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The Rolls-Royce R is a British Aircraft engine that was designed and built specifically for air racing purposes by Rolls-Royce Limited. Nineteen R engines were assembled in a limited production run between 1929 and 1931. Developed from the Rolls-Royce Buzzard, it was a 37-litre (2,240 cu in) capacity, Supercharger V-12 capable of producing just under , and weighed . Intensive factory testing revealed mechanical failures which were remedied by redesigning the components, greatly improving reliability.
The R was used with great success in the Schneider Trophy seaplane competitions held in England in 1929 and 1931. Shortly after the 1931 competition, an R engine using a special fuel blend powered the winning Supermarine S.6B aircraft to a new airspeed record of over . Continuing through the 1930s, both new and used R engines were used to achieve various land and water speed records by such racing personalities as Henry Segrave, Malcolm Campbell and his son Donald Campbell, the last record being set in 1939. A final R-powered water speed record attempt by Donald Campbell in 1951 was unsuccessful.
The experience gained by Rolls-Royce and Supermarine designers from the R engine was invaluable in the subsequent development of the Rolls-Royce Merlin engine and the Spitfire. A de-rated R engine, known as the Griffon, was tested in 1933, but it was not directly related to the production Rolls-Royce Griffon of 1939, of the same exact bore/stroke and resultant displacement figures as the "R" design. Three examples of the R engine are on public display in British museums as of 2014.
The introduction of articulated connecting rods was regarded as a "nuisance" by Arthur Rubbra, a Rolls-Royce engine designer, as there were inherent problems with the arrangement. The complicated geometry meant that a pair of rods had different effective lengths, giving a longer stroke on the articulated side; consequently the cylinder liners on that side had to be lengthened to prevent the Piston ring from running out of the cylinder skirt. Articulated rods were used in the Goshawk engine, but were not embodied in the later Rolls-Royce Merlin, for which Arthur Rowledge had designed a revised blade and fork system.Rubbra 1990, p. 60.
Later production R engines featured sodium Poppet valve stems for improved cooling, while additional modifications included a redesigned lower crankcase casting and the introduction of an oil scraper ring below the piston gudgeon pin; a measure that was carried over to the Merlin engine. A balanced crankshaft was introduced in May 1931, and the compression ratio on the "sprint" engines prepared for that year was raised from 6:1 to 7:1.
The ignition system consisted of two rear-mounted, crankshaft-driven ignition magneto, each supplying one of a pair of spark plugs fitted to each cylinder. This is common practise for aero engines, as it ensures continued operation in the case of a single magneto failure, and has the advantage of more efficient combustion over a single spark plug application.Gunston 2006, p. 60.
A not-so-obvious cooling measure was the deliberate use of a Air-fuel ratio, which accounts for the frequent reports of black smoke seen issuing from the engine exhaust stubs.Eves 2001, p. 208. Although this robbed the engine of some power, it increased reliability and reduced the possibility of detonation in the cylinders.
The development of special fuel was attributed to the work of "Rod" Banks, an engineer who specialised in fuels and engine development. After using neat benzole for early ground test runs, a mixture of 11% Avgas and 89% benzole plus 5 (cc) of tetra-ethyl lead per Imperial gallon (4.5 L) was tried. This blend of fuel was used to win the 1929 Schneider Trophy race, and continued to be used until June 1931.Eves 2001, p. 230. It was discovered that adding 10% methanol to this mixture resulted in a increase, with the further advantage of reduced fuel weight – particularly important for aircraft use – due to its lowered Relative density. For the 1931 airspeed record attempt acetone was added to prevent intermittent misfiring; the composition of this final blend was 30% benzole, 60% methanol, and 10% acetone, plus 4.2 cc of tetra-ethyl lead per gallon.
On an early test run the R engine produced and was noted to Idle speed happily at 450 revolutions per minute (rpm). With increased boost ratings and fuel developed by Banks, the R engine ultimately developed at 3,200 rpm; well over double the maximum power output of the Buzzard.Lumsden 2003, p. 198. The engine was further tested and cleared for limited sprint racing at at 3,400 rpm and +21 lb (1.45 bar) of boost,Gunston 1989, p. 139. but this capability was not used due to concerns with the S.6B's airframe not being able to withstand the power, and the inability of the aircraft to lift the extra fuel required to meet the increased consumption.Lumsden 2003, p. 199.
Ground testing of the R involved the use of three Kestrel engines: one to simulate a headwind or airspeed, one to provide ventilation of the test area, and another to cool the crankcase. Superchargers could be tested on a separate rig that was driven by another Kestrel engine. Eight men were required to run a test cell, led by the "Chief Tester" who had the tasks of logging the figures and directing the other operators. One of these chief testers was Victor Halliwell who later lost his life whilst on board the water speed record contender Miss England II. The conditions in the test cell were particularly unpleasant; deafness and tinnitus lasting up to two days were experienced by test personnel even after plugging their ears with cotton wool. Development time was short and the deafening sound of three Kestrels and an R engine running at high power for 24 hours a day took its toll on the local population. The Mayor of Derby stepped in and asked that the people endure the noise for the sake of British prestige; subsequently testing continued for seven months.
In the course of a 25-minute test an early R engine would consume 60 Gallon (gal) (270 L) of pre-heated castor oil. The majority of this was spat out of the exhaust ports and smothered the test cell walls, milk being given to staff to minimise the effects of this well-known laxative. Up to 200 gal (900 L) of the special fuel blend had to be mixed for each test, 80 gal (360 L) of which were used just to warm the engine to operating temperature. The same Blade pitch propeller used for flight trials was fitted throughout these tests.
Engine starting was achieved by a combination of compressed air and a hand-turned ignition magneto; however, starting problems were encountered during pre-race testing at Calshot due to moisture in the air and water contamination of the fuel. A complicated test procedure was devised to ensure clean fuel for competition flights since more than 0.3% water content made it unusable.Holter 2002, p. 40. As expected, minor engine failures continued to be experienced, and to counter this engines and parts were transported at high speed between Derby and Calshot using an adapted Rolls-Royce Phantom I motor car. Travelling mostly after dark, this vehicle became known as the Phantom of The Night.Holter 2002, p. 41.
The pre-production Griffon I shared the R engine's bore and stroke,Staff 20 September 1945. " The Rolls-Royce Griffon" Flight, p. 309. www.flightglobal.com. Retrieved 29 October 2009. but was otherwise a completely new design that first ran in the Experimental Department in November 1939.Lumsden 2003, p. 216. Although this single engine was never flown, the production version, the Griffon II, first flew in 1941 installed in the Fairey Firefly.Lumsden 2003, p. 217. A significant difference between the R and the production Griffon was the re-location of the camshaft and supercharger drives to the front of the engine to reduce overall length. Another length-reducing measure was the use of a single magneto (the R had two, mounted at the rear), this again was moved to the front of the engine.Rubbra 1990, p. 118.
Further possible development work on the R engine was discussed in The National Archives' file AVIA 13/122, Royal Aircraft Establishment, proposal relating to destructive testing of Rolls-Royce R engines, October and November 1932 AVIA13/122 (Air Ministry and successors: Royal Aircraft Establishment (from 1988, Royal Aerospace Establishment)). National Archives, Kew (UK). www.nationalarchives.gov.uk. Retrieved 15 October 2009. which contains a proposal from the Royal Aircraft Establishment dated October and November 1932, to test four engines to destruction. This document states that there were five engines available for test purposes, the fifth to be used for a standard Type certificate at high revolutions.
Although not directly related to the Spitfire, the Supermarine engineers gained valuable experience of high-speed flight with the S.5 and S.6 aircraft, their next project being the Rolls-Royce Goshawk-powered Supermarine Type 224 prototype fighter aircraft. Technological advances used in the R engine, such as sodium-cooled valves and spark plugs able to operate under high boost pressures, were incorporated into the Rolls-Royce Merlin design.Price 1982, pp. 19–20. The author Steve Holter sums up the design of the Rolls-Royce R with these words:Holter 2002, p. 46.
During the 1929 race at Cowes between Great Britain and Italy, Richard Waghorn flying the Supermarine S.6 with the new Rolls-Royce R engine retained the Schneider Trophy for Great Britain with an average speed of , and also gained the world speed records. The records were subsequently beaten when Richard Atcherley later registered higher speeds when he completed his laps of the circuit.Price 1986, p. 11.Eves 2001, pp. 171–197. The Italian team placed second and fourth using Fiat AS.3 V-12-powered Macchi M.52 aircraft. Another racing seaplane, the Fiat C.29 powered by the AS.5 engine attended the contest but did not compete.Eves 2001, pp. 244–245.
More comparable to the R engine was the Fiat AS.6 engine developed for the 1931 contest; effectively a coupled, double AS.5 that suffered from technical problems. With the assistance of Rod Banks, the AS.6 powered the Macchi M.C.72 to a new speed record for piston-powered seaplanes in 1934 of , a record that still stands as of 2009.Gunston 1989, p. 58.
In 1931 the British Government withdrew financial support, but a private donation of £100,000 from Lucy, Lady Houston allowed Supermarine to compete on 13 September using the R-powered Supermarine S.6B. For this race the engine's rating was increased by . RAF (UK). The Schneider Trophy – 70th Anniversary, The Build-up www.raf.mod.uk. Retrieved 17 October 2009. The Italian and French entrants however, failed to ready their aircraft and crews in time for the competition,Eves 2001, p. 206. and the remaining British team set both a new world speed record at and, unopposed, won the trophy outright with a third consecutive victory. "The Flight" was wound up within weeks of the 1931 win as there were to be no more Schneider Trophy contests.RAF (UK). The Schneider Trophy – 70th Anniversary, 1931 Report www.raf.mod.uk. Retrieved 17 October 2009. The original Trophy is on display in the London Science Museum along with the S.6B that secured it, as well as the R engine that powered this aircraft for the subsequent airspeed record flight. Supermarine Seaplane S.6B, S1595, Inventory number: 1932-532 (exhibit) www.sciencemuseum.org.uk. Retrieved 15 October 2009.
In 1932, Campbell stated that he "... was fortunate in procuring a special R.R. Schneider Trophy engine" for his land speed record car to replace its Napier Lion. Lent to him by Rolls-Royce, this engine was either R25 or R31. By February 1933 the car, named Blue Bird had been rebuilt to accommodate the larger engine and was running at Daytona.Jennings 2004, p. 237.
In late 1933 Campbell bought engine R37 from Rolls-Royce; and had also been lent R17 and R19 by Lord Wakefield, and R39 by Rolls-Royce. He then lent R17 to George Eyston. Once he had achieved the record on 3 September 1935 at the Bonneville Speedway, Campbell retired from further land speed endeavours.Jennings 2004, p. 273.
Lord Wakefield arranged for a replica of the Rolls-Royce R to be exhibited at the 1933 Motor Show, held at Olympia, London. A press report from the eventJennings 2004, p. 236. provides an insight into the public perception of the engine:
Blue Bird is now on display at the Daytona International Speedway.Jennings 2002, p. 277.
www.sirmalcolmcampbell.com. Retrieved 21 October 2009.
The care and maintenance of the Campbell's R engines was entrusted to Leo Villa, a Cockney born to a Swiss father, who was described as "the man behind the Campbells" and a central figure who "fitted the first nut to the first bolt". Villa learnt his trade of "aircraft mechanic" in the Royal Flying Corps; his first job was fitting Beardmore 160 hp engines to airframes.Holter 2002, p. 69. After World War I he worked for a motor racing company and participated as co-driver and mechanic in several races.
Villa was first employed by Malcolm Campbell in 1922, and continued in the service of Donald Campbell until 1967, when Campbell was killed during a record attempt on Coniston Water. He was the chief caretaker of their R engines until the last R-powered record attempt in 1951, after which his responsibilities centred on Campbell's jet engines. Villa's many responsibilities included installing and removing the engines, repairing and tuning them, and operating the compressed air and magneto for starting them. During the World War II years, he was responsible for the upkeep of Blue Bird K4 and the spare R engines, but unknown to him they had been sold along with K3. Villa eventually took the three R engines to Thomson & Taylor at Brooklands for long-term storage.Holter 2002, p. 79.Jennings 2004, p. 106.
His relationship with Malcolm Campbell was strained at times: Campbell, with no engineering background, would often question Villa's intimate knowledge of the R engine, but his relations with Donald Campbell were much better, as they were of a similar age. At Lake Garda in 1951 Villa noted the willingness of "Don" to help with engineering tasks, and the difficulties of working on the R engine:Holter 2002, p. 85.
| R1 | 7 April 1929 | Development engine. First test using neat benzole fuel. No power figures taken.Eves 2001, p. 226. | |
| 1 May 1929 | observed after 13 hours running. | ||
| 7 May 1929 | at 2,750 rpm, briefly run at at 3,000 rpm. Engine stripped, forked found cracked. Redesigned rods fitted and crankcase machined. The crankcase modifications decreased over-oiling by 75%, a new scraper ring was suggested to cure the remainder. Fuel/air distribution problem due to new manifold design – return to the original Buzzard manifold suggested. | ||
| R3 | 15 May 1929 | Development engine. Completed 15-minute acceptance test. at 2,750 rpm. | |
| 26 February 1931 | Back in development test house. Spot reading of at 3,200 rpm noted.Eves 2001, p. 229. | ||
| 21 April 1931 | First test with articulated connecting rods. | ||
| 23 April 1931 | at 3,200 rpm for 17 minutes – longest time at this power with new rods. | ||
| 24 April 1931 | Failed after 17 minutes when the main bearings collapsedHolter 2002, p. 37. | ||
| 25 April 1931 | at 3,200 rpm. Attempted 1-hour Air Ministry acceptance test but oil pressure was lost after 22 minutes. | ||
| 1 May 1931 | Failed after 2.5 minutes when the main bearing and connecting rods failed | ||
| 14 May 1931 | Failed after 17.33 minutes when supercharger slipper bushes seized | ||
| 15 May 1931 | Two runs of 29.5 minutes and 18.5 minutes, both terminated by broken exhaust valves | ||
| 29 May 1931 | Ran for 25 minutes fitted with sodium-filled valves. Heads failed | ||
| 14 July 1931 | Running with sodium-filled valves. | ||
| 28 July 1931 | Further attempt at the 1-hour test, crankshaft failure after 34 minutes. Rebuilt but experienced a second crankshaft failure after 58 minutes, power output of at 3,200 rpm noted just prior to failure. | ||
| R5 | 18 June 1929 | Development engine. Completed 15-minute acceptance test. at 2,750 rpm.Eves 2001, p. 227. | |
| 7 August 1929 | Completed first 1-hour full-throttle test. at 3,000 rpm. | ||
| 25 February 1931 | Back in development for 1931 race. Probably this engine that blew up at after dynamometer coupling failure. | ||
| R7 | 6 July 1929 | Passed 15-minute acceptance test. . Issued to RAF Calshot for test flying with minimum use of full throttle. | |
| Mid-September 1929 | Post race, installed in S.6, N248, for speed record attempt. | ||
| R9 | 4 August 1929 | Installed in S.6, N247, for sea trials and attempted first flight – aircraft refused to takeoff due to handling problems. All modifications to date were incorporated in this engine. | |
| 10 August 1929 | First flight, in S.6, N247. | ||
| 22 August 1929 | Returned to Derby having run 4 hr 33 min on the ground and 2 hr 52 min in the air. Overhauled and refitted to N247 for the race.Eves 2001, p. 228. | ||
| June 1931 | Rebuilt to 1931 specification. at 3,200 rpm. Cleared at Calshot for limited full-throttle use. | ||
| 12 August 1931 | Back at Derby with new design crankshaft. at 3,200 rpm for full hour. | ||
| R11 | 25 August 1929 | Flown in S.6 N248. "Notes on High Speed Flight, 1931" collected by Wing Commander A. H. Orlebar (T.3209), AVIA 13/112. National Archives, Kew (UK). www.nationalarchives.gov.uk.: Retrieved: 5 November 2010. Development engine in 1930. | |
| 1930 | Redesignated "R-MS-11" for Buzzard MS (moderately supercharged) development. | ||
| R15 | 7 September 1929 | Probably in S.6, N248, for the race. | |
| 26 June 1931 | Flown in S.6A N248,. | ||
| 22 August 1931 | Flown in S.6B S1595,. | ||
| R17 | April 1930 | Direct-drive engine for Henry Segrave's water speed record boat Miss England II, sponsored by Lord Wakefield.
at 3,000 rpm. Water-cooled [[exhaust manifold]]s. This was the only R engine originally made as an anticlockwise unit – hence it had a different crankshaft, camshaft and ancillaries. Contrary to Rolls-Royce convention it was given an odd engine number.Eves 2001, p. 202. | |
| 1935 | Lent by Lord Wakefield to Malcolm Campbell as a spare for land speed record attempt. | ||
| Lent by Sir Malcolm Campbell to George Eyston as a spare for land speed record attempt. | |||
| R19 | April 1930 | Direct-drive engine for Sir Henry Segrave's water speed record boat Miss England II, sponsored by Lord Wakefield.
at 3,000 rpm. | |
| 1935 | Lent by Lord Wakefield to Sir Malcolm Campbell as a spare for a land speed record attempt. | ||
| 30 June 1937 | Timed at in Blue Bird K3 with Sir Malcolm Campbell. | ||
| R21 | 6 July 1931 | First new 1931 engine, passed final inspection. . Installed in S.6B, S1595, for first flight 29 July. | |
| R23 | 30 July 1931 | Delivered to Supermarine. Fitted in S.6B S1596, for first flight 12 August. | |
| R25 | 9 September 1931 | Fitted in S6B S1596,. | Royal Air Force Museum London. Rolls-Royce R (exhibit) at the Royal Air Force Museum London navigator.rafmuseum.org. Retrieved 15 October 2009. |
| 13 September 1931 | Fitted to the S.6B, S1596 for first Air Speed Record runs flown by Flt Lt George Stainforth. | ||
| To George Eyston for Thunderbolt land speed record car.Holter 2002, p. 43. Later to RAF Cranwell. | |||
| R27 | 8 September 1931 | Flown in S.6B S1596, | London Science Museum. |
| 29 September 1931 | Fitted in S.6B S1595 (the Trophy-winning aircraft), and gained the air speed record at . | ||
| To George Eyston for the Thunderbolt land speed record car. | |||
| R29 | 3 September 1931 | Third 1931 race engine delivered. | |
| 13 September 1931 | Installed in S.6B, S1595, for the Schneider Trophy Contest. Aircraft flown by Flt Lt John Boothman won the Trophy | ||
| R31 | 13 September 1931 | Last of batch of 6 made for 1931 contest.Holter 2002, p. 31. Installed in S.6A N248 as reserve aircraft for the Schneider Trophy Contest | |
| R33 | 1933 | Development engine for the last two land speed record (LSR) engines. Installed in Campbell-Railton Blue Bird during construction at Brooklands.Holter 2002, p. 71. | |
| R35 | Development engine for the last two LSR engines. Thought to have been used as a mock-up model for display only. | ||
| R37 | Late-1933 | Bought from Rolls-Royce for £5,800 by Sir Malcolm Campbell for use in the Campbell-Railton Blue Bird car. | Filching Manor Motor Museum |
| July/August 1937 | Fitted into Blue Bird K3 by Saunders-Roe on initial build, later overheated and damaged due to cooling scoop problems.Holter 2002, p. 29.Holter 2002, p. 44. | ||
| 17 August 1949 | In Blue Bird K4 with Donald Campbell. This replaced the Goblin jet engine installed unsuccessfully by Sir Malcolm Campbell.Holter 2002, p. 30. | ||
| R39 | 1935 | "Factory spare" lent by Rolls-Royce to Sir Malcolm Campbell as a back-up (he already owned R37) for the 1935 land speed record attempt. | |
| Option given to George Eyston to use this engine as a spare for the Thunderbolt car. | |||
| July/August 1937 | Replaced R37 in Blue Bird K3 by Sir Malcolm Campbell. | ||
| 1 September 1937 | Takes water speed record in K3 at . | ||
| 17 August 1938 | In Blue Bird K4 raises water speed record again to with Sir Malcolm Campbell. | ||
| 19 August 1939 | In Blue Bird K4, new record of by Sir Malcolm Campbell on Coniston Water. | ||
| 10 June 1951 | In Blue Bird K4 with Donald Campbell, after R37 was damaged by overheating.Holter 2002, p. 84. | ||
| 10 September 1951 | Sank at Coniston Water in Blue Bird K4 during water speed record attempt by Donald Campbell, salvaged, hull broken up and burnt on the shore. Suspected structural failure of the boat's engine mounts after driveshaft breakage at . |
These three engines are the only ones listed by the British Aircraft Preservation Council/Rolls-Royce Heritage Trust. The Solent Sky museum's S.6A, N248, (a competing aircraft in the 1929 race as an S.6, and stand-by for the 1931 race, modified as an S.6A) does not contain an R engine.Ellis 2004, p. 75.
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