File:B&MR 2-8-0 Class D-4 3316.jpg

English: Burlington & Missouri River 2-8-0 Class D-4 3316 presumed at Philadelphia, Pennsylvania, sometime in 1903, photo by Baldwin Locomotive Works, Chuck Zeiler collection. This locomotive was built in 1903 for the Burlington & Missouri River (a subsidiary of the Chicago Burlington & Quincy) as class D-4 number 3316, renumbered in 1904 to CB&Q 3191, retired in June 1927. The B&MR received 2-8-0 class D-4 locomotives from both Baldwin (sub-classed D-4B) and Schenectady (Alco, sub-classed D-4A). A total of 100 D-4's were built, 75 by Alco and 25 by Baldwin, and at the time of their construction, they were the largest and heaviest locomotives on the Burlington system. They employed 12-inch piston steam valves actuated by Stephenson valve gear. The following is from Burlington Route Historical Society's Bulletin #29, edited by Hol Wagner: There were a number of differences between locomotives of the two builders, chief among them being the slope of the firebox and style and positioning of the domes (the bell and sandbox being transposed on the two builders versions). The two slightly different firebox designs were both examples of the "kinked" or "broken back" arrangement commonly used in the first years of the 20th Century on early wide firebox locomotives (which also employed two separate firing doors on the backhead). In this arrangement, the rear portion of the mud ring was horizontal, while the front portion sloped downward between the last two pairs of drivers. The downward slope was more pronounced on the Schenectady D-4's than on the Baldwins. The slope had the disadvantage of allowing the fire to slide forward on the sloping grates, gathering at the firebox throat under the fire-brick arch - the point of least fire activity - and choking the lower boiler tubes while leaving a hole in the fire at the point of the kink. Consequently, the Baldwin firebox, with its lesser slope (because it began further to the rear) was a more efficient design.