Mohawk & Manitou part 2

In this second part of his article on the two early Sunbeam V12 racing cars the noted authority on Sunbeam history, Anthony S. Heal, deals with the big post-war Manitou-engined model. It was the fastest car in the World in its day, surviving a trip through the Railway-straight fencing to put the Brooklands’ lap-record to 123.39 mph in 1922 and thrice breaking the World’s LSR, leaving this at 150.76 mph in 1925. It can now be seen in the National Motor Museum at Beaulieu. — Ed.

Throughout the war from 1914 to 1918 the Sunbeam factory was fully occupied in the design and manufacture of aero engines. The building of 16 hp Sunbeam cars and ambulances for the War Office had to be transferred to the Rover Company and the 200 hp Sunbeam-Coatalen Arab aero-engines were built under licence by four other firms. Licences were also granted for making Sunbeam engines in America and in Switzerland. More than a score of different types of Sunbeam-Coatalen aero-engines were designed and built and by 1919 the company had gained considerable experience of engines with six, eight, 12, 18 and 20 cylinders ranging from 150 to 800 hp.

With the return of peace in 1918 and the revival of motor racing it was understandable that Louis Coatalen should return to his conception of a 12-cylinder car capable of winning races and creating new World’s Records. Brooklands re-opened in 1920 and early in the year there were rumours about the car that the Sunbeam Company were building.

In May the first outline description appeared and the new 12-cylinder 18-litre single-seater was entered for the June meeting at Brooklands. It was not a very auspicious debut, for in a practice run on the morning of the race day. H. G. Hawker, the well known and experienced pilot, had a tyre burst when coming off the Members Hill banking and the car went through the corrugated iron fence on the Railway Straight. He was unhurt and the Sunbeam not seriously damaged. His second appearance at the August meeting was also disappointing for he stalled the engine on the starting line and was unable to get it restarted.

The first indication of the new Sunbeam’s potential was at the Gaillon hill climb in France when René Thomas broke the record for the hill at 108.6 mph. The regulations for the event stipulated two-seater bodies for the racing cars so a second seat and a fairing were rigged up on the left side of the Sunbeam’s single-seater body. The Mayor of Gaillon was photographed in this perilous looking seat but he did not occupy it during Thomas’ record climb.

On December 11th an attempt was made on short distance records at Brooklands but the start was delayed and sleet made the track slippery so no records were broken. H. G. Hawker made two runs and despite wheelspin, recorded 124 mph for the half mile and 121 mph for the mile.

When the first announcements about the new 350 hp car were made the Sunbeam Company were at pains to point out that the 12-cylinder engine was not a Sunbeam aero-engine but had been specially designed and made for the car. Louis Coatalen wrote in the “Brooklands Year Book 1924” that “the engine specially built for this car was based, so far as its design was concerned, on the very latest development of the Sunbeam `Manitou’ aviation engine. To adapt it for racing-car work several modifications were made.” Even if it was specially built for the car it certainly reflected the experience of aero-engines gained by the Sunbeam Motor Company during the war.

The aluminium cylinder blocks were cast in groups of three, set in two banks of six at an included angle of 60°. Steel liners and aluminium pistons, with three compression and one scraper ring, were provided. Unlike the “Mohawk” engine, in which the big ends of each pair of connecting rods worked side by side on the crankpin, articulated rods were used which resulted in a worthwhile reduction in the length of the crankshaft. It also produced the result that the stroke of one bank of cylinders was a bit longer than the other. Officially the bore and stroke were recorded as 120 mm x 135 mm but Louis Coatalen in the Brooklands Year Book says “the bore is 120 mm and the mean stroke is 138.5 mm and the total cylinder capacity 18,322 cc”.

The crankshaft, camshafts and connecting rods were all machined from solid billets of nickel-chrome steel. A train of spur gears at the front of the engine drove a camshaft on each bank of cylinders to operate one inlet and two exhaust valves in each cylinder. The latter were actuated by rockers as on the Sunbeam “Arab” aero-engine. Two twin-choke Claudel Hobson HC7 carburetters were mounted between the cylinder blocks and two 12-cylinder BTH magnetos, driven from what the French so picturesquely describe as the “cascade of pinions” of the timing gears at the front of the engine, fired two sparking plugs in each cylinder. The crankshaft, which was drilled for pressure lubrication, was carried on seven whitemetal-lined bearings. Dry sump lubrication was effected by three gear type oil pumps with an oil tank in the tail of the car.

The engine, multi-plate clutch and separate 4-speed gearbox were carried in U-shape sub-frame which was mounted at three points on the main chassis frame as the 1914 Grand Prix cars. A clutch stop was fitted to the clutch shaft and a large transmission brake behind the gearbox was operated by a long external hand lever. The universally jointed propeller shaft drove the bevel rear axle with a ratio of 1.5 to 1. No differential was fitted. The torque and thrust were taken by the half-elliptic rear springs, which were mounted on outrigger brackets further apart than the front springs. Two Hartford and two Houdaille hydraulic dampers were fitted to the rear axle with a pair of Hartfords at the front.

The steering box was centrally mounted behind the cylinder blocks with a universally jointed horizontal shaft to the off side drop arm. Early photographs of the car show steel artillery wheels but after H. G. Hawker’s accident at Brooklands, Rudge Whitworth wire wheels with 880 x 120 Palmer Cord tyres were used. The narrow single seater body had a short tail which contained the petrol and oil tanks and a “wind cutting cowl” was fitted in front of the radiator. Louis Coatalen quoted the power output of the 12-cylinder engine as 357 bhp at 2,500 rpm.

The second appearance of the 350 hp Sunbeam at Brooklands during the Easter meeting 1921 was nearly as disappointing as the car’s debut at the previous June meeting. Kenelm Lee Guinness had to retire during the Lightning Short Handicap due to gearbox trouble. But K.L.G. was not going to be beaten so the box was dismantled and first and second gears were put out of action leaving only third and top. Rather than disappoint the spectators, who had come with expectations of seeing the big car in action, K.L.G. made three attempts before he succeeded in getting the car off the starting line in third gear. Once away he made up for lost time with a lap at 120 mph. He was timed through the half-mile at over 130 mph. Although he had no chance of winning, by dint of a magnificent display of virtuosity and speed, he took second place to Count Zborowski’s Grand Prix Mercedes. The car’s capabilities had been well demonstrated and had made a great impression on those present.

Due to their pre-occupation with their entries for the Grand Prix de l’A.C.F., the Sunbeam Co did not again enter the 12-cylinder car at Brooklands until the September meeting when Lee Guinness again drove. He took third place from scratch in the Lightning Short Handicap and gained second in a very close finish to the Long Handicap, during which he averaged over 111 mph and covered the half mile at 135 mph. At Easter 1922 Jean Chassagne scored the Sunbeam’s first victory in a Brooklands race when he won the Short Handicap at 103.83 mph after lapping at 114 mph. But tyres were still the limiting factor for in the Long Handicap (8 1/2 miles) he had to slow up, when about to take the lead, due to the off side rear tyre losing its tread.

K. Lee Guinness also experienced tyre failure at the May meeting. After winning the Short Handicap from scratch at 111.42 mph he had his off-side front tyre burst on the Byfleet banking during the Long Handicap. The tread and the inner tube wrapped themselves around the stub axle which caused the car to swerve but Guinness managed not only to hold it on course but to finish the race in third place. His best lap was at 122.47 mph and his speed over the half-mile was 134.33 mph.

A successful attack was made on 18 May on short distance World’s Records. Standing start records for the half-mile, 1 kilometre and 1 mile were taken and flying-start records were set up for the same distances as well as for two miles. Runs were made in both directions which entailed driving the reverse way of the track. Guinness found coming off the Byfleet banking on to the Railway Straight rather tricky, as had Frank Newton with the Napier “Samson” during his record runs in 1908. The Sunbeam’s mean speed for the half-mile (fs) was 136.05 mph reaching 140.58 one way. The next day new World’s records were set up for 5 miles (116.75 mph) and 10 miles (113.13 mph) but tyre trouble supervened and the record run had to bc abandoned but not before a new Brooklands lap record at 123.3 mph had been achieved. This beat Nazzaro’s controversial record lap at 121.64 mph in the big FIAT in 1908.

The 350 hp Sunbeam had a charisma which made a strong appeal to some of those who drove and tended it. Among them was Sammy Davis who persuaded Louis Coatalen to let him try a few laps with the car. He wrote an account of his run in The Autocar for May 20th, 1922. He described it as too wonderful for words, a most inspiring experience. He found the driving seat unexpectedly comfortable so that opening the throttle was’like being hurled into space in a good armchair. He lapped at 110 mph and touched 140 mph on the Railway Straight. “To drive it at speed provides a sensation of a lifetime and a feeling of sheer exhilaration.

Bill Perkins, who was in charge of the car and tended it so assiduously, and Kenelm Lee Guinness, who got the best out of it on the track, had an admiration and affection for the big Sunbeam. Malcolm Campbell, too, soon became hooked on it for he persuaded Louis Coatalen to let him drive it at the 1922 Speed Trials on Saltburn Sands where he put up the fastest time of the day at 127.1 mph. He also made an attack on the record for the flying kilometre, achieving a mean speed of 134.07 mph (138.08 mph one way), thus improving slightly on Guinness’ World’s record at Brooklands in May. The Yorkshire Automobile Club’s timing had been by means of synchronised stop watches and Campbell was sorely disappointed when his performance was not recognised by the Commission Sportive as a World’s record. But he was very impressed by the Sunbeam’s performance and pressed Louis Coatalen to sell the car. Coatalen declined and its next public appearance was at the Essex Motor Club’s Speed Championship Meeting at Brooklands at the end of September when Lee Guiimess carried the unlimited (over 5-litres) Championship. He took the lead with a first lap at 116.64 mph and then eased off to a mere 110 mph. He won easily from J. G. Parry (Leyland 8) at 104.04 mph. It was his last race with the big Sunbeam, which he handled with such skill after its early performances. It remained in its shed at Brooklands for many months until the 1923 racing season had got under way.

Campbell was convinced that Sunbeam’s full potential had not been realised and that, on a course which allowed a longer run-in, to reach maximum speed before entering the timed section, it could attain higher speed than was possible at Brooklands. He repeatedly renewed his request to Coatalen. In June 1923 the Danish Automobile Club were to hold International Speed Trials on the beach at Fanoe which offered much more favourable conditions and eventually, barely a fortnight before the event, Coatalen agreed to sell. Campbell with Leo Villa and Harry Leach spent a hectic week getting the car raceworthy, for it had been neglected since its last run in September. The scavenge pump was broken and the three indirect gears on the mainshaft were stripped and “chawed” (to use Campbell’s expression). The Sunbeam factory offered to work non-stop to make a new shaft and gears (which were machined from solid steel all in one piece) if a suitable billet could be procured from Sheffield. Coatalen had provided the services of a stout-hearted Sunbeam mechanic, Webster, who drove through the night from Horley to Sheffield, obtained the steel and delivered it to the Sunbeam works at Wolverhampton next morning. The car meanwhile was loaded on to a train to Harwich and Campbell, with his two helpers, went to Liverpool Street Station to catch the boat train. Just as the guard blew his whistle Webster appeared, running, carrying the new gearbox shaft, and climbed aboard at the last possible moment. In his book “My Thirty Years of Speed” Sir Malcom Campbell gives a full account of the many problems and difficulties which the team encountered but the Sunbeam was got ready barely an hour before the start. Campbell had no opportunity to make a test run but the car was in good form and, with a two mile run before the timed kilometre, its mean speed each way of the course was 137.72 mph. The fastest run one way was at 146.4 mph, the best speed of the meeting. Although Campbell returned as “Fanoe Champion 1923” the Commission Sportive refused to recognise the new record as the timing apparatus had not been previously approved by them.

For its power the big Sunbeam was comparatively light (3,551 lb) and on full throttle at high speed it had a tendency to yaw to the right, proceeding crabwise, which was dangerous and called for considerable effort from the driver to hold the car on a straight course. During the winter a new body, with a longer tail and a headrest for the driver, was built and discs were fitted to the wheels to improve the aerodvnamics. To gain some degree of supercharge at high speed, a forward facing air duct was added to the twin inlets of the Claudel-Hobson carburetters but this was not found satisfactory. By June 1924 the car was ready and, before going to Fanoe in August, Campbell accepted an invitation to compete at Saltburn again. E. A. D. Eldridge with his big FIAT “Mephistopheles” and Parry Thomas with the Leyland were also to take part. Electrical timing apparatus had been installed, which was operated by the cars breaking a thread stretched across the course at the finishing line. It was not altogether satisfactory but it was an improvement on the manual method of the previous year. The Sunbeam was going well and with the new long-tailed body felt much steadier. Although the new apparatus failed to function on his first run, hand timing showed that Campbell had achieved 142.2 mph. His return run was at 143.39 mph. Discouraged by the failure to properly record his time, coupled with the drizzle and the incoming tide, Campbell packed up and left. Eldridge’s speed of 134.81 mph was recorded, but it seemed unlikely that it would be officially recognised as a World’s record.