Car Restoration Projects
Bentley Blower Car Zero – a Project of Draftsmen and Craftsmen
The Blower Continuation Series is the first customer-sales project delivered by the new Bentley Mulliner Classic portfolio, one of three new divisions of Mulliner alongside Coachbuilt and Collections.
The Blower Continuation Series is a run of 12 newly-built recreations of one of the most famous Bentleys of all time: the supercharged 41⁄2-Litre ‘Blower’ created for racing by Sir Tim Birkin in the late 1920s.
Forming the world’s first pre-World War II continuation series, these 12 cars were pre-sold to Bentley collectors and enthusiasts around the world.
After 40,000 hours of work, Bentley Mulliner completed the first new Bentley Blower in 90 years, with the delivery of Car Zero that was the prototype car for the Blower Continuation Series.
These highly exclusive customer cars are being crafted from the design drawings and tooling jigs used for the original four Blowers built and raced by Sir Henry ‘Tim’ Birkin in the late 1920s.
Specifically, Bentley’s own Team Car (Chassis HB 3403, engine SM 3902, registration UU 5872 – Team Car #2) has been the master model for the Continuation Series, with every single component laser-scanned as part of a wheels-up, sympathetic restoration.
From this data, 1616 individual parts 230 assemblies, including the completed engine, were designed and hand-crafted to create the new Blower. The total parts count was several thousand, when fixings and interior trim parts were included.
Each of these parts and assemblies has been created by a project team of Bentley Mulliner engineers, craftspeople and technicians, working together with a number of British specialists and suppliers.
Blower Car Zero was a dedicated test and development prototype, built in advance of the 12 customer cars and was subjected to months of durability and performance testing.
Finished in gloss black, with an interior in Oxblood red leather from Bridge of Weir, Car Zero made its debut on the new Bentley Motors campus in Crewe.
The creation process
The first step in creating Car Zero was an extensive analysis of the original design drawings and drafts that were referenced in the creation of the original Blower Team Cars, together with archived period photographs of the cars.
Following a piece-by-piece disassembly of the Bentley-owned, priceless #2 Team Car, an exceptionally precise laser scanning of the frame and its components led to a complete digital CAD model of the Blower.
From there, artisan specialists were recruited, to start manufacturing the components that Bentley Mulliner would bring together to form the first Blower.
Bentley’s Director of Mulliner, Paul Williams, commented:
“Seeing Car Zero come together over the last weeks and months has been astonishing.
“The very latest digital design techniques came together with genuine artisanal hand-crafted artistry – often using manufacturing methods true to the 1920s.
“It’s only through this fusion of old and new that we could craft these cars, with the skills of our engineers mirrored in those of our specialist suppliers.
“We’ve issued thousands of drawings and specifications for components, and watching them arrive into Mulliner and then seeing the car take shape has been hugely rewarding,” said Paul Williams.
From the outset, Bentley Mulliner sought to engage the very best specialists across the country to create componentry for the Blower Continuation Series in a manner befitting such a project and using traditional techniques passed down through generations.
The chassis was created in heavy-gauge steel, hand-formed and hot-riveted by the specialists at Israel Newton & Sons Ltd. This 200-year old company, based near Derby, traditionally makes boilers for steam locomotives and traction engines, and has the skills to forge and shape metal in a traditional way.
The Vintage Car Radiator Company, based at Bicester Heritage, crafted exact recreations of some of the Blower’s key components, including the mirror-polished, solid nickel-silver radiator shell and the hand-beaten fuel tank, formed in steel and copper.
Market leaders in the manufacture and restoration of vintage car radiators and components to the highest possible standards of craftsmanship and authenticity, they were the perfect choice to handcraft these tricky and vital components.
Leaf springs and shackles were made to original specifications by Jones Springs Ltd, a specialist in the West Midlands, with nearly 75 years of experience and a history that started in a blacksmith’s forge.
The Blower’s iconic headlamps were reborn by Vintage Headlamp Restoration International Ltd in Sheffield. This father and son team is world-renowned for silversmithing and ability to create vintage-design headlamps from original specifications.
Meanwhile, in the bespoke Mulliner Trim Shop in Crewe, a new ash frame created by Lomax Coachbuilders underwent final stages of carpentry, before Mulliner’s team of experts applied of 25 metres of highly specialised Rexine material to wrap the frame.
Hand-trimming of the body was then completed by Mulliner’s master craftsmen.
For Car Zero, the gloss black bodywork was paired with Oxblood red Bridge of Weir leather and matching trim. As per the originals, the seats were stuffed with a total of 10 kilograms of natural horsehair.
The ‘Blower’ engine
The engine for the first car in Bentley Mulliner’s Blower Continuation Series fired up for the first time in December 2020, on a dedicated test-bed at Bentley’s Crewe factory.
With the engineering prototype for the project, Car Zero, in build, the first engine was recreated by Bentley Mulliner, with the expert support of specialists.
While the engine was being built, a team of Bentley engineers began work to prepare one of the four engine development test-beds at Bentley’s Crewe headquarters. The engine test facility has been part of the Bentley factory since it was built in 1938.
The engine-test cells were originally used to run-in and power-test Merlin V12 aero engines produced by the factory for the Spitfire and Hurricane fighters of the Second World War.
Preparing the test-bed involved making a replica Blower front chassis to hold the engine, which could then be mounted to the computer-controlled engine dynamometer.
A new software version to measure and control the engine was written and tested, allowing Bentley’s engineers to monitor and run the engine to precise parameters.
As the Blower powertrain is considerably different in size and shape to Bentley’s modern production engines, a number of the original Merlin testbed fixtures that were still in storage at Bentley were utilised to adapt the test-bed to accommodate these special engines.
With the engine fully installed, first fire-up took place and the first engine went through its defined schedule of run-in before a full power test. The engines were tested across a 20-hour cycle, gradually increasing both engine speed and load conditions from idle up to 3500 rpm. Once each engine was fully run-in, a full-load power curve was measured.
Once testbed running was complete, the next step for Car Zero’s engine was real world durability. When the build of the car was complete it started a programme of track testing that entailed running for sessions of gradually increasing duration and speed, checking functionality and robustness under ever harder conditions.
The test programme was designed to achieve the equivalent of 35,000 kilometres of real-world driving within 8000 kilometres of track driving, simulating the undertaking of famous rallies such as Peking to Paris and Mille Miglia.
The newly-created Blower engines were exact recreations of the engines that powered Tim Birkin’s four Team Blowers that raced in the late 1920s, including the use of magnesium for the crankcase.
The Blower engine started life as a naturally aspirated 41⁄2-litre engine, designed by WO Bentley himself. Like Bentley’s 3-litre before it, the 41⁄2-litre brought together the latest individual engine technologies of the time: single overhead camshaft, twin-spark ignition, four valves per cylinder and, of course, Bentley’s now legendary aluminium pistons.
The racing version of WO’s 41⁄2-litre engine developed approximately 130bhp, but Bentley Boy Sir Tim Birkin wanted more. WO’s focus was always on reliability and refinement ahead of absolute power, so his solution to finding more power was to increase engine capacity. Birkin had a different plan: supercharging the 41⁄2; an idea that WO thought ‘corrupted’ his design and would lead to unreliability.
With funding from his wealthy financier Dorothy Paget and the technical skills of Clive Gallop, Birkin commissioned supercharger specialist Amherst Villiers to create a supercharger for the 41⁄2.
The Roots-type supercharger, or ‘blower’, was fitted ahead of the engine and radiator and driven directly from the crankshaft. Internal modifications to the engine included a new, stronger crankshaft, reinforced connecting rods and a modified oil system.
In racing tune, Birkin’s new supercharged 41⁄2-litre engine put out around 240bhp.
The ‘Blower Bentleys’ were therefore extremely fast, but, as WO predicted, also somewhat fragile. The Blowers played their part in Bentley history, including helping to secure victory for a naturally- aspirated Bentley Speed Six at Le Mans in 1930, but over the 12 races that the Blowers contested, a victory was never secured.
Chairman and Chief Executive of Bentley Motors, Adrian Hallmark, had the honour of driving Car Zero down Pyms Lane to mark the occasion, and commented:
“Today was a truly remarkable day, not just as a milestone in the Blower Continuation Series project but also for Bentley Motors.
“To drive the first new Blower in 90 years was a privilege and the quality of the car would make Sir Tim Birkin himself proud.
“The craftsmanship is exquisite, and I’m pleased to report that the car drives just as beautifully as our original Team Car,” said Adrian Hallmark.