User:Colin Douglas Howell/Galleries/Baltimore and Ohio vertical-boiler locomotives of the 1830s

The early locomotives of the Baltimore and Ohio Railroad were highly unique. Following the lead of Peter Cooper's experimental "Tom Thumb", through most of the 1830s the Baltimore and Ohio built its locomotives with vertical boilers, using a fan to provide draft and driving the wheels indirectly via gearing. In some ways this was following the practice of the old English colliery locomotives, but the B&O machines were far more powerful and much faster. The vertical boiler allowed a very short wheelbase which was well-suited to the tight curves of the B&O's early track.

Baltimore and Ohio "Grasshopper" locomotives, 1832
B&O's main locomotive type of the early to middle 1830s was the "Grasshopper" locomotive, developed by Phineas Davis and named for the motion of its mechanism. Grasshopper locomotives had a vertical boiler, with a blower driven by exhaust steam to provide draft, and twin vertical cylinders which drove a geared crankshaft via walking beams. The first Grasshopper was the Atlantic, built in 1832. Atlantic had an 0-2-2 configuration, and its crankshaft was geared directly to the driving axle. However, this allowed forces on the driving axle from the suspension to stress the gears, leading to irregular gear wear and breakage. Atlantic had a short life, being scrapped in 1835. All the Grasshoppers which followed it were 0-4-0s and had the crankshaft geared to a jackshaft which in turn drove the coupled axles via connecting rods. The jackshaft and rods isolated the gears from the suspension, eliminating the gear trouble Atlantic had suffered.

Despite their peculiarity, the Grasshoppers were powerful locomotives for their time and performed well. Some seventeen were built for the B&O, and several managed to stay in service for over fifty years. A few were preserved, including two at the B&O Railroad Museum. One of these, the former Andrew Jackson, was renamed Atlantic and superficially modified to somewhat resemble the original Atlantic.

Baltimore and Ohio "Crab" locomotives, 1837
Because of their vertical cylinders, the Grasshoppers tended to bounce at higher speeds. As a result, the B&O followed them with a horizontal-cylindered version, the "coal crab" or "Crab" type, developed by Ross Winans in 1837. This shared most of the Grasshopper's features, but replaced the vertical cylinders, pistons, and walking beams with rear-mounted horizontal cylinders and horizontal pistons and piston rods, all placed just above the line of the wheels. The Crab's name was inspired by the peculiar motion of its machinery: its pistons and crankshaft seemed to be pointed "in reverse" and appeared to be moving backwards while the jackshaft, side rods, and wheels went forwards.

Unlike the Grasshoppers, which were built in some numbers, very few Crabs were built, and only two ran on the B&O. Winans quickly moved on to locomotives which combined the Crab's basic mechanism with a greater number of axles and a conventional boiler. Like the Grasshoppers, the Crabs also enjoyed long service lives, not being retired until the 1860s.