The Development of the Rolls-Royce R-Type Engine recounted by The Editor
“The Battle of Waterloo may, or may not, have been won on the playing fields of Eton, but certainly the Battle of Britain was won at Brooklands and Calshot.”
The motor-racing enthusiast, being invariably keen to the extent of fanaticism, craves more than most to justify his interest and devotion in the eyes of ordinary, uninspired mortals. Yet, to do this is an unwelcome and usually fruitless task. The sane interpretation of the now classical and rather sweeping saying, “The racing car of today is the touring car of tomorrow,” (who, by the way, originated it ?) is clear enough to you, but is extremely difficult, if not impossible, to interpret for one’s horse-minded, rail-addicted elders. The advertising value of racing is easier to explain, its use as a means of increasing Axis-prestige even more so—recent happenings being fresh in the nation’s memory— but neither seems quite laudable as a complete justification for the game. In considering the development work put into the R-type aeroplane engine by Rolls-Royce Ltd, a dozen or so years ago, that Great Britain could win and retain the Schneider Trophy, true justification for racing comes to light. The remarkable care, attention, skill and devotion that went into the perfection of this particular Rolls-Royce engine comprises a story of endeavour as fine as that in any other sphere of human achievement. We see the truly artistic aspect of internal-combustion engineering and, as it is not in the least difficult to appreciate that the lessons learned from developing the R-type contributed vitally to the perfection of the “Merlin” engines which powered the Hawker Hurricanes and Supermarine Spitfires which defeated German aircraft in the Battle of Britain, a complete and glorious justification is offered for striving to win a seaplane race and break the Air Speed Record. As the Rolls-Royce “Griffon” engine, which has recently gone into service with the RAF, and which will be nicely in time for the Second Front, has exactly the same cylinder capacity as the R-type of 1931. This seems a most opportune time to recount the story of the latter’s development.—whether or not justification for the Sport is deemed necessary !
In 1927 this country won the Schneider Trophy race at Venice, Ft-Lt Webster, in a Supermarine S-5 with a 900-hp, geared Napier Lion engine, averaging 281.65 mph for the 2171/2 miles. For 1929 we had to stage the contest, and found a course at Ryde, IOW. It was decided that more powerful engines would be desirable for the Supermarine entrants, and Rolls-Royce Ltd, were asked to get busy. The British Government was, for once, interested in racing—mark the results ! The Rolls-Royce RAF engine at this time was the 825-hp, 2,000 rpm.”Buzzard,” and on this the racing engines had to be based, as time did not permit of design and development of an entirely new engine. A new-type supercharger, raised compression ratio, higher crankshaft speed and a more compact outline were applied to the “Buzzard” and 1,900 hp was realised at 2,900 rpm, from an engine weighing 1,530 lb. It is now history that F/O Waghorn, flying a Supermarine S-6 with the new engine, won the 1929 race at 328.63 mph for the 218 miles. In the course of the race WO Atcherley, in another S-6, set up a new 100 kilo world’s record at 282 mph, and after the race Sqdn-Ldr Orlebar broke the World’s Speed Record on two occasions with an S-6—first at 355,8 mph, later at 357.7 mph (both averages of double two-way flights over three kilos).
If we could win the race for the third year in succession the Schneider Trophy would rest for ever in this country. In view of this, it is to the Government’s extreme discredit that it decided not to finance the 1931 contest. In the end the late Lady Houston very sportingly put up 100,000, and the race became possible, but as only a little over six months remained, again new engines could not be built and Rolls-Royce Ltd, was forced merely to further develop the 1929 type, for installation in two of the original S-6 seaplanes, slightly modified—now called S-6A—and two new S-6B machines. It is with the story of the development of the 1,900-hp R-type of 1929, in this limited period of time, that we are now concerned.
To obtain the required horse-power increase with no increase in fuel consumption and no decrease in reliability, it was decided to increase engine speed, sc gear ratio, and the size of the air intake. While re-designing went on, special preparations were made for testing the new engines. Heenan and Froud built a special water-brake, which did not suffer from uncontrollable variations of load, blade erosion or water-boiling. The test house was freed of exhaust gases by using a “Kestrel” engine to blow air through the building, while electric fans in the roof cooled the crankcase and exhaust plugs of the engine on test ; before these precautions the air-intake temperature of the engine on the bed rose by 10 deg C, and power chopped by 100 bhp, also, the testers felt ill. Then, to imitate the air speed that the R-type wouId experience in flight, another “Kestrel” drove a 3,000 rpm fan which made a draught of 400 mph, pitot heads measuring the air-intake speed. Yet another “Kestrel” drove a supercharger test rig. The design department, the experimental department and the experimental fitting and machines shops, all at Derby, were the three departments of Rolls-Royce Ltd, responsible for the work, and they were directly under the control of the late Sir Henry Royce at West Wittering.
When an “R” was run-up for test eight men had direct charge of it—one at the engine controls, one at the waterbrake controls, one checking the tachometer readings, one checking cooling, one checking fuel consumption, one in charge of the “draught” “Kestrel,” one in charge of the “double boost” “Kestrel,” and, finally, the chief tester, who gave all orders and logged the readings and made out test reports. Even the public cooperated, as the Mayor of Derby appealed to his townsfolk to overlook the noise of the engines running with stub exhausts, at odd hours of the day and night, for a week before the race ! Certainly the Rolls-Royce experimental staff gave their wholehearted co-operation. For seven months or so they worked all hours, and many did frequent 24-hour spells, without complaint.
Some idea of the conditions in the testhouse during a half-hour full-throttle run can be gauged when it is said that, using ordinary cotton-wool to plug the ears, you were deaf for 24 hours afterwards and your head buzzed for a couple of days. Milk was served to the test-bed staff twice a day. The normal running-up procedure called for a period of 5 min idling at 1,000-2,000 rpm to stabilise temperatures before opening up ; the engines were started by a belt-drive from an electric motor. Lubricating oil was pre-heated by steam. The man in charge of test and development was a “mere lad” of about 26. J Pettitt-Herriot acted as Air Ministry liaison officer between Rolls-Royce Ltd, and Supermarine Aviation Works Ltd, from April to August, sorting out the installation problems, and thereafter was stationed at Calshot, where he was responsible to the Air Ministry for the installation, inspection and testing of the engines. The Derby works naturally sent a staff to Calshot, and in order to make the most a the flying time available, a high-speed lorry, in the form of a “Phantom I” Rolls-Royce car chassis fitted with an engine-carrying cradle, stood by to transport used engines to Derby and return to Calshot with reconditioned or new ones. The journey usually took about six hours, including loading.
The 1931 engines were required to run one hour at full throttle without blowing up. By the end of April a 20 min run could be achieved. By the middle of July a 30 min run was possible. On August 3rd an R-type kept going all-out for 58 min before the carburetter air-pipe split, covering everyone around with aluminium rivets—another crankshaft had broken as it had previously after 34 min. Then, on August 12th, the first non-stop hour run was accomplished, at an output of 2,350 hp, from an engine weighing 1,630 lb, equal to 11 oz per bhp, an achievement which, we believe, has never been surpassed. The achievement had been no easy one. New crankshaft and rods were used, and much re-designing was necessary before these would stand up and the white-metal big-ends take the load—nine tons on the centre main ! Side lashing of the big-ends, causing bearing failure, had to be combated and then, although engine speed had been increased by only 300 rpm, two or more valve springs would break after ten minutes’ running. A special rig was made and, after much experimenting, somewhat revolutionary springs were evolved which gave no more trouble. Another bother was loss of oil through the breathers. After one 25 min run the test-house was smothered, consumption being 112 gallons an hour. Weeks of research on combinations of different scraper rings and breathers reduced this to about 14 gallons an hour, also reducing oil temperature to approximately 80° C, inlet and 140° C outlet. The magnetos were a cause of concern, because vibration affected them and oil found its way right along the rotors to the points ; in the end every magneto nut was split-pinned. Lodge designed special X170 plugs which never gave any trouble, although when examined microscopically the majority were found to contain small metallic inclusions. The race sets were given a duration run and then sent back to Lodge for examination, re-polishing and new outer bodies. On one occasion a rod came out through the crankcase at 5 pm. The engine was off the bed by 5.30, dismantled by 7 pm and new drawings were got out and new rods put in hand between 8 and 9 pm. Before lunch next day the newly-assembled engine went on test. An elaborate history of all the components in each R-type engine was kept, so that the “running-life” of any part could be estimated, and even when two engines broke up in 24 hours the Rolls-Royce experimental department refused to panic. Incidentally, after the endurance run the engine was fully stripped and examined and was found to be in well-nigh perfect order. Outside the test-house the ground was quite hot, and in one place hollowed out, 15 ft away from the exhaust stubs ! It was necessary to mix accurately about 200 gallons of fuel before each test-run, some 80 gallons being needed to get any circulation through the system. Consumption at full throttle was approximately three gallons a minute.
The engineers at Calshot had no picnic either. Much research was necessary to get the fuel system functioning correctly, and Supermarines built a complete petrol installation rig for experimental purposes, carried out under actual flight conditions of speed and temperature. Installation of an engine in the fuselage caused many headaches. The bottom of the carburetter had a clearance of about 0.15 in longitudinally, and Superinarines constructed a special wooden “mock-up” of the front part of the aircraft and sent it to Rolls-Royce, Ltd so that each engine could be tried before delivery. Much transference of piping, etc, from one engine to another, with appropriate testing, was necessary when changing engines, and when all was ready it took six operatives about half an hour just to lower the R-type down and back the last six inches on to its bearers. Slow running at approximately 500 rpm was ensured by running each engine at Derby with a similar propeller to that used at Calshot. In damp weather the engines in the seaplanes would not start, due to moisture in the compressed air wetting the plugs, but, once started, the same plugs could be used throughout. Special methods of filling the wing radiators had to be resorted to, in order to obviate air pockets. When an engine was started it was run for 5 min in weak mixture at approximately 1,000 rpm, and the oil coolers were vented. The mixture was then richened and the throttle opened to about 2,150 rpm and 22 lb/sq in boost. Flight tests showed an air-intake velocity of 407 mph and enabled the double boost at Derby to be increased accordingly. The oil used was pure castor. The fuel, supplied by the Ethyl Export Corporation, in conjunction with Rolls-Royce Ltd, presented special problems. It consisted of petrol, benzol and methanol, and it straightaway dissolved the jointing compound in the tanks and choked the litters. Then the presence of only 0.4 per cent of water completely ruined it, and some very complicated procedures had to be drawn up for testing it and applied, in two ways, to samples taken from the barrels of fuel, from the samples taken from the float tank before and after every flight and also whenever fuel had been in the tanks for over 12 hours. If the water content exceeded 0.3 per cent the fuel was discarded. Similar elaborate processes were evolved for checking fuel, oil and coolant. consumptions, etc. In all, the race engines spent 10 hr 17 min in practice flights without a single failure.
It is now a matter of history that Ft-Lt JN Boothman flew his S-6B carefully over the 217.5-mile course at an average speed of 340.8 mph, to win the coveted Schneider Trophy for this country for all time. Before the race the practice engines were replaced by the final engines, and these were given a short ground run to check installation. A short test-flight was then made on each machine to check for full performance. The plugs were then removed and each cylinder bore inspected through the plug holes. New plugs were then fitted, the oil, boost, and fuel-pressure gauge pipe-lines blanked off to obviate trouble should they fracture during the race, the mixture lever set and locked and a final ground run given to test the new plugs. The fuel system was cleaned and filled with 140 gallons, the coolant header tank filled to leave 11/2 gallons air-space, and 161/2 gallons of oil, heated to 600 C. in special tanks on the pontoon, put in last of all. Boothman’s S-6B took 8 min to warm up on the pontoon, taxi into position, and take off. It was air-borne in 36 sec and landed 41/2 min later. To comply with the race regulations it stayed on the water with the engine idling for 4 min, and then took off in 37 sec. It entered the course at 3,200 rpm and a water outlet temp of 88 C. After 11/2 laps this rose and the engine throttled back to 3,100 rpm to maintain a steady water temp of 95 C. The 7 laps took 38 min 221/2 sec. 110 gallons of fuel, 111 gallons of oil and no water was consumed. The long trail of black smoke behind the machine increased as time wore on, probably because of wear in the scraper-rings. When stripped, neglecting the fatigue factor, the winning engine appeared quite ready to repeat, its magnificent and historic performance.
More was to follow! Using a petrol- less benzole, methanol and lead fuel to enable a greater throttle opening to be employed, the horse-power was increased to approximately 2,600. The carburetter passages were opened up slightly, petrol header-tank pressure raised and the fuel pumps run faster ; the fuel consumption rose from 0.6 to approximately 0.85 pts per bhp hour. This engine was installed in the S-6B No S1595 on Sunday, September 27th, and on Tuesday. September 29th Ft Lt Stainforth set up a new Air Speed Record at 408.5 mph. His four timed flights being at 415.2, 405.1, 409.5 and 405.4 mph, respectively. Tests had first to be carried out with the revised fuel system, and it was found also, that the induction pipe temperatures were so low that slight building-up trouble was experienced in the supercharger casing. This resulted in the engine running on six cylinders until it was thoroughly warm, and the vibration was so bad that it was feared that the rigging of the aircraft would be affected. Consequently, a special starting proceedure was adopted, the engine being warmed-up at slow speed until the water temperature reached approximately 83 C. It. was then shut down, the fin oil-tank covered up, and fuel drained completely from the supercharger casing. The engine was then restarted and given full throttle straight away, this method being adopted actually on the pontoon, on which Sqn Ldr Orlebar, Mr. Mitchell (designer of the. S-6B), Mr. Lappin (of Rolls-Royce Ltd) and many others were in attendance. For the record 100 gallons of fuel and 13 gallons of oil were carried. Take-off took 43 secs, and the first run over the measured section was made in level flight to check the new propeller. Afterwards Stainforth dived in at full throttle (3,400 rpm), reached a maxinium indicated speed of 420 mph, which fell to 405 mph at the end of the course. The engine was throttled down after each run and the average water temperature was 90° C, never exceeding 93 C. The flight lasted 27 min and fuel consumption was 913/4 gallons, or approximately 31/2 gallons per min. Thus the air-history of the Rolls-Royce R-type engine included bringing the Schneider Trophy permanently to Britain and enabling man to exceed 400 mph for the first time.
The engine was a V-12, 6 in by 6.6 in, a stroke/bore ratio of 1.10 to 1. The swept volume per cylinder was 186.6 cu/in, a total of 36.7 litres, and the clearance volume per cylinder 37.32 cu/ in, giving compression ratio of 6 to 1. The normal speed was 3,200 rpm, at which the piston speed was 3,520 ft per min, the bmep 254 lb/sq in, and the supercharger speed 23,904 rpm. Boost pressure with 400 mph intake blast was 33 lb/sq in, and the output was 2,300 bhp. The weight, dry, was 1,640 lb, a weight/power ratio of 0.51 lb per bhp, which, we believe, has never been bettered. Normal fuel consumption was 14 gallons per hour, and oil pressure 120 lb/sq in. The overall length was 8 ft 4 in, and the reduction gear ratio to the rh tractor propeller 0.607 to 1. The ignition timing was 37° before tdc, and the valve timing was : inlet opened 23° before tdc ; closed, 57° after tdc ; ex opened 60° before bdc ; closed, 23° after tdc. The supercharger absorbed some 360 hp at full throttle.
In 1930 Sir Henry Segrave had had two R-type engines installed in Lord Wakefield’s “Miss England II.” The boat struck a piece of driftwood while in full flight on Lake Windermere, and F Halliwell, chief tester at the Rolls-Royce experintental department, was killed instantly, Segrave dying in a few hours. Nevertheless, the record had fallen, at 98.76 mph. In 1931 Kaye Don took the salvaged boat to South America and achieved 103.49 mph, and, later, at Lake Garda, in Italy, 110.22 mph. Lord Wakefield then built “Miss England III,” with two of the latest R-type engines, and on Loch Lomond, in July, 1932, Kaye Don put the record to 119.81 mph. Then came Sir Malcolm Campbell’s attempts with “Bluebird,” powered with a single R-type engine. In 1937 he did 129.5 mph on Lake Maggiore, and later set the record to 130.86 mph, on Lake Hallwil.
Campbell was the first person to install the R-type engine in a car. At Daytona, in 1933, his Campbell-Special “Bluebird” established a new Land Speed Record of 272.46 mph and, with improved streamlining, 276.82 mph in 1935. Then, in September, 1936, Campbell went to Utah and recorded 301.13 mph—the first time a car had exceeded 300 mph.
As might be expected, Capt George Eyston now took a hand. His 6-wheeled, 6-ton “Thunderbolt” was given two R-type engines, one from the 1931 Schneider Trophy race-winner, and the other from the Air Speed Record S-6B. In 1937, at Utah, Eyston set the record to 312 mph and, re-designing a bit, to 345.5 mph in 1938, and finally, before he was vanquished by Cobb, to 357.5 mph. Incidentally, it seems the engines used may have been somewhat detuned, as the cars total bhp was quoted as approximately 4000, whereas one would have expected at least 4,700.
Thus was the R-type developed from its 1929 form, so that in 1931 race guise it gave 21 per cent increased power for a weight increase of only 61/2 per cent. Quite obviously the lessons learned in developing the R-type proved invaluable when the “Merlin” engine, in all its many mks, came to be built. Now, in readiness for the Second Front tasks, comes the “Griffon,” of equal capacity to the “Buzzard” and R-type, and, as announced before the Second Front opened, able to give 1,750 hp for take-off and 875 hp at economic cruising speed for a dry weight of 1,900 lb, or 1.09 lb/bhp, which compares with the 1,600 take-off hp, and 800 cruising hp of the more highly-developed of the 27-litre “Merlins,” which weigh 1,800 lb dry, or 1.12 lb/bhp. Britishers can say in all sincerity : “Thank God we have Rolls-Royce Ltd.”