Rolls-Royce Enthusiasts Club - for Rolls-Royce and Bentley Enthusiasts

The Silver Cloud and the S Bentley, side by side, showing their slightly different paint schemes.

THE DESIGN & DEVELOPMENT OF THE SILVER CLOUD/ S SERIES:

By John H. Craig (BC Canada)

Editor’s note: This article began as a talk given at a Historical Week-end of the RREC at Hunt House 2000 and was first published in this form in the September/ October 2005 issue of The Flying Lady, the magazine of the Rolls-Royce Owners Club.

It was toward the end of World War II at Clan Foundry, Belper about 7 miles north of the Main Works at Nightingale Road Derby that Ivan Evernden in 1944, was given the job of quickly designing a bodyshell to be made by the Pressed Steel Company, to fit on a six cylinder chassis which was basically an entirely new design that had been developed in 1939 and had had many miles of road testing on war-work during the period of hostilities. This car, as we all now know, was introduced in October 1946 as the Mk VI Bentley and some 6,500 cars were produced without any major change to the shape and a further 3,200 with just the change to the size and shape of the luggage compartment.

The Styling Department team consisted of Ivan Evernden as Chief Styling Engineer, with Bill Allen and Cecily.K.Jenner, the artist who was responsible for most of the illustrations in this article. They were joined by John P. Blatchley just before the Mk VI Bentley was introduced. It was this team who were responsible for developing ideas for the next model to replace the Mk VI and in 1951 Ivan Evernden made a confidential presentation within the Company to introduce the Styling and Engineering Departments suggested body style of the next new Bentley and Rolls-Royce car.

Within the Car Division this new design was called the Bentley Mk VIII and was planned to replace the Bentley Mk VI which had been introduced in November 1946. The Bentley Mk VI was the first complete car ever produced by Rolls-Royce and designed for the owner/driver market.

Customers in the United Kingdom, but more particularly in the USA, soon made it known that they wanted an owner/driver Rolls-Royce in preference to the Bentley and so the Rolls-Royce Silver Dawn was introduced in 1949 based on the Mk VI chassis and body shell, but with modifications, among other things, to the carburettor and the camshaft to give a smoother drive.

I noted a letter in the May/June 1996 issue of the Rolls-Royce Owners Club Flying Lady magazine commenting that the Silver Dawn seemed to bear a close resemblance to a Park Ward body on a 1938 Wraith. Because of the shortage of development time (less than two years) the Mk VI standard steel saloon body shell was indeed based on coachbuilder designs that had been in existence before 1939.

The Styling Department was headed up by two interesting men - Ivan Evernden, who had started with Rolls-Royce in 1916, and John Blatchley, who had joined the Rolls-Royce Aero Division at Hucknall in 1940. In 1921 Ivan was sent to West Wittering to work with Henry Royce. He became friends with Henry and was responsible for the introduction of the Phantom II short chassis Continental in March 1934. He also received an MBE for his very successful design work in installing and cooling the Meteor engine in the Cromwell tank. John Blatchley in 1936, at the age of 23, had been appointed Chief Designer of the coachbuilder Gurney Nutting and at the start of World War II joined the Rolls-Royce Aero Design headquarters at Hucknall. He was responsible for the development and design of a new cowling for the Merlin that improved the aerodynamics of British fighter aircraft such as the Spitfire and the Hurricane. In 1944 he joined Ivan Evernden’s team at Clan Foundry, Belper just in time to help with the finishing touches to the Bentley Mk VI body design. Later with Ivan he would be credited with the introduction of the Bentley Continental with the Mulliner body in June 1952.

In motoring circles in about 1938 in the USA, but not until 1946 in the UK , a “New Look” in motor car design was being discussed which was far more than merely changing the shape of the external panels of the then current designs. It was fundamentally a new design for a private motor. Its objective was to provide within a structure externally no larger than the then current orthodox car, a new one in which more intelligent use was made of the available space. Waste space was to be reduced and the mechanical features condensed. Apart from several earlier motor cars, and those few of novel design, the design of the motor car had been based upon the popular conception of the horse drawn carriage – the engine replacing the horse between the cart shafts, with the passenger accommodation toward or over the rear axle. Although there had been a steady tendency to depart from this original concept, even as late as 1950 a good looking car was considered to be synonymous with a long and tapered bonnet and the “Greyhound Look” .

The Packard Clipper and Super Clipper, which appeared in the late forties were among the cars to break with tradition in adopting a design in which a logical conception of the Form was given preference. The customer was no longer asked to sit over the rear axle - ‘steerage class’ in shipping circles. It was logical that the first examples of this new form should appear in the USA where the motor car had long since ceased to be a luxury toy of the amateur mechanic. The American customer looked upon the automobile as yet another ‘sitting room’ of the home, which engineers had been commissioned to make mobile for personal transportation. Like their homes, they expected it to be centrally heated and air- conditioned. The maximum percentage of the length and width of the vehicle was devoted to the accommodation of the occupants and their luggage. Soon other manufacturers followed. The car grew no bigger; in fact in many cases it was reduced in overall size and weight while giving increased interior accommodation. To provide room for these accessories some economy in the use of space for purely engineering purposes was essential.

With the Bentley Mk VI launched to the public at the end of 1946, the Styling and Engineering Departments were aware that it was merely a continuation of the 1939 range and they realized that the next new car would have to be significantly different and designed with this New Look in mind. Many different ideas were investigated but there were probably just three that contributed most to the eventual design of the Silver Cloud and “S” Bentley cars introduced in March 1955 . It seemed obvious that the New Look could not be applied to a Mk VI chassis, but to get a true idea of this an experimental car, Chassis 10-B-VIII, with the radiator and engine moved forward and fitted with a standard Mk VI body moved forward relative to the rear wheels, was completed in February 1951. It was soon realized that this combination produced an undesirable styling effect, but did give the opportunity for some development testing to take place. This car was scrapped off after some 8000 miles in February 1952

 

Chassis 10-B-VIII with Mk VI standard saloon body

Another Styling Department design was contracted out to the coachbuilders, Abbotts of Farnham, Surrey for them to build the body on a 127 inch wheelbase Silver Wraith chassis with a six cylinder engine. This car was subsequently known as the Bentley Farnham and is shown here. When delivered in April 1949 it weighed 4,788 lbs and was 300 lbs heavier than planned. It will be noted that it dispensed with the traditional radiator shell in favour of a cowled front. It was designed according to the “New Look” and was finally scrapped off in 1951 after completing 28,000 miles.

 

Bentley Farnham with body by Abbott.

Yet a nother Styling Department design named Bentley Estoril and drawn with the New Look in mind was given to Park Ward, the coachbuilder owned by Rolls-Royce, who delivered the completed car in June 1949. This car weighed 4,540 lbs and was 600 lbs heavier than a MkVI car. The car did some test programmes and was used by Lord Hives and Ivan Evernden for evaluation purposes. It also was finally scrapped off in August 1951 after completing about 32,000 miles.

 

 

Bentley Estoril with body by Park Ward.

From the valuable experience gained from these experiments the Styling Department came up with a further design called Bentley Mk VIII and a full scale mock-up of their ideas is shown here.

 

 

 

Bentley Mk. VIII saloon mock up.

The objectives for the new car were as follows:

  1. A car which would be materially no longer or wider than the Mk VI.
  2. An overall height 1½ inch less than that of the Mk VI with the same interior headroom over the seats.
  3. Increased leg room for the rear seat passengers.
  4. The body width at the windscreen pillars to be materially the same as that at the centre pillars, giving a wider front seat and a wider angle of driving vision. An increase in the scuttle width to provide space for a modern air-conditioning plant, and a larger wireless set with a separate speaker and large cubby holes.
  5. Improved forward visibility over the bonnet, radiator and wings, despite the driver’s lowered seating position.
  6. Increased and improved space for luggage, even though the lowered car and deeper back light reduced the boot height.
  7. Increased front wheel vertical movement, notwithstanding the lowered bonnet - and the ground clearance on maximum bump to be greater than that of the Mk VI.
  8. A total weight no greater than that of the current Mk VI. (4,200 lbs kerbside weight.)
  9. Load on the front wheels not to exceed that of Mk VI which was at a maximum consistent with the use of 6.50 x 16 inch tyres and a safe cornering speed.
  10. A front end style, which given a small modification to the bonnet and a few extra press tools, would match the Rolls-Royce as well as the Bentley saloon.
  11. A saloon body capable of production as a coupe with the use of the maximum number of standard body pressings, and fittings.

 

Mk V - Mk VIII comparison drawing

This drawing shows the Bentley Mk V of 1939 compared with a similar car designed according to the new principle, - identified as Mk VIII.

 The passenger space has increased in length from 89 inches to 97.25 inches while the wheelbase has reduced from 124 inches to 120 inches. It can be seen that the capacity of the new design is greater and that it is positioned more nearly amidships, enabling the rear seat to be lowered ahead of the rear axle and maintaining or increasing the interior headroom without increasing the overall height of the body. The luggage capacity is increased in spite of the lowered luggage boot top. The waste space between the radiator grille and the front bumper has been occupied by the moving forward of the engine and radiator, and the moving rearwards of the front wheels and front bumper. Consequently the overall length of the car is lessened and its wheel base reduced. This gives a smaller turning circle and also an increase in the overall rigidity of the car. In plan the body is widened out at the base to the full width of the car, while the width at the screen pillars is only a little less than at the centre pillars.

 

Line drawing: Mk VIII over Mk VI saloon.

This is a line drawing of the proposed Mk VIII car superimposed on the drawing of a Mk VI .

In order to lower the car and yet preserve the same headroom as the Mk VI, the rear seat had to be moved forward relative to the rear axle by 6.5 inches. The dashboard and steering wheel had to move forward a similar amount in order  to maintain the same body space as on Mk VI. Increased leg room for the rear seat passengers is achieved by the lowering of the rear floor more than that of the front floor, thereby increasing the space under the front seats into which the rear seat passengers could extend their feet.

If the engine and the front wheels had gone forward with the body 6.25 inches, the wheelbase would have been increased to 126.25 inches. To retain the 120 inch wheelbase the engine was moved forward about 3 inches - the dashboard moved with the body 6.25 inches and was curved around the back of the engine to accommodate the difference.

 

Mk VI and Mk VIII elevation drawing

This further pictorial comparison between the two designs shows how the seating accommodation was changed and the relative positions of the units of the body and chassis can be visualised. The demise of the time honoured front apron occurred when the radiator and grille moved forward with the engine, whilst the front bumper, with the front wheels, stayed put.

Special treatment was needed for the back of the car. Due to the lowered roof of the luggage boot necessitated by the lowered car and the lowered deeper back light, no longer was it possible to stack the luggage upon the spare wheel, which in turn was over the gas tank . One layer of the cake had to be taken away and housed in the space above the rear axle, vacated by the moving forward of the rear seat cushion and the squab. The gas tank, because of its relative freedom from shape restrictions was the obvious candidate for this position. The spare wheel was lowered to the limit set by the specified ground clearance, taking with it the luggage boot floor. Access to the spare wheel, which was then low down and behind the rear bumper, was a problem which was solved by placing the wheel in a tray which, being hinged at the front, could be let down at the back by a screw and nut device actuated by the wheelbrace on a hexagon in the boot lid opening.

 

Spare wheel access and stowage.

In spite of its lowered roof caused by the new design of lowered car, the luggage boot could be given a greater capacity and a better shape than that of the Mk VI.

To carry out these changes in the general layout of the vehicle an entirely new chassis frame had to be envisaged. Relative to the rear wheels, the frame cruciform had to be moved forward with the engine, and the pan of the front suspension move backwards with the front wheels. In the plan view, the body changes called for few chassis modifications. The screen and front seat sections are widened out to swallow up the tail of the front wing, so causing useless air space under the front wing to be absorbed into the bonnet, scuttle and body space. The moving forward of the screen pillars and the consequent widening of the scuttle made possible the hinging of the front doors upon the screen pillars without any lost space for the occupants legs and feet during egress from the car. Ivan Evernden commented that doors hinged in this manner gave a

 

Bentley Mk VI general arrangement drawing

This drawing shows the Bentley Mk VI saloon. It is 16ft overall in length with a 10ft wheelbase. The overall width over the front wings is 69.00 inches and the width over the rear wings is 71.00 inches. The overall height is 5ft. 4.75 inches .

Bentley Mk VIII general arrangement drawing

  Here is a drawing of the proposed Bentley Mk VIII saloon. It is 16 ft 4 inches long, but retains the 10 ft. wheelbase. The overall width is 69.75 inches and the overall height is 5 ft. 3.75 inches. It is 4 inches longer, 0.75 inches wider and 1 inch lower in height than the Mk VI, but has a lot more room for the passengers and their luggage. It will be noticed that the chassis frame ghosted in the plan view has parallel sides at this time.

The front to rear wheel weight distribution is important in ensuring good road handling and a smooth ride. By moving the mass of inhabitable portion of the body proper, together with the occupants, forwards from the rear axle by 6.5 inches and also by moving the engine, gearbox and clutch about 3 inches forward, a very considerable increase in weight would occur on the front wheels if nothing was done to compensate for it. Calculations showed that an increase of 28 lbs was imposed for each inch so involved.

 

Bentley Mk.VI & Mk VIII relative axle weights .

 

The effect of the front wheel loading if no weight saving occurred is shown here.

It was calculated that the body of the Mk VIII would weigh approximately 108 lbs more than that of the Mk VI due to its greater bulk, unless design changes were effected in its construction. A very high percentage of this increase would fall on the front wheels. Both cars are shown as carrying 2 front and 2 rear passengers with 100 lbs of luggage and this is what is called the " laden condition". This shows that the Mk VIII front wheel load would increase by an unacceptable 260 lbs. Experience had shown that for a light steering and stable cornering characteristics, the front wheel load of the Mk VI should not be exceeded, particularly if the then current 6.50 x 16 inch tyre was to be used at the pressure which would give a comfortable ride. The 8 cylinder cast iron engine fitted to an experimental car, 11-B-V (nicknamed The Scalded Cat ) had demonstrated that fact. Therefore, it was imperative to save weight in the design of the car and particularly weight which would be carried by the front wheels.

The current Bentley Mk VI weighed in at 4,172 lbs and it was planned that Mk VIII should be no heavier than 3,920 lbs. This was regarded as optimistic, as previous experience had shown that the weight generally grew as the model developed. Nevertheless, it was projected that the front wheel load would only rise by 34 lbs and the rear wheel load would drop by 395 lbs in the unladen state

In designing the new chassis, efforts to reduce its weight by using an aluminum engine, lightened gearbox & front brakes, aluminum gas tank and other items were projected to save 244 pounds. The projected change in body weight was calculated in detail as follows :

BODY WEIGHT INCREASES.

  • Body Item. Weight
  • Windshield increased area 5.0 lbs
  • Doors. Metal frame tops and size. 40.0 lbs
  • 5 inch wider front seats 10.0 lbs
  • Extra floor 8.0 lbs
  • Wider bonnet 8.0 lbs
  • Extra scuttle 0.0 lbs
  • Larger back light 0.4 lbs
  • Dashboard 4.6 lbs
  • Extra roof & screen rail 2.0 lbs
  • Increased centre pillar 2.0 lbs
  • Extra bonnet at front 2.0 lbs
  • Increase length of rear boot 8.0 lbs
  • Increase in length of rear wings 5.6 lbs

Total Increase 108.4 lbs

BODY WEIGHT SAVINGS.

  • Body Item . Weight
  • Delete spare wheel door. 9.0 lbs.
  • Radiator grille & shutters 5.5 lbs.
  • Deletion of front apron 3.0 lbs.
  • Delete rear wheel spats 12.0 lbs.
  • Aluminium doors 58.5 lbs
  • Delete sunshine roof 7. 0 lbs
  • Aluminum boot -lid 6.5 lbs
Total decrease 101.5 lbs

This gave a projected increase of just under 7 lbs.

The need for these lightened chassis components, particularly the aluminium engine, the lightened gearbox, front brakes and suspension, was very real if the new car was to handle as well as the older one. Also the savings in weight of the body, chiefly by the use of light alloy in places such as the bonnet, front wings, doors and luggage lid were needed to compensate for the increased size of the body.

 

Mk.VI & Mk.VIII axle weight change.

 This sketch shows the front and rear wheel loading after incorporating the weight changes. In the laden condition the front wheel loading has changed from the original 260 lbs increase to only 55 lbs increase.

Having determined the form which the vehicle should adopt and having solved some of the engineering problems which the new form involved, the stylist was able to embark upon the task of ‘tailoring’ the form. Certain limitations were imposed upon the style to be used. The front end had to be capable of suiting both a Bentley and a Rolls-Royce car without serious increase in the tool charges involved. Both of the world-renowned traditional radiator shapes had to be preserved so that either car would be immediately recognised by the small boy in the street. Despite the cowled type radiator on some experimental cars, the Board had indicated that the traditional shapes must be maintained on all future models .

The style chosen had to be modern yet restrained. While the ‘New Look Form’ imposed limitations which made inevitable some resemblance to the then latest American and Italian cars, the style adopted had to be one which would become, with the passage of time, distinctly British. A degree of modernity seemed essential since, it was thought, the car might not meet the buying public until 1952 and would have to last for at least four more years without becoming outmoded. As we now know, the car did not get to the market until 1955 and in essence lasted for another eleven years after that, and could probably have continued for longer, it was so well liked. For this reason thin pillars, a relatively low waist line giving deep window glasses and a large back light were adopted. The polished metal frames for the window glasses, which were a feature of the best of Rolls-Royce coach built cars, were the subject of a special design and production investigation. Their inclusion added just that necessary relief to the design, without the addition of useless chromium plated mouldings. A further advantage they possessed lay in the fact that their fabrication could well be feasible only on a car in the price range and production rate of the Rolls-Royce and Bentley.

 

Rolls-Royce version of Bentley Mk VIII. Saloon mock up.

Here is the equivalent mock up of the Rolls-Royce version and which was to become known as the Silver Cloud. This was the state of the styling design in early 1950 and we are all well aware that the car that was first delivered some five years later was quite a lot different from these original mock ups. It will be noted that the Licence Plate number is JPB400 which are the initials of John Blatchley.

The interior styling had also to receive special attention, particularly with a view to giving an air of luxury to the seating. A type of cushion and squab construction had been developed and tested to economise in the use of trimming and leather. Although bucket or armchair front seats had been projected, the alternative of a bench-type seat had also been developed and featured a special diaphragm in the centre to ensure that the effect of weight on one side was not transferred to the other side ( from driver to passenger and vice versa).

The provision of adequate door seals to exclude draughts and dust from the body interior entailed the use of a modern type door lock of higher efficiency than that of the time honoured spring loaded bolt design. At the same time, twisting exterior door handles were not convenient to install and could well become illegal protrusions on such a wide body. Consequently a modern design of ‘push button’ handle had to be developed in keeping with the styling of the body. It was decided that the interior door handle should be incorporated in the door pull, so providing an enhanced degree of protection against the doors being opened inadvertently. The state of the design of the interior door pull grip and catch as at 1950 is shown here.

Interior door pull sketch.

The curved windscreen, whilst not moving the glass in line of normal vision farther from the driver’s eyes, provided just that requisite increase in room to enable the central portion of the instrument board to be part of the screen capping. This in turn enabled the radio set to be raised, giving more freedom for the occupants’ knees and allowing for the inclusion of a separate and larger speaker.

  Dash layout sketch.

This was the state of the proposed design in 1950. Commodious cubby holes and a glove box are also a feature of this new design.

 Even as early as 1950 the Engineers at Crewe were aware that air conditioning was required in some parts of the world, but generally speaking this was usually considered to be a heater and not a cooler! It took a few more years to make everyone realize that if so much time and effort was to be spent on reducing the noise level inside the car, then it was stupid to have to open windows or the sliding roof to let in air, since both noise and dust came in at the same time. An efficient air conditioning system therefore became essential and at this time the Engineers commenced work designing and developing the sophisticated two level system that was eventually first introduced on the Camargue in 1975 and the Silver Spirit in 1981.

As far as the Bentley Mk VIII was concerned it was decided to incorporate a sophisticated car heater and demister into the design of the dashboard and the scuttle. Fresh air was taken into the body via a large scuttle top ventilator in a cool or heated condition. Under extremely cold conditions re-circulated heating of the air into the body could be used.

Sketch of Heater/demister system layout.

This sketch shows the thought process in respect of the mock up Body shown in Figure No.4. Pivoting ventilation flaps were designed into all four door windows. These flaps were to be capable of being moved through an angle approaching 120º to permit of forced draught ventilation by forward motion of the car. As an aside these became fixed when full air conditioning was eventually introduced in 1959. The windscreen is demisted and defrosted by two wide ducts in the screen capping rail. They are to be fed with hot air from the car heater by means of a powerful blower fan.

The back light was to be electrically heated with fine heater wire embedded between two laminates of glass to prevent misting and frosting up and was wired to be left on during the winter and off in the summer.

The idea of producing a Standard Drop-head Coupé by making use of the body tooling for the saloon was to be able to offer for sale a coupe body at a price not materially greater than that of the saloon. To do this it was essential that the coupe should have a construction in which a high percentage of the saloon body pressings would be employed as well as a large proportion of the hardware, seats, and trimming. The ‘NEW FORM’, with its almost parallel sides in the plan view made this task relatively easy in the case of the Mk VIII compared with the Mk VI in which the contraction of the head towards the windscreen caused the hood when folded to unduly narrow the rear seat width.

Line drawing of projected Mk.VIII Drop Head Coupé.

A scale drawing of this projected Drop Head Coupé on Bentley Mk VIll is shown here and the same body design would be used on the Roll-Royce variant. The rear seat of the Mk. VIII , being much farther forward of the rear axle than that of the Mk VI, can be lower. This enables a low and sleek appearance to be given to the design of the hood. No longer does the hood, when folded down, steal valuable room from the luggage boot, since it was to occupy space above the gas tank.

 As at April 1950 the Engineering and Styling Departments reported that good progress was being made toward expediting the completion of the first prototype car. The V-8 aluminium engine had done a considerable amount of development running. A model chassis frame had been built and a sample of the new method of carrying the spare wheel had been made and tested. A mock-up of the dashboard and the scuttle had been produced and tests were being carried out on the new ‘fresh air’ heater and windscreen demisting plant. About the middle of 1950 the Engineers and Marketing executives were able to view these plans for Mk VIII and concluded that the design was not yet ready for production attention. It was therefore considered necessary to introduce the ‘face lift’ for Mk VI which had been developed as Mk VII and this design was introduced as the ‘R’ Type and Big Boot Silver Dawn in 1952.

The Company also decided that it was not yet ready to move to monocoque body construction and it was decided that the method of building the next car should continue as a completed chassis and fitted with a body; either a standard steel saloon produced at Crewe, or a body built by a coachbuilder on an individual basis, as was current at the time. Many of the projected details discussed earlier in this article were modified in the light of this decision ; in particular it meant that the gas tank and heater and demister units would be considered part of the chassis and not the body.

To allow coachbuilders to have a chassis it was necessary to be able to road test completed chassis with slave bodies at Crewe before dispatch to Lillie Hall in London and the Coachbuilder. Hence the gas tank could not be fitted behind the rear seat above the rear axle and the spare wheel would have to be fitted within the body shell, but below the luggage boot floor so that it could miss the rear cross member of the chassis frame. Thus, the gas tank could be fashioned so that it fitted below and around the spare wheel. Indeed later versions of the car also had an extra tank fitted inside the left rear wing tail

In 1951 the Styling Department was transferred from Clan Foundry, Belper in Derbyshire to the Car Division factory at Crewe. Ivan Evernden, who was reaching retirement age, was appointed Chief of Special Projects and John Blatchley was promoted to Chief Styling Engineer and about the same time Martin Bourne joined Bill Allen in the Styling Department. It was this team who styled the "’R’ Type Bentley and became responsible for the next stage in the development of the Mk VIII.

Under John Blatchley the project of the new standard steel saloon body to replace the Bentley Mk VI and the Rolls-Royce Silver Dawn became known as the Bentley IX, but it was more commonly known in the company by the code name. “Siam” and “Siam Dawn”. The wheelbase was increased to 123 inches and a quarter scale model of Siam is shown here.

Quarter Scale Model of Bentley IX – Siam

“S” Series Chassis .

The Mk VI chassis of 1946 had parallel side members, whereas the Mk VIII (‘S’ series) chassis shown here has strong boxed side members running from the narrow front suspension pan at the front to the wide rear cross members carrying the rear suspension springs. This frame was extremely strong and had great torsional rigidity. The narrow front pan enabled a double wishbone suspension to be designed with increased vertical road wheel movement to give a smooth ride and good turning circle and the resultant wider rear cross member enabled the rear springs to have a lower rating for a comfortable ride, but also increased rear roll stiffness to improve road handling.

Despite the good development of the aluminium engines - there were two: the 3.7 litre six cylinder eventually used in the Austin Princess ‘R’; and the now well proven V-8 designed by Jack Phillips - it was decided to retain the six cylinder in line engine but increase its capacity to 4.887 litres and fit it with a new six port aluminium cylinder head. It was decided to standardize the fitting of the automatic gearbox to enable the engine mounts to be softer to reduce noise transfer to the body, and the idea of making the bulkhead fit round the back of the engine was discarded. As a result it became necessary for the wheelbase to be extended to 123 inches. However, with the new front suspension it was possible to still retain a very good turning circle.

Calculations showed that the overall weight would be in the order of 4,144 lbs to 4,256 lbs and because of this it was necessary to develop a new wheel and tyre size - 8.20 in x 15 inch diameter. This had the Dunlop and Avon engineers working overtime and indeed when the first cars were available for sale in 1955 only the Avon tyre had been approved by the Rolls-Royce engineers although Dunlop were not long in catching up.

It is worth recounting that the ‘S’ series was the first car from Rolls-Royce to use unified threads for the nuts and bolts - today they are called fasteners. Previously Rolls-Royce had always used Whitworth and British Standard Fine threads, but to Rolls-Royce special specification with flat tops to the threads. The flat top to the thread was a Henry Royce design. Another first was that all fasteners were torque tightened. Previously all nuts were tightened by hand and Sir Henry Royce had calculated the length of the spanner for each size of screw thread and had also decreed the length of the ‘ tommy bar’ to be used with each box spanner. Drawings of these spanners and tommy bar lengths could be seen on the walls of the assembly shops at Nightingale Road, Derby . I recall that a tommy bar only 2 inches long was the maximum allowed for a 2 BA nut. Sir Henry Royce was of the opinion that a skilled mechanic could correctly tighten all the nuts using the correct length spanners and/or tommy bars that he stipulated. It was significant that when put to the test, nuts tightened in this way were in fact found to be tightened to the torque tightness which was decreed correct in 1955. Once more confirming the genius of Sir Henry.

Another very important first on ‘S’ Series was the decision by Rolls-Royce engineers to use Molybdenum Disulphide based lubricants in the assembly of the rear springs and other areas of the chassis in which sliding motion between two parts had to be lubricated. Molybdenum disulphide in ground powder form was found to have much better performance characteristics than the better known graphite, and Moly Sulphide greases continued to be used up to the introduction of the Silver Spirit range.

It was also realized that unacceptable road noise heard within the body of the Mk VI was transmitted by the body mounts and this was an area in the new car that had to be improved. It was realized that any metal to metal connection between the body shell and the chassis was a path through which undue road and chassis noise could be transmitted to the interior of the body. To eliminate this it was decided that there should be no metal to metal connection between the chassis and the body and to achieve this the body would be mounted on special rubber mounts and the steering column should be rubber mounted from the chassis. Unfortunately it was not possible to dispense with the speedometer cable which was still required to operate the odometer and this became the only metal connection between the body and the chassis. If modern electronics had been available in the 1950’s this speedometer cable would have been replaced with an electrical connection, thus removing this last remaining metal connection between the chassis and the body.

The ‘Siam’ body was fitted to the chassis on sixteen rubber mountings, one under the radiator and the remaining fifteen on the body, and in order to give the minimum transference of sound and vibration it was essential that each mount supported the same load and that every rubber mount was compressed equally. To achieve this, special mounting equipment was designed and each chassis mount on the chassis frame was fitted with a cradle to allow of vertical adjustment. The chassis frame has six mounts along each chassis side member and there are two near the centre just behind the cruciform and one on the rear cross member . The sixteenth mount is below the radiator on the front pan and carries the radiator, wings, and valances. The rear end of the valance is fixed to the scuttle or bulkhead with slotted holes to provide adjustment. Thus the body can be ‘floated’ on the fifteen body mounts and the mounts correctly adjusted before the valances are secured to the scuttle. Special equipment was designed which consisted of ten hydraulic rams inter-connected by high pressure hose and capable of being inflated from a high pressure air supply. Each ram had a cradle for attaching it to an outer body mount and the body could be supported on these rams to enable each body mount to be secured with its rubber mount being correctly loaded. This proved to be a very unique and successful way of isolating the body from unwanted road and chassis vibrations and reduced the noise experienced by the occupants to a very significant degree.

Incidentally, if the body is removed in service from the chassis for any reason it is necessary to use this special equipment when remounting to ensure maximum success.

S Series Instrument panel

The instrument board remained nearly as was designed in 1950, although the timer-type turn signal switch could not be put in the centre due to the rear view mirror mounting and so it was put on the extreme right or left depending on the steering wheel position. In order for the rear view mirror to be in the correct position relative to the rear window it was necessary for the mirror to be mounted on this stem or be hung down from the top of the windscreen on a longer stem, which idea was discarded.

Siam Chassis complete.

The new heater and demister system was part of the chassis and is shown here on the side of the valances. It can be seen that the system underwent extensive redesign and development from the system drawn in 1950. Fresh air was taken from the front of the car at the point of maximum pressure below each headlamp on either side and passed through a heat exchanger mounted on each side of the engine valance. One side directed air to the windscreen through vents in the capping rail and the other directed air to the lower portion of the body as the heater. Control of volume and temperature was achieved by the use of vacuum operated flaps and water taps controlled from pull and turn controls on the Instrument Panel. High power fan blower motors were installed in each duct to augment the ram airflow achieved by forward motion of the car. This installation can be seen in the illustration which is a chassis all ready to go to a coachbuilder.

1955 Production Rolls-Royce Silver Cloud sedan

1955 Production Rolls-Royce Silver Cloud Drophead Coupe

 The results of the Engineering and Design Departments work are shown here in the Silver Cloud sedan and coupe and there is no doubt that John Blatchley, along with Bill Allen and Martin Bourne, produced a car design which has stood the test of time

The ‘S’ series and the Silver Cloud were introduced in March 1955 and were received by the Motoring Press and the buying public with acclamation. A quote from one of the motoring magazines Test Report of the day stated :- “There is no doubt that the car fully justifies the admiration, even glamour, which attaches to its name throughout the world in countries where cars of quality are understood and appreciated”. The gestation period was at least nine years and the cost enormous by 1955 standards. I believe the suite of press tools for the body shell alone was in the 5 to 8 million pound sterling range (approximately US 10 to 16 million dollars).

Although many of the ideas that were considered in 1950 were not incorporated in the 1955 Silver Cloud and ‘S’ Series, it is for the record that they were incorporated in the Silver Shadow and also in the Silver Spirit when these cars where subsequently introduced. Items such as the spare wheel mounting and the position of the gas tank are just two such ideas which readily spring to mind.

There were about 2,360 Silver Cloud and 3,100 ‘S" Bentley cars built between March 1955 and July 1959, making a total of 5,460 or an average of 1,260 cars per annum - a significant increase over the 750 per annum of prior years. Approximately 44% were to the Silver Cloud specification.

In 1959 the Silver Cloud II and the Bentley S2 were introduced. They were fitted with the now well proven V8 engine initially of 6320ccs capacity designed by Jack Phillips, together with an under front wing air conditioning unit In 1962 the Silver Cloud III and Bentley S3 were introduced with many further refinements including twin headlamps and redesigned front wings.

 John H. Craig, July 28 2005.