Radically different approaches to car design and manufacture

Paul Boughton
There is a strong argument against continuing to build and use fossil-fuelled cars, though, to be fair, automotive manufacturers are improving the sustainability of their products. But are the mainstream automakers inherently the wrong organisations to make step changes in how we fulfil our need for personal mobility? Paul Stevens looks at what independent designers and consultancies are proposing.

In the October 2009 issue of European Design Engineer there was an interview with Hugo Spowers of Riversimple. Spowers made his name as a designer of race cars but left the industry because of concerns about its environmental impact. He subsequently started Riversimple to enable a fresh start to be made, with new attitudes to automotive design, manufacture and, equally importantly, commercial interests. His design for an urban car is based around a hydrogen fuel cell, which enables the car to be compact, lightweight and very fuel-efficient (Fig.1). Moreover, the car is designed for a life of 15-20 years and customers will lease, rather than buy them. The lease (or 'sale of service') business model also extends to Riversimple's suppliers - even those of consumables such as tyres. This approach encourages suppliers to continually develop better components (more efficient fuel cells or wheel motors, or longer-lasting tyres, for example) that can be retrofitted to the cars during their lifetime so that both the car users and the suppliers benefit.

Another important element of Riversimple's philosophy is that the car's design will be released on an open source licence so that small, local companies can start building cars and/or developing the design. By removing the barriers to entry, the market will be far more dynamic than the conventional automotive industry, resulting in improvements reaching customers more quickly - and benefitting the environment sooner.

Riversimple's urban car uses a carbon fibre composite monocoque to provide an optimal combination of stiffness, strength and low weight. Although this material is difficult to recycle, Spowers calculates that a body made this way is more sustainable than one fabricated from steel, plus it is more cost-effective over the vehicle's lifetime and does not increase the price for the consumer. Since Spowers was interviewed for European Design Engineer in 2009, Riversimple has been joined by Christopher Reitz, who previously headed the design team at Fiat, where he was responsible for the Fiat 500, before moving to Alfa Romeo. The first task for Reitz is to take the existing design for the urban car and develop it to a stage where 30 can be built for testing in the UK city of Leicester, with users getting their first cars in the summer of 2012. These will be trialled for a year, with drivers providing feedback on their experience.

Another former race car designer, Professor Gordon Murray, has also taken a holistic approach to the design of a lightweight urban car. Initially his firm, Gordon Murray Design, created the T.25 as a compact, lightweight city car (Fig.2). The T.25 is a three-seater with a rear-mounted three-cylinder petrol engine. Having subsequently teamed up with Zytek Automotive, a UK-based company with extensive experience in electric and hybrid vehicle powertrains, an electric version of the car has been designed, known as the T.27.

Pure electric

Based on the T.25, the T.27 is a pure electric vehicle using a 25kW motor and 12kWh lithium-ion batteries. Recycled materials are incorporated within the innovative composite panels that add stiffness and integrity to the 'exoframe' primary structure. However, one of the most important aspects of the design of the T.25 and T.27 is Gordon Murray Design's low-energy iStream manufacturing process, which utilises a monocoque but with body panels that are attached mechanically in order to reduce assembly time and complexity, and minimise the cost of accident repairs (see panel page 12).

Thanks to the simplified assembly process, the manufacturing plant can be one-fifth of the size of a conventional factory, which could reduce capital investment in the assembly plant by approximately 80 per cent. Yet the flexibility of this assembly process means that the same factory could be used to manufacture different variants or models - even the T.25 and T.27 could be built concurrently. Gordon Murray Design also says that the iStream process is a complete re-think on high-volume materials, as well as the manufacturing process, and will lead to a significant reduction in CO2 emissions over the lifecycle of the vehicles produced using it. According to the company, the iStream composite monocoque brings Formula One technology to mass-production vehicles, with significantly higher specific energy absorption rates compared with conventional bodied cars.

Far from being a design exercise, the T.27 is well on the way to being ready for production. In January 2011 Gordon Murray Design announced that the T.27 had been subjected to its first crash tests at the MIRA (Motor Industry Research Association) facilities. The crash test was the mandatory EEC 40 per cent offset deformable barrier front high-speed impact and the T.27 passed with zero cabin intrusion (Fig.3). This result is an endorsement for the iStream manufacturing system that delivers reduced weight and cost without compromising safety.

Concept cars

While Riversimple and Gordon Murray Design are making progress towards production-ready vehicles, Swiss company Rinspeed is continuing to create concept cars that are perhaps less likely to make it into production. For example, the 2009 Rinspeed iChange concept was described as the world's first car whose body adapts to the number of passengers on board (Fig.4). For Rinspeed boss Rinderknecht, the vehicle is more than just a clever concept car: "The iChange is a symbol for the fundamental changes the auto industry undergoes worldwide. And it is clear that only those companies will survive that have innovative answers for the demands of a new automotive era."

In seconds a streamlined one-seater sports car transforms into a comfortable car with ample room for three - achieved at the press of a button that causes the rear end of the car to pop up. And the reason for this transformation stems from the basic idea behind the iChange, which is that the energy demand of a vehicle depends mostly on its weight, the type of engine it uses and its aerodynamic properties. The extremely lightweight car weighs only 1050kg, with power coming from an electric motor and a choice of battery packs, one for short-range and the other for long-range journeys; the pop-up rear end means the car's aerodynamic properties are adapted to suit the number of vehicle occupants.

While other cars are encumbered by exteriors that can accommodate up to seven passengers even if they are only transporting a driver, the iChange's adaptive body means that the lone driver is conveyed in a teardrop-shaped car that offers optimal aerodynamic properties and, therefore, minimised energy consumption. If more than one person needs to be transported, the expanding rear provides room for two passengers. As a result of the increased weight and the altered aerodynamics, the energy consumption increases - but only when passengers are carried.

More recently the same company has announced the Rinspeed Bamboo. Many interior components are made from bamboo fibres, but the four-seater, open-top Bamboo sets out to awaken the longing for sun, summer, lightness and easiness - and the desire to be at the beach.

Neither the Bamboo nor the iChange are likely to go on sale imminently, but it is a real possibility that the urban cars from Riversimple and Gordon Murray Design could be on the road soon. And although the major automotive manufacturers will continue to unveil concept cars that attempt to address our future needs, these companies are so intimately involved with conventional production methods and business models that they are, in truth, unlikely to present us with a step change that can make a major difference to the way we perceive and procure personal mobility. Let us hope, therefore, that the independent design houses find the right formula in terms of customer appeal, commercial success and sustainability.

iStream manufacturing process

This innovative iStream vehicle manufacturing process developed by Gordon Murray Design utilises a separate body chassis assembly process. During the first part of the process the powertrain, wiring harnesses, brakes, suspension and all major components are fitted directly onto the chassis prior to the body panels being fitted.

Body panels are delivered to the line pre-painted and are 'married' to the completed chassis near the end of the assembly process, thereby helping to reduce the risk of paint damage.

All external panels can be mechanically fixed to the chassis, which aids the assembly process efficiency and simplifies repairs to accident damage.

Other advantages of the iStream process include the way in which the chassis can be used as a standard platform on which different variants or vehicles can be built - even on the same production line. Entirely new variants can also be introduced quickly and with minimal investment in tooling, and existing vehicles can be modified either to change the specification or to make cosmetic changes.

A strategic advantage of the iStream process lies in the fact that a central plant could be established for manufacturing frames and painted panels, which could then be distributed to small assembly facilities located close to the points of demand.

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