British Rail Class 55

The British Rail Class 55 is a class of 6-axle diesel-electric locomotive built by English Electric in the 1960s. It is better known as the Deltic, a name derived from its opposed-piston Napier Deltic engine which has a cylinder arrangement resembling an inverted Delta.

Cylinder arrangement of the Napier Deltic engine
The Napier Deltic engine was originally developed for the Royal Navy in the 1940s. Due to the fact that opposed-piston engines did not have any cylinder heads and hence were smaller and lighter weight than conventional engines, they were the engine of choice for British motor torpedo boats during the Second World War.

The Class 55 has not one, but two 18-cylinder Deltic engines, producing a total of 2,460 hp. Twenty-two of the units were produced; all of which served on the East Coast Main Line hauling express trains at 100 mph between London King’s Cross, Leeds, and Edinburgh until the introduction of the InterCity 125 in 1978. The Deltics saw the end of their service in 1981.

Six Deltics have been preserved today. One of them remains mainline registered (55022) and is seen in excursion runs (video below: 55022 in action).


Anonymous said…
Huh. Very interesting. Love the graphic of the cylinder arrangement. Also some interesting history on its development!
Anonymous said…
3300horsepower i think you'll find.

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