Origin of the Napier "Lion" design.

[jerryw]

In Alec Lumsden's book, "British Piston Aero-Engines...etc", on p 164, he says, "The Company (Napier Ltd) was also asked to build Sunbeam Arab engines. These were not satisfactory and Napier (i.e. Montague) was convinced he could design something better. In July 1916, he had begun design of a 12-cylinder, broad-arrow layout, PROBABLY INSPIRED BY A ROYAL AIRCRAFT FACTORY PROPOSAL (my emphasis).
Is there any evidence, anywhere that Lumsden's statement is true or was this just a myth that has floated around the literature for some time?

 

[Bretoal2]

I thought Lion was said to be designed by Arthur Rowledge ?

 

[Bretoal2]

From "Napier's Redoubtable Lion", by Karl E. Ludvigsen CIMechE MSAE,

Napier Lion History

"Sensibly consulting with the Air Ministry to gain an understanding of their requirements, Napier and Rowledge were told that a desirable engine for their purposes would produce 300 bhp at an altitude of 10,000 feet and would not be run at full throttle below that height. Pioneered by Junkers as well as Georg Bermann for BMW, this concept was rapidly spreading among German engine builders including Opel and Maybach. Napier was invited to create a similar 'overcompressed' engine, in which a key element would be a higher-than-normal compression ratio.

A fundamental decision would be whether the new engine would be cooled directly by air or indirectly by water. Rowledge explained why water cooling was their choice: 'We may claim for the water-cooled engine that almost all the great performances in the air have been accomplished by machines fitted with this type of power unit, since the days when the brothers Wright fitted a four-cylinder water-cooled engine in their machine and succeeded in making the great advance in flying with which their name is associated. Further, we may always expect that it will be possible to build a faster machine with a water-cooled engine than with an air-cooled engine. With water cooling the temperature of the engine is under better control to meet the great variations of temperature met with in flying at different altitudes. The problem of heating the mixture pipes and the carburettor is also considerably simplified.

The two engineers cast a rule over the specific requirements of the engine they were to create under Napier project number E64. For faster fighters and heavier bombers they needed at least 450 horsepower. This pointed to a 12-cylinder engine, albeit one with the lightest practicable weight. [Initially the designers considered an 18-cylinder triple-bank engine under their project E59 but reverted to the 12-cylinder configuration over concern about crankshaft torsional resonance.] Low fuel consumption would be a criterion together with a shape amenable to packaging. To meet these parameters they created a type of engine that had not hitherto existed."

So, it seems that the "inspiration" of the RAE did not necessarily lead to a water-cooled,12-cylinder W engine, but mainly revolved around the principle of overcompression.

Regards

Alain

 

[AMCKen]

Earliest W-type would have been the 1906 Anzani? Of course, it was just 3 cylinders, not 12.