Boston & Maine 4-8-2 "Mountain" Type Locomotives


The Boston & Maine Railroad's last purchase of steam locomotives was its Class R-1 "Mountains" built by the Baldwin Locomotive Works. These eighteen 4-8-2s (road number 4100 through 4117) each weighed 416,100 lbs and were some of the heaviest 4-8-2s built in the United States. They had 28 x 31 cylinders, 73" drivers, a 240 psi boiler pressure and a tractive effort of 67,900 pounds.

Each of the B&M "Mountains" carried a name in addition to its road number. These names were selected from contest entries and were assigned as noted below.

Thirteen of these locomotives (road numbers 4100 through 4112) were sold to the B&O in 1947 and the remaining five were retired in 1955 and 1956 and were scrapped shortly after.

Class Details by Steve Llanso

Class R-1 (Locobase 4410)

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

There were four R-1 classes comprising 18 engines -- all were named in contests.

R-1a (1935) works numbers 61822-61826. Loaded weight was 416,100 lb.

4100 Endurance

4101 Hannah Dustin

4102 Cardigan

4103 Oliver Wendell Holmes

4104 Bee & Emma

4105 Powwow River

R-1b (1937) works numbers 62033-62037. Loaded weight was 416,100 lb.

4106 Little John

4107 Intrepid

4108 Lily Pons

4109 Bumble Bee

R-1c (1939) works numbers 62318-62319, 6232. Loaded weight 414,960 lb

4110 Calvin Coolidge

4111 Trojan

4112 Swallow

R-1d (1941) works numbers 62536-62540; weighed 415,200 lb.

4113 Black Arrow

4114 Invincible

4115 Casey Jones

4116 American Progress

4117 Hercules

When fitted with 73-in drivers, R-1c had 67,000 lb of tractive effort. Coffin feedwater heaters concealed in the smokebox.

4100-4112 were sold to the B&O in 1947as T-4 class 5650-5612 as the B&M dieselized. The last 5 remained in B & M service until 1955-1956.

Specifications by Steve Llanso
Locobase ID4410
RailroadBoston & Maine (B&M)
Road Numbers4100-4117
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase19.25'
Engine Wheelbase44.17'
Ratio of driving wheelbase to overall engine wheebase 0.44
Overall Wheelbase (engine & tender)92.67'
Axle Loading (Maximum Weight per Axle)68900 lbs
Weight on Drivers269400 lbs
Engine Weight416100 lbs
Tender Light Weight372700 lbs
Total Engine and Tender Weight788800 lbs
Tender Water Capacity20200 gals
Tender Fuel Capacity (oil/coal)22.5 tons
Minimum weight of rail (calculated) on which locomotive could run112 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter73"
Boiler Pressure240 psi
Cylinders (dia x stroke)28" x 31"
Tractive Effort67918 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.97
Heating Ability
Firebox Area475 sq. ft
Grate Area79 sq. ft
Evaporative Heating Surface4511 sq. ft
Superheating Surface1924 sq. ft
Combined Heating Surface6435 sq. ft
Evaporative Heating Surface/Cylinder Volume204.18
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation18960
Same as above plus superheater percentage24648
Same as above but substitute firebox area for grate area148200
Power L131987
Power MT1047.06




Introduction and roster provided by Richard Duley. Class details and specifications provided by Steve Llanso of Sweat House Media.