Overview
Designed around relatively basic technology, the 73-tonne locomotives produce 1,000 horsepower (750 kW) and can operate at up to 75 mph (121 km/h). Designed to work light mixed freight traffic, they have no train heating facilities. Locomotives up to D8127 were fitted with disc indicators in the style of the steam era; when headcodes were introduced in 1960 the locomotive’s design was changed to incorporate headcode boxes. Although older locomotives were not retro-fitted with headcode boxes, a few of the earlier batch acquired headcode boxes as a result of repairs. Unusually for British designs, the locomotive had a single cab. This caused serious problems with visibility when travelling nose first, though in these circumstances the driver's view is comparable to that on the steam locomotives that the Class 20s replaced.
The Class 20 saw only limited service on passenger trains. A small number were fitted with a through pipe for steam heating, primarily for use in conjunction with a Class 37 locomotive on the West Highland Line. Otherwise their use was limited to summer relief services, particularly to Skegness often under the adopted title of The Jolly Fisherman starting from various places including Burton-on-Trent, Stoke-on-Trent, Derby and Leicester. Also occasionally other holiday resorts on the east coast of England, occasional duties as a pilot, and short distance diversions of electric-hauled trains over non-electrified lines.
The shift of light mixed freight to the road network left British Rail with an oversupply of small locomotives. The Class 20s, however, could work in multiple and so handle heavier traffic. Most spent the majority of their working lives coupled nose to nose in pairs to provide a more useful 2,000 hp (1,500 kW) unit and to solve the visibility problems.
Most have now been withdrawn but a few remain with DRS and other minor and industrial operators. Several that are usually operated singly have been fitted with nose-mounted video cameras in order to solve the visibility problems.
The Série 1400 locomotives of Portuguese Railways (CP) are based on the BR Class 20s.
Read more about this topic: British Rail Class 20