Right from the start, Bentley Motors’ racing success was built on thorough, meticulous preparation and a preparedness to learn from experience.
“Everything split-pinned and nothing too much trouble”, as racing manager Nobby Clarke put it. Lessons learnt were carefully analysed and with each passing year Bentley improved their motors, their pit procedures and team discipline. W O was very clear in his own mind about the value of motor racing: “I would have been perfectly content to see our cars circulating round Le Mans in inglorious solo solitude so long as the Daily Mail gave us their front page on Monday morning!”
Frank Clement drove a series of highly developed 3-litre racers at Brooklands between 1921 and 1923. Lessons learnt here were applied to the first team of 3-litres sent to the Isle of Man for the 1922 Tourist Trophy race, where they performed creditably against out-and-out racing cars. W O’s attention to detail can be seen in his realisation that fitting a standard petrol tank in addition to the 22 gallon underfloor tank would allow them to run without a pit stop. Three tanks were hurriedly shipped over from the Works and fitted.
When W O first heard of Le Mans, he thought the whole venture mad. But he helped Duff prepare his car for the first race in 1923 and lent him Works driver Frank Clement. W O went over to watch the race and said that Le Mans soon got into his blood. Duff’s 1924 car was fitted with substantial stoneguards to the petrol tank, radiator and headlamps, following damage from flying stones in 1923. Another detailed touch was the “T” bar radiator cap, insulated to prevent the driver burning his hands. “T” bars were added to the petrol tank cap as well, and bigger petrol tanks fitted as the regulations changed, allowing refuelling only after twenty laps or about 200 miles had been covered. The gargantuan petrol tanks fitted to the Works Bentleys may look like an affectation, but nothing the racing team did was unplanned. Under racing conditions, petrol consumption doubled; on a 3-litre to perhaps 10-11mpg, a 41/2-litre 8-9mpg, a Speed Six 6-7mpg. With refuelling stops allowed at about 200 miles, this resulted in tanks of about 25 gallons on 3-litres in 1925/6, 30 gallons on the 41/2-litres in 1928, and 39 gallons on the Speed Six in 1929/30.
After 1924, the innovations on the team cars came thick and fast. By 1927, the Works cars had an extra oil tank under the scuttle, connected to the oil filler neck. As soon as the driver noticed the oil pressure gauge cavitating on corners, all he had to do was turn a tap and more oil was fed into the sump. With oil consumptions at Le Mans of 100 miles per gallon for 3-litres, about 150 mpg for the 41/2-litre and about 180 mpg for the Speed Six, this was necessary! Many years later Nobby Clarke said that maintaining oil pressures on the racing cars was a nightmare on the early 3-litres.
Particular attention was paid to pit procedures, to save time. The oil filler neck was extended outside the bonnet, so that it did not have to be opened. With bonnet straps often demanded by regulations, this saved a considerable amount of time. A “treacle tap” (it is, literally, an off-the-shelf tap used in treacle barrels) was fitted into the side of the sump, operated by a lever by the oil filler neck. The driver had only to invert an oil can into the oil filler neck, and any excess oil drained into a tray placed under the car. The treacle tap thus ensured the correct oil level in the sump without the driver needing to measure out the oil. By 1930, this had been made completely foolproof, the tap tripped shut when the driver first pressed the clutch pedal to get away. This sort of attention to detail prevented mistakes that could easily arise with tired drivers in a long race.
Quick-action cam-operated caps for oil, water and petrol were first developed by Bentley. These saved time and prevented problems from crossed threads or damage to the threads if the cap was dropped; again, eliminating the possibility of mistakes, learnt from things going wrong. By 1930, the petrol tank neck was about 6″ in diameter. Into this the driver dropped a huge galvanised steel funnel, designed to take up to four two-gallon cans at a time. The driver refilled by taking these churns off the pit counter and simply upending them into the funnel; these were the days before gravity feed from tanks on the pit roof. The drivers needed to be fit, and in the days before the Le Mans race each year they would practise their pit stop procedure against a stopwatch. Wire mesh replaced glass in windscreens, and spring loaded catches were fitted to the hood in 1926/7 when the hood had to be raised for the first twenty laps. W O drilled in the message that every second saved at the pits was worth a good distance on the road, and reduced the demands made on the car.
Engines were specially selected and carefully built up for racing, with generous clearances between the working parts. Chassis were also built up specially in the racing shop, with extra reinforcing as needed and additional shock-absorbers to cope with the rough surface at Le Mans and at Brooklands; ride quality was not a consideration, keeping all the wheels on the ground was. Although the racing cars were very much faster than the production cars, a not infrequent cause of customer complaints, the team cars were made out of standard production parts with few exceptions. Straight-cut gears were used in engines and back axles in place of spiral bevel gears, racing magnetos were used, along with special pistons and valves. No effort was made to save weight. The performance of the racing cars resulted from meticulous preparation and attention to detail, tuning by expert mechanics, and accepting absurd oil consumptions.
The one aspect of the cars that the racing team never really solved was the problem of brakes. By 1930, the cars had smaller diameter shoes with thicker linings and a cable adjuster operated by a handwheel on the floor in front of the driver’s seat. This adjuster gave enough movement to take up the brakes from new to completely worn out. Even with the best linings available and with finned drums to dissipate heat (the drums, incidentally, are 400 mm internal diameter – nearly 16″), the brake linings would be down to the rivets by about the 20th hour. By then the drivers were “in the groove” and just had to cope.