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The Golden Arrow

12 cylinders, 6 camshafts and in 1929, the fastest car in the world

by Julian Edgar

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It was in March, 1929 that Major H O D Segrave of Britain beat the existing Land Speed Record, driving the Golden Arrow. Evocatively named, it was also beautifully designed and built – a far cry from some of the other Land Speed Record contenders then roaring along Daytona Beach. 

Designed by Captain Jack S Irving (many people at the time retained their WWI rank), everything but the engine was purpose-designed and built for the very special car.

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The engine comprised the ‘broad arrow’ 12 cylinder Napier Lion series VIIa liquid-cooled design, as used in the record-breaking Schneider Trophy seaplanes. The Schneider Trophy aircraft were then the fastest in the world.

The ‘broad arrow’ configuration used two cylinder banks in a V, with the third bank rising vertically. The cylinder banks were spaced at 60 degrees and used a common crankshaft. The four-throw crankshaft (very short and so stiff) was driven by three connecting rods on each pin and using plain bearings. (The crankshaft used roller bearings.) 

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The 24 litre displacement was formed through cylinders having a bore of 5½ inches and a stroke of 5 1/8 inches. The compression ratio was variably quoted as being 10:1 or 12:1; one Claudel Hobson carburettor was used for each cylinder bank.  

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Intake manifolding comprised rather basic log-type manifolds and the exhausts were just short stubs poking through the bodywork. 

Specific fuel consumption was 0.44 pints per hp per hour (very good) and the fuel was a special BP brew to suit the high compression. Ignition was provided by twin magnetos and maximum engine speed was 3,600 rpm. 

Despite its huge capacity and 938hp output, the engine had a relatively low mass of 391kg, helped no doubt by its milled alloy block and alloy heads. 

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Two hollow overhead camshafts per bank were used to drive the four valves fitted to each cylinder. (So six camshafts driving 48 valves!) 

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Each cylinder was separately water jacketed, with these jackets being formed through sheet metal pressings. The engine was dry-sumped, with the oil tanks being positioned within the flanges of the main chassis members. 

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The water cooling used surface-type aircraft radiators, formed from deeply corrugated tanks. In addition, ice-cooling could be switched-in by the driver – something that proved very important to the record-breaking run.

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Behind the engine was the vacuum servo-assisted clutch, a multi-plate design with a 1.5 ton clamping pressure. The three-speed gearbox gave theoretical maxima of 81 mph, 166 mph and 246 mph. The gearbox drove two output driveshafts, with these geared-up rather than down, and rotating at 4,900 rpm at maximum engine speed. 

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The driveshafts passed either side of the driver and rotated in opposite directions to drive crownwheels located on the solid rear axle. The split drive allowed the driver to be seated far lower than if he were positioned above a single driveshaft. 

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The girder chassis frame used channel section main members, 13 inches in depth and 4 inches wide, braced by tubular cross-members. The completed car had a mass of 3.5 tonnes.

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The front and rear solid axles were suspended by stiff semi-elliptic springs and were further located by radius arms. 

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The front wheels were steered through a bevel gear reduction steering box that controlled each front wheel independently; that is, there was no lateral steering connecting link at the front axle. 

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The front wheels used four degrees of castor and steering shimmy was damped by fibre pads placed at the bottom of each kingpin. Three turns lock-to-lock was provided with no power assistance. 

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Brakes comprised fabric-lined shoes working within 17 inch drums fitted to each wheel. Vacuum assistance was provided. At the time, it was suggested that after closing the throttle, the car would run for a further 4 miles if the brakes were not applied. 

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Tyres were Dunlop, 37 inches in diameter and 7 inches wide; at maximum speed these rotated at 2,300 rpm. On a specially constructed testing machine, the tyres could withstand 240 mph for 25 seconds. At Daytona, the maximum speed through the measured mile took about 15 seconds. 

The Golden Arrow was a masterpiece of contemporary aerodynamic streamlining. Its frontal area was an amazingly small 11.6 square feet. This tiny frontal area was achieved by a streamlining approach that separately addressed the engine/cockpit and the wheels, allowing airflow to occur between these sections. 

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The engine cover, very tightly following the shape of the engine heads, was modelled on the Schneider trophy seaplane. A shaped undertray was used under the rear of the vehicle to reduce lift. The car had 7 ½ inches ground clearance and a maximum height of 44 inches. 

Extensive wind tunnel testing was used in its development: the centre of pressure was 20 inches above the ground, 92 inches from the front axle and 72 inches from the rear axle. 

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The wheelbase of the car was 13 feet and 4 inches; the track was 5 feet. These, it was suggested at the time, were not much different to a large contemporary private car – but at 27 feet 6 ½ inches, the length was massive. 

The Run

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On March 11, 1929, Henry Segrave was on the beach at Daytona. 

There was a light mist blowing in from the sea as he headed north, changing gears at 3,200 rpm, the latter occurring at over 170 mph. Part way through the run, a burst water pipe drenched Segrave in steam and hot water, making vision difficult, but he was able to switch to the ice cooling and could again see.  

Tyres were changed at the end of the run and he returned, this time the major problem being a gulley hit at top speed – this twisted the car and partly damaged a radiator, in addition to making it  difficult to keep the car straight. 

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The average speed through the flying mile was 231.362 mph, making H O D Segrave (as he was then universally known) the holder of the World Land Speed Record. This lifted the speed an astonishing 23.894 mph over the previous record holder; however, such was the pace of record breaking in those days, the Golden Arrow held the record for less than two years. 

You can see the Golden Arrow at the National Motor Museum, Beaulieu, Hampshire, UK.

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