Deltic Design
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1-  The first section, Deltic Design, has been changed from one to four pages to load faster on the web. It should give the reader a good understanding about how incredible these engines were.

2-  The second section, Deltic Manual, actually links to a great site hosted by Alan Sandoval. Alan scanned the Napier Deltic Engine Training Manual and published it for ptfnasty viewers.

    The manual is displayed with Adobe Acrobat
    If you do not have Acrobat loaded, he has provided a free copy at the site. This is worth the trip.


In 1944, an Admiralty committee was set up, under the chairmanship of Sir Roy Fedden, to investigate the possibility of developing a high-speed, light weight, compression-ignition engine, which could replace the contemporary gasoline engine. After much investigation, a contact was placed with the English Electric Co., Ltd. (the parent firm of D. Napier and Son, Ltd.), for the development of an engine, the basic proposals for which were submitted by Mr. N. Penwarden then a first-class draughtsman at the Admiralty Engineering Laboratory. 

Development work on the Deltic engine was started in 1947 and the first unit was completed in March, 1950. By January, 1952, six engines were available for full development and endurance trials. Two of these units were fitted for operational endurance trials in H.M. fast patrol-boat P.5212. In this vessel the units proved to be an outstanding success and represented a major technical advance on any compression-ignition engine so far developed.

Everyone who had anything to do with the Coastal Forces branch of the Navy, where high-powered gasoline engine installations were involved were always presented with a serious and unavoidable risk of fire and explosion. They immediately became interested in the new Deltic engine.

The striking realization of the compactness of the Deltic engine was gained  after their installation in an ex-German E-boat, known as fast patrol boat 5212. This was originally driven by three Mercedes-Benz Diesel engines of about the same power as the Deltic. Two of them were removed and replaced by Deltics; the center one was retained. The remaining German engine was about twice as long as the Deltic.

The components of the engine were small enough to permit the use of the most modern aircraft engine materials and manufacturing techniques, and this made possible the use of such items as fully-hardened crankshafts, thin-wall lead-bronze bearings, and case hardened and ground gears, which, at the designed ratings, gave extremely long life.


Deltic Engines are opposed piston, liquid cooled compression-ignition engines operating on the two stroke cycle and employing a mechanically driven turbo-blower. Charge-air coolers are integral with the turbo-blower unit. 

Deltic engines offer substantial advantages where weight and space affect the performance of the installation and often make possible machinery arrangements previously considered impractical. Deltic engine (213565 bytes)
The triangular arrangement of the 18 cylinders results in a compact engine, consisting structurally of three cylinder blocks forming the sides and three crankcases, one at each apex of the triangle. This arrangement fully exploits the mechanical simplicity of the opposed piston design. Short crankshafts are used, and as each crankpin carries one inlet and one exhaust piston, the loading on all crankpins is identical and the reciprocating forces are balanced within the engine. 

The power transmitted through each crankshaft is therefore identical, and torsional vibration is controlled by the use of quill-shafts in tune with viscous dampers secured to each crankshaft. These features combine with the characteristics of a fast running, multi-cylinder, two stroke, to produce a smooth running engine with a maximum-to mean torque of less than 1.03 to 1. 

Being supported on flexible mountings, Deltic engines provide an installation virtually free from vibration.

Deltic engines with their basic advantages of light weight and compactness, combined with high power output, are further enhanced by a low installed maintenance factor. The complete interchangeability of common parts and components, such as auxiliary pumps and control units, permits the extensive use of the repair-by-replacement technique.  Engine - front (100191 bytes)

Major units of the engine, such as the blower, phasing gear case , and reverse-reduction gearbox, are also interchangeable, thus reducing servicing time.  One advantage in reducing the time equipment need remain out of service, is the ease and speed with which a complete engine can be changed.
This results in the maximum availability of the vessel. 

The reverse-reduction gearbox for use with marine engines, and the water and oil circulating pumps, are integral and included in the quoted weight

Engine - rear (117890 bytes)