SANTA FE AND THE ARTICULATED LOCOMOTIVE
Alfred Bruce, Director of Steam Locomotive Engineering at American Locomotive Company ALCO comments that the first Mallet compound articulated engines were constructed in the United States in 1903 and 1904 by ALCO for the Baltimore & Ohio. This was 16 years after the European railroads which developed and used the Mallet compounds in considerable quantity.
Baldwin Locomotive Company built its first Mallet compound in 1906 as a 2-6-6-2 for the Great Northern Railway as a road engine. The 2-6-6-2 was by far the most built articulated engine in American railroad history. So popular that it was built until the end of steam locomotive construction in 1949 when C&O 1304 was constructed new by Baldwin. C&O 1304 is currently under restoration by Western Maryland Senic Railroad today.
Baldwin followed this design with the 2-8-8-2 for the Southern Pacific in 1909. This was also to prove to be another extremely popular locomotive wheel type. Not to be outdone with these successes and the articulated compound Mallet craze, Baldwin built for the Erie Railroad in 1914 several triplex engines. The infamous 2-8-8-8-2 type 6 cylinder tank locomotives of which only 3 were ever built.
In the midst of this Mallet compound craze in America the Atchison Topeka & Santa Fe jumped in with both feet in 1909 with the construction of "Prairie Mallets" from Baldwin of which were two 4-4-6-2 passenger compounds and two 2-8-8-2 helper compounds. Santa Fe touted the long rigid boiler, 73 inch drivered speedsters as the "largest and most powerful passenger locomotives in existance." First numbered ATSF 1300-1301 this was later changed to ATSF 1398-1399.
Santa Fe followed these engines with another unique passenger engine in 1911. These were 2-6-6-2 articulated locomotives that according to Alfred Bruce did not feature low and high pressure cylinders. Other sources record them as all Mallet compounds. It is certain that of the 65 engines constructed a total of 7 locomotives featured a hinged boiler. Santa Fe ordered these passenger articulated speesters with 69 inch drivers.
Alfred Bruce considers these flexable boilered Santa Fe 2-6-6-2 as unique because (1) the first use of an outside bearing trailer truck to support a fully wide firebox mounted behind the drivers. (2) the use of the "hinged boiler" in two sections with each section bolted to an articulating frame over which it rode. A flexable "hinged boiler" bellows joined the two units that sealed only firebox flue gas. (3) the actual steam producing boiler was only the 19 foot flue section over the rear engine unit. The front boiler section was instead a large flue gas feedwater heater unit which was built to the full diameter of the rear pressure boiler. This was variously described as "Baldwin feedwater heater and Santa Fe design reheater and superheater" or 'Jacobs superheater" or "combustion chamber - reheater/superheater"
This "flexable accordion" boiler section joining the front and rear units did not contain steam pressure - it merely sealed firebox flue gas to the locomotive stack. As such it burst regularly owing to the buildup of cinders which when compressed popped the rivits. A ball socket joint connection was developed and tried.
If all this was not enough, Santa Fe also constructed in their own shops another series of ten articulated Mallet compounds of the 2-10-10-2 wheel type using the railroads existing 2-10-2 locomotives for the high pressure units. Added to these were new Baldwin built 2-10-0 forward frame constructions as the front low pressure locomotive sections. These home built engines were numbered ATSF 1300-1310.
Finally Santa Fe tempted fate one more time, by considering an over the top construction of a 2-8-8-8-8-2 locomotive. This plan got as far as requesting Baldwin Locomotive Works to draw up plans for the "greatest Mallet of all time" - the QUADRAPLEX DOUBLE COMPOUND! This engine was to feature two cabs one for the fireman and one for the front of the locomotive engineer location.
After 1915 Santa Fe became a "rigid frame" steam locomotive railroad and their designs moved forward to what would eventually be the SANTA FE BIG THREE - passenger ATSF 3460 "Hudson" 4-8-4 type - passenger ATSF 2900 "Northern" 4-8-4 type - and freight ATSF 5011 "Texas" 2-10-4 type. Locomotives of superlative quality and construction unequaled throughout the world!
Gone would be the days of the "Prairie Mallet" and of the whimsical engineering of the past - in the vast steel wheel turning wild wild west!