Quote:
Originally Posted by daepp
One of the great articulated locomotives from the 20th Century. A truly great American accomplishment. So long they had to be hinged in the middle. Two complete separate engines/boilers in one locomotive. Some were compounded - used the steam more than once. The Baldwin Big Boy won a prestigious mechanical engineering award for design and complexity. I got to see one pulling the Cajon grade about 12 years ago - a sight to see (and hear)!!!
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Articulated locomotives, including the Big Boy, were not exactly "hinged in the middle". The two seperate sets of drivers articulated under a common boiler. Early "Mallet" style engines were both articulated and compounded, with two distinctly different types of cylinders driving the two seperate sets of drivers. In a "compound" Mallet, the rear cylinders are driven directly off of boiler steam, and their exhaust drives the front cylinders. The front cylinders are noticably larger on a compound Mallet, running at much lower steam pressure than the rears. More modern articulated locomotives were "simple" rather than "compound" driven, with all four cylinders running directly off of boiler steam. This was considered more efficient than a compound locomotive. The Big Boy was one such locomotive. Here is a true "Mallet", or articulated compound.
