'The only way... • Equipping a vehicle with anti-locking brakes
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all round would be the only way of obtaining automatic brake distribution according to load ON a recent visit to Fr. Kotz and Sane, the well-known axle makers of Weihl,
West Germany, I was introduced to Mr. H. Rosier as "the man all our customers consult on braking problems", and the measure of this compliment may be gauged by the size of the company which now employs a staff of 2,500 and has been making axles for world markets for over a century. One of Mr. Bosler's most important technical exercises is to provide expert advice to the makers of all types of vehicle on brakingforce distribution problems.
By law in Germany, solo vehicles with a rating in excess of about 14 tons gross, and trailer outfits grossing at more than 28 tons, must be equipped with regulating valves that vary the braking of each axle according to the static load, and it is probable that this ruling will also be applied to lighter vehicles in the near future. Whilst he commended the usefulness of the system as a means of • obtaining better overall braking efficiency and improved control, Mr. Bosler pointed out that its use was a palliative in that it did not respond to dynamic variations of axle loading. Such variations, he emphasized, were the major obstacle in achieving uniform efficiency when running light or laden and with loads of differing centres of gravity, and the only way in which the difficulty could be overcome would be to fit an anti-locking mechanism to all the wheels. No known system was commercially suitable.
Two different systems
This view accords with my own line of thought on the subject, which originally was inspired some five years ago when driving a Jaguar equipped with Dunlop Maxaret antilocking brakes on the tyre company's skid patch. This proved the effectiveness of the system (applied to the wheels of both axles) in terms of improved braking efficiency on a wet, smooth surface, straight-line deceleration and retention of steering control. In a test about a year later, arranged by Lockheed Hydraulic Brake Co. Ltd., I drove a Morris Minor on a skid patch and in this case the anti-locking system (evolved by Lockheed) was applied to the rear wheels only; when the front wheels locked, the device prevented breakaway of the rear wheels and loss of directional stability. In both tests the car spun out of control as the restut of an unbalanced yawing couple when the system was "made inoperative".
In addition to the increase in effective road adhesion afforded by a rotating wheel (according to Mr. Basler an improvement of about 15 per cent is obtainable) it raises the transverse stability of the axle, which as indicated in the account of the tests, is its most advantageous function with regard to vehicle handling and control. As shown in the demonstration of a modified Maxaret system by the Dunlop company early in September, an anti-locking device can be effectively employed to combat jack-knifing of an articulated vehicle by applying it to the driving axle of tractive unit.
At first sight these comments would appear to have little bearing on the potential value of an anti-locking system as a means of distributing braking force according to both static and dynamic load variations; initially it was necessary to outline the proven claims for the principle, particularlybecause they represent the normal basis for evaluating its merits. Obviously, for applications to heavy commercial vehicles, automatic accommodation of load variations is by far the most important potential.
The explanation of this potential is simple. If none of the wheels of a vehicle will lock, all the braking force available can be equally applied to each wheel without overbraking any of the wheels. For example, if the driving axle of an articulated outfit were lightly loaded because of a heavy tail load on the trailer, the wheels of the axle normally would tend to lock before the wheels of the trailer (and initiate jack-knifing) but if the braking force were limited to the extent it could be applied without locking, the axle carrying the heavier load would automatically absorb a greater braking force. And so on all round! • The question as to whether the braking of front wheels should be increased or whether trailer axles should be braked before the tractive-unit axles would no longer have to be considered, given that the system were capable of locking the wheels of all the axles.
What hope is there that this potential can be realized?
Costly and complicated
Anti-locking systems are costly and in general are mechanically complicated. The cost of applying the system to all the axles of a multiwheeler could well be exorbitant, and maintenance might be a problem.
Skid detection and control by electrical means might, however, offer a form system that could be built at a considerab reduced price and would be virtually foe proof. According to Mr. Bosler, sor American aircraft are equipped with system based on the use of an electric generator in each wheel, the braking mec anism being de-energized when the curre generated is reduced below a critical outpi which is a function of wheel r.p.m. The ty of generator fitted to the aircraft is r known, but for commercial-vehicle applic tions it should be possible to incorporate very simple unit in the wheel-bra assembly. Presumably the problem of e cient and uniform generator operation at I very high temperatures produced by braki have been overcome in the aircraft applii tion.
Bodywork flexing
Subsequent to the preparation of notes on which the above observations based, I discussed the subject with Dr. Gorge, of the MAN company, at FISITA congress in Munich. Dr. Gorge I given a detailed appraisal of the effects bodywork flexing and the lack of it on handling of commercial vehicles and spi with authority on control problems. In opinion, the application of an anti-lock system would not be operationally feas because of variations in dynamic loadin Following this disclaimer of the syste merits,. I searched through a pile of Lear papers, and in a 1961 SAE publication anti-skid braking devices, Mr. J. W. Kinc in conclusion referred to their partici advantage for commercial-vehicle appl tions and stated that such units we "automatically adjust the braking at e wheel in accordance with the weigh carries, in addition to correcting for tyre ground variation".
Although improvements in braking ef ency and control are the most impor advantages offered by the system, it is noteworthy that its use could obviate cc damage to tyres in the event of emerge braking on a dry surface. It should also some latitude with regard to brake-sho brake-pad adjustment and provide appreciable overall reduction in tyre even if hard braking on dry road normally avoided.