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Car of the Month

More on Bentley in these books:

Bentley R-Type

Taylor: Original Rolls-Royce & Bentley



Car of the Month - August 2011
Bentley Experimental Car, 1938, #9-B-V
Sports Saloon by Park Ward

Bentley Experimental Car

This Bentley Experimental car was built to the specification for production Bentley Mark V – and indeed Park Ward erected the coachwork on a chassis from the first batch of 50 production Bentley Mark V chassis the company had started to build from July 1938 onward. In frontal appearance this car was up-to-date, e.g. the sidelamps were integrated into the top of the front wings whereas previously separate units had been found. Its paintwork was 'dernier cri' - an attractive metallic falcon blue. One of the first examples of 'real' metallic paintwork to be applied onto a car in Europe as the art to make proper metallic paint had only recently been developed in the USA. After an initial test-run of some 14,000 miles during the winter of 1939/1940 a B60-engine from the 'Rationalised Range' substituted the car's MkV-engine.

The 'Rationalised Range' was a new strategy to apply common parts across a series of different chassis for various markets and models. Such should utilise common components, e.g. pressings, suspension, steering, brakes, instruments – and engines. What was code-named 'B-range' would be 4-, 6- and 8-cylinder in-line engines, being of the same design and having many common parts. Hence valves, valve guides, pistons, bearingsand many other components were all to identical measurements and thus less expensive in production and interchangeable. The development of first batches of such cast iron engines with overhead inlet and side exhaust valves towards the end of 1938 had reached a point where it was an appropriate decision to use the Experimental Cars as "rolling test-beds" for these.

Experimental car #9-B-V and other prototypes did run "tens of thousands of miles on war-work during hostilities" (W.A. Robotham in Silver Ghosts and Silver Dawn; Forty-four years with Rolls-Royce, Constable, London 1970, page 197) and thus the manufacturer had an up-to-date design for a range of chassis with a tremendous amount of pre-production testing.

Left: Rolls-Royce B60 engine (here a version with service recorder and two speed governor);
right: Rolls-Royce Silver Wraith engine. Both units were 6-cylinder in-line engines of 4 1/4 litres capacity. Indeed the Silver Wraith’ engine was developed from the B60-engine, although re-fined to a certain degree with an aluminium cylinder head instead of a cast iron one. Rolls-Royce Silver Wraith, Bentley Mark VI and later Rolls-Royce Silver Dawn were fitted with engines of identical design.

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Hence it is fair to assume that the post-war cars Rolls-Royce Silver Wraith, Bentley Mark VI and – launched at some later date – Rolls-Royce Silver Dawn and Bentley R-Type did owe a lot of their superior technical components to the tersting exectuted with Experimental Cars from the immediate pre-war period and among these especially to #9-B-V. That can be detected in the layout of silent front suspension, engine mounting and the brake-servo's new design, too. As but one example hereunder illustrations of independent front suspension of pre-war and post-war models for comparison:

left: Design of independent front suspension of Bentley Mark V, not brakes operated by rods so linked and located that they swing through the same arcs als the wheel-mounting members
right: Design of independent front suspension of Bentley Mark VI, note hydraulic front brakes

This Experimental Car’s exhaust system became substituted by a twin exhaust (later found on the right-hand drive Bentley Mark VI “Big Bore”) and tests were carried out with a Stromberg carburettor (later standard on Rolls-Royce Silver Wraith and left-hand drive Bentley Mark VI).

When development testing resumed 'on larger scale' in 1945 the fitting of hydraulic brakes (hydraulic front-brakes became series-standard from the very start on Rolls-Royce Silver Wraith and Bentley Mark VI) and testing of tyres suitable for Bentley Mark VI are worth to be mentioned. In 1946 the car – after a period of inactivity as production of the post-war models had started – was passed to the Transport Department of Rolls-Royce's aero engine factory at Derby where it remained in use until February 1949 before finally Experimental Car #9-B-V was scrapped.

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