Adam Wilkins

AC Brooklands celebrates record‑breaking centenary

One hundred years ago, the AC Brooklands was the first 1.5-litre to average 100mph for an hour. In a time when big capacity engines, such as the 28-litre Fiat S76, were clamouring for speed records, the team at Thames Ditton approached the problem with sophisticated engineering and a dedication to weight reduction that Lotus’s Colin Chapman would make his own several decades later.

Development of the AC Brooklands was funded by the businessman and racer SF Edge, who invested heavily in AC Cars in the 1920s. It’s a completely bespoke toolroom car designed for the purpose of record breaking and shares nothing with the contemporary production cars.

Chief designer John Weller developed the four-cylinder engine which had a highly sophisticated specification for the time, including an overhead camshaft and four valves per cylinder. A second car was built for Raymond Mays, who would later found ERA and BRM, but its supercharger meant it was less reliable. The intention was that the engine would end up in a production car, but it never came to be. It was Weller who designed AC’s six-cylinder engine which went on to have a long life in numerous models.

With around 80PS (59kW) at its disposal, the Brooklands claimed the 100mph average for an hour at the Weybridge banking in the hands of works driver John Joyce, which means at times it was likely to have been travelling at around 115mph. “That’s exceptional for a car that weighs about the same as an Austin 7,” comments the car’s owner Freddie Smith. The car also contested the Junior Car Club 200-mile racing in 1922 and ’24, finishing third on both occasions.

The car’s competitive life continued after its record breaking run. It won the Brighton Speed Trials two years in a row and held the test hill record for many years. It was further developed with twin-spark ignition, a bronze cylinder head and further lightening with an extensively drilled chassis and rear axle. The rear brakes were brought in board and weight saving was taken to such an extent that even the valve stems were hollowed out.

AC sold the car in the mid to late 1920s and it was only used for a couple more years. From 1929 to the early 1960s, it was left in storage until it was dug out to go racing again in the hands of Denis Jenkinson. That bronze cylinder head had been designed for performance rather than longevity and suffered with porosity. It was cast aside and Riley engine was fitted in its place to keep the car running. It proved a great way to preserve the original. “It safeguarded the original engine for when technology and people’s thinking moved on – there was still and engine to copy that cylinder head.”

That job fell to Freddie Smith’s father, who commissioned a new bronze cylinder head when the car was restored it. It has made an appearance at FOS before, when it formed part of the Brooklands centenary celebrations in 2007. Bringing it back here 100 years after its record-breaking run was a special moment. Says Freddie: “I get goosebumps every time I drive it. It’s fabulous to drive. The gearbox is beautiful and everything feels so balanced. It feels like you’re getting into a nice old comfortable pair of shoes. It needs looking after now, it’s done everything it needed to do.”

Photography by Pete Summers.