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At the very core of the Aston Martin Valkyrie is the carbon tub. An absolutely critical piece to the project, it is easy to overlook what a complex and time consuming element this was to engineer.
State-of-the-art is an over-used term, but in the case of the Aston Martin Valkyrie it is barely sufficient. The driving force of this car is the most gifted mind in Formula One history. The carbon tub was primarily designed by the Red Bull Racing F1 team. It was engineered to highest possible standards by Aston Martin Special Operations and painstakingly hand-crafted by Multimatic, world-leaders in carbon fibre manufacturing.
Valkyrie is built around the most aggressively and obsessively optimised road car monocoque ever built. No tub before it has been designed and built to a brief as strict, nor paid such close attention to the ratio of strength versus weight or fulfilled such a multitude of critical roles. The tub is the core chassis structure; major aerodynamic surface; two-seater cockpit and safety cell. That’s why when you sit in a Valkyrie not only are you placing yourself at the very epicentre of the car, but you’re immersing yourself in the philosophy by which the entire car was created.
Carbon fibre road cars originally took their lead from Formula One. Carbon was first used to construct a Formula One car tub in 1981. It provided significant strength, weight and safety advantages. The downside was prohibitive cost, formidable technical challenges and labour-intensive nature of working with this new wonder material. Therefore, it was over a decade before the technology transferred into road car construction, with the Jaguar XJR-15 and McLaren F1.
Over 30 years on and a carbon tub remains the preserve of the hypercar elite, but the desire to build higher volume, lower cost carbon fibre supercars has led to advances and innovation in cheaper carbon fibre-based materials and speedier automated manufacturing processes. These low cost, high volume tubs possess some of carbon fibre’s inherent strength and weight advantages, but they are achieved by a dumbed down, cost driven process. They are therefore, a very different prospect to the tub that exists in Valkyrie. It applies cutting edge principles, materials and methodology employed in Formula One and therefore the design and construction.
Every Aston Martin Valkyrie tub is built by hand from 14 separate preforms of precisely cut and shaped using aerospace grade T800H high strength carbon fibre. The shape, size and positioning of every single piece, or ply, is defined by Red Bull technologies using Finite Element Analysis, just as it is with Red Bull’s F1 tubs, with every piece of carbon fibre specifically aligned and positioned to give the required strength capabilities for that particular area of the tub. Expert composite manufacturing engineers and laminators follow a highly detailed manufacturing manual that outlines the 121 separate operations required to complete the 950 man-hour process.
The build process is an operation of incredible accuracy. During the laying-up process Multimatic also build-in specially machined titanium inserts. These are added to provide load-bearing fixing points for the suspension and engine, and also serve as datum points when the upper and lower sections of the carbon fibre structure are bonded together. Manufactured from aerospace-grade Titanium, each insert is a perfect piece of industrial sculpture. They are precisely machined from solid material to ensure flawless quality, maximum strength and minimal weight, a total of sixteen inserts are required in the construction of every Valkyrie tub.
Each set of inserts requires 58 kg of raw material, but by the time the complex manufacturing process has been completed some 91 per cent of that has been machined away, leaving the complete set of finished inserts weighing just 5 kg. By the time the last Valkyrie tub is completed more than 58,000 kg of raw titanium billets will have been machined. The scrap Titanium from the machining process will be recycled to produce further Titanium forgings and billets. In fact, Aston Martin used so much titanium during the project, they caused the global commodity value to go up!
It then takes five hours to bake each tub. During this period the special structural resins contained within the ‘pre-preg’ T800H carbon fibre material can cure and harden to give the tub its strength. Once cured, the upper and lower tub sections are freed from their moulds, or ‘tools’, and sent for machining on a dedicated DMG five-axis machine. Each tub requires 60 hours of machining. During the course of the Valkyrie build programme this DMG machine will run 22 hours-a-day, every day, for two years.
The upper and lower tub sections are bonded together using aerospace adhesive agents. The bonding gap between upper and lower sections is just 0.5 mm, with the two halves of the tub squeezed together in a purpose-made hydraulic press. The tub sections are located by 8 interlocking points, plus a tongued and grooved joint which runs around the full length of the surface interface to fully lock-in the two sections. A conventional tub design would have two or three datum points, used solely as a means to control the union of upper and lower sections.
The Valkyrie uses eight datum points to increase the precision and to add strength in strategic areas. This requires absolute precision in the manufacture of the tub sections, as none of these datum points are machined after the tub sections are removed from the tools. Put simply, the tolerances are so small, there is no room for error.
The Valkyrie’s suspension system uses torsion bars. At the front these bars need to pass rearwards through the tub, from the suspension mounting points back towards the A-pillars, so a pair of holes are bored deep into the tub’s structure. Using a special fluid damped tungsten carbide Mapal head tool the bores are made to a depth of 496 mm with breath taking precision -bore diameter accuracy is to within 30 microns, and concentricity to 50 microns. To maintain absolute consistency and accuracy the Mapal tool is replaced after just eight operations. This final high accuracy deep boring operations is the final step of the 121 complex manufacturing process, by the time the chassis reaches this station more than 1,500 hours would have been consumed between manufacturing engineers and high precision robotic machines to create the Valkyrie chassis.
A complex engineering process is complex enough for and F1 car but the road legal elelement adds considerable complexity to the design of the tub. An F1 car doesn’t have a roof, a windscreen or doors. It doesn’t need an A-grade surface finish (this is the typical high standard of finish applied to any road car parts that are visible to the owner). Valkyrie must tick all these boxes and countless more, yet still adhere to stringent weight saving protocols that apply rigorous scrutiny to every single component.
The automotive industry mind set is to complete a project on time and within budget. With large scale production you need to deal in certainties. The F1 mind set is to effectively start from a position beyond what you know is possible, for anything less is to accept there are no better ways or more efficient solutions. Valkyrie is the sum of exploring those unknowns and solving engineering challenges that exist on the edge of what’s possible.
Highlight Summary:
950 man-hours to lay 14 separate preforms of carbon fibre material into the forming tool
•Position and orientation of every piece dictated by Red Bull’s Finite Element Analysis
•Once autoclaved the tub requires 60 hours of machining on a DMG five-axis machine
•Each tub uses 16 large inserts machined from 58 kg of aerospace-grade Titanium
•Finished inserts weigh just 5 kg
•Front suspension torsion tubes require two holes bored into tub to a depth of 496 mm
•Machining accuracy to within 30 micron bore diameter, concentricity of 50 microns (one millionth of a metre)
•Upper and lower sections of tub located by eight datum points and special surface joint built to nominal surfaces with only 0.5 mm of bond gap
•Almost 80% of the tub surface is shaped to perform an aerodynamic function
•Windscreen is the most curved ever fitted to a road-legal car
•Typical wishbone loadings into the tub of around 160,000 Newtons which equates to 16,300 kg acting as a point load into the CFRP/TI chassis