The reference for locomotives and railcars


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Boston & Maine class P-4
United States | 1934 | 10 produced
P-4a No. 3710 “Peter Cooper”
P-4a No. 3710 “Peter Cooper”
collection Richard Driver

The last ten Pacifics that the Boston & Maine purchased were also the last Pacifics that Lima manufactured. Their task was regional traffic over distances of up to around 200 miles, and they were designed for an average speed of 70 mph or 113 km/h. The firebox contained three thermic syphons and arch tubes. The coffin feed water heater was concealed in the smokebox. Initially there was a skyline casing on the top of the boiler, which was later removed. The locomotives from the two production years 1934 and 1937 were designated P-4a and P-4b. They were given names that were chosen in a competition among kindergarten children and students. Only 3713, which is currently being overhauled in Steamtown, has been preserved.

Built1934, 1937
Axle config4-6-2 (Pacific) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase36 ft 11 in
Fixed wheelbase14 ft
Total wheelbase77 ft 7 in
Service weight339,200 lbs
Adhesive weight209,500 lbs
Total weight580,000 lbs
Axle load68,900 lbs
Water capacity12,000 us gal
Fuel capacity37,000 lbs (coal)
Power sourcesteam
Estimated power3,600 hp (2,685 kW)
Optimal speed56 mph
Starting effort40,918 lbf
Power Plant
Driver diameter80 in
Boiler pressure260 psi
Expansion typesimple
Cylinderstwo, 23 x 28 in
Grate area66.9 sq ft
Firebox area320 sq ft
Tube heating area3,528 sq ft
Evaporative heating area3,848 sq ft
Superheater area966 sq ft
Total heating area4,814 sq ft
Calculated Values
steam locomotive
last changed: 01/2023

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