Metrology

Measuring and enforcing the highest standards of dimensional accuracy is especially important for a vehicle, where multiple components become sub-assemblies.

To take just one example, the retractable Flying B mascot that adorns the bonnet of the Flying Spur, which smoothly deploys and retracts only because each component in its complex control assembly is made to close and consistent dimensions. It is illuminated and linked to the keyless entry system as the driver approaches the car, yet it must also retract automatically in the event of an accident. To achieve this precise choreography and to ensure that it sits perfectly centred within its plinth, elements of the Flying B system have tolerances as low as 0.15 millimetres.

As well as measuring individual surfaces and components to microscopic levels of accuracy, the Metrology team measures entire vehicles. The department is home to what are termed ‘cubing’ reference vehicles; an entire vehicle body machined out of solid aluminium that acts as a template against which panels and interior components are measured. The cubing Flying Spur is the ideal Flying Spur against which all others are measured, every millimetre of its body scanned using high accuracy digital cameras to create a complete and precise map of the car.

“Imagine an issue at the prototype stage where the panel gap between grille and bonnet is a millimetre too large, “explains Micheal Stockdale. “Does the fault lie with the grille, or the bonnet? The cubing reference vehicle provides the answer, because it’s made to the precise dimensions of the CAD data.”

Materials expand when warm and shrink when cold, so it’s essential that measurements are taken at a consistent reference temperature. Within the Metrology area, air conditioning keeps the area at a steady 20°C. But for components that demand the highest levels of precision, there’s an inner sanctum called the High Accuracy Measurement area, where a dedicated climate control system ensures that the temperature never deviates by more than half a degree Celsius. Within this area are three gigantic granite blocks to which components can be clamped for the ultimate in stability, essential for an accurate reading. But first, the components to be measured have to soak in the atmosphere – literally. “A large component like an engine block might have to soak at a consistent temperature for up to a week, so we can be sure that it’s 20°C all the way to the core” explains Micheal Stockdale.