Historical Notes: Shock Absorbers

Author

A. B. C.

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68

To be brought to an undignified standstill, in a vintage car, right in front of an East End ‘bus-queue by a dismal, clattering noise and to walk back, amidst laughter, to retrieve a completely detached shock-absorber is not a pleasant experience, but was part of the cross that the writer had to bear “in the cause” recently, and gave ample excuse for pondering on the story of these devices during the rest of the journey. In any case, the offending shock-absorber had stayed “in one piece” for at least 24 years, and that is more than can be said about some of its modern counterparts, but one could hardly expect a ‘bus queue to appreciate that fact!

Until 1902, when Mors pioneered them, such things were not considered at all, presumably because ordinary touring speeds were not high enough to make their absence felt, and in racing the “bounding” so frequently spoken of was all considered as part of the sport.

One’s mind boggles at the skill demanded of the racing driver of those days over the pavé roads with the rear wheels liable to “hop out” sideways at the least, provocation, and without inside knowledge one wonders how much the absence of shock-absorbers contributed to the Paris-Madrid disaster?

Imagine the driver’s skill, for example, as he comes up to pass a slower car, pulling down the camber at perhaps 70 m.p.h., peering through the clouds of dust, and doubtless praying that the bounding car will not “chime in” with the natural frequency of the road inequalities and put a swift end to his car and his motor race. Truly, in those days, they were masters! Think of the sheer “guts” required to deliberately “drive through” such a critical synchronisation, like running, hard across a springy plank, trusting that the fall of your feet will not coincide with the natural frequency of the plank, when your common sense shouts out that the sensible thing to do is to slow down and be sure that it doesn’t. Ugh!

Théry, on the Richard Brasier, was the first racing motorist to experience the full joys of motoring with shock-absorbers and he won the “Gordon Bennett” in 1905 so equipped. Says Mr. Gerald Rose of this important occasion, “… one of the things most noticed at the time of the race was the difference in running of the Mercédès and Théry’s Brasier, the latter appearing to move so smoothly and to hold the road so well . . .” Truly a happy example of the lessons motor-racing helps to teach. The Brasier’s shock-absorbers consisted basically of a small drum attached to the chassis side-member, with a lever attached to the axle by a link, the lever operating a “band brake” which encircled the aforesaid drum. The typical friction device soon followed, but it should be remembered that for some time the leaf springs in themselves were capable of acting as shock-absorbers, quite effectively, too, in badly engineered cases. Naturally, such a big step forward in the progress of the motor car could not long escape the notice of Mr. S. F. Edge, who grasped his ever-ready pen and wrote to the Car Illustrated in 1906, expressing himself in the following terms. “… I was led to make experiments from noticing last year at the races at Brighton how the six-cylinder Napier racer seemed to glide and did not bounce in any way like other cars which were running. Many people had an idea that it was some peculiar construction to the car, and although this may be so to a certain extent, the main reason I have found from tests was the result of the Napier road equaliser, which is a very simple device that Mr. Napier designed for use on racing cars . . .” Edge goes on, of course, to say how much better the six-cylinder Napier is than the ordinary four-cylinder as a dust raiser, and finally adds “… everyone who drives a motor car hates the dust that is raised, and therefore it is, I think, the duty of every user to obtain some form of shock-absorber or road equaliser which will, at any rate at any given speed up to thirty-five miles an hour, reduce the dust behind the car by at least 50 per cent., simply by making the wheels stick closer to the ground and not bounce. The result of these experiments has so impressed me that I have made arrangements for next year that every six-cylinder Napier car is fitted free of charge with this device, which is known under different names, some effective, some ineffective, but I think it well to give prominence to the fact that a comparatively inexpensive device can materially reduce the raising of dust …”

No doubt having six-cylinders and shock-absorbers arguably prevented the raising of dust (and sold Napiers), but the ordinary member of the motoring public of those days most certainly did not accept shock-absorbers for those reasons. Shorn of technicalities, he looked to them to do two things. First, he wanted them to make his motor car more comfortable to ride in, and second, if he wanted to go fast, he wanted them to keep his motor car on the road. It is important to put the things in that plain and simple manner because, before 1914 at least, the term “shock-absorber” did not mean quite the same thing as it does today. Strictly, to fulfil his first need our hypothetical motorist wanted shock-absorbers, and for his second need, dampers. “Shock-absorber” really implied “auxiliary spring.” The matter is made more complicated by the fact that some of the earlier auxiliary springs had a measure of hydraulic damping designed into them, and some basically friction devices, such as the “Gabriel Snubber,” had auxiliary springs within them, but without going into full details of the constructional features of each proprietary type (and they were many and fascinating) it is best perhaps that we stick to the basic terms of shock-absorber and damper.

Taking shock-absorbers first, in spite of the lurid claims advertised by the various manufacturers, the problem was somewhat complicated. If you possessed a good car in the days before the first war which already had good, flexible springs, then you might well “do it a mischief” by fitting, say, a pair of “J.M.s,” imposing though they might look between the two parts of your three-quarter elliptic rear springs. If, on the other hand, your fancy alighted upon a car with a stiff and poorly engineered springing system, then, purely from the comfort point of view, you might easily revolutionise it by the self-same purchase. Equally, it could happen that if your auxiliaries had a natural frequency that counteracted that of the main road springs, you achieved a real measure of damping, but that would probably have been pure chance. It all depended, too, on what state the main springs were in, as they themselves could show widely differing characteristics when greased or rusty, and it is perhaps typical of the somewhat confused thinking that existed in some quarters, that one can still see on practically adjacent pages of the old motoring journals devices advertised for forcing spring leaves apart to grease them (and gaiters to encase them in when greased), and devices to increase the friction between the individual leaves of the springs, both, needless to add, claiming to better the riding qualities of the motor car. The clue, of course, lies -in the vastly different requirements of the pure tourist and the”speedman” of the day, and in order to better comprehend the problem, it is instructive to motor a modern car without shock-absorbers. If the speed is kept below 30 (speeding, of course, in those days, and highly illegal), and the trip is taken when there is little traffic about, an extremely comfortable ride results, as Austin Seven owners will no doubt be aware. Space will not permit of a detailed description of the many shock-absorbers marketed in those far-off days, like the Parsons, which had pneumatic rebound damping. It was, perhaps, typical of many others that fitted snugly between dumb iron and main leaf, and are now but picturesque relics of a past age, and who will forget the “Neverjahs” and other auxiliaries for Model “T” and “Baby” Austin? Some were hydraulically damped, but there were difficulties here, viscosity of the operating fluids available at the time rose rapidly with temperature, glycerine and the castor and mineral oils, the fluids most commonly used, all suffered this disadvantage, and of course the amount of work absorption on the rough roads of the time tended to be high in the shock-absorber cylinder. Eventually suitable fluids were produced, but their absence in the early days certainly caused the demise of many a promising hydraulic device.

As regards dampers, the early friction devices of the normal “scissors” type did not differ greatly from the very well-known André or Hartfords which were common in most cars of the vintage period, after which the hydraulic age dawned. The “Gabriel” snubber, already mentioned, was another approach to the problem, consisting of a coil of webbed strapping, rolled round a spring-loaded “dumbell,” but although it offered great advantages in that it offered no resistance to the upward bump of the axle, it equally failed to allow the axle to fall freely into a pothole, and if not potholes, at least road depressions were still very common in the ‘twenties.

The “Classic” friction damper, even in some of its later forms, although foolproof and everlasting and always easily adjustable, could not escape the consequences of the fundamental law that the coefficient of static friction exceeds that of moving friction, and therefore the static friction had to be “broken” on encountering a spring deflection, an obviously wrong characteristic fundamentally. In spite of this apparently serious disadvantage, however, it is proper to recall that during the vintage period, and indeed right up to the coming of the X-braced chassis and the pressed-steel motor car, it was the combination of the chassis, the springs and shock-absorbers that produced “the ride,” the apparent technical error of the combination of leaf spring and the full friction damper often being countered by the natural flexing of the chassis itself, and only when both wheels hit a transverse obstruction squarely did a real “crash” take place.

As soon as the “all in one piece” motor car appeared in the ‘thirties, independent front suspension quickly became a necessity, and no longer could the friction device hope to hold its own, even in a form that was adjustable while the car was going along. True, taking motor racing as a guide, Bugatti tried to extend the life of such devices by pioneering the “de Ram,” an exceedingly clever instrument that combined the friction and the hydraulic shock-absorber in one unit, and most of us can recall how the roadholding of Bira’s “Romulus” was enhanced by the fitment of the same auxiliaries, but the writing was all too obviously on the wall before 1936.

Hydraulic shock-absorbers, in the sense that we now know them, were by no means new at that time, as anyone may see by looking closely at Anthony Heal’s 1908 Hutton car at a V.S.C.C. meeting, and they divided themselves fundamentally into vane and piston types when they did become more or less standard fitments to all production cars. Crudely put, the idea was to cause the axle to squirt a viscous fluid through a small aperture and/or valve, allowing a comparatively free commencement to the axle deflection, building up a heavy resistance in the case of large deflections, and applying a high degree of damping to the return of the axle to a neutral position. Double-acting versions, of course, applied the same measures to the descending axle. Constructionally there were several interesting varieties, but basically, as has been said, they were based either on pistons sliding in cylinders, or on vanes displacing the oil in an annular “cylinder” with a “reaction block” inside. The operating fluid was practically unaffected by temperature change, and it and spares for the shock-absorbers themselves became commonly available at all local garages. Here again, the specialist manufacturer came into his own, and still continues to monopolise the field, few manufacturers today making their own shock-absorbers.

Space will not permit of going into further details, but as motorists we should certainly be appreciative of the contribution that these fitments make to safe and speedy motoring, and if we are sometimes tempted to feel that the modern ones cease to function properly after very short periods on the road, we must remember that they are cheap and mass-produced, very good value for money, and in many cases, just don’t get the attention that they should have. And surely that is the real trouble behind a lot of the complaints about modern motor cars! — “A. B. C.”

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