1:4 sized model of the Napier Deltic engine.
The Deltic engine was produced as a result of a need for the Admiralty to use diesel powered fast patrol boats. The Second World War has shown a number of vulnerabilities in using petrol powered engines, most notably flammability.
The engine is a two-stroke opposed piston compression ignition (diesel) engine having three or six banks of three cylinders in a triangular arrangement. At each corner of this equilateral triangle is situated a crankshaft, each crank having an exhaust (fork) and inlet (blade) connecting rod from the two adjacent cylinders.