MOTORDOM

Greymouth Evening Star, 22 April 1938, Page 9

MOTORDOM

NEWS OF THE ROAD

(By

“Gearbox”)

MOTOR FIGURES.

TOTALS EXCEED 278,000. The latest compilation of motorvehicle license figures prepared by the Transport Division of the Post Office shows what a formidable task faces this Department next month, wthen the re-licensing process will begin, the new plates having to be used on June . These figures, which include all registrations up till March 31, show that there are 278,350 motor vehicles on the register, and as the registrations since that date have been well maintained, it can be assumed that the licenses to be issued’ from May 2 will exceed 282,000. Special facilities are being organised by the Post Office to have the time of motorists, and the re-licens-ing process will be Well distributed throughout the Dominion among 357 Deputy Registrars. Hhose who take out their new license on May 2 or as soon afterwards as possible will avoid the inconvenience which will arise if the re-licensing of the 282,000 vehicles is too long delayed. An analysis of the types of licensed motor-vehicles and their distribution, i with a comparison of these figures < with those of the corresponding date in 11)37 shows the following points of importance: —

Increases in the number of licensed a motor-cycles occurred in only two of 1 the licensing districts, these being c Auckland (35) and' Gisborne (44). The i substantial rise in the total of li- a censed motor-vehicles described as r “Others” is due mainly to the increasing popularity of trailers, which have ci to be licensed separately from the 1 propelling vehicle and are included in i

the general figures. Details of niolor ownership in the West Coast licensing districts as at March 31 last and the variation Jn numbers, compared witli March of last year, are as follow: — Westport—Cars, increase 136; trucks, I); others, I); cycles, decrease 6. Gi eyinouth—Cars, increase 223; trucks, dccicase 7; others, increase 59; cycles, decrease 37. STARTING A CAR. NEW FORM OF DRIVE. The mechanism used in most cars to-day for the engagement of the selfstarter pinion with the teeth of the flywheel is one of those rather crude engineering compromises which has proved quite satisfactory in practice. Nevertheless, it. is generally agreed that the mechanism does engage with the stationary flywheel teeth with rather more of a shock than is desirable, and when, as sometimes happens, the strong coil spring designed to absorb some of this shock breaks, the impact of the engagement is sufficiently severe to play some havoc with the teeth u* 1 both the self-starter and flywheel gears.

For these reasons, the announcement by one of the most prominent English manufacturers of electrical equipment that it has developed a new form of starter drive is of more than ordinary interest. The standing of the firm in question is sufficiently high to indicate that the drive probably will be found on a number of 1938 models. The new device is a modification of the type now used, but the strong shock absorbing coil spring is eliminated and its place taken by a rubber and a friction device.

The design is lather difficult to explain without the aid of diagrams, but without going into technicalities, it may be stated that in it provision has been made to overcome the difficulty met with when the engine stops in such a position that the starter gear, in endeavouring to enter into engagement. meets the flywheel teeth end-on, a, difficulty which normally can only be overcome by engaging a gear and rocking the car so that the engine is moved slightly. In the new device the starting motor is safeguarded against such excessive strains as are produced by a back-firing engine, and it is said that no matter how high the strain imposed on the drive no damage can result.

TYRE "WHINE.” The roughening of the surface of paved roads to give better skid resistance for tyres is not without problems for the tyre manufacturer, in many cases the roughening is done by running a cleated wheel over the road, the wheel leaving a pattern at regular intervals. Research on tyres has already shown that much running noise comes the regular impact of the tread blocks on the pavements, and it has been found that by arranging the spacing of these blocks to break up the regularity of impast the noise is reduced. Patterning on the road surface itself has also brought a problem of noise, and a tyre manufacturing concern suggests that this is similar to that of the tyre tread, an effect of regularity. Once this regularity is broken up it predicts elimination of the “whine.”

ON DECARBONISING. The decarbonising of the combusion chambers of a car or truck engine is a matter that sooner .or later requires attention. The usual signs that indicate that it is time to decarbonise are a tendency for the engine to knock when running slowly on full throttle, and a tendency to roughness and loss of power. Some car manufacturers recommend that the first freeing of carbon from the combustion chambers should be carried out after about 3000 miles have been covered, so that the inlet and exhaust valves can be ground in. This may not be necessary, but it is advisable from the point of view of good service over a long period. It ensures that the valves are seating properly, counteracting the effect of any slight warping of the cylinder block and enabling the engine to deliver full power.

DIESEL ENGINE.

MODERN MOTIVE POWER. Disasters such as that which befell the Samoan Clipper strengthen the • case for the wider adoption of a form of motive power which uses a less dangerous type of fuel than petrol (writes N. M. Goddard, in the Sydney “Morning Herald”). About 1895 Rudolf Diesel first suggested the method of operation which has made his name famous, and in the intervening years the principle has been extended and modified until there are dozens of forms of engine which embody the basic principle while differing considerably in detail. The essential difference between the Diesel engine and the petrol engine is that the fuel is injected into the combustion space of the cylinders in a “solid” form. It is not injected until it is actually required, and charge is fired, not by some auxiliary means, such as a spark plug, but by the high temperature of the relatively highly compressed air confined in the combustion chamber of the cylinder. This separate delivery of the fuel into the space wherein it is to be burned means that it need not be of a volatile nature. Any fuel that has the necessary heat content and that can be conveniently handled and forced in-

to the cylinder may be used. The primary objection to the Diesel or compression ignition engine, to give it a name which is now often used,

is weight. The earliest types, which had the extra burden of auxiliary air compressors, ran at low speeds and weighed from 350 to 5001 b per brakehorsepower. Continuous refinement in design and improvement in the properties of metals have lessened the weight considerably and have enabled much higher speeds to be , obtained. Engines for buses can now be produced weighing not much more than 101 b per brake horsepower, the weight including the clutch and gearbox. In engines designed for aeroplanes the weight, per brake-horsepower has been brought down to under 3ilb. These are tremendous improvements, but the weights are still about double those of the more highly developed petrol engines. This, of course, is a severe handicap, and until the discrepancy can be more nearly corrected the heavy oil engine cannot hope to make much headway in aeroplane installations, where a saving in .deadweight is more important than in any other branch of mechanical transport. At present there is some discussion whether the term Diesel should be applied as freely as it is. It is used generally to indicate any in which the fuel is supplied separately from the air that is afterwards to support its combustion. In the first forms the fuel was sprayed into the cylinder at the time when the energy of the fuel was to be delivered by a jet of air at a pressure in excess of that of the

air trapped and compressed within the cylinder, the air jet being supplied by an auxiliary compressor driven by the engine itself. In the modern form of engine, known usually as the compression-ig-nition engine, the fuel is mechanically delivered in measured quantities without the assistance of the air blast and without prior mixing with air. In both ignition of the injected fuel is brought about by the heat generated by air compressed inside the cylinder, a form of ignition which has the high-ly-desirable quality of comparative freedom from deterioration or “knock” often associated with high compression petrol engines, for although the ignition takes place in a relatively short space of time, it occurs comparatively steadily. To some extent, there is a reversion in the compression-ignition engine to carburettor principles. When air is injected with the fuel there is immediately the beginning of combustion which continues as long as the fuel injection lasts, but when the fuel is injected without air it arrives in a comparatively solid lump, and some form of earburation must occur before it can become a sufficiently diffused charge which will ignite or deliver its energy. There is thus a delay between the arrival of the fuel and the beginning of the combustion.

If this delay is so long that a large proportion of the fuel is vaporised before it begins to ignite, there is likely to be a comparatively sudden explosion or “knock” rather than a comparatively steady burning and correspondingly steady pressure on the piston. It is for this reason that the characteristic of the fuel must be chosen to comply with fixed conditions of temperature and time, so that part will form an inflammable mixture and ignite while the balance remains unchanged momentarily in order to supply the later steady combustion. The modern engine is by no means a machine which will successfully burn any heavy oil.

STEERING LOOSENESS. There are. in the majority of steering systems, approximately 7 points where looseness will develop apart from the actual steering column, axle, wheels and other associated parts. These include the rods and steering arms, which take all the shocks from the road. Modern design largely embodies spring-loaded ball joints at four points, and regular inspection and lubrication is essential to ensure reliability and good results. The steering arms and drop arm from steering box or spindle must be kept tight. The box itself must be tight on its mounting, either on engine or frame. Pronounced looseness may indicate the necessity for re-conditioning or adjustment at some definite points of the assembly, and this is one thing which no wise motorist will neglect when it becomes evident, as life is dependent upon safe and sure "steering control. VIBRATION. The operator of a motor-yehicle is frequently warned of any condition of excessive wear or looseness by the setting up of a knocking or vibration. Worn universal joints, and consequently loose propeller shaft, are prolific offenders in respect, of vibration, and sometimes .general tightening, if carried out in time, will provide a remedy. Vibration can result from loose engine hearers, misaligned gearbox, in-

ternal engine wear, bent shafting, : loose accessory mountings (magneto, ■ generator, etc.), loose wheels, rims, j hub bearings and other components. . General tightening is the cure in many ; instances of parts, and setting of align- t ment. A shaft out of centre will al- ] ways have. a "period” of vibration, and the condition should be rectified. i CARS IN AMERICA. The most complete survey of a na- J l inn’s automotive statistics’ ever taken lias been recently concluded by the ' United States Department of Com- , meree. The investigation disclosed the f mazing, fact that 7,000.000 American families owning motor cars have in- ' comes of less than £4 per week. That total represents 34 per cent, of all the cars registered in the United States.. The survey showed that 55.5 per cent of the cars are owned by families with incomes of less than £6 per week, and that 73.1 per cent are owned by families earning less than £8 a week. The initial low cost of new and used cars in America, plus low petrol prices and automobile taxation, all contribute towards this amazing situation. As a

mutter of fact, it is the working class in America that provides the major market in that country for new and reconditioned cars. Actually less than 3 per cent of that nation’s automobiles are owned by families with incomes as high as £2O a week. Official figures- also disclosed how important the automobile has become in American agricultural life. Amongst middle class farm families, having an average income of from £6 to £7 per week, the average annual expenditure for food was £7B 15/-; for motor transportation £3B 15/- (use of automobiles for farm tasks was deducted) : for clothing £27 15/-, whilst the household expenditure averaged just under £27. Medical care-averaged £l6 per iinnum. It will be seen from Ihe statistics that, in the basic needs of the American farmer, motor transportation actually ranks second to food.

Number. Increase. Increase per cent. Cars 190,554 ■ 20,550 12.09 Trucks 47,020 1,471 3.23 Olliers . . 17,896 3,633 25.47 Cycles . . 22,880 1,321* 5-46* *Decrease.