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carbon fibre sports car component
Photo: © Sharon Ann Holgate


Driving materials forward


by Sharon Ann Holgate
Materials World
July 2017, pages 34-37

Modern materials play a major role in the evolution of extreme high performance sports cars. Sharon Ann Holgate speaks to bespoke motor manufacturers about the materials and processes used to create their latest models.

    The current generation of bespoke supercars and sports cars relies on carbon fibre composites, specialist alloys and advanced design and manufacturing techniques for their extraordinary shapes, speed and handling characteristics. Pushing the boundaries of materials use and processing is enabling small, craft-based companies to create cars with truly unique qualities.

    ‘The key to sports car performance is weight. You can add massive power to nearly any car, but lightness means faster acceleration, shorter braking distances, less inertia when you enter corners and much greater control. To be as light as possible, you need advanced materials technology,’ said Steven Wade, copywriter for Swedish bespoke supercar manufacturer Koenigsegg Automotive, which was founded by Christian von Keonigsegg in 1994 to create the ‘perfect supercar’.  

    Koenigsegg’s latest model, the Regera – a hybrid combining electric motors with a V8 internal combustion engine that can reach 300km/h (186mph) from a standstill in 10 seconds – has a chassis tub made from carbon fibre with an aluminium honeycomb sandwich construction that weighs just 72kg. Carbon fibre is also used for the exterior and interior panels, steering wheel, seats and several engine components including the cam covers, airbox and intake plenum.

    The Regera’s six-spoked ‘Tresex’ hollow carbon fibre wheels contain 750 individual pieces of carbon fibre and takes an artisan 10 days to make. They weigh around 40% less than Koenigsegg’s lightweight alloy wheels. Wade explained that ‘lighter wheels mean faster acceleration off the line as well as minimal rolling inertia, which is critical both when braking and cornering at speed.

    Carbon fibre can be shaped into nearly any form, giving an aesthetic finish, with some opting for a clear coating over the carbon fibre exterior instead of paint. Alloys and metals used include Inconel for the exhaust headers, chosen for its lightness and heat transfer properties, titanium for other exhaust components that need to be lightweight, and gold for sections of the engine bay for its appearance and heat reflection capabilities. In addition, the ultra-high molecular weight polyethylene, Dyneema fibre improves the impact resistance of carbon fibre composites and gives additional chassis crash protection.  

    Almost all the components are designed and hand-made in-house by the design and engineering workforce at Koenigsegg’s production facility in Ängelholm, Sweden. In-house manufacturing enables low volumes to be made as required. Koenigsegg works with suppliers to evaluate emerging materials for potential use on its cars. ‘The industry is constantly evolving and we have to keep ourselves plugged in to the constant change cycle of materials technology.’

Traditional craftsmanship

    Morgan Motor Company, UK, has been hand-making sports cars since being founded by HFS Morgan in 1909. The materials used for its vehicles must be both lightweight and ‘lend themselves to hand production,’ says Jonathan Wells, Head of Design at Morgan. All of its models are based on aluminium, ash wood and fine leather. ‘We practice traditional coach building for the bodies of our vehicles. This means using an ash wood frame as a non-structural “coat hanger” upon which aluminium panels are hand beaten. Ash is easy to sculpt, source and sustain, and is a static wood in terms of how it adopts moisture and moves throughout its life. Aluminium is soft and easy to manipulate. Recently, we have explored carbon fibre, hand-worked over a wooden frame to lower weight on our electric platforms,’ explained Wells.

    The design and manufacturing phases of Morgan vehicles are a mixture of traditional and modern.  Morgan’s EV3, an all-electric 150-mile range three wheeler, currently in development, takes under nine seconds to go from 0–62mph (0–100km/h), weighs less than 500kg, has a carbon fibre bonnet, tonneau cover and side pods.

    Following analysis and development of new designs via 3D visualisation software, finite detail CAD analysis is performed. The resulting data feeds into the heavy processes including pressing, superforming (specialist hot forming), CNC machining and casting carried out by suppliers. Drawings are also created from the data to inform ‘the more artisanal hand crafted techniques used to create in-house components such as the wooden frame or leather interior trim,’ Wells explained.

    Light machining forms part of some in-house processes. Aluminium panels and ash wood pieces, for example, are machine cut before being hand assembled or formed to create the car’s frame. As new materials and methods are adopted, labour skills are consequently updated. ‘Our craftspeople are always learning. The skills and techniques required to expertly handcraft a Morgan car are built up and passed down over generations. We have employees that have been with the company for more than 50 years as well as many apprentices,’ said Wells.  

Using new materials

    New materials and processes are fundamental to the Elemental Rp1, a road-legal track day car that went into production in 2016. The Rp1 goes from 0–60mph (0–97km/h) in 2.8 seconds, has F1 and Le Mans inspired aerodynamics, and an F1 driving position – it is the brainchild of ex-McLaren engineer John Begley, who founded the UK-based Elemental Motor Company in 2012 to bring his idea to market.

    Some of the car’s carbon fibre components are manufactured using common methods for moulding and curing prepreg (pre-impregnated with activated resin) carbon fibre. But a variant of these processes – Elemental’s patent-pending CarbonAl technology – creates the Rp1’s 68kg tub. This has a carbon fibre dash panel, side pods and structural cross beams, bonded to front and rear bulkheads and a floor made from laser-cut aluminium sandwich panels. Peter Kent, Composites Director at Elemental said, ‘For the tub, we’ve used standard aerospace or motorsport materials with well-known properties, but we’ve come up with ways to keep the processing time down and create one-piece components that don’t require gluing.’

    Carbon fibre is expensive, so is used solely where its strength or aesthetic qualities are essential. ‘For every engineered product, materials selection is key. We’ve only used carbon fibre where we really need to,’ said Kent, who previously worked for McLaren’s F1 team and on the McLaren P1 road car. The support structures for the Rp1’s lights and parts of its bodywork are made from aluminium, for example, while the wheel arch liners are manufactured from Coats Synergex via UK-based manufacturer Shape Machining’s automated ‘ShapeTex’ hot forming process.

    Synergex is a customisable thermoplastic composite recently developed by industrial yarn manufacturers Coats. For the Rp1’s wheel arch liners, which need to be stiff, lightweight and tough, the Synergex fabric consists of carbon fibre commingled with nylon. The ability to tailor the fibre alignment, and also build up thickness locally, means Elemental is investigating other applications for the material. ‘This material is state-of-the-art and there are a lot of possibilities with it,’ explained Kent.

Trickle-down effect

    For Apollo Automobil, a German supercar manufacturing company that is developing a new car under the project name ‘Titan’, due to debut in July 2017, carbon fibre is key. Its earlier Apollo N model, which goes from 0–100km/h in three seconds, features carbon fibre body panels but has a tubular chrome molybdenum steel frame. By contrast, the entire chassis – central monocoque and front and rear sub-frames – of the new car will made from carbon fibre, says Norman Choi, CEO of Apollo Automobil. ‘This gives a lot of advantages in terms of rigidity and weight and increased flexibility in the design of the car,’ explained Choi.

    ‘An all carbon fibre chassis allows us to adopt more organic shapes, and create a tighter package that leads to better aerodynamics,’ adds Ryan Berris, Apollo’s General Manager for North America. In general, reducing the weight of cars is the simplest and most cost-effective way to create efficient automobiles that meet the legal requirements for road use.

    While the monocoque of Apollo’s new model will be made from a wide weave of carbon fibre known as a ‘race weave,’ which is stiff and so gives the chassis good torsional rigidity, the exterior panels will be formed from an innovative tighter weave that creates an aesthetic depth effect.

    Although its specialist engineers develop some of the materials and components used in Apollo’s cars in-house, others are sourced or created via partnerships with outside suppliers. Currently, Apollo’s materials scientists are developing new textured materials that can be interwoven with carbon fibre to create a bespoke surface finish. Berris predicts that some of the carbon fibre components Apollo has recently developed will eventually move into mainstream automotive use. ‘The hypercar segment is usually the test bench for future technology and materials, and they slowly trickle down once they become more cost effective.’

    With new materials and production processes in development by bespoke manufacturers, supercars look set to provide ever-increasing levels of performance and design innovation. Some aspects are likely to become standard in the cars most of us have in reality, rather than just in our fantasies. 

© Sharon Ann Holgate. Reproduced with permission of Materials World.
http://www.iom3.org/materials-world-magazine

CARS   MATERIALS WORLD


Boxed content from multi-author Pedal to the Metal! feature 


by Sharon Ann Holgate
Flipside
November 2013

Q&A

Home-grown drag racer Alec Coe does a burn-out before each methanol-fuelled rail drag car race in the UK’s Supercharged Outlaws class, because it's essential to leave a layer of rubber on the racetrack that gives the dragster grip as it rockets away from the start line, he tells Sharon Ann Holgate.

    How do you do the burn-out? ‘You drive your rear wheels into what they call the burn-out box, which is a section of track with water laid down on it, then just floor the accelerator. The water allows the wheels to spin freely, reducing the load on the gearbox and back axle. The wheel speed is around 200 mph (321 kp/h), and the tyres actually grow by 4 to 6 inches (10.2 to 15.2 cm) in height because they are so flexible. The dragster gradually comes out of the water and when it gets on to the dry tarmac, the tyres really smoke. You can't touch the tyres after— they're so hot they’d blister your hands.’

    Hang on, your tyres grow? ‘The tyres are really, really soft to give them grip, and because they need to expand once you've picked up speed. The bigger the tyre gets, the quicker you're going to run. If my tyres are 33 inches (83.8 cm) high and 15 inches (38.1 cm) wide, when they expand they will go up to probably 38 inches (96.5 cm) high.’

    But how does that actually help you to go faster? Dr James Brighton, head of the Centre for Automotive Technology at Cranfield University explains: ‘As the tyres revolve faster and faster they grow due to centrifugal force because their side walls are very flexible. This increase in tyre radius makes for a quick run because it acts like an automatic gearbox, without the weight and efficiency penalty, but still keeps the dragster engine operating at the optimum rpm (revolutions per minute) to give maximum power throughout the run.’

    Does the burn-out do anything else to your tyres? ‘Yes, it cleans the tyres. The hot, soft tyres pick up every bit of stone and dust. If you left the line with dirty tyres, one could be dirtier than the other and lose traction. The back axle has a locked differential, which means both rear wheels rotate at the same speed, so if one wheel loses traction the car is going to turn, and you need the car going dead straight. You need to pump the tyres up identically. About half a pound difference in pressure from one side to the other could mean half an inch difference in tyre height, which could turn you left or right.’


Fast Facts 

Top Fuel Dragster

  • Runs on a 90% nitromethane 10% methanol fuel mixture.
  • Custom-built V8 engine produces 8000 bhp.
  • Burns 1.3 gallons of fuel a second during a race.
  • Pulls 6g from the start line.
  • Accelerates faster than a NASA rocket launch.
  • Each rear tyre costs $700.
  • Top speed over 300 mph (482 kp/h).

 

Q&A 

Start Your Engines

Seasoned drag racer Lee Gallimore races methanol-fuel adapted drag cars at the Shakespeare County Raceway in Warwickshire. Here he tells Sharon Ann Holgate how it feels to race a drag car.

    What does the acceleration of a drag car feel like? ‘My car will go from standing still at the lights to 18.3 m down the racetrack in 1.04 seconds. The acceleration is very, very fierce. We're pulling around 3.5 to 4 g from the start line. It took me six years to get comfortable with that.’

    How do you get a fast start in a race? ‘You have to slow your breathing to bring your heart rate down so it will control the adrenaline, and the blood pressure in your brain. As soon as the four amber lights flash on, that's when I’ll leave, so I'm just going over the line as the lights change. It takes about 0.2 or 0.3 of a second from your eyes focusing on that light for your brain to react and tell your foot to press the accelerator. What we try to do is beat the brain function by anticipating the light before it has actually gone green.’

    Do you feel the acceleration for the whole run? ‘There is constant pressure of g force from the minute the accelerator goes to the floor to when the car rolls to a stop. At the top end of the run, when it's stopping with the parachute, you can pull more than during the acceleration and it snatches you forward into the safety harness.’

    Many drag racers have lost their lives since the 1950s—doesn't that scare you? ‘It's a very dangerous sport. But we know what the dangers are and do everything we can before we get in that race car to make sure it is safe. Every nut, bolt, and bracket is checked, as are the brakes and parachute. You never, ever take the car for granted. We also have a safety harness, helmets, neck restraints, a fireproof suit, and a roll cage.’

© IET. Reproduced with permission.

CARS