Thursday, 15 November 2012

AC cars

Almost as though nothing much had happened since 1939, in 1945 AC Cars at Thames Ditton restarted manufacturing the same sort of car as it had before the war. It used the aluminium single overhead camshaft 1991cc wet liner 6-cylinder, designed in 1919 by John Weller. The engine had been shown at the first London Motor Show following what used to be called the Great War. The post-Second World War AC 2 Litre had half-elliptic leaf springs, a stout chassis and it was largely hand-made on old machine tools. It was just as well the car-starved market of the time was not choosy.

It said a great deal for AC that the old design had lasted so long. The rather lugubrious saloon, in which Weller’s engine was installed, was obviously not long for the automotive mainstream. The headlamps were sunk into the wings and the radiator grille curled, otherwise there was little to distinguish it from 1930s counterparts. It held its own only so long as cars remained in short supply. Once the market returned to normal it was no longer competitive.
AC had been essentially a sports car manufacturer so, with the 2-seater market once again in view, it responded to an approach from John Tojeiro. His designs for sports-racing cars were working well in British amateur racing. The formula he followed was simple, not to say simplistic, owing something in its conception to the BMW 328 of the 1930s. Tojeiro’s ladder-type frame was in the shape of an H, with two 3in (7.6cm) diameter parallel tubes joined by a cross-tube in the middle, with independent suspension mounted on welded fabrications at both ends. The body style was cribbed, without much alteration and certainly no acknowledgement, from a contemporary Ferrari. The result was the AC Ace.
It was an instant success. The frame was stiff, the handling spectacularly good for 1953 - it would still be commendable ten years later - and a coupe version, the Aceca was added in 1955. By a process of steady evolution an excellent, intuitive design improved. When disc brakes became available they were included; this was not a preserved undeveloped design, although a top speed only just over 100mph (160.1kph) did not make the best of the exemplary road holding. As an alternative to the old 102bhp Weller engine, in 1958 AC offered the Bristol (née BMW 328) 2litre with 125bhp, giving both Ace and Aceca well over 115mph (185kph) and taking the Ace into the connoisseur class.
The Ace-Bristol lasted until 1961. Bristol, perhaps unwisely, discontinued the engine and as an alternative AC offered a rather unsatisfactory modified Ford Zephyr pushrod of 170bhp. It had scant refinement, great weight and was unworthy of a hand-made premium priced, well proportioned 2-seater. Its only virtue was to keep things going until something better turned up.
Help was at hand. Led by the colourful Texan Carroll Hall Shelby (1923-2012), the prototype AC Cobra of 1962 was basically an Ace chassis altered to accommodate a Ford V8 engine. It had stout wheel arches to cope with wider tyres and more than twice the horse power of the Ace Zephyr.
For bravura, few cars could match a well-tuned Cobra. There were two models, one with a 4.2 or 4.7litre V8; then from the middle of 1965 a 7litre giving up to 345bhp in road trim and a top speed around 145mph 233.3kph). It could manage a standing quarter-mile in under 13sec.
Such performance made demands on a chassis so more changes were wrought. One of the first was rack and pinion steering. There had been a tendency of racks and pinions to lock-up at inconvenient moments, so until that was curbed many designs carried over from the 1930s continued with drop-arms and drag links. The Cobra's suspension had to be brought up to date as well, combined coil spring and dampers with wishbones, replacing the transverse leaf springs.
The Cobra went under a lot of names. Sometimes the AC part was dropped altogether and it was known as a Shelby Cobra, a Shelby American or sometimes a Ford Cobra. AC engaged Tojeiro again 1958 to design a space-framed, de Dion axled car for racing. There was another stretched Cobra, for which Frua produced a lookalike body to its Maserati Mistrale, calling it simply the 428. It was fast, around 140mph (225.3kph) stylish but not very successful. Only 86 were made, a survivor the firm's sole exhibit for years at the London Motor Show long after production ceased. The design had really outgrown the proprietors, the staid deeply conservative rather dour Hurlocks, who had bought the company in 1930. You felt they neither understood nor really quite approved of the cult status the Cobra had achieved. It had not been what they had in mind at all. All that noise and speed was scarcely gentlemanly.

From: Sports Car Classics: Original road tests, feature articles and motoring columns by Eric Dymock. Amazon £3.08 or $4.99. Pictured 1) AC Ace 2) AC Ace-Bristol 3) AC Aceca and 4) 39PH the Le Mans Ac Cobra track tested by Eric Dymock and featured in Sports Car Classics.


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