It is true, as Mr B J Walsh of Loughborough pointed out in his letter (MOTOR SPORT, December 1986), that the increasing use of anti-lock brakes may increase the number of rear-end shunts. However, this does not detract from the value of such braking systems if one has to pull up quickly on slippery surfaces when no other vehicle is following, and one can think of many circumstances when this can happen. Our correspondent’s suggestion that ABS-braked cars should carry warning signs at the rear recalls those 4WB red triangles which were fitted to vintage cars, when four-wheel-braking was still rather novel; one remembers them on Sunbeam, Morris and other cars of those days.
Obviously, if one car could pull up from, say, 30 mph in 40 ft, and it was being followed too closely by a vehicle which needed, say, 120 ft in which to stop from the same speed, something nasty might well happen. The solution, then as now, was not to drive too close to the vehicle ahead. It is interesting that this problem, seen as quite alarming as four-wheel-braking grew in popularity, had been just about resolved before the end of what are now referred to as the vintage years.
Brakes on the front wheels had been about before the First World War, notably on Argyll, Arrol-Johnson, Crossley and Isotta-Fraschini, but it wasn’t until after the Armistice, when cars were becoming faster and roads more crowded, that the general run of car manufacturers began to see that they would have to come to grips with the problem of stopping wheels that were pivoted for steering purposes. Competition is a great stimulus, and what one maker provided was bound to be copied. I suppose that when Sir Herbert Austin gave his baby Austin, novel in 1923, brakes on all its wheels, albeit with very tiny friction surfaces, it become obvious that rear-wheel anchorage alone would not be good enough for much longer.
Now that effective braking is virtually universal on all cars, it is amusing to look back on what a furore 4WB caused in their pioneering days, from the viewpoint of car-owners and for the technical complexities they presented to design offices. For example, I can recall, as a boy, hearing a relative stating in no uncertain terms over dinner that he never, wanted to own a four-wheel-braked car, because of the danger of a front wheel locking up and depositing him in a ditch. Ditches, like 2WB, were still frequently encountered then, and for some years he held out – but his last two or three cars had 4WB and he thought nothing of it . . . At the time, though, this view was not uncommon. In the vintage A7, which has never stopped very well anyway, caution dictated that at first only the hand brake worked on the front wheels — for emergencies!
In spite of the eventual appearance of 4WB on the A7, those makers who had offered 4WB before the war were reluctant to pursue this road for some time afterwards. Early in 1921, though, the idea was beginning to be revived. The advent of the fine 37.2hp Hispano Suiza at the Paris Salon, with powerful brakes on all wheels applied via a gearbox-servo (to which Rolls-Royce’s eyes turned some years later), aroused much interest. Delage, Excelsior, Darracq and others soon came up with their own systems.
In Paris, the STD concern carried out some convincing experiments, and with 4WB on a V8 Darracq they proved that, with rear-brakes only, it took far longer to stop than with braking on all wheels:
Such figures could not be ignored. In addition, it was seen that locked wheels as one end of a car had a pendulum effect, swinging the sliding wheels out of line into the dreaded sideslip on a 2WB car. If all wheels were braked this did not happen, so the race to fit 4WB was on.
Motor racing might be said to have paved the way, since Peugeot, Delage, Fiat and Piccard-Pictet had used 4WB in the 1914 French GP — although this did not prevent defeat by the team of 2WB Mercedes. Before the end of 1921, a racing Boulogne type Chenard-Walcker was submitted at Brooklands to an RAC-observed test of the efficiency of the Perrot-Hallot system, in which front-wheel-only brakes were applied through a Hallot servo. (It has always seemed odd that only the front wheels carried brake drums, but the back wheels were braked via the transmission). Again, the results were convincing. The car stopped from 30 mph in 30 ft, from 40 mph in 60 ft, and from 50mph in 100 ft. Some years later I remember being most impressed when a chauffeur demonstrated a circa-1925 Buick landaulette, although it had but external-contracting 4WB.
Yet, as I have said, not everyone was convinced. Tom Norton, of the Automobile Palace, Llandrindod Wells, was favourably impressed with 4WB on a 70-mph French car he sampled in Wales, where he had encountered a 1910 Crossley with such brakes still in good fettle; but someone else, when looking for a high-grade British car with such brakes, was informed by a “leading motor firm” that they could not be used with safety except on straight roads without dangerous interference with the steering, and even then side-slips would be caused if the front wheels were on different surfaces. Restricted front-wheel lock was also a criticism.
Another antagonist was the well-known fast-car exponent, H R Pope of Cannes. In the summer of 1923 he was using two cars, a 1914-type 100 hp and a modern 3-litre; both, I assume, Italas, neither of which had 4WB. His argument against 4WB was that they made people drive faster into corners, which could stress tyres to the point at which they burst; more serious accidents, he suggested, were the result of tyre bursts than any other cause. He said he had lost an order because the car concerned didn’t have the new braking, but when the customer got a car that did, he “had good reason to regret it”. No reason for this was given, but Pope quoted the absence of such braking on first-class chassis and noted that although to his knowledge, the 1913 100 by Isotta-Fraschini had the most marvellous 4WB, Lancia, Fiat and Itala did not then adopt them, nor did French and British car makers. When, Pope said, manufacturers such as Rolls-Royce, who had reason to be proud of their reputation, adopted 4WB, he would be a convert to them for the use of the “man in the street”; meanwhile, those who abandoned buying a car because it did not have 4WB were in need of motor-education!
I think the cars Pope was using were probably my old GP ltala and a new Tipo B1S of the same make, and that he was piqued that this company had not yet fitted 4WB. He was all in favour of such brakes on racing cars although he thought they encouraged ordinary drivers to go too fast; a specious argument adopted in more recent times in respect of seat-belts and now against anti-lock brakes.
Pope was soon under fire in the motoring Press. The owner of an Hispano Suiza whose servo brakes had given no trouble in 5,000 miles, J Ross MacMahon, designer of the Palladium car, had been testing 4WB ruthlessly. He said he had found no problems, although rumours had reached him beforehand of cars overturning, developing steering problems and wearing their tyres out. To this, Pope replied that he had driven a 28/95 Targa Florio Mercedes from Stuttgart to Nice via Switzerland, but did not use its 4WB because he did not like them, but this was countered by an Hispano Suiza owner of 35,000-miles’ standing, who said he would not buy another car unless it had the Birkigt brakes (the Sunbeam which won the 1923 French GP had Hispano brakes, he said), and by someone who thought the Lancia Lambda had the best brakes of all. Pope was reminded that Itala had, in fact, used 4WB back in 1921, but he replied that the company had tried Isotta-Fraschini-type brakes but would not standardise these until they were foolproof . . .
Sir Harold Bowden, who had both 37.2 hp Hispano Suiza and 40/50 hp Rolls-Royce cars, was another who praised the brakes on the former, and obviously thought R-R should soon adopt them, and he was supported by the Marquis of Cholmondeley, who was fully in favour of the Hispano servo-brakes after the performance of these cars in the Boulogne races of 1922 and 1923 and by three Hispanos, getting from Paris to Nice in about 12 hours. And so it went on, with 4WBs obviously in favour, although the danger of getting rammed in the rear was forecast in 1923, and the new Paris taxis had Attention: Freins Avants signs on their back number plates.
Meanwhile, enlightened designers set about the problem in various ways. The Perrot system was widely employed, with different linkages for working the universally-jointed, chassis-mounted shafts turning the brake cams; and many adopted the Isotta-Fraschini method, in which an operating shaft was carried in the front-axle bed, terminating inside the brake drum, with a specially formed cam unaffected by the turning of the wheels. Hotchkiss also carried the operating shaft on the front axle, but ball-jointed levers and links coupled this to a cam at the top of the drum. The sports SPA of 1922 had a clever solution, with left-and right-handed threaded sleeves on the aide, drawn together or forced apart by a central lever; a tie-rod connected each sleeve to a bell-crank at the axle ends, which entered the drum, forcing apart the brake shoes with a special wedge— a foretaste of something Girling brought out years later.
Rolland-Pilain was even more ingenious, using pistons to push the brake shoes apart; each piston was within the drum, and moved by hydraulic means from little pumps on each axle, which the brake cables actuated. Rolls-Royce were wondering about compressed-air actuation, and Panhard about expanding the shoes by rack-and-pinion.
Whitehead later offered a proprietary cable-set, for fitting to Essex, Ford, Morris and similar cars and used on Raymond Mays’ Brescia Bugatti; Mercedes and others operated the brake-cam with a rod passing through the steering-pivot; Lemoine had a flexible shaft beneath the aide; Farman had already introduced a worm-and-sector device to compensate for wear on the brake linings; and Itala (at last!) preferred the cable system of operation, with front and rear compensation by multiple pulleys. Those who found the additional anchors called for more effort at the pedal used various kinds of extra leverage, HE with skew gears over the king-pins. Some engineers took much trouble in easing off the brakes of the wheel on the inside of a corner, by bevel-gear balance-mechanisms and other means. For a time Bugatti had hydraulic brakes with the piston forming the pedal and one old 2WB diehard was heard to comment that 4WB meant more points to lubricate.
However, there was no stemming the desire for 4WB anchors. Of the cars available here in 1924, only 28% had such brakes; but by 1925 47% were so equipped, and 4WB were optional on a further 6%. By 1926 the number of 4WB cars had risen to 75%. By 1927 the figure was up to 88%, and thereafter only a handful of not very notable cars relied on two-wheel-only anchors. The mechanical servo-motor of the heavier cars, as pioneered by Hispano Delage, Sunbeam, Renault and others, and later adopted by Rolls-Royce, was giving place to the vacuum-servo actuated by inlet-manifold suction, which I believe Parry Thomas first used on the 2WB 1920 Leyland Eight before selling the idea to Dewandre. The 1921 French GP had been won by a Duesenberg with “water brakes”, and by 1924 Triumph were using the Lockheed hydraulic system, which provided automatic compensation of all brakes with no need for mechanical compensators. Up to the war such obvious simplification, pioneered in America by Chrysler (and used here tentatively by Horstman), was a rarity, but the 1926 Triumph took 90-100ft to stop dead from 40 mph.
Some fine pre-1914 cars which were still running well were now taken off the road because their owners found them dangerous among the many new cars with better means of stopping quickly.
In a period of almost universal 4WB, the motor papers had to include braking figures in their road-test reports. The need to quote stopping distances in the magazines led to the question of how to measure them. In the aforementioned Darracq tests, sand bags had been thrown from the car at the point where the anchors were applied, to mark the place from which the distance should be measured. This was too crude, and when a 14/60 hp Lagonda saloon was tested under RAC observation at Brooklands in 1927, a Very pistol was attached to the offside running-board so that coloured powder could be fired onto the track as the brakes were applied, the trigger having been coupled to the brake mechanism. (The Lagonda stopped in 160ft from 50 mph – 55 ft from 30 mph). Most of us just braked from a convenient mark, and when The Motor put up distance-markers on the Brooklands finishing-straight in 1931 for the benefit of its testers, others, myself included, gratefully poached this facility!
The Autocar began publishing braking figures from about 1924 and was later to standardise the figures to the distance needed to stop from 30 mph, which was realistic, as this became the legal town speed-limit in 1936. The Motor published pull-up distances from a number of different speeds, with braking graphs.
For a time, the possibility of rear-end shunts remained, even between cars with 4WB, as stopping power varied considerably. Without searching for extremes, a Windsor would come to rest in 80 ft from 40 mph and a vacuum servo-braked 2 1/2-ton Minerva in only 56 ft, at a time when the Fiat 509 needed 133 ft, and a Swift Ten 110 ft. But by 1930 it had rather nicely stabilised, and at least those with 4W B had little to fear from one another at town speeds.
For example, the average stopping distance of all the cars tested by The Autocar that year was 36.15 ft from 30 mph, the Continental cars averaging 33 ft. By 1931 the figure had fallen to 35.6 ft, with American cars better than most; for 1932 the figure was 33.2 ft, with little to choose between British, Continental and USA cars. By 1933 it was down to 31.7ft, the worst performance being 44ft by a 7hp Jowett Kestrel saloon, the best 25 ft by a Rover Ten Special saloon and a 1 1/2-litre Singer four-seater. 1934 showed 30.8 ft, 1935 30.5ft — with little to choose now between cars from different countries. By this time the boffins were trying to work out whether any better distances were possible, and theory was stretched when a 3 1/2-litre Hotchkiss was recorded as stopping from 30 mph in 21 ft.
Motor has since abandoned brake-tests, and Autocar is more concerned with pedal pressures than with the distance in which a car can retard itself — it still publishes pull-up figures, but with the gear lever in neutral, whereas the old testers used what engine braking was available to them, while standing heavily on the pedal. . .
The disc brake arrived and Rolls-Royce eventually abandoned their beautiful but complex mechanical servo, following Citroen with power-hydraulics, for their Sliver Shadow. With the advent of anti-Iock braking, even on quite low-priced Fords, we have now made much progress, so far as this aspect of car safety is concerned. WB