The Wolfhound engine

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aero and automotive engines and engineers

Some details of the 1941 Armstrong Siddeley 24 cylinder Wolfhound aero-engine project
by Richard Hodgson.

This article first appeared in a different form in "The Sphinx" magazine of the Coventry Branch of the Rolls-Royce Heritage Trust. Please use your Web Browser's "Back" button if you want to return to this article after visiting any hyperlink which are shown in bold dark blue. Please click here to go to the list of articles on this site's home page.

Various searches and enquiries over the past nine years have failed - quite lamentably - to locate any Wolfhound drawings save for reference to just a minor one. Work on the 6 x 4 24 cylinder Wolfhound air cooled aero-engine begun in earnest in about the spring of 1941 when it was realised that, for two quite separate reasons, the Deerhound was unlikely ever to become a production job. The new engine design was initially known as the 24 cylinder engine, but soon the name of a quite different discarded 7 x 4 28 cylinder project of Colonel Fell, the previous ASM chief engineer was adopted. The original design concept was by Stewart Tresilian, ASM's chief engineer (1939 - 1942), and J. B. Bucher, the Head, and founder, of the Stress Office. Bucher was much later to be brought in as Technical Director of Blackburn gas-turbines. T. P. de Paravicini also played an important early role, though he was soon to concentrate on gas-turbine matters. [He produced a pamphlet in about September 1941 and a booklet (with Brian Slatter, his very bright post-graduate student) in about October 1941 on gas-turbines. Unducted fan engines were also proposed in that pamphlet - possibly the first published proposal, though Brian Slatter recently said that, with the benefit of hindsight, the UDF proposals were not workable. Copies of both were retained for well over 50 years by the late Mervyn Cutler and may be posted on this site in due course].

The Wolfhound appears to have been formally cancelled in October/November 1941 for reasons that are too long to set out here - but which were covered in a long talk to the Roll-Royce Heritage Trust on the later ASM dog engines. The Ministry (M.A.P.) then ordered that all details and drawings of the Wolfhound be forwarded to Rolls-Royce. It was hoped that a former Armstrong Siddeley or Roll-Royce employee had kept something. However, up to early May 2000, nothing has come to light, save that the late Sir David Huddie kindly let me know that he had briefly seen the drawings when Rolls-Royce received them.

The known details of the Wolfhound. mostly taken from one file in the Public Record Office are:

24 cylinders (6 x 4), 6" bore x 5.5" stroke [or possibly their near metric equivalent: 150 x 140mm], about 60 - 61 litres. The cylinder dimensions were thus almost square;

Cylinder and head generally similar to the Deerhound Mk.111, but scaled up;

Piston similar to the latest Deerhound Mk.111, but an additional 10mm longer;

Direct air cooling of exhaust valve guide by air ducts within the head itself;

2800 rpm engine speed - higher than previous practice to help with detonation;

Head to barrel had been a weak link on the Deerhound Mk.111. If required, integral barrel and head in aluminium alloy, if possible cast and with pre-fabricated fins - as requested for the MK.111 in 1940, but never sanctioned [by the Board!];

Contra-rotating air screw;

Mounting by cantilever suspension picking up from the rear cylinder heads braced by the camshaft covers. Engine designed ab initio in power plant form;

Initial power output 2600-2800hp;

Designed with the possibility of a two-stage supercharger to be designed by W. H. ("Pat") Lindsey [who, sadly, died on 8th May 2000];

There was something very unusual about the eventual poppet valve and spring arrangement, but the form is still unknown - the answer may be in a classified patent application, if any copy still exists.

The discarded earlier Wolfhound 28 cylinder (7 x 4) proposal of Colonel Fell was criticised in 1940 on the grounds of several estimated severe major periods in the running range by Tresilian and J. B. Bucher when they were first considering the design of a engine in the 2500hp range. Part of the aim was to increase cooling space between the cylinder banks. Pressure was put on the Ministry by Bristol and Rolls-Royce to cancel the Wolfhound project during Summer/Autumn 1941. There is some evidence to suggest that the Ministry had [slight] regrets about the cancellation in 1943.

As a matter of record, the only former ASM engineer that I spoke to who immediately recalled the 1941 Wolfhound being a 24 cylinder design was the late John Densham, who had never worked on the project! The late Pat Lindsey told the author in the early 1990's that he knew nothing about the details of the project save for being asked by Tresilian whether he could design a two-stage supercharger for a "new engine" at relatively short notice if required. The answer was yes! (though he was never to be asked to design it). From other Public Record Office papers and a set of papers recently discovered by Patrick Hassle at Bristol, it is possible that much of the early 24 cylinder Wolfhound design work was carried out as a Bucher and Tresilian "private" project.

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