The Truth About Motors

NZ Truth, Issue 1150, 15 December 1927, Page 15

The Truth About Motors

SILENT RUNNING

Lighter Valve-gear In Use For Modern Cars

The demand for a silent, dignified car, which will convey its owners wherever and whenever they wish with as little noise as possible, has induced automobile manufacturers to devote their attention towards the production of smooth running l , silent, motorcars.

THIS prejudice against noise was apparent in the earlier days of motoring-, and, according to the English "Motor," may account amongst the wealthier clientele for the success of the 40-50 h.p. Rolls Royco, as those models were exceptionally quiet, right from their inception. Besides, the enormous volume of motor traffic traversing the roads to-day would be most unbearable if the present - day cars were as noisy as their predecessors

The timing 1 gear of a high-speed en- ! gine is considerably stressed and difficult to silence. On many modern cars helical wheels are used for this purpose, while another solution lies in tho use of silent 'Chains, so long as provision is made for adjusting the tension of them when required.

Turning: to the engine, it is obvious that on a power unit of the poppetvalvo type the most noise is caused by the valve gear. Great efforts have, however, been made to quieten it, and whereas only three or four years ago it was considered almost impossible to produce an o.h.v. engine which ran as quietly as one of the side-by-side valve type, we can now quote numerous examples of overhead valve engines that are as quiet as, if not quieter than, a good side - valve unit.

This quietness is iiiiiiiiiiitiiiiiiiiiiiitiinitinifiiititiiriiiiiii obtained largely by the use of lighter valve gear, made possible by developments in metallurgy. Lighter valves call for lighter springs to return them to their seatings and put less stress upon the timing wheels, cam-shafts, tappets and so forth. Moreover, the increasing use of oil-cushioned 'push-rods and tappets accounts for the quieter operation of many engines. A certain amount of noise from the valve gear was amplified by thin aluminium cover-plates either over the valves in the cylinder head or concealing the tappet heads, valve stems and springs on the side of the cylinder block. Thicker plates or those lined with felt do not amplify. A feature of interest is found in the Frontenac cylinder heads for Fords, in which a felt pad about l%in. thick is laid on the top of the overhead valve rockers and serves to deaden any noise and to hold and distribute lubricant. Except on racing engines, ball or roller-bearing cam-shafts are not employed, despite the reduced friction which they afford. The reason is that, for the most part, plain bearings are much quieter than those of the ball or roller type.

Sound can also be lessened by the use of composition fabric wheels, while one of the most forward steps in that direction is the scientific arrangement of the teeth so that they engage over practically the Avhole of their area, thus reducing the likelihood of chatter and noise occurring, while at the same time greatly increasing their durability. So far, we have dealt with poppet valve engines because they are in the majority. Various types of valve gear have at one time or another made their appearance, perhaps the most successful of these being the Knight sleeve valve.

In this the piston moves up and down inside one or two concentric, sleeves, in which ports are cut, that at certain positions coincide with apertures in the other sleeve and cylinder walls.

These sleeves are positively operated by small connecting rods from a special crankshaft which takes the place of the camshaft of an ordinary car. It is obvious that if all the parts are properly fitted the operation of this type of engine will be exceedingly quiet.

KEEPS AN EYE ON THE SPEEDOMETER Traffic-policeman Morrison, whcge special "beat" is the stretch of bitumen between Wellington and Petone.

BAD DRIVERS

Laboring Along In Top Gear

Most drivers certainly treat their vehicles well, but there are others whose idea of driving is restrioted to filling with petrol, oil, and water, getting into top gear, and staying there.

THEY let the engine labor to its last * gasp on a hill, even when a change down is obviously inevitable, and can be made more easily at the correct time. The same thing happens in traffic; they crawl along on top, slipping the clutch, and when an opening does present itself, attempt on top gear to accelerate from a crawl. Too many drivers appear to be afraid of missing or crashing a. gear, and so hang on to top as long as possible. But is it not better to

11111 until the gearbox is mastered? So long as the gearbox retains a mastery over the driver, . the engine is going to suffer. Tfrat brings up the question of braking, and recalls a valuable piece of advice to "drive on your throttle, and your brakes will never need relining." That may be a bit of exaggeration, but at bottom it expresses the truth. Brakes are mainly for use in emergency and for holding a vehicle when it is stationary. Brakes are even used with the accelerator right down, and not uncommonly one sees a driver rushing up

to a cross road, only to apply the brake fiercely until another car has

cleared; others drive close behind another vehicle, and have to pull up sharply when the latter stops. Of course, speed is essential in transport, but methods like that do not lower the average time of the journey by a second. Certainly fierce application cannot be avoided at times, but they should only be caused by other people—the foolish pedestrian who will not look where he is going, and the equally foolish driver who cuts in too sharply. Sensible braking and long tyre life go hand in hand.

Keep the battery fastened securely in the box, either by installing or wedging with wood. If it moves the jarring will break either the ground wire at the frame or terminals at the battery.

If a fuse is burned out and no spare ones on hand, wrap a piece of tinfoil around an old fuse, and replace it. Be sure, however, there is no short circuit to drain the battery or do other serious 'damage.