We are covering the build of Koenigsegg Agera RS chassis 128 from start to finish here on the Koenigsegg website.
Chassis 128 will be the first Agera RS to be fully homologated for the United States.
Station 1 is where it all begins at the Koenigsegg factory. This is where the various carbon fiber parts, along with the fuel tank, are bonded together to make our monocoque chassis.
The monocoque is one of the core elements of any Koenigsegg’s capability because of its light weight and extreme torsional rigidity, or stiffness. We’ll talk a little more about that later.
First, let’s look at how we build the tub chassis in the Agera RS.
It’s an autoclave cured, pre-impregnated carbon-fiber construction with an aluminium honeycomb core structure (the same as used in Formula 1, for increased crash protection). An aluminium fuel tank is integrated into the tub chassis, inside the hollow box sections, in order to give the fuel tank maximum protection and to give the car the best possible weight distribution in combination with the most optimal packaging available. The total weight of the whole chassis and fuel tank is just over 90 kilograms, or 198 pounds. That’s super-light in anyone’s terms.
We start with the basic component parts – the bottom section of the chassis and the fuel tank.
The fuel tank is very advanced with built in anti-slosh walls and flaps, for optimal fuel distribution and pickup. It holds 82 liters.
For this entire section of the build, the parts are bonded together using an industrial epoxy adhesive.
Why bond the sections together?
If you bolt carbon parts together – welding is not possible, of course, because it’s carbon fiber – you get a stress point of force where the bolt is. Carbon is by far the strongest material compared to its weight, but it does not particularity like high point loads because it is fibrous. By using an adhesive, we’re able to get a full bond across the whole surface area where the two parts meet.
We’re talking about a large surface area and super-strong adhesive here, capable of holding around 36.1 Newtons or just over 3.5kgs per square millimeter. That’s 2370kgs or more than 5,200lbs per square inch – a lot more than the weight of the entire car. And we use a LOT of this adhesive on every section of the chassis. In fact, the amount of adhesive used on the Agera RS is more than enough to stick a couple of fully loaded Airbus A380s to the underside of the Oresund bridge (if the surfaces were suitable).
To make sure every mm of the bonding surface has enough adhesive, it is applied very generously. When the parts meet in the assembly jig and are being squeezed together, the excess adhesive is wiped off. This way we ensure consistent, secure bonds across the entire chassis, albeit at the cost of some extra adhesive.
Here’s an example:
In the picture below, the tank is already in place and Micke is applying more adhesive to the seams where the carbon and the fuel tank meet. Raul is readying the next load of adhesive so that the top section of the tub can be bonded.
Tim and Raul continuing the preparation…..
….. before fitting the top section of the tub.
It’s a case of ‘rinse and repeat’ for the nose section, the center tunnel, the windscreen section and the rear rollover bars. All have to be positioned perfectly and bonded into place.
Why is this all done manually?
The one thing you won’t see anywhere at the Koenigsegg factory is a robot. We are a small volume manufacturer. Our chassis component parts are built using consistent molds, but built by hand. In fact, many Koenigsegg parts are so complex that the only tool advanced enough to create them are skilled human hands. This way we can create a lighter more advanced car with more advanced components compared to more “mass produced” hypercars and thereby gain technical and performance advantages.
For example the dashboard is integrated as one piece with the hollow A-frame for the front window. In any other car this area would easily consist of 6 to 10 pieces. In a Koenigsegg, it is one hollow, immensely strong piece, and that also allows for the roof to be stored in front of it in the luggage compartment. This part can only be created with skilled hands.
Designing our car is a very human-centric process. Building one of them is, too.
Along the way, everything is measured and then measured again to ensure that panels are precision aligned. The roof is a key element here. Because the roof on every Koenigsegg is a removable item, the distance between the A-pillar and the rear rollover bar is crucial. Final alignment will be done in the jig, but Raul is measuring the gap with a laser (note the red dot on the rollover bar) to ensure that it’s right as the work progresses.
The ventilation chamber for the windscreen is installed at this point. Raul is seen in the pictures below both sanding and then bonding the surface.
When all the work is done and everything aligned, the jig is finally closed. The adhesive has a 90-minute window for basic movement/realignment and any excess is removed/cleaned during this window. It takes a further 7 days for the adhesive to cure completely.
Let’s talk about why we do this, then. Why do we build the chassis the way we do and why is torsional rigidity such an important component of the way we build a car at Koenigsegg? We’ll put the Koenigsegg chassis into perspective by looking at some more well-known cars first.
A Chevrolet Cruze is a generic, modern compact car. It has a torsional rigidity figure of 17,600 Nm per degree.
The Mini Cooper from early this century is a more sporting economy car. It has a torsional rigidity figure of 24,500 Nm per degree.
The Ferrari F50 is a performance car legend and a true collectible. It had a torsional rigidity figure of 34,600 Nm per degree.
The Porsche 918 Spyder is a contemporary of the Agera, also with a removable roof. It has a torsional rigidity figure of 40,000 Nm per degree.
The monocoque in the Koenigsegg Agera RS has a torsional rigidity figure of 65,000 Nm per degree.
Those figures should give you a feel for different cars and their level of structural stiffness. So what does it all mean?
In simple terms, it means that the car is very, very resistant to twisting or flexing when under pressure (e.g. at 1.8g’s in a corner). All cars benefit from a stiffer chassis but it is more expensive and more complex to create than a less stiff chassis, especially if you are looking for low weight, good space and good ergonomics.
One thing that many people don’t understand is that a stiff chassis actually allows for softer suspension and a more comfortable ride compared to a less stiff chassis if you set it up that way. The reason for this is that a stiffer chassis allows the suspension to do more of the work. With a less rigid chassis, the chassis flexes and moves when the suspension moves and this has to be considered when you design the suspension movement. Also a less stiff chassis has a more noticeable “judder” when driven on uneven surfaces, as the structure of the car resonates with the bumps. This is known as the resonance of the chassis.
Running hand-in-hand with rigidity is weight and to some extent, engine power. If you have a heavy car with poor rigidity then it will be more prone to flex as the laws of physics put stress on the chassis in the corners. The more power and speed, the more flex you will be prone to. If you make the car lighter, the inertia will be less and it will relieve this stress to some degree. Many readers might have enjoyed some seat time in a Mazda MX-5 (Miata). The NA series MX-5 has relatively weak rigidity (6000 Nm) but is super-light with an engine output appropriate for the car, which helps explain it’s fun nature on the road. A lot of MX-5 owners stiffen the car using aftermarket braces and suspension.
It’s all about knowing what your customers want. Koenigsegg customers want the best performance car in the world and a lightweight car with a super stiff chassis is the best foundation for superb handling in a comfortable car.
And that’s exactly what we build.