Composites boost performance of track day car

Track day events have become increasingly popular in the last decade with many motorsport enthusiasts taking to the circuit to get a first hand taste of what it's like to travel around without a speed restriction. The trend has seen a number of mainstream manufacturers bring to market track-ready versions of production vehicles, to cater for individuals that want to drive cars optimised for the track.

The movement has since gone one stage further and has spawned a number of small niche vehicle manufactures to go at it alone and produce cars specially designed for performance and driving experience. These include vehicles such as the Ariel Atom, the Caterham 620R and the BAC Mono.

While road legal, this new breed of ultimate track day cars resemble go-karts on steroids, often featuring just one or two seats, no roof and a power to weight ratio that will make most enthusiasts smile.

To build a fast car you need some basic ingredients: low and central centre of gravity, lightweight materials, and a powerful engine. But it is not all that simple; refinement and elegance are at the heart of every great British sports car and having the right ingredients doesn't necessarily make a delicious meal.

This was the premise for the BAC Mono; build a car aimed at, 'drivers who seek a purist driving experience and for whom design, engineering excellence and performance are of paramount importance'. While all of that might raise an eyebrow with the more practical individual, the finesse, elegance and performance that the car delivers is an impressive engineering feat.

Increasingly, carbon fibre thermoset composites are being used to edge performance. Indeed the material itself, with its distinct weaved pattern, has come to symbolise speed and quality. Optimising composite materials, manipulating their properties, and fully exploiting the materials potential is vital to their successful application. But, it is not easy to get right.

One company that knows all about this is Huntington based TRB Lightweight Structures. The company was approached by BAC to develop an optional lightweight carbon fibre floor for the BAC Mono as an optional, additional performance, extra. It would replace the standard, three-part floor made of wood. While the standard floor was fit for purpose, it was an obvious area for optimisation and development.

Sandra McQueen, chief marketing officer at TRB, says: "At the moment the carbon floor we developed with BAC is a high-performance option, but following the success of that project, BAC is considering making the lightweight floor standard."

Fine Designing
TRB set about using a high strength carbon fibre weave with an epoxy resin. The fibre and resin system was selected specifically to maximise strength. This combination meant that the floor could be made thinner and therefore lighter.

The next step for TRB was to produce the three-part wooden floor as a single carbon fibre part. This optimisation meant it was able to reduce the floor weight by 15kg, an impressive amount considering the lightweight nature of the Mono in the first place, with wood already considered a fairly lightweight material.

BAC Mono development driver, Oliver Webb, helped bring about the improvements. He says: "On the floor, combined with a few other parts, we saved 50kg. In a car that only weighs 600kg that's incredible. You always want that centre of gravity central and as low as possible, and the floor is a big part of that.

"Like F1, people now realise how important weight is. F1 cars used to have 1200hp, now they are 1.6l turbo engines that go faster, so it has all changed and lightweight materials are a big part of that."

Composite materials can be highly variable, with the resin, fibre and process having a huge effect on the end properties and surface finish. Getting the mix right requires expertise and there are always compromises to be made. During the development of the floor system, TRB found the single piece floor slightly compromised stiffness. However, it was a trade off that was deemed necessary to increase the performance.

"We spent a lot of time talking about the different densities of carbon fibre that would allow us to produce parts that were both lighter and stronger," says Webb. "And there is always compromise. What we try to find is that sweet spot for the application. If it was for me to enter races then we would make it as light as possible and accept it might only last a few races. But, as it is a car for the public road we need it to last much longer."

The outcome for the BAC Mono is that its performance floor has become hugely popular and may soon become a standard feature for all of BAC's future builds. However, this wasn't all down to the performance gained on the track, the factory also benefited from the improvements.

As the standard wooden floor is made in three sections, each is heavier and harder to assemble and fit than the single piece carbon fibre floor. While manufacturing the floor in a single piece takes more time to produce, a greater saving is made during assembly that means the overall floor can be produced more quickly.

"The whole top section of the car goes on as a solid single piece," says Webb. "You then have a lightweight paint on the top but really that's it. Even the rear wings are fully attached and are connected to the floor next to the arches, and the arches next to the wings. So that is all one piece of the body.

"And all that allows BAC to increase sales. The quicker we can get the car off the jig and on to its own wheels the better. And, optimising the floor allows us to do that."

Justin Cunningham

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