The Bentley Mark VI Saloon A New Design Offering Sustained High Performance and Enlarged Body Space
WHEN the new Bentley Mark VI was announced in May, 1946, it was apparent that it was a very different car from any of its predecessors. The latter constituted a consistently successful series of cars built between 1933 and 1939 in which (apart from an enlargement in bore) there was no basic dimensional change or substantial modification in specification. The Mark VI, on the other hand, represented a complete breakaway, both in respect of engine design, chassis layout and size of body. The engine, although unchanged in bore and stroke, now has the cylinders cast integral with the crankcase and the exhaust valves are laterally placed in the block. The detachable head carries vertical inlet valves operated by push-rods and connected to the inlet manifold by direct inclined ports. An orthodox four-speed gearbox with direct drive on top and the three upper ratios synchronized is now used in place of the previous geared-up top, and the characteristic Bentley friction servo motor now operates a mechanical brake system connected to the rear drums and an hydraulic system in the front wheels.
The frame of the Mark VI model is deep and cruciform braced, giving a very large increase in torsional stiffness over the previous design, a development of special importance now that the front wheels are independently sprung by wishbones – and coil-spring system. The wheelbase of the new car is shorter than its predecessor by 6 ins., and both engine and passengers are grouped much farther forward, the distance from the centre line of the front wheel to the main screen pillar having been reduced from 59 ins. to 45 ins. In consequence, although the rear-seat passengers have been brought forward on the frame, there is a very great increase in passenger space, which, as one might expect, is particularly noticeable in the rear compartment of the car. The seats are also now higher from the floor than they were, the distance from floor to roof having been increased by 4 ins.
In sum, whereas the older models offered perfect accommodation for two, but somewhat cramped quarters for four, the new car offers ample leg and elbow room for four people and the possibility of easily carrying five. These changes have been effected without increasing weight and, as a consequence of the improved characteristics of the engine, without impairing performance. The top-gear acceleration up to 50 m.p.h. is almost identical with the pre-war models, but above this speed the new car shows to considerable advantage, gaining 3.7 secs. in the 50-70 m.p.h. range and 4.3 secs. when timed between 60-80 m.p.h. Maximum speed also shows an increase of some 5 m.p.h. and, in consequence, a genuine 90 m.p.h. is no longer a figure which can be reached only in special circumstances, but a speed that can be readily obtained and maintained in the ordinary course of day-to-day running.
Utmost Comfort
In favourable circumstances the Mark VI will undoubtedly approach the three-figure mark, so that there are few cars that can compare with it, either in respect of maximum speed or acceleration. This should not lead either the motoring critic or the intending purchaser to assess the car as a sports model, in the sense that this term is sometimes used as a synonym for the near-competition type of car. As one can infer from the price, the Mark VI is intended to appeal to the well-to-do middle-aged as a special type of luxury carriage, distinguished from others of its kind by an outstanding ability to make fast, long journeys reliably and with the utmost bodily and mental comfort to both drivers and passengers. It is definitely not a car in which the engine performance has been raised to the highest pitch by the sacrifice of other desirable qualities; nor is the chassis and suspension so schemed that the car may be hurled round comers from sheer joie de vivre.
In other words, the Bentley is pre-eminently fast on runs of 300 miles or more and would not claim to be unique in the number of miles which can be covered in any given hour.
The superb ability of the car over long ranges is a product of smooth and quiet performance, first-class steering and control, and powerful but effortless braking. At all speeds over 20 m.p.h. on top gear the engine is truly turbine-like, whilst should second or third gears be required, the passenger who misses the motion of the driver’s left foot and right hand will find it almost impossible to detect that direct drive has been abandoned. For this reason, on winding country roads third gear can be continuously engaged in order to achieve maximum powers of acceleration.
The change itself is effected by the traditional rigid lever in a right-hand gate, the former having been shortened and the latter brought farther back, as compared with previous Bentley models. These changes have improved the entry and exit for the driver, but have placed the lever in a somewhat awkward position for quick changes, although doubtless “knack” could be acquired. For downward changes of gear, the synchronizing mechanism will completely govern the situation, but double-declutching can be recommended if a rapid change from top into second is demanded. Normal upward changes involve some delay, the engine taking an appreciable time to lose r.p.m. when the throttle is closed. The average driver performing normal brisk motoring will rarely need to change gear, starts being conveniently made in second, and third being a most useful ratio for continual use in town traffic.
Smoothness and Accuracy
A car of this kind will be frequently used in London, and it is, therefore, worth commenting upon the absolute smoothness of the clutch and the accuracy and positiveness of the steering. which enables the car to be taken through crowded streets like a model of much smaller dimensions.
Tyre scream can, however, be embarrassing in towns, as it will arise on sharp corners even at 10 m.p.h., and is further induced by the manner 40 m.p.h. feel like the legal limit, a deception not abetted by the speedometer, as this instrument is innocent of more than 2 m.p.h. optimism throughout the speed range.
On the open road the car demonstrates the pronounced understeer characteristics which one would expect from a suspension design embodying low-rated springs and a front antiroll bar. It is, in consequence, naturally stable directionally and at all speeds free from wander or deviation, even in face of sudden crosswinds. This feature is, of course, particularly valuable when maintaining cruising speeds of 80-90 m.p.h. over straight, open roads.
By making full use of the effective ride control on the rear shock dampers, rolling on sharp radius curves is reduced to reasonable limits, in view of the weight and general proportions of the car, but the whole nature of the design prevents the model from being at its best under these conditions. Moreover, the straight-running characteristics are bought at the price of some slowness in response to the helm, particularly at high speeds. The car can, however, be put on to a given line of curve with great accuracy and held on to it with consummate ease.
Excellent Brakes
Safety at high speeds is immensely enhanced by the combination of excellent stopping power in the brakes with low pedal pressure. The latter, indeed, are so modest that it was difficult to get accurate readings on the normal pressure instrument.
Servo braking has been a feature of Bentley designs for many years, but on the new car the braking figures are substantially better than anything previously recorded because a greater proportion of breaking effort is now applied to the independently suspended front wheels.
Good lights are equally important to fast driving in this country. In keeping with its character of providing fast transport on immediate call, the Bentley has generous-sized head lamps, set well above the road in a position such that minor surface irregularities do not cast shadows.
At Montlhéry, maximum speed tests over a flying quarter-mile did not prove satisfactory, unduly low speeds resulting from unfavourable combinations of wind and gradient over the available measured stretches. Unexpectedly, the lap speeds proved rather better than those over awkward opposite quarter-miles, and these are undoubtedly slightly short of the autobahn maximum of the car.
On repeated tests, with one lap to accelerate from rest, the car immediately recorded a timed lap at around 94 m.p.h., then settled down to lap at speeds ranging between 91 and 93 m.p.h. for an apparently indefinite period. The same results, one lap at 94 followed by laps at 93, were obtained with two drivers, one of whom held the car down the banking slightly and the other allowed it to follow its natural course.
A brief spell of timing from outside the car confirmed the utter absence of mechanical or exhaust noise, although the rumble of tyres was audible half a mile away and the heavy car was actually loosening concrete from surface joints on the bankings. At the end of the tests, which indicated a maximum speed of certainly 95 m.p.h., the car was driven back to Paris and on towards Ostend and England, as quiet, flexible and comfortable as at the beginning of the day.
In instrumentation and minor controls the Bentley comes up to the expected standard. The steady and consistent speedometer is flanked by ammeter, oil-pressure gauge, radiator thermometer and level gauge serving alternatively fuel tank and oil sump. Ignition and lighting switches may be locked in any desired setting by a single key. Trafficators, with an almost inaudible time switch, are controlled from the centre of the screen rail.
Inadequate Interior Details
The car tested had the standard four light steel saloon body, and it must be said that this is not wholly satisfactory, either in respect of external appearance or interior amenities. The wide, individual front seats have fore and aft adjustments but none for height, and lack centre arms to steady the driver, or a squab shape which will effect the same purpose. Stowage space for handbags or books is virtually non-existent, and for such important items as maps quite inadequate. Additionally, although an efficient interior-heating system is used, with provision for additional high- temperature blast to defrost the screen, the fact that the screen is fixed results in inadequate ventilation in hot weather. A scuttle ventilator is provided, but, for aerodynamic reasons, is, of course, of little use when travelling at high speeds.
In sum, the Mark VI is not only a new design, but an entirely new kind of Bentley. It retains the silence of running and astonishing durability and reliability which have won so much fame with its predecessors. Compared with them, it goes faster in far greater body space. It will be found particularly suitable for motorists who have, in the course of their affairs, to cover long distances at high speeds, and although, with two exceptions, it is the the car was most expensive car in the world to-day, owners should be well satisfied with their bargain.
RIGHT GEARS
Set in a position which Interferes little with entry to the car, the right-hand gear lever is well within the reach of even a short driver.
EXPRESS CARRIAGE
Sleek lines hint at the high performance of the Bentley, masking the roominess of the new coachwork. The famous painted radiator remains almost unchanged. though set forward and flanked by recessed headlamps.
Reprinted from “The Motor” – Temple Press Ltd. Bowling Green Lane, London, 1947
