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Lancashire & Yorkshire Hughes 4-6-4T “Dreadnought Tanks”

London, Midland & Scottish class 5P

Great Britain 1924 10 produced
Locomotive Magazine, August 1924

Based on the class 8 “Dreadnought”, George Hughes developed a tank locomotive that was also intended for express service. Thanks to the trailing bogie, it now had a 4-6-4T wheel arrangement. The boiler with Belpaire firebox basically resembled the original, but was somewhat lighter. There were no changes to the 75-inch (1,905 mm) diameter driving wheels and the four 16.5-inch (419 mm) diameter cylinders.

Although they had been developed for the Lancashire & Yorkshire Railway, the ten locomotives were directly delivered to the LMS in 1924 and were designated class 5P. They were also known as “Dreadnought Tanks”. However, due to their heavy weight, their possible uses were limited, so that they could only be used between Manchester and Blackpool. A further order for 20 was therefore converted into class 8. The tank locomotives were withdrawn from service between 1938 and 1941.

Technical data

General

Built
1924
Manufacturers
Horwich
Wheel arrangement
4-6-4T (Hudson)
Gauge
1,435 mm (Standard gauge)

Dimensions and weights

Length
15.20 m
Wheelbase
12.29 m
Service mass
101.6 t
Adhesion mass
56.9 t
Rigid wheelbase
4.14 m
Axle load
19 t
Water capacity
9,093 l
Fuel capacity
4.1 t (coal)

Boiler

Grate area
2.75 m²
Firebox surface
16.723 m²
Tube heating surface
168.805 m²
Evaporative heating surface
185.528 m²
Superheater surface
31.866 m²
Total heating surface
217.4 m²

Power plant

Driver diameter
1,905 mm
Boiler pressure
12.4 bar
Expansion type
simple expansion
Cylinders
four, 419 x 660 mm

Power

Power source
steam
Estimated power
1,081 kW (1,470 PS)
Starting effort
128.5 kN

Calculated values

Factor of adhesion
1 : 4.35
Optimal speed
51 km/h
Power-to-weight ratio
10.6 kW/t
Heating Surface Equivalent
332.9 m²
Cylinder volume/HSE
1 : 1,094.74
Adhesive weight/Total
1 : 1.78
Tractive force/Heating surface
1 : 12.34
Grate area/Heating surface
1 : 79.05
Firebox/Tube surface
1 : 10.09
Total/Superheater
1 : 5.82
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