MOTORING NOTES

Manawatu Standard, Volume XLV, Issue 126, 1 May 1925, Page 11

MOTORING NOTES

“When we study the phenomenon of high-speed shimmying we begin to wonder why ears never shimmied before. Tjie causes have always beep present, in kind, if not in degree. The mechanical iihproyenmpts in tpe latest automobiles have, however, pot only made shimmying forces more potent, bpt have “removed much of the opposition offered them by the earlier cars.

“Every effort was made to provide Comfort and safety independent of road conditions. But tlipse refinements in themselves served automatically to enforce the speed laws. Wpep the sinooth road invited a flurst qf speed something seemed to seize ’ tjie front wheels and tp demonstrate how rapidly it could turn them from left to right and then back again.

“The origin of the shimmy seems to Jie in the 'front axle. Supported _ between the tyres below and the springs above, the axle is spt in motion by every inequality of the road surface. If pne wheel strikes a small buipp tlje axje begins to see-saw up and dowq. Thfs vibratiop induces a peculiar motion pf thd >yheels which changes direction with every reverse! of the axle motion.

The resignations of Dr. Harty and Mr H. Amfis from the executive pommittee of the Wellington Automobile Club were received with regret at a recent meeting. The chairman, Sir Joseph Ward, asked them to reconsider their proposed withdrawal, but both replied that owing to the difficulty of attending meetings due to professional ties, they had no option but to withdraw. A hearty vote of thanks to the retiring members was recorded on the minutes.

Some idea of what is done in a motoring way in South Africa is conveyed in a letter to the Canterbury Automobile Association from the secretary of the Transvaal Automobile Club. It states that motoring conditions m South Africa ajre governed proyincialj.y, Each province has its own motor ordinaries. Ip the Transypal one car owner has to pay £2 14s 6d tax, in Orange Free State £2, in Cape province £6, and in Natal £lO, Municipal vehicular taxes are 15s a wheel.

The track at the Melbourne motor drome has already demonstrated that given the opportunity Australian cyclists are little inferior to the world’s best pace followers. Recently a brilliant effort was recorded by R. Johnson behind motor-cycle pace on this track, when he made a successful attempt on H. Opporman’s 5 miles Ausrtralian record of 6mins 10 l-ssees. Riding in great style, Johnson reduced the figures to smins 3secs, thus averaging nearly 60 m.p.h. for the 5 miles. The last third of a mile was ridden at a speed of 62} m.p.h. With moi-e practice behind pace this rider gives Eromise of being one of the world’s est..

“The fact that not all cars are subject to this trouble shows that shimxnyipg is avoidable. Although some cars shimmy with balloon tyres and plain axles, and others shimmy with balloon tyres and front wheel brakes, many cars similarly equipped operate noi-mally throughout their eptire speed range. There must be some trick of design that will banish the shimmy bogie. The secret has not been discovered, but it lies chiefly in the distribution and the suspension of the units mounted on the frame, together with the design of the frame itself. The effect of position and of height of both the power plant and the body is especially open to investigation as a possible cause for shimmying.

“The action is necessarily quite rapid. Ip a weljrdeveloped shimmy the wheels reverse about fifteen times per second. There seems to be a rate, however, beyond which the wheels do not respond to the axle vibrations, and when this rate is exceeded the car does not shimmy- The frequency with which the axle vibi’ates depends upon three factors-—the weight of the axle, the air pressure in the tyres and the stiffness of the springs. A heavy axle, low air pressure in the tyres and the soft spring all lower the frequency of vibration. _ It is evident, then, that the means intended to make the car safe and comfortable may defeat their own purposes by bringing the vibration rate within the range that will promote shimmying.

A most necessary adjunct to the car is a windscreen wiper. The great utility of these devices has now become generally recognised. There . are many varieties and the number of different devices is increasing. The simple hand-operated, wiper fills the bill in most cases, but a large proportion of users favour something more effective in keeping a clear view through the screen, so that we have automatic wipers of various types. Some of these operate from the exhaust, others by the suction of tjie engine, while yet others are electrically driven. Perhaps the latter are most effective, since they can remain in operation irrespective of the functioning of the engine. They take little current and are supplied from the lighting and starting accumulators. There is no doubt that the use of an automatically operated screen-wiper makes for safety in driving, for bad weather conditions under which it is impossible to drive at speed with a hand-operated wiper; the only alternative is the open view and the loss of the screen protection is a most uncomfortable method of progression.

An important subject discussed at a recent meeting of the American Society of Automobile Engineers was the question of wheel wobble or shimmy, which has attracted considerable attention since the introduction of balloon tyres. No positive solution of the problem seems to have been reached, and many divergent reasons for the cause were presented. There was a sharp ‘difference of opinion between the passenger car engineers and those of the tyre industry, many of the former, according to Automotive Industries, being inclined to saddle balloon tyres for niuch of the blame, while the tyre engineers pointed out that shimmy or wheel vibration was a question for technical discussion long before the advent of the low-pressure tyres. “The safe, sane and unfailing remedy for high-speed shimmying is to drive at a reasonable speed,” said Professor H. A- Heubptter, •pf the engineering experiment station of Purdie University, who is making an extensive investigation into the_ causes for shimmying and its remedies. “With the advent of the low-pressure tyre and front-wheel brake,” says the professor, “the motor car has developed some new steps that were never planned for it. The problem of frontwheel vibration is of recent origin. It is confronting the automobile industry at a time when riding comfort and safety at high speed were supposedly assured. Tyre manufacturers have responded to the popular demand for comfort by producing a tyre suitable for low-inflation pressures. This

tyre could absorb a bump the size of a paving brick without a quiver. FAST AS FLYING. POWERFUL NEW RACING CAR. OVER 200 MILES AN HOUR. LONDON, April 17. Malcolm Campbell, the holder of many records, js building a racing car of 460 li.p., capable of developing 700 h.p. It will trgyel at a rate of over 200 miles an hour. The car has 12 cylinders, each the size of a small car engine. They are fed by three carburettors. Ignition is supplied by two magnetos. Westinghouse compressed air brakes are on each wheel. The car will require three miles to gather speed and to glow down. Tyre-making and armament firms are at present experimenting with the object of turning out a sufficiently strong body and tyres. A private car of this type would be taxed £450 a year. WORLD’S SPEED RECORD. BROKEN BY PAUL ANDERSON. At Sellick’s Beach, Adelaide, Paul Anderson on a motor cycle made a new world’s speed record of 128 m.p.h., thus beating the world’s record made fly the famous English rider, le Vack, at 123 m.p.h. During the same afternoon Anderson broke the world’s lightweight speed record, on a 3} h.p. machine at 103 m.p.h. The previous speed record for this class of machine was 101 m.p.h., made on an English machine. The weather was dull and cloudy, and conditions on Sellick ; s Beach were bad for racing, but nevertheless Anderson flew along the sands, his machine looking like a scarlet comet. All previous beach records made by Ralph Hepburn at Sellick before his departure for U.S.A. were broken by Anderson, as well as the two world’s records mentioned above.