Midland classes 690 and 780
Great Britain 1869 26 produced
From 1869, the Midland Railway had tank locomotives built with two coupled axles and a trailing, two-axle bogie for the London suburban lines. The first six came from Beyer, Peacock & Co. in 1869 and are known as class 690. 20 more came in 1870 from Dübs, which were almost identical in construction and were designated class 780.
They had a double frame that also served as a water tank. All locomotives initially had a condensing apparatus, which was later removed from most. Johnson later rebuilt them with a new boiler and cab. In the 1923 grouping, all came to the LMS except for one, which had been withdrawn in 1921. The withdrawals of the others took place between 1924 and 1935.
Technical data
General
- Built
- 1869-1870
- Manufacturers
- Beyer, Peacock & Co., Dübs & Co.
- Wheel arrangement
- 0-4-4WT (Forney)
- Gauge
- 1,435 mm (Standard gauge)
Dimensions and weights
- Wheelbase
- 6.93 m
- Service mass
- 44.4 t
- Rigid wheelbase
- 2.44 m
Boiler
- Grate area
- 1.579 m²
- Firebox surface
- 9.662 m²
- Tube heating surface
- 92.253 m²
- Evaporative heating surface
- 101.915 m²
- Total heating surface
- 101.9 m²
Power plant
- Driver diameter
- 1,575 mm
- Boiler pressure
- 9.7 bar
- Expansion type
- simple expansion
- Cylinders
- two, 432 x 610 mm
Power
- Power source
- steam
- Estimated power
- 261 kW (355 PS)
- Starting effort
- 59.2 kN
Calculated values
- Optimal speed
- 27 km/h
- Power-to-weight ratio
- 5.9 kW/t
- Heating Surface Equivalent
- 150.2 m²
- Cylinder volume/HSE
- 1 : 1,188.47
- Tractive force/Heating surface
- 1 : 12.14
- Grate area/Heating surface
- 1 : 64.54
- Firebox/Tube surface
- 1 : 9.55
