British Leyland's brand new car

“As the engine demands no longitudinal space on its own account a car only 120 in. long can accommodate four persons and a substantial luggage locker, and four-fifths of the overall width is available for these purposes. The transverse triplane engine/transmission layout not only plays a paramount part in achieving this but also, by offering front-wheel drive, confers a remarkable combination of comfort, stability, and traction. The driver is conscious of the behaviour of his car when

1. Driving in a straight line on a level road.
2. Cornering.
3. Climbing a hill.
4. 2 and 3 in combination.

“For cases 1 and 2 some degree of understeer is desirable to confer stability.

“To ensure understeer it is desirable to load the front tyres more than the back tyres in order to diminish their cornering power, and this is commonly done by placing the mass of the engine and gearbox well forward in the frame. The transverse engine mourning fulfills this requirement and the act of putting torque through the carcase of the front tyres also diminishes their cornering power and thus enhances the understeer effects obtained by carrying 60% of the weight on the front wheels. Hence the car is inherently dynamically stable.

The transverse engine mounting, coupled with the general configuration of the vehicle, also plays an important part in securing aerodynamic stability. With increase in road speed the centre of wind pressure moves steadily forward, and if it advances sufficiently ahead of the centre of gravity a side wind acts through a long lever to prise the car off the straight course. On the Morris Mini Minor cars the centre of gravity is naturally far forward and the relatively long, parallel, sides of the body behind the C of G act in themselves as a strong stabilising influence. Hence so far as stability on the straight is concerned a front engine driving the front wheels is superior to any other combination.

“In strong contrast, with a rear engine, driving the rear wheels, the rear tyres at once support the greatest weight and transmit torque, and therefore have the least cornering power, and the C of G is far back and the lever effect of the forward centre of air pressure thereby enhanced. The rear-engined car is thus inherently unstable both dynamically and aero-dynamically. The former condition can be ameliorated by low front tyre pressures and a strong anti-roll bar; the latter by fins if they are made large enough, but very few stable rear-engined vehicles have yet been produced; some critics might say none. On corners the front-drive car understeers with power applied. Contrariwise, shutting the throttle at once slows the car and reduces the cornering radius and the natural instinct of the average driver when going too fast is thus turned into a valuable safety measure.

“In the hill-climbing condition weight is transferred from the front to the back of the car and hence load is taken off the front, and added to the rear wheels. If, however, the front wheels are initially loaded 50% more heavily than the back they continue to carry adequate weight for traction on dry roads up to a gradient of 1 in 3, and thus have an ample margin for all normal motoring in any part of the world. On slippery surfaces some of these assessments of merit must be revised. When cornering or when on a straight road in the presence of external excitations such as of external excitations such as side winds or road camber, the exceptional traction ability of the rear-engine car is offset by difficulty in control if slippery surfaces cause the rear wheels to spin and the car to sideslip.

“In this event the spin must be suppressed by reducing power and, at the same moment, steering control restored by a counter movement. If overdone this results in a slide in a sense opposite to the original and, unless the driver be skilled, to a further series of tail slides which mar increase until the vehicle becomes completely out of control. But whereas wheelspin on a rear-drive car promotes an already inherent disposition to oversteer (which can only be corrected by shutting the throttle) on the front-drive car wheelspin exaggerates an existing understeer condition which can easily be countered by laying on more steering lock whilst at the same time maintaining traction by keeping the throttle in some degree open. So on slippery roads driving a front-driven car is relatively easy and it may, with no great skill on the part of the driver, ascend hills of sub-critical gradient by rising superior to adverse external forces to which rear-driven car’s, and particularly rear driven cars carrying more weight on the front wheels than on the back, all too easily succumb’. We see then that the rear-engined rear-drive car has outstanding traction ability if the driver is sufficiently skilled to avoid wheelspin or to take the right action if this occurs. The conventional layout favours cornering at limiting speeds by a driver able to use the throttle to help the steering. In all other circumstances the well-designed front-drive front-engine car shows to advantage to a degree which lessens manifestly the burden of the average individual and thereby adds to the sum of road safety.”

After coping with the publicity for many subsequent BMC f.w.d. cars, Pomeroy severed his connection with Austin/Morris but did similar work for the Ford Motor Company. Such a strong advocate for front-drive cars might appear to be in a tongue-in-cheek situation, because, apart from the V4 Taunus Ford, there were no f.w.d. Fords, none at all emanating from Dagenham. Perhaps fortunately, Pomeroy’s task was to publicise the big Mk. IV Zephyr and Zodiac cars in their new V6 formation, a design ably carried on, with revised i.r.s. and other modifications, in the present Consul and Granada Fords. My friend evaded any retraction of his opinions about front-drive, rubber-suspended cars by concentrating on the new Ford power unit. Of this he wrote as follows and, as BL have a V8 engine in the Triumph Stag and V12 engines in their Jaguar XJ12 and Daimler Double-Six and thus might well be using a vee-cylinder-layout for their new model, the remarks bear reiteration:

“If the mythical Man from Mars was to observe the different types of car built all over the world, the first thing he would see is that American cars are twice as large and are driven by engines three or four times more powerful than European cars. If he were to look deeper, he would see there are major differences in the type of engine used—that two out of three American cars coming off the production lines have their cylinders arranged in V-formation, whereas in Europe very few are of this type. Here, the ‘in-line’ engine is used, with one exception, by all major manufacturers.

“If he were now to turn his eyes to the rear end of the car he would see that in the USA about 19 out of every 20 cars made have a rigid axle beam connecting the rear wheels. But in Europe about three in every four have the rear wheels independently sprung; that is to say, all four wheels are independently attached to the car and movement by any one of them has no direct influence on the behaviour of the others. He would see between three and four out of every ten British cars with this feature.

“If our celestial observer were now to switch his gaze to a Grand Prix motor race he would see that none had in-line engines, and all had independent rear suspension. He would quickly discern that these vehicles are built to the very highest standards of performance and safety, with the latter (expressed in stable high speed on corners) even greater in importance than sheer engine power.

“He might then wonder what are the special merits of the V-type engine and of all-independent suspension . . . and if, as it would appear, they are very considerable, why they are not universally used? And, for that matter, why their application is so notably different on either side of the Atlantic.

“An unbiased commentator would explain the matter to hint in the following terms.

“On both passenger cars and racing cars, the length of the engine is highly important. On the former, every extra inch means so much less leg-room for passengers within a fixed overall length. On the latter, the longer the car the heavier and less manoeuvrable it becomes. In the USA, where engine powers range from 150 b.h.p. to well over double this figure, engines would be intolerably long if cylinders of the required size were placed one behind the other. This layout would also make for a bad engine in that the extra length of the crankshaft would make it liable to severe vibrations—damaging to itself and unpleasant to the occupants.

“If, to avoid these disadvantages so far as possible, the cylinders were crowded closely together, with the piston stroke greater than the diameter, there would be high piston speeds, leading to friction losses, and the hot test parts of the engine (such as the exhaust valve scats and spark plug bosses) would be crowded together, tending to overheat and distort if engine power was held at a high level for long periods; valve sizes and areas are also restricted, and limit specific power. As a further point, although the shorter the crankshaft the better from the viewpoint of removing unwanted vibration, the worse it is in respect of bearing areas supporting the loads imposed on it.

“With the cylinders in V-formation, it is possible to have a piston diameter larger than the stroke (which gives low piston speed with low wear and low friction losses, coupled with abundant water-cooled spaces between the internal hot spaces of the engine. In addition, a short, vibration-free crankshaft can be supported in bearings of entirely adequate area.

“The more powerful the engine and the greater number of cylinders it has, the bigger the advantage of V-formation; so it is natural that the typical American engine of 180 b.h.p, should have eight cylinders in V, and the typical 60-b.h.p. European engine should have four cylinders in-line—more especially as the in-line engine is, size for size, the cheapest to build.

“If more than 60 b.h.p. and if more than four cylinders are required the V-formation becomes extremely advantageous and although not widely used in Europe it is significant that this-type of engine is chosen by Rolls-Royce and Daimler in Britain, Mercedes-Benz in Germany and Ferrari, Lancia and Maserati in Italy for what are recognised to be the leading models in each country.

“The magnitude of the advantage derived from placing the cylinders in a V on a 3-litre engine developing 150 b.h.p. can be seen by comparing the new Mk. IV V6 Ford power unit with the 2 1/2-litre 114-b.h.p. Mk. III six-cylinder in-line unit it replaces. In return for a 20% increase in engine capacity power is up by 32%, although crankshaft speed has only risen from 4,800 to 5,000 r.p.m. By reason of a slight shortening of the stroke, piston speed is almost unchanged, the smaller engine developing peak power at 2,500 ft./min. and the new type at 2,375.

“It is when we examine the weight of the engine that we see how the new configuration pays off. Bare weight is reduced from 401.4 lb. to 379 lb., which is 5%, and weight in relation to power from 3.5 lb./h.p. to 2.52 lb./h.p., or by 30%.

“So far as space is concerned, the length of the crankshaft is cut from 29.93 in. to 20.41 in. (32.5%), and length front the from of the cylinder block to the clutch plates from 28.77 in. to 19.52 in., or by 32.5%. In absolute terms, the new engine is 91 in. shorter and 22 lb. lighter than the old in-line type, despite which it develops an additional 30 b.h.p. and 52 lb./ft. torque. In the 2 1/2-litre Zephyr version there are similar savings in size and weight and, without increment of capacity a bonus of 12 b.h.p.

“The rewards that follow the introduction to Europe of an unusual engine layout, although more expensive, are therefore selfevident. Less evident, but of little less importance, are the returns from the substantially increased investment in all-independent suspension.”

Whether or not the 1973 BL motor car has an in-line or a vee engine, we shall soon know. At the same time speculation as to whether it will ride at the back on metal cartsprings, like Marina, or on the ingenious Alex Moulton rubber suspension all round, as pioneered on the 850-c.c. Mini and interconnected fluidly on subsequent BMC small cars will end. Of the latter system, all those years ago, Pomeroy had this to say:

“Metal springs, be they leaf, coil or torsion bar, respond in exact proportion to load; that is to say in 100 lb. will compress the spring 1 in., 200 will compress 2 in. and so on. But as the laden weight of a small car may vary in ratio of 1.0 to 1.5 various arrangements have been proposed to give the suspension system a variable rate; for example, 100 lb. deflecting through 1 in. but say 70 more being required for the next 1/2 in. and say 100 lb. for the next 1/2 in. in this case a load of say 370 lb. in place of 200 lb. would be carried with a total deflection of 2 in. These arrangements are for the most part complex and unsuited to large-scale production, and for this reason the solo driver of small cars has had to endure a rough ride dictated by the mathematics of the fully laden situation.

“As with the engine and transmission layout so with the suspension, Morris Mini Minor marks a technical breakthrough in offering for the first time on a really large production vehicle independent suspension by rubber to all four wheels applied in such a fashion as to secure a marked variation in suspension rate with no complication in construction and a most economic use of material. Rubber is an expensive material and cannot be used on a small cheap cars unless full advantage is taken of the exceptional energy absorbing characteristics, i.e., it must be highly stressed and some of the mechanical elements including the linkages must also be stressed to a very high level.

“On the Morris Mini Minor the four Moulton rubber buffers have a weight of only 6 lb. yet they support the fully laden weight of the car, amounting to 1,800 lb. To achieve this very favourable ratio the suspension linkage is arranged to multiply the wheel load by five and the interconnecting ball joints are thus very heavily loaded. In sum the successful application of these rubber springs, with all their advantages of light weight, natural self-damping, and variable rate has depended upon the successful solution of the ball joint problem . . . Thus this combination of the Moulton spring with mechanical development in the ball joint serves to secure comfort with exceptional road worthiness at the rear end of the car unsprung weight is reduced to a minimum by a complete elimination of an axle beam—the wheels are located on trailing arms in such a manner as to have a vertical rise and fall with the implication that the roll centre at the rear of the car is at ground level, and as the roll couple at the front is therefore greater than that at the rear basic understeers results. Parallel motion of the rear wheels exerts a beneficient influence in two other respects. Rear end steering caused by changes in the camber angle as the wheels rise and fall is eliminated and so is sideways shake of the back of the car caused by the changing angle of the rear wheels which is common to both the conventional live axle and to swing axle cars. For these reasons the driver enjoys a noticeable uniformity of ride and handling and the rear-seat passengers can, it they wish, slumber undisturbed by mental apprehension or by disagreeable physical buffeting.”

The last expression of expert opinion would presumably be difficult to justify when L.P. began to publicise the big Ford, which did not enjoy front-drive and rubber suspension, but fortunately they did have i.r.s., subsequently used in much-improved form. There was a time when, after satisfactory service from a Morris Mini Minor and subsequently a Morris 1100, I stated in print that I had little use for cars with prop.-shafts. Since then, however, I have had no reason to complain of the road-holding of a Rover 2000TC and a BMW 2500, achieved in the case of the former with an ingenious de Dion back axle and with the latter by well-contrived semi-trailing-arm aided in both cases by Pirelli Cinturato and Michelin radial-ply tyres.

In recent years the great improvement in tyres of radial-ply and bias-ply types has diluted much of the argument in favour of front-wheel-drive, by endowing front-engined rear-drive cars with an excellent road-holding and cornering performance, unless on abnormally slippery surfaces. So, whether this long-awaited and to Britain vitally important all-new BL model is of Marina or Issigonis layout, we can observe, as Laurence Pomeroy reminded us 14 years ago, that: “Just over a hundred years ago the American Ralph Waldo Emerson wrote: ‘The logic of Englishmen is a logic that brings salt to soup, oar to boat. Their mind is not dazzled by its own means but locked and bolted to results’.” And we can fervently hope that the layout of the new model, and its performance on the road, not to mention the immense productive and service facilities which lie behind it, will demonstrate that what was observed in 1850 continues true in 1973.

“But”, you may be saying, “surely you know what the new BL confection is going to be like!” To which I must, until June, turn a deaf ear, contenting myself with remarking that Motoring News recently endorsed Lord Stokes’ optimism for his “exciting new model”.—W.B.