A handsome and perfectly balanced design, the four-door Park Ward body on the 41-litre Bentley.
THE 4-LITRE BENTLEY
A DE LUXE SPORTS CAR IN WHICH SMOOTH AND REFINED PERFORMANCE ARE SUPPORTED BY STRIKING ACCELERATION, AN ALL-OUT SPEED OF 93 M.P.H., AND SPRINGING AND BRAKES WHICH INSPIRE CONFIDENCE
Two years ago a road test of the 8litre Bentley appeared in the pages of MoToR SPORT and the writer still remembers vividly the lightness of control and the amazingly smooth and silent running which the trial run revealed. As one had hoped and anticipated these valuable characteristics have been retained in the new model, which differs from the 8i-litre only in having a larger engine. For all its smoothness the 41litre engine delivers a quite unexpected increase of power, and even when carrying a substantially built four-door saloon the latest Bentley sets up new standards of acceleration, while the all-out speed is naturally improved as well. Driving the car through London traffic, there is little to suggest the high performance obtainable on the open road, though the close-set steering wheel, the controls all ready to hand and the good visibility leave no doubt as to its suitability for handling at speed when the opportunity occurs. A gentle murmur from the engine, coming as it appears from a great distance, i8 all one knows about the source of power, and the car wafts along noiselessly on top gear almost down to walking pace, picking up cleanly
when the accelerator is depressed. In a word, a car of perfect manners, well suited for playing the town-carriage when the owner’s work or pleasure takes him into streets and built-up areas. The performance in top gear is equally striking at higher speeds, and unless the absolute limit of performance is required, there is rarely need or even inclination on a main road run to drop down to third. Main road hills such as those leading up to the Devil’s Punch Bowl near Hindhead, with a gradient of perhaps I in 12, and usually climbed at sixty on third by the average sports car could be negotiated at 65-70 m.p.h. on top with the Bentley in a silent and effortless climb. Undoubtedly the Magic Carpet up to date I If there is a legitimate reason for the utmost haste, a train to meet, a forgotten appointment or just a fine summer day when one’s feelings of joie de vivre
The acceleration chart of the 41-litre Bentley
become irrepressible, the Bentley is more than competent to cope with the situation. The car has obviously been conceived as a whole, and the various components work together to make fast driving a thing of certainty. The springs are damped by special hydraulic shockabsorbers of Bentley design and the car can be cornered really hard without a sign of rolling. An adjusting lever on the steering-wheel boss allows the damping effect to be adjusted when travelling over bad roads, but except when running slowly over rough surfaces the selfcompensating principle of the shockabsorbers makes it unnecessary to ease back the lever. The steering is pleasantly high-geared, is remarkably light in action without being subject to snatch and has “a useful self-centring action, while the steering lock speaks of extensive testing in the Alps.
The brakes work as suavely as do the other controls, giving a gentle slowing effect when lightly used and yet bringing the car to rest without a swerve in 57 feet from 40 m.p.h.
With a car like the Bentley no one speed can be given as the best cruising speed, since the engine is practically inaudible at any pace, and there is no suggestion of fuss even at the top end of the range. 70-75 m.p.h. with the engine running at 3,500 r.p.m. is a gait which eats up the miles with a minimum of effort. The allout speed timed over a flying half-mile at Brooklands was found to be 93 m.p.h. At this speed the car ran perfectly steadily and quietly, though there was a certain amount of movement of the front wings. As has already been noted, the excellent top-gear per
formance of the 41-litre Bentley makes one almost forget the delightful gearbox, which is dead silent on the three upper gears and which on third and top has the smoothest and swiftest synchro-mesh mechanism we have ever encountered. At 4,500 r.p.m. the speeds on the indirect gears are 34, 55 and 75 m.p.h., while peak revs, are reached at 94 m.p.h. on top gear.
Even with a comparatively heavy saloon body the car seems to toy with the 4.1 to 1 back-axle ratio, and with open-coachwork one could probably employ with advantage the 8.9 to 1 gear which is also available, and which at 4,500 r.p.m. would give a speed of just on 100 m.p.h.
As will be seen from the graph, the acceleration of the car is remarkably good, especially the figure of 10 m.p.h. to 60 m.p.h. in 134 seconds. A standing halfmile was covered in 32i seconds, the speed on passing the half-mile post being 83 m.p.h.
The driving position was ideal with the controls all close to hand, and a high and deep screen and thin roof pillars. The seats needless to say were luxurious in their softness, with ample support for shoulder and thigh, our only criticism, a purely personal one, being that we should have preferred the driving seat with a rather more upright back. The rear of the car is set out so as to give a really high degree of comfort for two passengers, with ample elbow-room, foot-wells which give stretch to the longest legs. The back seats are well forward of the rear axle, and ample head-room is provided in spite of the low roof-line, so that for comfort there is nothing to choose between back and front seats. The dash-board is laid out with characteristic good-taste, with the speedometer and the rev.-counter right under the driver’s eye. Special points we liked were the map-light, a lamp concealed in the scuttle and shining down when required in front of the passenger. The other unusual feature was the lamp switch, by which either one or both head-lamps can be used when in the
dipped position. In many Continental countries it it compulsory to show two lights forward on all occasions—wing lights are ignored—so this system of switching provides for all occasions. P.100 headlamps are fitted, a guarantee of powerful driving light, and the dipping mechanism is controlled by a foot-switch on the floor-board. The body fitted to the car we drove was a standard four-door saloon built by Messrs. Park Ward, and as the illustrations show, its distinguished and almost classic lines are perfectly in keeping with the fine workmanship and outstanding performance of the chassis. A sunshine roof
is fitted and the rear panel hinges down to give access to a spacious luggage boot. To appreciate to the full the thoroughness and care which goes into the construction of the chassis it is necessary to visit the works at Derby, and. to see each part subjected to the closest scrutiny between each operation. A mere glance under the bonnet will tell almost as much
to the practised eye, for every nut looks hand-made, every flange fits as though it were the only one of its kind, while the very throttle and ignition controls work as smoothly as those of a microscope. The engine is identical in design with that of the 3i-litre car. The cylinderhead is of cast-iron, the overhead valves are vertically disposed and are operated by push-rods, and one sparking-plug per cylinder is used. The ignition is by coil, and a spare unit is mounted alongside the one in use. By changing over a plug and lead, the spare coil can be brought into action in a matter of seconds. The ignition is automatically advanced by means of a centrifugal governor and a further hand-control, which is only required for starting or slowrunning, is carried on the
steering wheel. Two S.U. carburetters are used, and an air-filter and silencer of remarkable size completely ‘overcomes powerroar and the hiss of the
incoming air. The carburetters are supplied by means of a double electric petrol-pump. The rear tank holds 18 gallons, of which two gallons are a reserve supply brought into use by a tap under the bonnet. The petrol consumption works out at 13 m.p.g., and what is really remarkable on a high-efficiency unit like the one under review, the engine runs perfectly smoothly on No. I petrol, without recourse to leaded mixtures. A mixture control is fitted to the steering column to facilitate starting in cold weather.
The cooling water is pumpcirculated. Thermostaticallycontrolled shutters are fitted to the radiator, and a fan is also standardised. Turning to the lower parts of the engine, the cylinderblock is made of cast iron, while an aluminium crankThe which
case is used. The crankshaft, which is statically and dynamically balanced, runs in seven main bearings, and the sump holds two gallons of oil. The engine is carried in the frame on a special form of rubber mounting. Engine and gear-box form a single unit, with a single-plate clutch carried in the bell-housing between them. The perfect functioning of the gear-box which has synchro-mesh on third and top and constant-mesh on second gear, has already been referred to. Equally interesting is the servo-motor, which reduces the effort required to apply the brakes. A shaft driven by worm gears from the layshaft of the gear-box carries a disc and when the brake pedal is depressed what is in effect a disc clutch is forced ito
contact with the revolving disc. The drag produced is utilised to apply the brakes, in conjunction with the pressure exerted on the pedal, and if the servo were to fail, which is highly improbable, the pedal would still operate the rear brakes.
The drive is transmitted to the rear axle through an open propeller shaft with two needle-bearing universal joints. The rear axle is fitted with hypoid bevel gears, bringing the incoming drive below the centre line of the axle and so making it possible to get a low floor level without a shaft-tunnel. The chassis is built with a view to the reduction of weight without sacrificing rigidity, and so is deepest amidships, tapering off towards the front and rear dumb-irons. The side members are swept up over the front and rear members in order to obtain a low centre of
gravity. The springs, which are of exceptional length, have each individual leaf, ground and fitted together before assembly. In conjunction with the controllable shock-absorbers, which deserve a special word to themselves, they provide a suspension range, which gives equal satisfaction when ambling gently through town and driving flat out on a 300-mile journey.
The shock-absorbers are of the hydraulic double-piston type, partly self-compensating. An oil pump fitted to the gearbox is in communication with the controlvalve of each shock-absorber by piping, and as the road speed mounts, the damping effect of the shock-absorbers is increased. The hand-control on the steering column has a further over-riding effect, limiting this damping to the amount which personal taste or road conditions dictate.
Two other items of technical interest demand mention. One is the worm-andnut steering-gear. The principal working parts are a steel worm and a nut lined with white metal. In order to obtain the high standard of accuracy and lightness required by the makers, these pairs of components are ” run-in ” for several hours on a special machine, ensuring perfect freedom and response as soon as the car is put on to the road. The other unusual feature is that all the electrical gear with the exception
of the lamps and the battery is made at Derby. Besides ensuring that it comes up to the high standard of accuracy achieved in the other component parts of the chassis, the beautifully finished switches and even the smoothly moulded bakelite covers for the coil and the distributor are a source of pride to the owner who shows a proper appreciation of his car.
After nearly three years in the hands of private owners it has not been found necessary to change a single item in the lay-out or specification of the 81-litre Bentley, and our road-test of the ” 41 ” suggests an equally trouble-free future for the latter car, which incidentally is guaranteed for three years. Mr. E. R. Hall has already demonstrated the speed and reliability of the smaller car under racing conditions by finishing twice in second place in the strenuous R.A.C. Ulster Tourist Trophy race, and the damt of the 41-litre car in the Grand Prix d’Endurance at Le Mans will be awaited with the keenest interest.
Matters of Moment, October 1979
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