.e. the steam is used twice in separate cylinders. Mallet is pronounced Malley...
A simple explanation of compounding follows:
The high pressure cylinders use the steam first and are the smaller of the two sets, the steam is then passed to the larger low pressure cylinders where the steam is used again. It was supposed to be more efficient, but the complication was maintenance intensive, and the locomotives were actually slower than simple expansion locomotives. Which is why SP converted the compounds to simple expansion in later years.
SP lingo was that all articulateds were known as Mallets regardless of whether they were simple or compound.
The AC's were built as simple expansion locomotives, so the A designation in the class descriptor.
On the SP, a 2-8-0 was known as Consolidation, hence the 'C' in the x-8-8-x drivered locos and the 2-6-0 were known as Mogul's, hence the M in the x-6-6-x locomotives.
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This document prepared and maintained by Richard.A.Percy.
All Corrections, Additions and Flames should be aimed at Richard Percy firstname.lastname@example.org
This document © 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008. Richard.A.Percy