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Gordon Murray has had an illustrious career working at Brabham Formula One Team as Technical Director, winning two world championships (1981 and 1983) during his 17 years with the team. Gordon joined McLaren Racing as Technical Director in 1988 and three consecutive championship wins (1988, 1989 and 1990) followed. In 1990 Gordon moved away from Formula One, after 50 Grand Prix wins, to enable him to concentrate his efforts on establishing a new Company for the McLaren Group — McLaren Cars Ltd, now assimilated into McLaren Automotive.
The Company’s first project, the F1 Road Car is still regarded as the world’s best engineered car. A racing version won two world sports car championships and the Le Mans 24-hour race on its first attempt in 1995. At McLaren Cars Murray completed several other successful projects culminating with Mercedes-Benz SLR McLaren programme.
Lightness has always been a critical design criterion for Murray. From his early involvement with the (Light Car Company) LCC Rocket, still the world’s lightest and fastest, road legal, racecar, to his appointment to the Lotus Advisory Council last year, he has always echoed the Chapman design ethic. In the context of his current activities, if we are allowed to paraphrase the great man, the current approach at Gordon Murray Design (GMD) would be “for sustainable transportation just add lightness.”
The focus at GMD at the moment is the T.27 Electric City Car and the T.32 electric sports car for Toray Industries Inc. There are a couple of other vehicle programmes, but they are still very much under wraps.
The first objective is focused on the UK and building a consortium to get the T.25 and T.27 into manufacture. GMD will then focus on the rest of Europe from an export perspective. The vehicles would be on general sale two years after the consortium has been established. Ultimately GMD are in the business of selling iStream licences rather than making cars.
The T.27 is both a prototype electric car and a test bed for the new iStream manufacturing process. The contention at GMD is that stamped steel has served us well in the past in vehicle production, but that it is no longer the best way to cope with our global transportation challenges.
Gordon Murray puts it very succinctly: “We are all facing the beginning of what promises to be the next industrial revolution and we will have to apply all the lateral thinking and innovation we can muster to solve the problems we face with energy, pollution and congestion.”
iStream
Apologies for labouring the Lotus connection, but it is palpable. One of Chapman’s great early road cars was the original Lotus Elan — it was not without its faults (I owned one), but it was the first time we had a steel chassis underlying a glass fibre composite body. And if we fast- forward a couple of decades Lotus Engineering pioneered the Lotus Variable Vehicle Architecture. The similarities in approach to iStream are spooky — two great engineers adopting a similar approach to a similar problem — that’s never happened before.
The iStream process seeks to reduce all costs associated with developing a vehicle, from factory development and assembly to tooling design and end of life. Whereas the traditional approach to vehicle manufacturing sees stamped steel used for the body structure, GMD's innovative iStream manufacturing process uses lightweight composite panels bonded to a tubular metallic frame.
iStream is being developed as intellectual property for GMD which it intends to license to companies wishing to diversify into the car market. However, in order to make iStream successful, GMD must prove that a vehicle, which relies on composite panels for much of its structural integrity, can meet strict performance targets. To do this, GMD has developed a number of demonstrator vehicles including the T.25 and T.27 that utilise the iStream philosophy.
The iStream assembly process has several discrete phases. During the first part, the powertrain, wiring harnesses, brakes, suspension and all major components can be fitted directly onto the chassis prior to the body panels being fitted.
The body panels are delivered to the line pre- painted and they are ‘married’ to the completed chassis near the end of the assembly process, helping to reduce paint damage normally associated with a standard assembly line. All external panels can be mechanically fixed to the chassis.
The construction method allows the chassis to be scaled in size for different products with each new design requiring only low-cost tooling and software changes. This flexibility means that the chassis can be used as a standard ‘platform’ to deliver different vehicle types and model variants e.g. car, urban delivery van, taxi, emergency support vehicle, just like the Lotus VVA does with folded steel and aluminium extrusions.
Combining this flexibility with the separate chassis and assembly lines means that the same factory could be used to manufacture many different variants. Entirely new model variants can be produced with significantly reduced lead times from concept to market.
Simplified assembly with easier access reduces assembly times and the risks of inline damage — avoiding the additional delay and cost associated with rework.
Pre-painted body panels mean that there is no need for a paint shop in the assembly plant, which removes the complications associated with VOC emissions.
Mechanical fixing of body panels is quick and low-energy and they impart exceptional stiffness to the whole assembly. It also makes future repairs relatively simple, as replacement panels are quicker and easier to fix.
There is also the future potential to adapt the factory to take in ‘used cars’ to be upgraded or refurbed, reusing core parts such as the chassis and running gear with significant environmental benefits including reduced landfill and recycling at end-of-life.
This process could also be used for cosmetic updates to suit customer preferences, as replacing body panels is relatively simple.
Overcoming the Challenges of Composite Design through Simulation
Composite materials have been used in the aerospace industry for many years because of their lightweight and high-performance characteristics, but the issue of product weight is not limited to aircraft. Automotive manufacturers are increasingly viewing the material as a method of minimising mass and fuel consumption.
The material has many design challenges. Composite ply layer stacking order and fibre direction creates a huge number of design variables to take into account when simulating complex events such as crash. Furthermore, the inherent high cost of the material can lead many to view composites as the preserve of high-end sports vehicles.
Selecting an Experienced Simulation Development Partner
GMD is a small, focused and highly talented company with a huge amount of vehicle engineering pedigree and experience. The iStream project requires a deep understanding of the behaviour of composite material and how it can be modelled accurately to prove its suitability as a structural component.
GMD is an established user of Altair's HyperWorks suite of simulation technologies. When the company was looking for an external partner with simulation expertise, Altair ProductDesign, was the natural choice. Altair is able to link its software development business with its engineering services, allowing Altair ProductDesign to apply experiences gained during projects to influence directly the functionality and accuracy of the software suite. This was a key decision factor for GMD who saw the interaction between the two businesses as a crucial differentiating factor over other product development companies.
Streamlined Model Build
Altair ProductDesign was asked to improve the virtual modelling of the composite materials used in iStream to achieve correlation with physical test results.
The first task was to build accurate material models for the iStream sandwich panels. The panels are considerably lighter than metal alternatives while maintaining strength and stiffness as well as being inexpensive to maintain and avoid many corrosion issues.
To model the structure effectively requires detailed modelling of the glass fibre laminates, soft core and the structural adhesive used to bond the panels to the frame. GMD tasked Altair ProductDesign with creating a highly tuneable CAE model of an iStream chassis in order to appraise the load paths in frontal and side dynamic impacts. Using Altair’s HyperWorks suite, Altair ProductDesign suggested a finite element modelling method that utilised 1D beam and shell elements for different parts of the vehicle structure with much of the model creation work conducted by Altair’s offshore capability to speed up this time consuming phase.
This is the big win — the ability to model and simulate accurately, complex 3D structural interactions with vastly dissimilar materials is no easy task. And to do it in such a way that it confirms physical test results is a real bonus both for design and design verification. Once you have calibrated the technique it can be reused on new, similar projects.
HyperWorks is the ‘stand out’ CAE product of the moment with an effective easy-to-use multi-physics solver appropriate to the solution of complex 3D structural interactions, with multiple materials. Extensive CAD integration and automation of functions, frees engineers to use their creativity and talents to innovate, rather than focusing the majority of their time on data input and management.
HyperWorks has modules that can solve most, if not all, of the development tasks with only one licence agreement and one software family. The flexible HyperWorks licensing system allows you to use the modules companywide, which is especially useful for small companies. This helps to consolidate software costs, to be flexible in the use of the software, and to intensify collaboration of different CAE users and locations.
he method developed for GMD allowed the analysis stage to inform the design stage directly through the creation of representative virtual models of the composite material developed much earlier than in a standard development process. Design direction can be quickly explored, manipulated and assessed, but without creating compute intensive analyses.
Accelerating the analysis process enables GMD to investigate more design variations rapidly and achieve the optimal design configuration in a much shorter period of time.
Defining Material Behaviour
Understanding the behaviour of the composite materials is a crucial step in the development cycle as the level of knowledge within the automotive industry is not as mature as it is with metallics.
Once a level of confidence in the material behaviour at a component level is achieved, the material simulation moves beyond discrete components and onto a system characterisation level. Here, sub and full systems are analysed, allowing the engineers to view the interaction of each part on the surrounding components during loading.
Altair ProductDesign and GMD will carry out a range of virtual simulation tests using HyperWorks’ RADIOSS solver to define the material’s behaviour under various loading conditions including crash. The virtual testing process is performed with an understanding of the physical test requirements to ensure that results can be correlated effectively without the need to repeat tests unnecessarily.
Conclusion: Developing Innovative Vehicles with Added Confidence
As the analysis and correlation to physical test stages of the project become finalised, Altair ProductDesign will continue to work with GMD and develop the iStream structure to improve crash performance. The use of advanced materials requires innovative methods of design and validation to ensure that they perform at the highest levels without compromise to safety. The combination of simulation expertise from Altair ProductDesign and the vehicle development and composite expertise of GMD has been a highly effective partnership that will help to prove the value of the innovative iStream process.
“Working directly with the Altair ProductDesign team and how they integrate and interact with Altair’s software division and all the other components of the organisation has been invaluable to us,” said Simon Maher, Senior Stress & Materials Engineer, Gordon Murray Design.
