In 1930, George Emerson, the General Superintendent of Motive Power & Equipment wanted to prove his theory that a water-tube firebox was practical. He had the B&O order two "Mountain" type locomotives from the Baldwin Locomotive Works, one (Class T-1, road number 5510) equipped with a water-tube firebox and the other (Class T-2, road number 5550) with a conventional type firebox. These two locomotives were identical except for their fireboxes and had 27.5 x 30 cylinders, 74" drivers, a 250 lbs boiler pressure and exerted 65,000 lbs of tractive effort. Number 5510 weighed 384,000 lbs and number 5550 weighed 1,000 lbs more. Emerson wanted to operate the two locomotives in similar service and then compare operating and maintenance costs. This experiment was never completed and the two "Mountains" were used until the early 1950s.
In the early 1940s, the B&O decided to build "Mountain" type locomotives to help with the increase in traffic caused by the war effort. From 1942 to 1948 it built forty of them (Class T-3, road numbers 5555 through 5594) in its Mt. Clare Shops in Baltimore, MD. These locomotives were built to the same general specifications which included 27 x 32 cylinders, 70" drivers, a boiler pressure of 230 psi, a tractive effort of 65,100 lbs and a weight of 375,000 pounds. There were some variations in the features of these locomotives as shown in the chart below. The Class T-3s were retired in 1960.
The B&O bought thirteen 4-8-2s from the Boston & Maine. They were given road numbers 5650 through 5662 and were designated as Class T-4 and were used until 1958.
There are no surviving B&O "Mountains". The Class Ts (numbers 5500 & 5501) were scrapped in 1953. Class T-1 number 5510 was scrapped in 1951 and Class T-2 number 5550 was scrapped in 1952. Some of the Class T-3s and T-4s were scrapped in the early 1950s. In 1957, all of the remaining T-3s and T-4s were renumbered in the 700 series. The T-4s were retired in 1958 and the T-3s lasted a little longer, but by 1960 all of the B&O "Mountain" had been scrapped.
|Class||Qty.||Road Numbers||Year Built||Notes|
|T-3||3||5555-5557||1942||Vanderbilt tenders with 15,000 gallons of water and 26 tons of coal.|
|T-3a||1||5564||1943||Same as T-3 except it had roller bearings on all axles.|
|T-3b||3||5565-5567||1943||Same as T-3 except it had large square tank tender with 20,000 gallons of water and 25 tons of coal. (no roller bearings)|
|T-3c||7||5585-5591||1947||Roller bearings on pony, tailing and tender axles. Same tender as T-3b.|
Firebox heating surface included 42 sq ft (3.9 sq m) of arch tubes.
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. They also had 14" (356 mm) piston valves instead of the 16" (406 mm) valves feeding the 2-10-2s.
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.
One of two Mountains built by Baldwin in 1930 to test the Emerson watertube firebox alongside a conventional stayed firebox. 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).
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.
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.
Like the T-1, the T-2 soldiered on solo until 1951.
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.
|Principal Dimensions by Steve Llanso of Sweat House Media|
|Railroad||Baltimore & Ohio (B&O)||Baltimore & Ohio (B&O)||Baltimore & Ohio (B&O)||Baltimore & Ohio (B&O)|
|Number in Class||2||1||1||40|
|Locomotive Length and Weight|
|Driver Wheelbase (ft / m)||19.25 / 5.87||19.25 / 5.87||19.25 / 5.87||18.25 / 5.56|
|Engine Wheelbase (ft / m)||41.33 / 12.60||44.59 / 13.59||44.59 / 13.59||40.58 / 12.37|
|Ratio of driving wheelbase to overall engine wheebase||0.47||0.43||0.43||0.45|
|Overall Wheelbase (engine & tender) (ft / m)||89 / 27.13||91.16 / 27.79||88.10 / 26.85|
|Axle Loading (Maximum Weight per Axle) (lbs / kg)||69,300 / 31,434||65,900 / 29,892||65,000 / 29,484|
|Weight on Drivers (lbs / kg)||275,000 / 124,738||260,000 / 117,934||260,000 / 117,934||255,000 / 115,666|
|Engine Weight (lbs / kg)||400,000 / 181,437||384,000 / 174,180||385,000 / 174,633||375,000 / 170,097|
|Tender Loaded Weight (lbs / kg)||259,300 / 117,617||273,000 / 123,831||273,000 / 123,831||265,000 / 120,202|
|Total Engine and Tender Weight (lbs / kg)||659,300 / 299,054||657,000 / 298,011||658,000 / 298,464||640,000 / 290,299|
|Tender Water Capacity (gals / ML)||15,100 / 57.20||18,000 / 68.18||18,000 / 68.18||20,000 / 75.76|
|Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)||18 / 16.40||20 / 18.20||20 / 18.20||25 / 22.70|
|Minimum weight of rail (calculated) (lb/yd / kg/m)||115 / 57.50||108 / 54||108 / 54||106 / 53|
|Geometry Relating to Tractive Effort|
|Driver Diameter (in / mm)||74 / 1880||74 / 1880||74 / 1880||70 / 1778|
|Boiler Pressure (psi / kPa)||210 / 14.50||250 / 17.20||250 / 17.20||230 / 15.90|
|High Pressure Cylinders (dia x stroke) (in / mm)||30" x 30" / 762x762||27.5" x 30" / 699x762||27.5" x 30" / 699x762||27" x 32" / 686x813|
|Tractive Effort (lbs / kg)||65,128 / 29541.60||65,150 / 29551.58||65,150 / 29551.58||65,152 / 29552.49|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.22||3.99||3.99||3.91|
|Firebox Area (sq ft / m2)||383 / 35.58||866 / 80.48||474 / 44.05||388 / 36.06|
|Grate Area (sq ft / m2)||89.17 / 8.28||92 / 8.55||92.30 / 8.58||70 / 6.51|
|Evaporative Heating Surface (sq ft / m2)||5593 / 519.60||5403 / 502.14||5489 / 510.13||3950 / 367.10|
|Superheating Surface (sq ft / m2)||1305 / 121.24||1340 / 124.54||1365 / 126.86||1071 / 99.54|
|Combined Heating Surface (sq ft / m2)||6898 / 640.84||6743 / 626.68||6854 / 636.99||5021 / 466.64|
|Evaporative Heating Surface/Cylinder Volume||227.88||261.98||266.15||186.27|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||18,726||23,000||23,075||16,100|
|Same as above plus superheater percentage||22,284||27,600||27,690||19,481|
|Same as above but substitute firebox area for grate area||95,712||259,800||142,200||107,980|