THE GEARBOX

Southland Times, Issue 22508, 16 February 1935, Page 19

THE GEARBOX

MODERN IDEAS. MANY SHORTCOMINGS. Car designers, ever since motoring commenced, 1 have endeavoured to evolve an infinitely variable gear and so obviate the many disadvantages of the conventional “mangle” type of gearbox. While the quest is not yet ended, the idea is growing steadily nearer attainment, writes The Bulletin. While it must be admitted that modern gearboxes require but little skill in their manipulation, as with synchromesh gears, free-wheeling and automatic clutches a child can operate the gearlever, without fear of damage, every modern designer is fully aware that conventional gearboxes abound in shortcomings. Every motorist knows that his engine power falls away rapidly as the revs, drop until, at idling speed, only perhaps one-sixth of maximum power is available and, except under exceptionally favourable circumstances, it is impossible to use peak engine power. No sound arguments can be. propounded in favour of the retention of gearboxes, for even eight-speed gears, while in some slight degree improving road performance in the hands of faddists, have introduced added complication in adjustment and involved greater cost in maintenance. The great stumbling-block in the way of progress has been that designers have insisted that a transmission system must be “solid” to be efficient, meaning, of course, that when the clutch is. engaged power must be transmitted through metal to the road wheels. Early Types.

Seven years ago two Continental experimenters, Constantinesco and De Lauvaud, proved by different methods how futuile were these conventional ideas. Constantinesco, with his infinitely variable transmission, incorporating a pendulum control and special form of roller clutch, ran a standard car for some months under official observation without recourse to clutch or gear-lever, and the power unit was rated at h.p. About the same time tests of the De Lauvaud schwaschplate free-wheeling differential demonstrated conclusively that with this device motorists could change gears. at random once the car was in motion without releasing the clutch, and, further, that the rear wheels would not slip in soft or greasy going, the wheel on solid ground taking the drive. Despite the undoubted efficiency of both these ingenious principles, they were never produced on a commercial basis simply because the “solid” drive, with its attendant high cost of production, is insisted upon. Indirect Transmission. That convention should so stultify progress is astonishing when we realise that engineers, long before cars were first used, knew the utility and efficiency of fluid transmission as applied in connection with water turbines. Later in marine engineering fluid transmissions in connection with electrical power plants gave an infinite range of speeds. In the case of electricity, the considerations weighing against application to the motor car have been prime cost and excessive weight—of course a car cannot be hydraulically propelled—but these experiments in other fields have served a useful purpose in broadening the vision of designers and turning their thoughts away from conventional channels. It seems probable that automobile transmission, principles, will undergo revolutionary changes in the near future, and, while the gearbox may still be retained in. some instances as a subsidiary unit, perfection in applying the substituted principle should result in its total elimination. In reviewing the 1935 models, one is impressed with the consistent endeavour on the part of designers to improve transmission systems. Synchromesh gears, with attendant freedom from worry in gear-changing, are now standard equipment in almost every model. Though a number of self-change gearboxes have been fitted, they only partly approach the ideal, for, successful though they may be, each suffers from the same disability—that in any particular ratio the motor cannot deliver its maximum power except for brief periods. Slipping Clutches. Were it possible to fit some type of clutch wherein a progressive slip could be obtained whilst the drive was in some particular ratio, we would m effect secure an infinitely variable gear —unorthodox, perhaps, mechanically, yet effective. In this connection we have two outstanding examples. The Newton centrifugal clutch fitted to a number or English cars incorporates a series ot bob-weights which, as engine speeds increase, progressively apply the. load to friction surfaces through a series ot springs, and so permit peak power to be developed by the engine at any road speed. The other design is the AustmHayes automatic frictional transmission, which, after having been submitted to practical tests for some has now been adopted as standard practice by one of the leading English manufacturers.

Automatic Transmission.

Motorists will be extremely interested in this ingenious system chiefly because the only control provided is a miniature lever for purposes of selecting ahead, neutral or reverse, after which the ratio automatically vanes to suit the speed or grade over which the car is being driven. . Differing somewhat in design, Alvis have this year adopted a traffic clutch in which the object is to permit slip, with consequent enhanced power output on any given gear. In this ingenious clutch the flywheel, or disc, is bolted to the driving shaft, and m its centre is a doubly-flanged annulus. Within the outer circle of this disc-clutch shoes are mounted on pivots passing through, the disc and have their linings facing the outer circumference. Coil springs in compression, carried by ra^l ?- y_ r ;s " posed guide bolts, contract the shoes in an inward direction; consequently when the driving disc exceeds a certain revolution speed centrifugal force causes the shoes to open outwards, at first lightly so that slip may take place, and then, as speed increases, with suificient force to totally eliminate slip and provide a solid drive. . While these novel schemes will in some measure improve existing transmission methods, they are at best merely a compromise. Any device depending solely upon “slip” f° r its effective operation is fundamentally unsound and certain to be superseded by more effective measures.