When AC Cars Alarmed Bentley Motors

Back in 1922, one of the most meritorious achievements at Brooklands Motor Course was the “Double-Twelve-Hour” record established by Capt John Duff in his own 3-litre Bentley four-seater, at an average speed of 86.79 mph. This fine performance by the driver who had previously raced the old 10-litre Fiat and who had nearly met his end when the 200 hp Benz had taken him over the top of the banking is well documented. Nor have I any intention of again debating what the Bentley’s chassis number was!

The “Double-Twelve” aspect of this 1924 record implies that, to appease those residents living close to Brooklands who objected to the noise therefrom (although they had mostly come to live there after the war, knowing full well that Brooklands had been active since 1907, a problem that faces the proposal to revive motor-racing at Goodwood at the present time — how selfish people can be!), the car had been locked away during the night, so Duff’s run had had to be done in two spells of 12 hours each. For those not conversant with Brooklands (but what Motor Sport reader isn’t!) it has to be explained that when S F Edge made his epic 24 hours run at 65.91 mph on the 60 hp Napier, driving through the night and using 24 Dunlop Tyres, this was in 1907, and even then it started some complaints.

No matter! Duff’s “D12” record was a splendid show. He had been out of the Bentley for only 15min 31sec, doing all the driving himself, the car was not far removed from catalogue specification, it ran virtually trouble-free, and consumed only six Pirelli tyres (one burst). This performance must have materially increased interest in the comparatively new 3-litre Bentley, for which Duff was an agent.

“D12” records are shown in the table. In 1922 Duff could have claimed World records but he had only registered the many he took in this “D12” stint as British and Class-E records. His victory at Le Mans in 1924 with Frank Clement in his own lone Bentley was another great boost for the by-now popular 3-litre sports car from Cricklewood. But then the Montlhery Autodrome opened near Paris and with no noise restrictions (it was some eight miles from the city and the French were more tolerant of motor-racing than those stuffy English householders) it was possible to run for an unbroken 24 hours, as Edge had done at Brooklands in 1907 using the car’s headlamps and roadmenders’ lanterns round the Brooklands’ perimeter. The surface of the new French track was also smoother than that of the already-ageing Brooklands concrete. Both factors encouraged record-bids and that for the full two rounds of the clock was seen as a greater feat of physical and mechanical endurance than having a break in between. If a driver elected to tackle the task without a relief, this was obvious; and I suppose it could be argued that even the car was better off on a continuous run, unless some means had been provided for heating its engine after the night’s rest it had on a “D12” attempt. (No work on the car was permitted, of course, during the period while it was locked away.) So at the Paris track the 24-hour record was very much a target to aim at.

First to achieve this were Gros and Martin, with a 2-litre 16-valve two-seater Bignan. They took the 24-hour record in 1924 at 75.86 mph (1820 miles). Had Capt Duff claimed the World record in 1922 (he had done 2082 miles) they might have achieved only Class-record honours, although it is uncertain whether the FIA would have seen fit to make a distinction between a “D12” and a 24-hour run. As early as January 1925 Vizcaya had hopes of the 24-hour accolade, and started with a Bugatti. On his solo drive he broke some intermediate figures, but in the night ice formed on the steep Montlhery banking and after he had been circulating for nearly ten hours a tyre burst and under the slippery conditions the Bugatti slid downwards and rolled over several times. Vizcaya was only bruised but his run was over. (For 500 miles he had averaged 82.4 mph.) Meanwhile, the track measurers had revised the Bignan’s record to 77.3 mph (1855.02 miles) and it had managed one hour at 82¼ mph.

Next to try was Sunbeam, using the GP 2-litre which had won, driven by Segrave, at San Sebastian. No solo effort this. He was to be joined by Conolli and Parry Thomas, all three drivers conversant with the track, Thomas with the big Leyland. But 24 hours is a long time for a racing car to cope with. The hope had been to set the record to 100 mph, stopping every four hours for fuel, four fresh tyres and a fresh (?) driver. Segrave had a riding mechanic with him when he started off first, as the senior driver. However, February snow was in evidence and although the speed was up to better than 102 mph after 500 km, heavier snow showers and engine trouble brought Thomas to a final halt, after he had been lapping very fast, at 4hr 35min 26sec.

It was by now apparent that Renault was keen to possess the coveted 24-hour record, with a four-seater 9.1-litre 45 hp car, which would be good publicity for the sports version of their mammoth production chassis. They allocated the job to Garfield and Plessier, the latter their Works Manager. They kept going for quite a time, securing 17 honours, at not far short of 104 mph for 500 miles, on a preliminary run.

It is now that AC comes on the scene. The little Thames Ditton concern had the audacity to send over a 2-litre six-cylinder car and Thomas Gillett, their works manager, for him to make a solo onslaught on this tough-to-beat target. Renault felt it justifiable to wait a while before making another attempt but they were unwise… Gillett was not exactly a racing driver although he had assisted with shorter-distance AC records at Brooklands. He now had the support of S F Edge the AC factotum, assisted by Sidney Smith, ex-Napier, the Hon Victor Bruce and Norman Freeman, Dunlop’s Competition Manager. Just as well, for the driver had forgotten to bring his all-important competition licence and only Edge’s promise that it was valid and that telegraphic proof of this and the AC’s engine size would be obtained from the RAC, enabled the run to start. Throughout it was said that the French official starter was on tenterhooks in case confirmation was not received and he had authorised an unqualified driver to start; it was almost at the end of the 24 hours that the telegram arrived.

Gillett had to wait, anyway, until the racing that May day had ended. He then drove off into the evening, at around 6.50pm, with thunderstorms and rain threatening. But the sports-type AC with its high-sided single-seater racing body and, for Montlhery, a straight-through exhaust system, and no front brakes, ran well and after an hour at 87½ mph Gillett increased his speed. The plan to stop every three hours for petrol, oil and fresh tyres was adhered to. Early on there was a scare when the water level was found to have dropped drastically but as the engine temperature remained if anything low, no action was taken except to check the radiator contents carefully at each subsequent stop and although the ambient heat rose the following day, no trouble occurred. The night had been moonless and very dark and the trackside lighting arrangements not very satisfactory. However. Gillett coped admirably. The new ss 28 x 3.75in Dunlop racing tyres also proved excellent; as a precaution six were changed but they could have gone further.

The 12-hour record fell at 986.58 miles, With Gillett remarkably consistent, his laps varying by only a fraction of a mile hour after hour and the pit stops hardly affecting this. He consumed grapes, biscuits and milk and was massaged as time allowed. The AC was stationary for only 1 hr 4min. The Bignan engineers and drivers were spectators and at the finish their driver Martin was one of the first to offer congratulations. In fact, it was only towards the end of his long and lonely stint that Gillett seemed a little way from his best. But on hearing that he had the World’s 24-hour record at 82.59 mph (1982 miles 119 yds) he brightened up and agreed to continue for a full 2000 miles, at 81.3 mph, the run ending dramatically as another thunderstorm flooded the track. The Bignan’s record had been broken by just over 180 miles, or 5.29 mph. From time to time during the run a Rolland-Pilain, a Panhard Levassor, Parry Thomas’s 1½-litre Thomas Special and Mrs Stewart’s Rudge motorcycle had been allowed on the track but their drivers and rider had done their best not to impede Gillett, who said he found Montlhery faster than Brooklands but more tiring due to the lack of a straight on which one could relax. The AC used Rudge centre-lock wheels, KLG plugs, one of which was changed, Shell petrol fed to a Solex carburettor and Castrol oil.

This wonderful British achievement spurred Renault into action. Soon afterwards their 45 hp four-seater was out and took useful intermediate records. But not that for 24 hours. A nut from the exhaust system came off and flew into the flywheel-fan, causing the engine to overheat, and then the timing-chain broke and two hours were lost in replacing it with one culled from another 45. But Louis Renault had had the four-seater ballasted to full load to qualify the 45 as a sports car. It was afterwards sealed and officially compared with 50 standard 45s, and found to be the same except for bigger jets, a forward-facing air intake and higher gear ratios. Returning to Montlhery the Renault finally raised Gillett’s World’s 24-hour record to 87.63 mph, with the same two drivers.

John Duff now had his try. He may have been sorry that he had not claimed World’s honours for his 1922 “D12” record or he may have felt that another bit of publicity with which to prod potential Bentley customers was due. His one win at Le Mans in 1924 had been aided by Bentley Motors and they now partially sponsored the 24-hour bid. Duff used his own Le Mans car, but equipped with a special Weymann fabric two-seater racing body having hinged side panels to close the cockpit to shoulder height after the driver had got in. The pistons were modified, and two Solex carburettor and Splitdorff magnetos fitted. The streamlined tail enclosed the back seats. Duff was ready by September 1925 but was conscious that the Renault had gone pretty fast. He had Dr Benjafield as co-driver. Their first attempt was marred by heavy rain which reduced visibility, and after the 1000 miles had been done at 97.7 mph, the I2-hour record was missed by 12 kilometres. Time had been lost when No 3 exhaustpipe broke away, and had had to be juryrigged, then caused another stop for more permanent repairs. After 18¼ hours the bottom bevel of the oh-camshaft drive failed and it was all over. I wonder whether John Weller, who designed the AC’s engine, gave a wry smile, remembering how his chain drive with Weller-tensioner had stood up to the full distance? Perhaps not, because the AC Six had gone out again intent on regaining its record lost to the far-larger-engined Renault but mysteriously disappeared without anyone knowing why, although rumours whispered of engine or transmission failure… (Incidentally, Gillett seems to have run a café on the Portsmouth Road, probably after leaving AC Cars when financial losses loomed in 1927. At all events, many years later I had tea there and saw on a wall a framed photograph of what was obviously the 24-hour AC but, as I recall, no-one then knew why it was there…)

At this stage AC Cars of Thames Ditton had proved superior to Bentley Motors of Cricklewood, with Renault in the ascendent. However, as Paris Salon and Motor Show time approached in 1925, Duff was back again, with Woolf Barnato as his co-pilot. This time all went splendidly. The Bentley ran very consistently, at around 59 seconds a lap, or at over 96½ mph. It came in at three-hour intervals for a driver-change and fuel replenishment, but the bonnet remained shut throughout. Only six Dunlop tyres were changed and although fog hampered the drivers during the night the record was taken handsomely, at 95.02 mph (2280.9 miles), a grand show by a 3-litre car. So like all good stories, this one should have had a happy ending, enabling enthusiastic Bentley chaps to sleep soundly in their beds.

It would have had, if W Bentley himself had not set his heart on being the first to put the coveted 24-hour figure to 100 mph or over. Why this record had seemed so important to W is a matter of speculation. Perhaps because Louis Coatalen had criticised him for using what was really a 1914 GP engine in his cars whereas Sunbeam had modern twin-cam power units in their racing cars. Coatalen pressed the point home by finishing second at Le Mans in 1925 with the new 3-litre twin-cam 12-valve sports Sunbeam, in spite of a long wheelbase and cantilever back springs from his touring-type chassis, in a race in which both Bentleys retired. W Bentley would have noted also the intention to try to take the 24-hour record at 100 mph with a Grand Prix Sunbeam and when that failed he was probably inspired to attain this goal, in case Coatalen might try again.

In March 1926 he was ready. A 3-litre Bentley with a very light single-seater body was taken across the Channel, with W himself in command, his drivers Barnato, Benjafield, Clement and Kensington Moir, along with many mechanics and lots of equipment. The body broke up, then rain intruded. But they were at it at last, planning driver changes every three hours. But plug changes were also needed and, although some records were captured, the Bentley was some 300 miles behind the Renault’s figure after 12 hours, and after 16hr 21min a valve spring broke and the valve stem fractured. This elusive trouble persisted, two engines bursting as valves fell into them. W tried again in June 1926 with a third new engine. This time George Duller, the ex-jockey, was in the team but heavy rain stopped play at 16½ hours, although the Renault’s 12-hour record had fallen, at 100.92 mph. Lap speeds of about 102 mph left a very slender margin for the entire run at over “the ton” and it all fizzled out when Duller skidded on the slippery Montlhery banking and hurt himself; a mechanic (Walter Hassan no less, who was to go on to great things in the racing firmament) decided to keep the car going until another driver could be found and also crashed badly, being unconscious for a long time. The team then packed up and returned home. It is said that W had spent months at Montlhery supervising the attempt. But as Bentley Motors was reaching a low ebb at the time and there was the new 6½-litre model to promote, it seems more likely that he made many journeys to and from Cricklewood, which would have been quite possible, with the regular Imperial Airways flights then operating between Croydon and Le Bourget. He always regarded the 24-hour record fiasco as the bitterest of his Bentley memories…

In any case, W must have known that Renault also had their sights on 24 hours at over 100 mph. They were building a single-seater fabric saloon 45 (proper protection for the driver), sans front brakes, for the onslaught, a car I find very fascinating. By July 1926 all was ready. Changing all four 33 x 5 in tyres every hour, with 14 men to manage these pit-stops (the shortest taking 52 seconds), the American Ellery Garfield, Plessier and Guillon keeping the pace of the 120 mph 2¼ ton car down to 2250 rpm during the night hours, 2500 rpm in daylight, the Renault took World’s and Class-A records, up to the intended 24-hours at 107.89 mph (3589.4 miles). The last triumphant lap was done at 118.74 mph, to set the seal on Renault supremacy. The rest of the 24-hour story is told in the tables.