Glorious impracticality

Conceived as a race car for the road, the Strathcarron uses a motorbike engine, lightweight composite construction – and no compromises, as David Fowler discovers

At the Geneva Motor Show, on a small corner stand next to Bugatti, just round the corner from Bentley’s show-stealing Hunaudieres concept car, a small, yellow sports car from a little-known British company was also drawing crowds. The firm was Strathcarron and the car, a fully-functioning prototype, was the SC-4, a stripped-down, no-frills, lightweight car for people who think the Lotus Elise makes too many compromises towards comfort. Its aluminium honeycomb chassis draws on race-car experience and it is powered by a British-made 1,200cc, 125bhp Triumph motorcycle engine. It weighs just 560kg.

On the strength of last month’s show appearance, the company says it took £1m worth of orders. It plans to have the car in production next year, in race trim as the SC-3 as well as the road-going SC-4.

Colin Spooner, technical director of Strathcarron Sports Cars, calls the car `a four-wheeled motorbike, not for everyday use, purely for fun’. Spooner is an ex-Lotus engineering director who felt Lotus had lost its way after the death of founder Colin Chapman and its sale to General Motors. He left the company to set up Chapman Associates, an independent automotive consultancy based on `Chapman’s approach of lateral thinking, solving problems by making things simpler rather than more complex’.

For years, Spooner had been trying to persuade Lotus bosses to go back to its roots with a car like the SC-4. Eventually it did something similar with the Elise, but Spooner says the SC-4 is `what the Elise set out to be. Even for Lotus the marketing pressures are enormous’.

Hence the Elise, which most people might think of as fairly uncompromising, ended up with some weather protection, for example. `We took a more radical approach. It allows us to keep to the concept of simplicity, purely functional. Everything on the car is there to make it work. It’s a race car for the road with the same response and feel. There are no concessions to practicality: it’s what Colin Chapman described as “glorious impracticality”. But to a small number of people that will be very attractive.’

This niche market had also been identified by Ian Macpherson, car enthusiast and chief executive of Strathcarron & Co, the company founded by his father, Lord Strathcarron, and which acts as an agent for component suppliers to automotive manufacturers.

Macpherson believed there was a market for a relatively inexpensive (less than £20,000), lightweight sports/race car. He began talking to contacts in the industry, starting with Adrian Reynard, boss of Reynard Motorsport. During 1997 he assembled a team including Reynard and Spooner, and found 15 investors who put up enough – about £1m – for phase one. The objective was to build a prototype, and get it to a motor show to attract enough investment to put it into production. Spooner reckons the next phase, including gaining low-volume approval allowing up to 500 cars to be sold in the UK annually, will take 11 months from when the funding target is achieved. About 85% of this funding is now in place.

Reynard was not an investor, but was awarded the contract to develop the prototype, with Spooner as technical director to keep the project going in the right direction. AKA Consultancy Design Realisation Services won the styling contract.

Reynard was asked to meet a number of criteria with its chassis design. These included: that the car should achieve high performance; it must be safe, both actively in its handling and passively in its structure; it must be raceable; and it must be affordable – with a price of less than £20,000 – and insurable.

By the end of last year, Reynard had produced a running prototype. It is based around a body tub which uses a sandwich aluminium honeycomb structure. Hexcel Composites, formerly part of Ciba-Geigy, advised on bonding techniques and fabricated the chassis, which was cut from sheet by an NC machine, folded and bonded together with riveted reinforcing plates at joints.

Spooner admits to being surprised at this solution, which is not cutting-edge technology. `It’s the approach that would be used for a 1960s race car monocoque,’ he says. He had expected it would be cheaper and lighter to use a fibre reinforced plastic material with a Nomex core, typical aerospace technology for forming bulkheads. `But it turned out to be more expensive and more time-consuming to make. It would have cost a lot more money to get equivalent stiffness from plastics.’

The British designed and made Triumph motor cycle engine was used because it was thought it would contribute to the feel of the car, with a high power-to-weight ratio, the ability to rev to 9,600rpm, and the fact that it came already mated to a six-speed sequential gearbox. Reynard and Hewland Engineering designed a final drive and reverse for it.

Spooner had initial misgivings but once the engine was installed in the chassis and tried out, everyone was convinced it was the right decision. Spooner’s doubts centred on the need to meet emission and noise requirements which are stricter for cars than bikes. He is confident these can be overcome, once the engine is fitted with an engine management system and fuel injection rather than carburettors. `The mechanical geometry of the engine will allow us to meet the regs,’ he says.

The engine is a 16-valve, four-cylinder, twin-overhead cam engine and characteristics such as valve overlaps are not dissimilar to a car engine. Triumph also makes a 900cc three-cylinder engine which produces the same power `but it has wild cam timing. There’s no way we could have got that to work,’ Spooner says.

A steel space frame structure bolted to the rear of the body carries the engine and suspension mounting points. Originally, a twist-beam axle set-up was used but because this had insufficient lateral stiffness, it has been changed to a de Dion tube. This works well but has the disadvantage of higher unsprung weight. Both front and rear crash absorbing structures have yet to be designed, and Spooner says that it may be preferable to switch to wishbones, if the rear crash structure takes a suitable form.

No doors

There are four body panels: a front panel, a back panel and two side ones – and no doors. As there are no door openings in the chassis tub, this contributes to very high stiffness. Externally visible panels will be aluminium pressings to give a better surface finish, although early cars may take the more usual route of glass reinforced plastic panels.

Spooner says the prototype delivered by Reynard towards the end of last year worked extremely well, though there were problems – for example, the cooling system proved inadequate, and there were problems with that panel fit and shape. But Spooner says: `We faced the major problem of turning it into a credible show car, both superficially and technically.’

Around the same time, Reynard decided that designing road cars was not the way it wanted to go. `I would have been more than happy to continue with them but they decided to retire gracefully,’ says Spooner.

So Chapman Associates spent the first two months of the year in an intensive race to refine and re-engineer the car for the Geneva show. This included improving the ergonomics and re-tooling the body panels, bringing in firms Spooner knew from his Lotus days to help. `We started just after Christmas and re-detailed the car to a standard I felt we would need for the future,’ says Spooner. In the process, the design was refined to a stage beyond that strictly needed for a show car, but Spooner argues: `I saw it as an opportunity to make real progress.’

The rest of the development is likely to take place in a similar way, with Dove Company Design working on panels and homologation work at the Millbrook proving ground.

Spooner is confident of being able to meet the cost target. `It’s difficult, but then there aren’t that many components in it,’ he says. One of the keys will be the cost of bought-in components, but he says the company has already done a good deal with Triumph.