MEASUREMENT & MONITORING
MEASUREOF PERFECTION
BENTLEY
Bentley’s in-house metrology team under the microscope
Deep in the heart of the Bentley factory in
Crewe is a large, airy and air-conditioned
workshop that visitors, even out of a
government lockdown, will never see.
It’s packed with the kind of precision
instruments you’d expect to find in a space
agency facility or university science lab.
It’s here that Head of Metrology Michael
Stockdale and his 25colleagues measure
every part of a Bentley to the highest
standards of precision.
Metrology is the science of measurement,
and it’s fundamental to the quality,
performance and longevity of every
Bentley that each component is made
to consistently precise dimensions.
Stockdale and his colleagues can
measure every part of each model Bentley
makes, from the smallest washer to body
panels and interior trim, and ensure that
no component strays from the close
tolerances prescribed for it. “We have
the tools to measure everything from
the graining of leather to the surface of
a cylinder bore, down to fractions of a
micron” explains Stockdale.
Having measured components
individually, they are measured again as
sub-assemblies and once more as part of
the finished vehicle. Thus, the Metrology
team plays a vital role in ensuring that near
perfection is repeatable.
THE PRECISE CHOREOGRAPHY
OF THE FLYING B
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,
whichsmoothly 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 theFlying Bsystemhave tolerancesas
low as 0.15millimetres.
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TOLERANCES FINER THAN A
SINGLE RED BLOOD CELL
Laymen use ‘a hair’s breadth’ as a
description of the tiniest imaginable
measure, but such a term would be too
imprecise for Bentley’s Metrology team.
As Stockdale points out, a human hair
can be anything from seventeen microns
toover one hundred and fifty microns thick.
In contrast, there are instruments within
Metrology that can measure down to
0.5microns.
A micron is one millionth of a metre, and
a human red blood cell is 5 microns in
diameter. Not every component of a Bentley
needs to be measured to tolerances of less
than a micron, but there are some.
As an example, Stockdale cites the
crankshaft at the heart of Bentley’s 6.0-litre
W12 engine, the most advanced 12-cylinder
engine in the worldwhich powers the
new Flying Spur. Spinning at up to 6,000
rpm, the crankshaft converts the immense
downward forces generated by the pistons
into rotary movement that powers the
wheels. Though invisible to the naked
eye, each of the twelve machined bearing
journal surfacesin which the crankshaft
sitsfeatures minute grooves that hold a
microscopic film of oil.
By using a high accuracy Perthometer (a tool
designed to measure surface finishes) the
Metrology team can verify that those minute
grooves are within their definedtolerances,
in turn ensuring that each W12 engine
produces both the immense power and
lifelong durability its owners would expect.
A FLYING SPUR CARVED FROM
SOLID ALUMINIUM
As well as measuring individual surfaces
and components to microscopic levels
ofaccuracy, 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 actsas a templateagainst
which panels and interior components are
measured.The cubing Flying Spuris 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
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.”