What is a Deltic?
Deltic was the nick name given to the twenty two English Electric type 5 locomotives purchased to head the British rail fleet on the east coast mainline in the early sixties. The name was adopted in homage to the prototype locomotive trailed on BR in the fifties, which in turn had derived its name from the unusual diesel power unit hidden beneath its skin.
The Napier designed and built Deltic engine, originally developed for post war motor torpedo boats, is unique in terms of cylinder configuration as it has its cylinders arranged in triangular banks of 3 (see pic left). These banks have a crankshaft in each of the triangle corner points, which in turn connect to pairs of opposed pistons. Each bank has 3 cylinders, 6 pistons and 3 crankshafts.
Explaining how a deltic engine works is no easy task, but this wonderful machine can be visualised from this rather neat video clip developed by Justin Watkins.