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  Astra RNR2 Cosworth
 

  Article Image gallery (8) Chassis (1) Specifications  
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Country of origin:Great Britain
Produced in:1970
Numbers built:2
Author:Wouter Melissen
Last updated:October 29, 2012
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Click here to download printer friendly versionIn 1966 the talented British amateur racer Roger Nathan and leading aerodynamicist Frank Costin teamed up to created the Costin-Nathan racing car. Powered by a diminutive Hillman Imp engine, it combined Costin's slippery design with an unusual monocoque chassis constructed from plywood, much like Costin's earlier Marcos GTs. Despite the unconventional design, the car was remarkably successful both in the hands of Nathan himself and other customers.

By 1969 the writing was on the wall for closed cockpit sports racers with the lighter, open cars coming to the fore. Nathan recognised these developments early and started developing an open version of the existing design. His original partner, Frank Costin, had already left the company, so the Costin-Nathan name was dropped. Instead the new car was known as the Astra, inspired by the Royal Air Force motto 'Per Ardua ad Astra'. The first model was known as the RNR1; short for Roger Nathan Racing.

A development of the earlier designs, the RNR1 also featured the trademark plywood monocoque chassis. Its primary advantages were the relative light weight and high rigidity. Attached to both ends of the chassis were steel tubular subframes, onto which the suspension, engine and gearbox were bolted. At the front, the suspension consisted of double wishbones, while the rear-end featured reversed lower wishbones, top links and twin trailing arms. Girling disc brakes provided the stopping power.

While his previous cars used Imp and later BMW engines, Nathan opted to use a two-litre version of the venerably Coventry-Climax FPF engine for the Astra. Famously based on a fire-pump engine, the twin-cam 'four' produced around 180 bhp in this guise. This was mated to a Hewland FT 200 gearbox. The car was clothed in a fibreglass body that was built by Williams & Pritchard. They converted the existing design penned by Costin to a Spider. Despite the relatively heavy engine used, the completed car weighed less than 500 kg.

Nathan debuted the new Astra in March of 1969 at Mallory Park and immediately claimed the car's first victory. Another win followed a fortnight later but the glory was short-lived as the RNR1 was soon dwarfed by rivals using the much more powerful Cosworth FVA. Nathan quickly responded and readied an FVA equipped RNR1. This turned the small Astra's fortunes once more and Nathan continued to race successfully in national events. Several customers also showed an interest and it is believed 5 RNR1s were built.

Encouraged by the success of the Astra in its debut season, Nathan used the winter months to fine tune the design. Seeking to improve the handling, particularly under braking, the front suspension received the most attention with changes to the geometry and all-new, lighter uprights. Dubbed the RNR2, the modified car also received the latest Cosworth FVC engine. Displacing just under 1.8 litre, it was good for around 245 bhp. Two new Astras were built ahead of the 1970 season; one for Nathan himself and the other for Guy Edwards.

A clutch problem in practice delayed the RNR2's debut until the prestigious BOAC 1000 km at Brands Hatch. Partnering with Mike Beckwith, Nathan fought his way up the highly competitive field to finish 16th overall. In national events Nathan did manage to score a couple of wins but the latest Chevrons and Lolas were clearly quicker. Edwards also added a win to the tally of brightly liveried machine late in the season. For 1971, he switched to the latest Lola.

Nathan realised he had taken the development of the car as far as he could and retired his RNR2 after winning the Martini Trophy at Silverstone. He had hoped his performance as a driver would have attracted the interest of other teams but when no drives materialised, he left motor racing altogether. In the five seasons the Costin-Nathans and Astras were raced, the unconventional machines more than once managed to upset the established teams and manufacturers. This can be attributed to both Costin's original design and Nathan's skill behind the wheel.

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  Article Image gallery (8) Chassis (1) Specifications