How Halford broke the mould with DIY special
The renowned aero-engine designer gave the works teams of the 1920s a run for their money with his own long-distance racer
It was excellent that the famous Halford Special was at last year’s Celebration of Brooklands Centenary, in the care of James Cheyney. It was Major Frank Halford who made use of the cylinder blocks from the V8 wartime Airdisco engine of which many unused ones were obtainable from the Air Disposal Board. This led to the 60hp Cirrus engine for the DH Moth, which was the first practical light aeroplane that resulted in the formation of clubs for would-be pilots all over the British Isles. Halford went on to design some extremely successful aero-engines for the Napier Company, notably the H-formation 24-cylinder 2238cu in (36,674cc) sleeve-valve Sabre which gave 3053bhp at 3850rpm. After the war he designed jet engines for the De Havilland Vampire and Comet.
A reader, Mr Alan Brodie, has sent us some fine period photographs of the Halford Special, some of which I had not seen before. Mr Brodie’s father John worked with Halford on both car and aero-engines, and his son found the photos among his effects only recently. Alan Brodie continued the racing tradition, as he became a mechanic for Bob Anderson’s Formula 1 Brabham, and later ran a successful Formula 5000 team.
Frank Halford began racing at Brooklands with a Bamford & Martin Aston-Martin. He had won his very first race in the special AM built to hopefully take records from the successful AC team. This AM had one of the four-cylinder 16-valve twin-cam engines in an exceedingly narrow chassis, the body a mere 18½in wide. The record bids were not attempted because, it was said, that every time the car, called ‘Razor Blade’, got up to 100mph the off-side front tyre flew off. Surely such a special car for such an important task would not have been abandoned before a new set of tyres had been tried or attention been paid to a displaced stub-axle, or whatever? Could this have been a story to disguise the AM being unable to perform as required? If so it was scarcely upheld when, in the same year, 1923, Halford had lapped at 99.81mph in ‘Razor Blade’, attaining his race win with all tyres apparently intact, and at 99.01mph in his very next race (seventh from the scratch mark) with hardly time to change tyres. Can anyone solve this long-standing puzzle?
With the need to cope with increased handicaps and to have a car suitable for long-distance races Halford designed and built the Halford Special. It had a twin-overhead-camshaft six-cylinder engine of 63x80mm to provide a short stroke and keep the capacity within the 1½-litre limit.
There were short fingers, pivoted to the inside of the inclined valves to give a good entry for the cams onto the valve stems. The deep light-alloy cylinder block and crankcase contained the six steel liners, in contact with the coolant water, sealed with rubber rings. The seven-bearing crankshaft ran on plain bearings. The dural con-rods ran directly on the gudgeon-pins, a feature based on Halford’s aero-engine experiments. Conventional white metal big-ends were used. The cylinder head was of cast-iron with no gasket between it and the cylinder block. The camshafts were driven by a train of spur gears at the rear and ignition was by two BTH magnetos driven from the camshaft gears and protruding through the bulkhead. They fired special 12mm KLG sparking-plugs, two plugs per cylinder.
A significant link with aero-engine practice was a turbo supercharger, exhaust driven, sucking from the carburetter. This centrifugal blower was set below the sump, feeding to the crankcase though a connecting passage. This was revolutionary for a British racing car at the time. However, it was replaced by a normal Roots-type supercharger situated ahead of the car’s radiator and driven by a universally-jointed shaft from the crankshaft, the starting handle operating through it.
Two such engines were built, the output of the first one quoted at 96bhp at 5300rpm and the second 120bhp at 5500rpm with 11lbs boost from the supercharger. These engines were installed in a two-seater Aston-Martin (OR-1, the original Southampton number?) with Perrot-type front-wheel brakes, thought to be the one previously raced by George Eyston and Barlow and now entered as the AM-Halford.
At Brooklands in 1925 it did not give good results, but in 1926, presumably with the later engine, it was very different. Halford obtained two first places, with a fastest lap of 109.92mph, and two seconds, one from the scratch mark with two laps at 109.74mph, and a third place.
In the 1925 JCC 200-Mile Race Halford managed fourth place, in the kind of contest for which he had intended his car should be used, after delays due to loss of water and petrol. But it was in the 1926 RAC British GP at Brooklands that the Halford Special, painted green, was mixing it with the Delage and Talbot teams, when the universal joint of the aged Aston-Martin failed. In that year’s ‘200’ Halford came in sixth in the 1½-litre class in spite of a stripped gear in the gearbox.
During 1927 Halford was not available, so Eyston, who was also driving a B&M Grand Prix Aston Martin, deputised for him, to no avail. But the Major must have been very happy with the performances of his own car and there was an additional accolade. The BARC had decided to stage a beauty contest among the cars before racing commenced, and the Halford Special with its immaculate white body, aquamarine chassis, and black wheels, with a tiny plaque at the top of its radiator inscribed ‘Halford’, was the first winner; but the idea was soon abandoned.
When Halford became too busy with the aero-engines his car was acquired by Lord Ridley and then went to Dudley Coram, after which the trail grows cold, so far as I am concerned, until it joined in the Brooklands celebrations last year in the care of Mr Cheyney from New York.