Baltimore & Ohio 4-8-2 "Mountain" Locomotives in the USA

Class T (Locobase 196)

Data from tables in 1930 Locomotive Cyclopedia and B&O to 1954 Assorted Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also "Test Locomotives of 4-8-2 and 2-6-6-2 Types on the B&O", Railway Age, Volume 91, No 2 (11 July 1931), pp. 46-49, 55, 268. (Many thanks to Chris Hohl for his 22 September 2017 email reporting unlikely boiler pressure values for 177 entries. A Locobase macro caused the error .In addition, Hohl's 4 July 2018 email supplied the Railway Age report that corrected the production date and noted that the boiler pressure setting and tender capacities had changed by 1931. His 20 April 2020 email corrected the engine & tender wheelbase.)

Two engines built by the B&O using class S 2-10-2 boilers (Locobase 1036) on a shorter wheelbase. The 5500 had 29" (737 mm) diameter cylinders while the 5501 had the square dimensions shown in the specs; original boiler pressures was 210 psi. They also had 14" (356 mm) piston valves instead of the 16" (406 mm) valves feeding the 2-10-2s. Firebox heating surface included 42 sq ft (3.9 sq m) of arch tubes. Sellers supplied the Type BF exhaust feedwater heaters on the right side and Class K non-lifting injectors on the left side.

Chris Hohl pointed out that tender capacity had increased to 18,000 US gallons (68,130 litres) of water and 20 tons (18.2 metric tons) of coal by 1931; it weighed 269,000 lb (122,016 kg).

Although 74" drivers promised a good dual-role engine, the B&O did not follow up on this design, possibly because the boiler was in fact too long for a four-axle driving layout. Both retired in 1953.

Class T-1 (Locobase 3097)

Data from B&O Staufer Locomotive Diagrams (Medina, Ohio: Alvin Stauffer), p. 94 supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange collection. See also "Test Locomotives of 4-8-2 and 2-6-6-2 Types on the B&O", Railway Age, Volume 91, No 2 (11 July 1931), pp. 46-49. (Thanks to Chris Hohl for his 20 April 2020 email correcting the wheelbase and adding information on the T-1's later tender.) Works number was 61569 in November 1930.

One of two Mountains built by Baldwin in 1930 to test the Emerson watertube firebox alongside a conventional stayed firebox of the T-2 described in Locobase 3098. In the Emerson, a 40" (1016 mm) diameter drum ran along the centerline over the grate and from front sheet to back head. Headers at the top and bottom of the firebox were connected by two rows (190 tubes total) of 2 1/2"/63.5 mm diameter water tubes. The top header was joined to the drum by 13 4" (102 mm) diameter nipples on each side.

The value of the Emerson firebox was held to be the much greater heating surface it offered to the fire. From 474 sq ft (44.03 sq m) of evaporative surface, including syphons, in the stayed firebox, the surface expanded 82% to 866 sq ft (80.45 sq m) in the Emerson (including the 83 sq ft/7011 sq m of arch tubes). Sellers supplied the Type BF exhaust feedwater heaters on the right side and Class K non-lifting injectors on the left side.

Unfortunately for such designs, the system was prey to vibration, insufficient insulation, maintenance headaches. Moreover, it didn't after all offer much of an advantage. The T-1 and the articulated KK-1 were the only watertube engines supplied to the B&O.

The T-1 remained in service long enough to trail a large tender that carried 23 tons (20.9 metric tons) of coal and 22,000 US gallons (83,270 litres) of water. It weighed 350,000 lbs (158,758 kg) and increased engine and tender wheelbase 11 ft (3.35 m) to 101' 7+" (30.97 m).

Class T-2 (Locobase 3098)

Data from B&O Staufer Locomotive Diagrams (Medina, Ohio: Alvin Stauffer), p. 95 supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also "Test Locomotives of 4-8-2 and 2-6-6-2 Types on the B&O", Railway Age, Volume 91, No 2 (11 July 1931), pp. 46-49. (Thanks to Chris Hohl for his 20 April 2020 email correcting the wheelbase and adding information on the T-2's later tender.) Works number was 61554 in November 1930.

This was the conventional, stayed firebox variant of the Mountain tested by the B&O against the T-1 (Locobase 3097), which had a watertube firebox. As part of the firebox heating surface, the T-2 had 18 sq ft (1.65 sq m) of arch tubes and 95 sq ft (8.8 sq m) of thermic syphons. Sellers supplied the Type BF exhaust feedwater heaters on the right side and Class K non-lifting injectors on the left side.

The T-2 later trailed a tender that carried 23 tons (20.9 metric tons) of coal and 15,800 US gallons.(59,803 litres) of water. Its loaded weight came to 298,400 lbs (135,352 kg)., and contributed to a total wheelbase of 91' 1 7/8" (27.79 m)

Like the T-1, the T-2 soldiered on solo until 1951.

Class T-3b/T-3c (Locobase 193)

Data from B&O to 1954 Assorted locomotive diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. (Many thanks to Chris Hohl for his 22 September 2017 email reporting unlikely boiler pressure values for 177 entries. A Locobase macro caused the error .)

Similar T-3b class numbered from 5565-5594. 40 locomotives built by the B&O from 1942 to 1948 using boilers from retired 4-6-2 and 2-8-2 engines. The frame was cast steel with integral cylinders. The shops fitted several different fireboxes to engines in this class. One was a 363 sq ft (33.7 sq m) unit that included 35 sq ft (3.25 sq m) of arch tubes and 14 sq ft (1.3 sq m) in a single thermic syphon. The second added the syphon and 49.9 sq ft (4.65 sq m) of circulators to the basic 314 sq ft (29.17 sq m) of grate surface. The third added one more circulator to bring the total to the 388 sq ft shown in the specs. A fourth, apparently mounted only on certain T-3Bs, added 72 sq ft (6.7 sq m) of circulators to the grate area and achieved the same firebox heating surface area.

Last T-3 retired in 1960.