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Baldwin Mallet vs. Conventional LocomotivesAuthor's Note: In this section of Baldwin Record 65, Baldwin moves on to a discussion of the relative advantages of Mallet Articulated Compound Locomotives over conventional locomotives. Baldwin points out that subject to their limitations, simplest devices are best, and that axiom is certainly true with locomotives. On the other hand, given conditions that existed in 1908, a certain amount of complication is essential and simplicity must be sacrificed to secure a satisfactory design. Restricting conditions on locomotive design include stability of road bed, weight of rails, grades, curves, speed required, amount of load to be hauled, gauge of track, and the limits of height and width through which a train must pass. Modern ideas of economical railroad operation also demand the use of the fewest number of trains to handle the traffic. The weight of trains on almost all roads is limited by the hauling capacity of locomotives, which in turn is limited by the conditions just named.
Additional horsepower requires additional heating surface and grate area. This in turn requires larger boilers. On standard 4' 8 1/2 inch railroads, maximum boiler diameter is limited to around 7 feet by the gauge and other clearance requirements. Given that this diameter has already been reached, additional boiler capacity must be accomplished by increasing the length of the boiler. The heaviest rigid frame locomotives in 1908 were the Santa Fe Type locomotives with a total weight of 287,000 pounds with 234,000 pounds over the driving wheels.
Production at the time Record 65 was published was 150 locomotives for the AT&SF. While these engines were successful, the rigid wheelbase of 19 feet six inches. In comparison, a Mallet with six pair of driving wheels increasing tractive power, has a rigid wheelbase of only 10 feet, gaining an advantage allowing them to take curves more easily. Baldwin felt that while the Santa Fe locomotives were successful, they were approaching a practical size limit for rigid frame locomotives. With ever increasing demands for more pulling capacity, the Mallet appears to be most suitable to meet this need. The honor of delivering the first large Mallets fell to the American Locomotive company who in 1904 constructed for the Baltimore & Ohio Railroad a twelve wheel Mallet locomotive with two six-coupled sets of driving wheels. This engine, shown at the Louisiana Purchase Exposition carried 334,000 pounds on its driving wheels.
The Baldwin Locomotive Works wasn't far behind. To continue with this section, select the page on Photos and Builder Specifications. |
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