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The reference for locomotives and railcars

Boston & Maine class P-4

United States 1934 10 produced
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.

Technical data

General

Built
1934, 1937
Manufacturers
Lima
Wheel arrangement
4-6-2 (Pacific)
Gauge
1,435 mm (Standard gauge)

Dimensions and weights

Wheelbase
11.25 m
Total wheelbase
23.65 m
Service mass
153.9 t
Adhesion mass
95 t
Total mass
263.1 t
Rigid wheelbase
4.27 m
Axle load
31.3 t
Water capacity
45,425 l
Fuel capacity
16.8 t (coal)

Boiler

Grate area
6.215 m²
Firebox surface
29.729 m²
Tube heating surface
327.762 m²
Evaporative heating surface
357.491 m²
Superheater surface
89.744 m²
Total heating surface
447.2 m²

Power plant

Driver diameter
2,032 mm
Boiler pressure
17.9 bar
Expansion type
simple expansion
Cylinders
two, 584 x 711 mm

Power

Power source
steam
Estimated power
2,685 kW (3,651 PS)
Starting effort
182.0 kN

Calculated values

Factor of adhesion
1 : 5.12
Optimal speed
90 km/h
Power-to-weight ratio
17.5 kW/t
Heating Surface Equivalent
685.6 m²
Cylinder volume/HSE
1 : 556.09
Adhesive weight/Total
1 : 1.62
Tractive force/Heating surface
1 : 8.50
Grate area/Heating surface
1 : 71.96
Firebox/Tube surface
1 : 11.02
Total/Superheater
1 : 3.98
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