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London & South Western class M7
Great Britain | 1897 | 105 produced
British Railways No. 30053 in September 2014 at Bewdley
British Railways No. 30053 in September 2014 at Bewdley
Geof Sheppard

Dugald Drummond's first design for the LSWR was the class M7 0-4-4T tank locomotive, which was the larger successor to Adams' T1. While the driver diameter remained the same, over all the grate was enlarged, resulting in the heaviest British machine with this wheel arrangement. It was intended not only for suburban lines in London, but also for semi-fast trains. After a derailment at higher speeds, they were only used on suburban lines.

Between 1897 and 1911, 105 locomotives were built, differing in several details. These included different frame lengths, different arrangements of individual components such as the sandboxes and the reverser, which was initially a lever and later steam-operated. To reduce wear and tear, boiler pressure was reduced from 175 to 150 psi after high speed running on main lines was no longer necessary.

With the introduction of new locomotives on suburban lines, the M7 was increasingly used on branch lines. For this purpose, a larger number were equipped with push-pull controls, which initially worked using cables and pulleys. Later, a more reliable system that worked with air pressure was used. The retirements took place in greater numbers from 1958 onwards and were completed in 1964 after the M7 was replaced by modern standard steam locomotives, diesel locomotives and diesel multiple units. Two still exist today, of which 30053 is operational. It was based in Steamtown in the USA between 1967 and 1987 and is now stationed on the Swanage Railway.

Variantas builtreduced boiler pressure
General
Built1897-1911
ManufacturerNine Elms, Eastleigh
Axle config0-4-4T (Forney) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Length34 ft 8 in
Wheelbase23 ft 7 in
Fixed wheelbase7 ft 6 in
Service weight134,736 lbs
Adhesive weight79,072 lbs
Water capacity1,561 us gal
Fuel capacity7,280 lbs (coal)
Power
Power sourcesteam
Estimated power700 hp (522 kW)600 hp (447 kW)
Optimal speed23 mph
Starting effort19,756 lbf16,934 lbf
Power Plant
Driver diameter67 in
Boiler pressure175 psi150 psi
Expansion typesimple
Cylinderstwo, 18 1/2 x 26 in
Boiler
Grate area20.4 sq ft
Firebox area123.9 sq ft
Tube heating area1,068.1 sq ft
Evaporative heating area1,192 sq ft
Total heating area1,192 sq ft
Calculated Values
steam locomotive
passenger
tank locomotive
Dugald Drummond
last changed: 12/2023
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