Boston & Maine 4-6-2 "Pacific" Locomotives in the USA


Class Details by Steve Llanso of Sweat House Media

Class P-1 (Locobase 15155)

Data from B&M 8 - 1919 Locomotives books supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Works numbers were 47815-47824 and 48588-48589 in Julyl 1910.

The twelve P-1s were the B & M's first Pacifics. As the specifications suggest, these were typical, not remarkable passenger engines. They were delivered with the saturated boilers shown in this entry; steam admission to the cylinders came through 12' (305 mm) piston valves. Within a few years, the class was superheated; see Locobase 129.

After a couple of years, Alco supplied what would be the most numerous B & M Pacific; see Locobase 6630.


Class P-1a/b (Locobase 129)

Data from 1930 Locomotive Cyclopedia and from 1927 and 1947 Boston & Maine Description of Locomotives books supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. (Thanks to Chris Hohl for spotting a road-number anomaly.)

The twelve P-1s were the B & M's first Pacifics. The saturated boiler was soon replaced by the superheated vessel shown in these specs. In superheating the engine, the usual tradeoff of flues for tubes took the unusual route of replacing 2" tubes with 2 1/4" tubes. Were the original tubes too small for good gas flow when most were removed in favor of the superheater? They retained the 12" (305 mm) piston valves

In 1915, the shops fitted the 864 with a new firebox (well short of the usual interval for such a task.) Five--3600-3602 and 3605-3606--received Elesco K-24 centrifugal feed water heaters in October-November 1929 and February 1930.

Bruce Heald, in his Boston & Maine Locomotives (Arcadia Publishing, 2002), p 80, quotes Harry Frye from the latter's Minuteman Steam: "Though faithful performers, they were, for the most part, unexceptional engines and were referred to by some as the Budd cars of the steam era." (Harry A Frye, Minuteman steam: Boston & Maine steam locomotives, 1911-1958 (Littleton, MA : Boston and Maine Railroad Historical Society, 1982), p. 125.)

(Budd cars were Rail-Diesel Cars (RDC) with diesel engines under the center of the frame that were used for years for local passenger service. Locobase remembers his ride in a Budd car with a leaky exhaust manifold - killer ride, dude!)

After a couple of years, Alco supplied what would be the most numerous B & M Pacific; see Locobase 6630.


Class P-2b/c/d (Locobase 6630)

Data from 1927 and 1947 Boston & Maine Description of Locomotives books supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. (Thanks to Chris Hohl for his November 2013 email in which he flagged an error in the tender capacity that could be read either as 24,000 tons of coal or 24,000 gallons of fuel oil.)

The P-2 was an enlargement of the P-1 (See Locobase 129). Its boiler had ten more fire tubes and each tube and flue was a foot longer. When the P-2 was introduced, firebox heating surface included 29.5 sq ft of arch tubes.

A later reworking removed one of the arch tubes, but added 62.5 sq ft of thermic syphon. The B&M also fitted feed water heaters. Most were installed in the late 1920s-early 1930s. The railroad's 1939 accounting of feed water heater installations ran as follows:

Elesco K-24 Centrifugal Worthington 3BL

P-2b 12 8

P-2c 0 10

P-2d 17 22


Class P-3a (Locobase 130)

Data from 1927 and 1947 Boston & Maine Description of Locomotives books supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Enlarged P-2s with larger cylinders and ten tons more adhesion weight, but smaller boilers. Ten built in 1923 and delivered with Worthington 3B feed water heaters.

Retired in 1952-1955.


Class P-4 (Locobase 131)

Data from tables in 1947 Locomotive Cyclopedia and B&M 2 - 1947 Locomotive Classifications supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Works numbers were 7622-7625 in December 1934 (P-4a) and 7655-7659 in March 1937 (P-4b).

Firebox had 100 sq ft (9.3 sq m) of thermic syphons (3) and arch tubes, Coffin feedwater heaters concealed in the smokebox.

The National Park Service's SteamtownRail Data Exchange's Special History Study on the P-4a 3713 notes that it and its sisters were designed to run easily at 70 mph (113 km/h) and travel 125 miles (201 km) on a tenderful of water and 250 miles (403 km) on coal. The study highlights the starring role these Pacifics played in the B & M's regional passenger service between such cities as Boston and Bangor (Maine), Worcester and Portland (Maine), Springfield (Mass) and White River Junction (Vt), and White River Junction and Troy (NY).

According to the NPS study: "When the Boston and Maine took delivery of its second order of Lima Pacifics in 1937 [these would be the last 4-6-2s Lima would build for anybody], it sponsored a contest among New England schoolchildren to name those ten engines and ten other passenger engines. The contest was open to any pupil in any community along the railroad and included students from kindergarten to the final year of junior high school. to the locomotive a plate with the name of the boy or girl who suggested the name, as well as the name of his or her school. The contest elicited more than 10,000 names for the 20 engines."

P-4a 3710 Peter Cooper

P-4a 3711 Allagash

P-4a 3712 East Wind

P-4a 3713 The Constitution

P-4a 3714 Greylock

P-4b 3715 Kwasind

P-4b 3716 Rogers' Rangers

P-4b 3717 Old North Bridge

P-4b 3718 Ye Salem Witch

P-4b 3719 Camel's Hump

3710-3714 were P-4a and delivered in 1934; 3715-3719 were P-4b and arrived in 1937.

Described by Drury (1993) as "a quantum leap." Retired in 1953-1954.

Specifications by Steve Llanso of Sweat House Media
ClassP-1P-1a/bP-2b/c/dP-3aP-4
Locobase ID15,155 129 6630 130 131
RailroadBoston & Maine (B&M)Boston & Maine (B&M)Boston & Maine (B&M)Boston & Maine (B&M)Boston & Maine (B&M)
CountryUSAUSAUSAUSAUSA
Whyte4-6-24-6-24-6-24-6-24-6-2
Number in Class1212821010
Road Numbers860-871860-871/3600-36113620-36893700-37093710-3719
GaugeStdStdStdStdStd
Number Built12821010
BuilderAlco-SchenectadyB&MAlco-SchenectadyAlco-SchenectadyLima
Year19101915191019231934
Valve GearWalschaertWalschaertWalschaertWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)13 / 3.9613 / 3.9613 / 3.9613.08 / 3.9914 / 4.27
Engine Wheelbase (ft / m)33.50 / 10.2133.58 / 10.2433.50 / 10.2134.12 / 10.4036.92 / 11.25
Ratio of driving wheelbase to overall engine wheebase 0.39 0.39 0.39 0.38 0.38
Overall Wheelbase (engine & tender) (ft / m)64.10 / 19.2964.10 / 19.5463.52 / 19.3666.50 / 20.2777.58 / 23.65
Axle Loading (Maximum Weight per Axle) (lbs / kg)55,400 / 25,12959,300 / 26,89868,900 / 31,253
Weight on Drivers (lbs / kg)142,000 / 64,410144,000 / 65,317157,850 / 71,600177,400 / 80,467209,500 / 95,028
Engine Weight (lbs / kg)219,000 / 99,337221,000 / 100,244249,350 / 113,103267,700 / 121,427339,200 / 153,859
Tender Loaded Weight (lbs / kg)140,000 / 63,503140,000 / 63,503159,200 / 72,212149,200 / 67,676240,800 / 109,225
Total Engine and Tender Weight (lbs / kg)359,000 / 162,840361,000 / 163,747408,550 / 185,315416,900 / 189,103580,000 / 263,084
Tender Water Capacity (gals / ML)6800 / 25.766800 / 25.768700 / 32.957700 / 29.1712,000 / 45.45
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)12 / 10.9012 / 10.9024 / 90.9015 / 13.6018.50 / 16.80
Minimum weight of rail (calculated) (lb/yd / kg/m)79 / 39.5080 / 4088 / 4499 / 49.50116 / 58
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)73 / 185473 / 185473 / 185473 / 185480 / 2032
Boiler Pressure (psi / kPa)200 / 13.80200.20 / 13.80200 / 13.80200.20 / 13.80259.60 / 17.90
High Pressure Cylinders (dia x stroke) (in / mm)22" x 28" / 559x71122" x 28" / 559x71122" x 28" / 559x71124" x 28" / 610x71123" x 28" / 584x711
Tractive Effort (lbs / kg)31,559 / 14314.9431,591 / 14329.4531,559 / 14314.9437,596 / 17053.2840,855 / 18531.54
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.50 4.56 5.00 4.72 5.13
Heating Ability
Firebox Area (sq ft / m2)187 / 17.37178 / 16.54273 / 25.37270.50 / 25.14320 / 29.73
Grate Area (sq ft / m2)50.20 / 4.6650.20 / 4.6653.50 / 4.9753.50 / 4.9766.90 / 6.22
Evaporative Heating Surface (sq ft / m2)3660 / 340.022720 / 252.693066 / 284.942992 / 278.073848 / 357.49
Superheating Surface (sq ft / m2)652 / 60.57823 / 76.49786 / 73.05966 / 89.74
Combined Heating Surface (sq ft / m2)3660 / 340.023372 / 313.263889 / 361.433778 / 351.124814 / 447.23
Evaporative Heating Surface/Cylinder Volume297.10220.80248.88204.08285.79
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation10,04010,05010,70010,71117,367
Same as above plus superheater percentage10,04011,96012,94712,96020,841
Same as above but substitute firebox area for grate area37,40042,40666,06665,52699,686
Power L1907618,74023,38318,97136,355
Power MT422.73860.72979.74707.281147.72

Photos

Reference