The 120 HP Argyll
Pioneer Sleeve Valve Aero-Engine
by Jerry Wells

The Great Engine Competition
In June, 1913 the British War Office per document “87/1545 N.& M.E.C.C. Form A”, announced that a competition for British-built aircraft engines would be held at the Royal Aircraft Factory, Farnborough, Hampshire, starting on 1 February, 1914. Entries had to be in by 1 August, 1913 (with a refundable entry fee of £50, about US $6,000) and engines were to be delivered by 15 January, 1914. A prize of £5,000 (approximately US $600,000) was offered for the winner and orders of up to £40,000 (approximately US $4.8 M) were promised to not just the winner but also to any manufacturer of “engines which fulfill requirements (and are satisfactory for use)”

Table 1. Entry List for the 1914 Engine Competition (G.B. National Archives)

Table 2. Details of the Engines Entered in the N & M Competition. (G.B. National Archives)

Table 3. Results for Engines that Completed at Least One 6-hour Test (G.B. National Archives)

Table 4. Argyll Engine Results as Published in the Judges' Report (G.B. National Archives)

Entries poured in (see Table 1); the Germans were there courtesy of the Scottish Beardmore Company which produced Austro-Daimlers; the French were very well represented via British built Monosoupapes, Salmsons, Anzanis and Renaults and more than a dozen British manufacturers paid their deposit.

The start of the competition was delayed by three months due to the Royal Aircraft Factory being inadequately prepared for the testing, but once underway, there followed two months of noise, oil smoke and petrol fumes and at the end of it all, 11 engines had done enough to be eligible for assessment. As can be seen from Table 3, two entries, the Green and the Gnome, scored three “V.G.I.” ratings and the Green with 10 “V.Gs” compared to the Gnome’s 4 got the nod from the judges. The Argyll performed moderately well but three broken crankshafts would not have gone unnoticed by those adjudicating! For the Green Co., winning the competition did them no favours at all—the production of Green engines during WWI was minuscule. Still, half a million dollars in prize money would have cheered them up!

The Performance of the Argyll Engine
As might be expected for such an important and comprehensive contest, a detailed report of all testing and findings was produced. The part pertaining to the Argyll engine is reproduced in figure 4.

Accompanying the written description was a summary chart (see Table 4); it would be interesting to know who made up this chart and who checked it before printing because the information in it barely lines up at all with the text description! For example, the chart claims that on 5 May the engine broke its crankshaft yet three days later it completed a 6 hour run! Then just three days after that, it completed a 9 hour 16 min run, which wasn’t required by the rules of the competition at all!

Table 5 is a summary of the information provided under the heading “Trials” compiled by the author. The unfortunate aspect of the Argyll engine was its weight. It wasn’t the heaviest engine in the competition but at 550 lbs (ex radiator), the 120 hp it produced resulted in a lb-per-hp ratio of 4.58, the worst figure of all the entries. If production had gone ahead, a weight reduction program would have been a high priority with aluminium junk heads and pistons in place of the steel variety a possibility. With a stronger crankshaft allowing an increase in revs to 1,400 (about the limit for propellers in those days) a respectable 145 hp should have been attainable.

Fig. 5. Transverse Section of the 120 HP Argyll Sleeve-Valve Aero-Engine. The little tap on the right side of the cylinder is a decompression valve.	ig. 6. Sketch Showing Relative Positions of the Sleeve, Ports and Cylinder in the McCollum Engine. 17=inlet ports, 18=exhaust ports, 28=sleeve valve.
Fig. 7. Later Version of the McCollum Engine. Note the sleeve is still exterior to the cylinder but movement is controlled from the base of the sleeve, not the top.	Fig. 8. The Prototype Burt Sleeve-drive Mechanism- with Wabble Crank and Sliding Pins

The Sleeve Drive Mechanisms
This is an aspect of the development of both the Burt and the McCollum engines which seems to have caused a lot of thought and experimentation from both inventors. They tried many different variations and even after that, changes by Continental, Bristol and finally Napier were introduced.
Some of the different drive trains used are summarized below:
1) Knight (1908) conventional crank, connecting rods, lugs-&-bolt (fig. 1).
2) McCollum (1909) two conventional cranks, push rods, rockers, lugs-&-bolt (fig. 1).
3) McCollum (1909) two conventional cranks, pins, lugs-&-bolt (fig. 7).
4) Burt 1 (1909) barrel crank, sliding pins, lugs-&-bolt (fig. 3)
5) Burt 2 (1909) wabble crank, sliding pins, lugs-&-bolt (fig. 8).
6) Argyll (1913) skew gears, barrel crank, sliding pins, lugs-&-bolt (fig. 5).
7) Sargent (1914) wabble crank, connecting rod, ball joint (fig. 1).
8) Continental (1925) skew gear, barrel crank, ball joint (fig. 1).
9) Bristol (1932) spur gear, crank, ball joint.
10) Napier (1939) skew gear, crank, ball joint.

The Demise of Argyll
At the end of the 1914 engine competition, the Argylls Ltd team packed up and returned to Scotland with their two test engines (and three broken crankshafts!). It would have been a sad homecoming not only because of the competition results but also they knew that, due to the precarious financial state of the company, its shut-down was imminent. This occurred on 17 June, 1914.

However, the Argyll name and the sleeve valve engine refused to die. As far as aero-engines were concerned, there was interest from the Royal Aircraft Factory, which not only offered Argylls a contract to build engines for them but also were keen to develop other sleeve valve engines using their expertise. The proposed aero-engine contract came to nothing but a V-12 sleeve valve engine based on the R.A.F. production model was built.

Peter Burt had a lot to do with this as evidenced by the design patent he filed in July 1915. Some idea of the envisaged machine can be gained from figure 9. The engine was to be a 60° vee with air cooled aluminium cylinders, water cooled heads and, with this particular design of sleeve valve drive, very long con-rods. The complexity of the head design is breathtaking—the cylinder (or junk) head was of conventional shape but was double-walled to allow water circulation; the unusual aspect of this particular junk head was the ring of ports (12) connecting the spark plug well with the annular space above the top of the sleeve valve.

Surrounding the sleeve valve itself was a tubular structure (again, double walled to allow coolant flow) illustrated in figure 11 lower left. It was made of copper, brass or steel because it was felt that aluminium would not be strong enough to cope with the combustion pressures. This insertable piece had the usual inlet and exhaust ports (4, 5) running through it but, in addition, there was a ring of ports (6) which were closed off by the top of the sleeve valve during the uppermost part of its travel. Outside of this was the upward extension of the aluminium cylinder (1) with ports cast into it and, finally, around the whole structure was an annular induction manifold (16) with carburettor attachment flanges on the inside of the vee. Thus, from the spark plug to the inlet manifold, there were seven layers of metal! “The channelled envelope (16) (i.e., the inlet manifold) is shaped to surround the various cylinders in each bank, so in effect to form a monobloc engine though the cylinders are formed separately.”- Burt, 1915. The exhaust ports discharged on both sides of the cylinder bank into collecting rails (9).

Even more complex was the intended gas flow path for the engine which was described by the inventor as follows, “Desirably, the air to be carburetted enters into a ported hollow head (13) projecting into the interior of the cylinder (1), the passage being so formed that the air is carried as closely as possible to the spark plug , so that the cold entering air may cool the part of the spark plug exterior to the cylinder (1); thence the air is led, more or less preheated, by way of the ports (12) and the air ports (6) controlled by the upper end of the sleeve valve (11), passing through the ports (6) to the passage (7), thence to and through the carburettor and thence to the passage (8) which communicates with the inlet ports (4).” Thus, it seems that, for this engine, Burt intended that all the air for the cylinders should be drawn from the spark plug wells via a very convoluted route. It doesn’t look feasible at all!

Fig. 10. Transverse section of the prototype Burt V-12 sleeve valve aero-engine with water-cooled cylinder head and air-cooled cylinder barrels. Cylinder head construction was much simpler than indicated in the patent drawing. Note deep cut-outs in sleeve bases to clear con-rods. Another interesting feature is the way the fuel/air mixture is routed around the top cooling fins. Note how the upper fins are sealed and connected to the intake manifold. This feature would consequently offer improved fuel vaporization and cooling. Therefore, it could be argued that this engine was triple cooled, water, air and fuel/air. (Glasgow University Archive Services)

Fig. 11. This shows sections through various parts of the cylinders and, at the bottom of the diagram, details of the sleeve drive mechanism. (Glasgow University Archive Services)

Conclusions
However, the V-12 sleeve valve engine, like its predecessor, the Argyll 6, never flew and the sleeve valve “torch” was passed to Continental Motors in the USA who, at the urging of Antony Fokker, built a 9-cylinder, sleeve valve radial adapted from a Wright “Whirlwind” base. This engine was displayed at various auto shows in 1927 but there is no evidence that it was ever run.
Back in Europe, the Bristol Company then embarked on a serious project to utilize the sleeve valve engine and, after much trial and tribulation plus the spending of a prodigious amount of money, a “Perseus” 9-cylinder engine finally lifted the Company’s test “Bulldog” IVA into the air in October, 1933 almost exactly 20 years after the little Argyll 6 first coughed into life.

References
Patents:
GB 190918,140 Burt
GB 191510,304 Burt.
GB 190914,629 McCollum
GB 190927,327 McCollum
US 1198061 Sargent, 1914

British War Office. Doc. #87/1545 1913.
British War Office. N.&M.E.C. Judges' Report 1914.

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