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The reference for locomotives and railcars

Great Western Railway class 157

Great Britain 1862 20 produced
Original variant Locomotive Magazine, January 1907

In 1862, Daniel Gooch designed ten standard gauge 2-2-2 express locomotives for the GWR which got the numbers 157 to 166. Built by Sharp, Stewart & Co., they got the nickname “Sharps”. They had double frames and the inside frame only extended from the cylinders to the front of the firebox, while carrying the load of all moving masses. The Firebox of these locomotives was higher than the boiler barrel. 

As early as in 1879, they were found to be too weak and scrapped. At the same time, ten similar locomotives were built under William Dean and got the same numbers. These now had a flush-topped boiler and a full-length inside frame. With a larger firebox and a somewhat smaller boiler barrel, the power had been increased in comparison to the 1862 locomotives. Also the wheelbase had increased from 16 feet to 17 ft 8 in. It remains unclear if any parts at all were re-used from the older locomotives.

As they were originally thought to be rebuilds of the earlier locomotives, they carried the nickname “Sharpies”. Another name given to the class was “Cobham” from the name of No. 162. A good part of the class survived into the 20th century, having got new boilers at least once. Some even got a Belpaire firebox. Most were withdrawn between 1903 and 1906, with 165 surviving until 1914.

Later Dean variant Locomotive Magazine, January 1907

Technical data

General

Property as built Dean 1879
Built 1862 1879
Manufacturers Sharp, Stewart & Co. Swindon
Wheel arrangement 2-2-2 (Jenny Lind)
Gauge 1,435 mm (Standard gauge)

Dimensions and weights

Property as built Dean 1879
Total wheelbase 4.88 m 5.39 m
Service mass 30.2 t 36.7 t
Adhesion mass 13 t 16.8 t
Rigid wheelbase 4.88 m 5.39 m
Axle load 13 t 16.8 t

Boiler

Property as built Dean 1879
Grate area 1.358 m² 1.793 m²
Evaporative heating surface 115.274 m² 112.809 m²
Total heating surface 115.3 m² 112.8 m²
Firebox surface 10.684 m²
Tube heating surface 102.126 m²

Power plant

Property as built Dean 1879
Driver diameter 2,134 mm
Boiler pressure 9 bar 9.7 bar
Expansion type simple expansion
Cylinders two, 406 x 610 mm two, 457 x 610 mm

Power

Property as built Dean 1879
Power source steam
Estimated power 224 kW (305 PS) 336 kW (457 PS)
Starting effort 36.0 kN 49.0 kN

Calculated values

Property as built Dean 1879
Factor of adhesion 1 : 3.55 1 : 3.36
Optimal speed 39 km/h 42 km/h
Power-to-weight ratio 7.4 kW/t 9.1 kW/t
Adhesive weight/Total 1 : 2.32 1 : 2.19
Tractive force/Heating surface 1 : 6.51 1 : 9.07
Grate area/Heating surface 1 : 84.89 1 : 62.92
Heating Surface Equivalent 166.2 m²
Cylinder volume/HSE 1 : 1,204.11
Firebox/Tube surface 1 : 9.56
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