MOTORING AND MOTORISTS

Evening Star, Issue 22277, 2 March 1936, Page 15

MOTORING AND MOTORISTS

LIGHTING-UP TIMES To-day 7.55 Tuesday 7.5:5 Wednesday ... 7.51 Thursday 7.49 Friday 7.47 Saturday 7.45 Sunday 7.44 REPLACING GASKETS HEED FOR ACCURACY It is important when replacing nn intake or exhaust mrnifold after an engine overhaul that the gasket should be set accurately in position, so that it does not overlap the volvo ports at any point and restrict the intake of mixture or the expulsion of the exhaust gases. If the gasket is seriously damaged or distorated it should be renewed, and it will sometimes be found that when it is placed on the studs of the cylinder block the holes do hot register accurately with the ports. Although it is unwise to attempt to trim a copper-asbestos gasket to put right that fault, it might be possibly to get it into the correct position by enlarging the stud holes so as to give the necessary " play," but if that is done care must be taken not to allow the gasket to slip out of alignment "while the manifold is being bolted on. If n light coat of jointing compound or gold size is given to the underside and the gasket is then pressed into position on the cylinder block, and the cement allowed to set, it will be held securely in place. Accurate fitting is most essential, for if there is any leakage on the exhaust side some of the fumes carrying carbon monoxide gas will oscape underneath the bonnet and may be driven back into the car, while n defective seal at the intake manifold will allow air to be drawn in, and so upset the balance of the mixture. The nuts which hold the manifold to the block should be tightened gradually and in accordance with the same method as that advised for tightening a cylinder head; that is to say, no one nut should be screwed fully home in advance of the others, but all should be tightened progressively, and in such order that the pressure is evenly distributed over the face of the manifold, and a perfect joint is obtained. If bonded asbestos gaskets are provided instead of the copper-asbestos sort, it is possible to trim the hole with a sharp knife to correct overlapping of the ports. Similar thoroughness is called for in respect of carburettor gaskets, for : f there is any clearance through which air can bo sucked in it will be impossible to adjust the carburettor correctly, ft should be seen that the flanges of the carburettor and induction pipe are clean and smooth, and if tihe old gasket is not in excellent condition it is far better to procure a new one and make sure of the work. A good makeshift in the event of its being necessary to replace a carburettor gasket when spares are not obtainable is to employ two or three thicknesses of blotting paper, which are laid on the flange of the carburettor and tapped or pressed until the pattern is impressed, and then trimmed to shape with scissors or a penknife, it might be advisable to soak the paper in engine oil before cutting out the gasket as described. Motorists have occasionally experienced baffling trouble because the gasket was so thin that the engine heat was communicated to the metal of the carburettor and raised the temperature of the fuel in the float chamber excessively. If that condition exists, the best course is to have a very thicK gasket made from fibre or asbestos. SELECTING SPARK PLUGS NEEDS OF MODERN MOTORS It is not so very many years ago that the selection of spark plugs was merely a matter of knowing the correct size and buying an approved make. With the gradual increase in compression ratios and the consequent stepping up of the power and speed of automobile engines, a considerable number of new factors have arisen which render the choosing of suitable spark plugs a matter deserving of a littles thought and study. Onco the fundamental facts have been grasped, however, it is a comparatively simple matter not only to diagnose the cause of plug failure, but also accurately select the correct plug for the particular conditions under which the engine operates. A condition which is necessarily incidental to an increase in power from an engine, is an increase in the temperature during the burning of the fuel. Extra heat must be dissipated, and this factor is one of the main reasons why a spark plug which suits a low compression engine will be unsuitable for the greatly increased power output from the high-compres-sion engine. A spark plug relies mainly upon its porcelain insulator to carry away the intense heat at the tip to* the "metal portions of the cylinder. Porcelain is used because of its high insulation properties, and its ability to stand up to high temperatures. Being a good electrical insulator, porcelain naturally is not a good conductor of heat, and it is therefore necessary to design the insulator in such a manner that it can cope with the heat to which the plug is subjected. This has given rise to the somewhat broad classification of spark plugs into three types—" cold," " normal," and ." hot." A " cold " plug is one in which the heat path is short, enabling the heat to be transmitted rapidly from the electrode to the landing on the cylinder. This type of plug is necessary for high-compression engines, or for those engines generally which are called upon to do heavy slogging work. In a " hot " plug, the heat path is long. Heat generated at the electrodes cannot get away rapidly, and as a result the electrodes and poreelain heat up and remain hot. Such a plug is still used in medium to low compression engines, and for some high-com-pression motors on very light duty. Leading spark plug manufacturers have increased considerably the range of spank plugs during the last few years, until to-day it is comparatively simple to select plugs which will I'uuc-

tion hot enough to burn off any oil or carbon lodging on the insulator and yet not reach such a temperature as to cause preignition or burning of the electrodes. Spark plugs fail prematurely for one of two' main reasons. .Either the plug has been running too cool or too hot. Evidence of too cold running is the fouling of the insulator with carbon and soot. Evidence of hot running is rapid gap growth, blistered or cracked insulators, or preignition. Since the introduction of ethyl petrols, and the almost complete elimination, of knocking, it has been possible to advance the spark much further, and to mako the combustion of fuel more complete. This .has resulted in more power and higher speeds being obtained, which naturally heats up plugs more than before. Almost invariably, when a change over has been matte from an ordinary white petrol to an ethyl grade, a change to the cooler type of plug will be found advantageous. The fact that the plug heats up on this higher grade petrol is a good sign, indicating that_ more of the heat energy of the fuel is being converted into power rather than being blown out through trie exhaust pipe as so much waste energy. Many faults in engine operation, such as excessive petrol consumption, preignition, and carbon deposits, can be traced to the incorrect selection of spark plugs. In fact, some of the high-compression engines now in use are so sensitive to the heat characteristic of spark plugs, that merely one step too hot or too cold will noticeably affect the performance of an engine. From the condition of the porcelain tip of a spark plug, the indication can be secured of the carburettor setting. If a new set of pings is installed, and after a' few hours' run they are removed for examination, the colour of the porcelain tip will indicate the carburettor setting. If the porcelain is black the mixture is too rich. On the other hand, if the porcelain is white, the setting is too lean. The, correct setting is indicated by a light tan stain right at the tip of the plug. Considering spark plug operation in general, it is epiite evident that a great deal of research and thought is behind the construction and design of plugs for modern engines. Wherever spark plug failure has occurred, it will be found almost invariably, that it is the application of the plug rather than the plug itself, which is at fault. In other words, either a " too hot " or " too cool " spark plug has been chosen for the particular engine. REGKLESS DRIVING A FAULT OF THE YOUKG According to a report in the London ' Daily Telegraph,' official figures show that the majority of accidents on the roads can be traced to young drivers. The question is stated to have been raised by Mr Justice Humphreys, who, fining an .18-year-old van driver at the Sussex Assizes for dangerous driving, said: " Time after time we have young men —it is always young men—charged with driving recklessly, because they have no sense of the responsibility which ought to be on anyone driving a motor car.'' On. being interviewed the head of the motor department of a leading insurance firm expressed agreement with Mr Justice Humphreys. Ho pointed out that premiums up to 75 per cent, above the normal were charged on types of sports cars principally driven by young men and women. "I do not think there can be any doubt that recklessness on the roads, chiefly a matter of driving small cars at terrific speeds, is more prevalent among the 3'oung than the old." he said. It is further stated that official statistics reveal that drivers between the ages of 21 and 26 are concerned in nearly as many fatal accidents as drivers between 31 and 41, and in far more than those between 41 and 51. The Ministry of Transport's last report on fatal road accidents gives the following figures for the total number of drivers involved in fatal accidents during 1933: Between 21 and 26 ... 2,060 Between 26 and 31. ... 1,830 Between 31 and 41 ... 2,224 Between 41 and 51 ... 1,249 An Automobile Association official pointed out that these figures were even more striking when it was taken into consideration that there were estimated to be considerably more drivers in the thirties and forties than in the twenties. EASY WHEEL-CHANGING The unpleasant job of fitting the spare wheel in the event of a puncture is often aggravated by the fact that the type of jack used is unsuitable for the car, or because the jack is not well lubricated. It should be of a size which allows it to be placed without difficulty under the car when a tyre is fully deflated, and should have ample extension so that the punctured tyre can be raised well clear of the road. A long handle is desirable, so that excessive stooping can be avoided. The threads of the jack, if gummed up with grit and oil, should be washed with petrol or kerosene, and then lubricated. When not in use the jack should be stowed in a small bag or wrapped in a cloth. DRYING GUT BRAKES FRICTION WHILE DRIVING The Automobile Association of California in a statement to members advises them when driving in the rain or just after the car has been washed to be on guard for wet brakes. It is pointed out that the basis of braking is friction, that friction causes heat, and that heat evaporates moisture. The recommendations are: — When driving away after a washing do so in low or second gear for a while and apply the brakes intermittently until sure that friction heat has dried them out sufficiently to restore them to good working condition. Use the brakes in the same way when driving in rain or o:i wet roadways

by "Radiator**

where any considerable amount of water is likely to be splashed on the brake parts. Manufacturers strive to procure brakes that are dependable under all conditions, but there are some factors over which they have no control. For example, in washing cars soapy water is quite likely to get on the brake lining. The lining also has a tendency to collect moisture when driving through water or during a heavy rain storm. The remedy is to evaporate the water by use of the brakes, meanwhile driving carefully until certain that normal braking control has been resumed. CASE-HARDENING SMALL JOBS There are occasions when it is necessary that a grub screw or other component should be dead hard if it is to give reasonable service before excessive wear calls for another replacement. Where facilities are available such parts as gudgeon pins, tappet heads, and the like arc hardened in hermetically sealed boxes, but excellent results can' be obtained by the open hearth method. A tin of case-hardening compound must bo obtained. The part to be hardened must be heated up until, when placed in the compound, the latter will tend to fuse onto it. The part, with the compound adhering to it, should be lifted with a pair of longnosed pliers or other means and again heated up until the yellow flame practically disappears. • A slightly deeper surface can be obtained by repeating the process, but a depth greater than about 1-C4in is scarcely possible. Whilst the component is still hot it should be plunged into cold water and kept on the move the whole time. Should it be of such form that it may tend to warp it should be plunged into the water whilst held perpendicularly. Mild steel, thus treated becomes a great colour and glass hard. Whilst emery cloth will touch it. a file should make' no impression whatever. CHEAP LIGHT GARS While British manufacturers have, thanks to a reduction of the Treasury tax and the demands of domestic and export markets, given great attention to the building of models which in respect of wheelbase, accommodation, and power, cannot be considered as " baby " types, many Continental factories hope to exploit a new field with cheap and small cars, which are designed to attract purchasers who are unable to afford a large outlay of capital, and who must keep running costs as low as possible. In France, tho Society of Automobile Engineers is seeking to encourage the production of cars to be sold at about £IOO, com, plete, with a maximum speed of 50 miles an hour, and an economical petrol consumption of about 90 miles to the gallon. The weight of such a car would be less than lOcwt. The aim is to induce manufacturers to design a model which will not compete in the existing market, but appeal to those who hitherto have not been prospective customers. One of the questions to be decided was whether a four or two-seater model was desirable, and a questionnaire was forwarded to 220,000 persons. A big majority of the replies received favoured a four-seater vehicle. Cheapness of upkeep is the principal object of the society, which aims at the evolution of a suitable and comfortable machine, whose all-in running costs, with a monthly distance of 600 miles, will not exceed £4 a month. In Great Britain there are several small cars which are listed at about £IOO. These machines offer excellent value for money, and are generally capable of a speed of 60 m.p.h., but their fuel mileage is far below the extremely low rate sought by the French Society of Automobile Engineers, and which probably will only be attainable with a small twin-cylinder engine. RIDGES AND DIPS LOSS flr STEERING COHTROL The wise motorist will find food for thought in the following article by Mr K. Miller in the ' It.A.C. Journal ' : The horizontal forces produced when taking corners are fairly generally known, on account of the dangerous proportions they are liable to assume under extreme conditions; but the forces brought into play when riding over shallow dips or the tops'of sharplycurved hills also are interesting, and can lead into danger under certain conditions. Among the cases dealt with by the legal contributor in the last issue of the " Journal " was one in which it was stated that " tho plaintiff was travelling towards a rise in a country road, on his correct side. The defendant's car was travelling on the wrong side of its road, from the opposite direction, up tho other side of the rise, the earn not being visible to each other." Here we have a case where centrifugal forces have been brought into play, though it may not appear obvious at first sight. Not much imagination is required to picture the two cars at the top of the rise, as if riding along the outside edge of a vertically placed circle, the centre of which is somewhere in the ground. Now, if we take a piece of string with a weight on the end, and whirl it round in a vertical plane, the weight will tend always to fly away from the centre of the circle, and, in the case of the cars, we mav think of the force of gravity taking the place of the string (because it holds the car on the rond, which is part of the circumference of a circle), and the cars taking the place of the weights on the end of the string. Therefore, in going over tho rise, a centrifugal force is generated, tending to lift the cars off the road, and this force will indeed lift the cars off the road at the top if they travel fast enough. A somewhat surprising fact in this connection is that all cars going over a rise like this will lift off the ground at exactly the same sne°d. For example, if a " baby " and a 10-ton lorry travel abreast over a hump-backed rise at speed they will lift off the ground ni the snui'.; instant.

The reader may still ask where the danger lies, apart from the fact of not being able to see the other side of the hill, and we shall proceed to explain. If the centrifugal force is pulling the car off the road, and gravity is pulling it down on to the road, the pressure between the tyres and the road will be the difference between these forces. The faster the car is travelling, and the sharper the hump, the smaller will be this pressure it being fairly easy to obtain the condition where no pressure exists between tlia front wheels and the, road, and under these circumstances turning the front wheels will have no effect on the car. In other words, steering control will he temporarily lost, even though the steering mechanism may be in perfect condition. This probably may account for the sentence appearing in the above mentioned case which reads: "At the top of the rise, when the cars came into view, the defendant gave no sign that he was going to turn on his correct side." The reaction between tyres and road may not have been sufficient to allow the car to respond to the steering, until the car had slowed down sufficiently for this reaction to make itself felt. All that we need to know, in order to get the speed at which the pressure between tyres and road will be zero, is the radius of the circle over which the car is travelling. If the radius (in feet), is multiplied by 32, we shall get the square of the sjieed in feet per second. A circle having a diameter of 121 ft would have a comparatively flat top. Let us see, therefore, the speed at which the pressure on a road having a hump radius of GOJft would he nil. 32 x 60| equals 1,936. The square root of 1,936 is 44. Therefore at 44ft per second, or 30 miles per hour, the road pressure would be nothing, and any car passing over the top of a rise like this at 30 m.ip.h or over would lose steering control at the top. This is, of course, on account of there being no friction between tyres and road, and the car would continue to travel in a straight line in spite of any change in the direction of the front wheels. When passing across shallow dips of approximately semi-circular form, similar forces are brought into play, but in this case the centre of the arc of the circle is above the road, and, as centrifugal force always acts away from the centre, gravity and centrifugal force will assist each other, and pressure between tyres and road is increased. If a car be travelling across a dip of GOJft radius at 30 m.p.h. the pressure will be douoled, which means that extra strain is placed on the springs. The pressures brought to bear on cars when travelling over dips of only a "few feet radius are very great, if taken at any speed. If a dip of 10ft radius be taken nt 30 miles per hour, the pressure on the car is more than seven times the weight of the car. It can be imagined, therefore, that the problem of spring design is not an easy one, for springs must be stiff enough to withstand pressures many times the weight of the car, and must not be so stiff that passengers will be thrown about like ipeas in a pod. ANIMALS £U THE ROAD SWERVING TO AVOID DOGS The natural instinct of almost every motorist is to swerve abruptly and brake hard in order to avoid a dog which has rushed suddenly in his path, but, unfortunately, such spontaneous good nature sometimes is the cause of serious risk or grave accident, and often defeats its own ends since the animal may suddenly halt or dart in another direction. There can be no dispute about the relative responsibilities. If, without endangering other road-users or oneself, it is possible by slowing down, blowing the horn, or swerving, to avoid running over a dog, then it is callous not to take every precaution, but motorists are not called upon to jeopardise human life or "pile up" their cars because of the folly of a domestic animal. Many dogs are sensible in traffic, and will pause at the roadside before crossing, and take immediate notice of a " toot," but those which rush out and snap at tyres or tear wildly about about the roads are not deserving of any exhibition of sympathy which involves risk to human beings or valuable, property. A sharp swerve or harsh braking on a slippery road might be disastrous, and in such circumstance the proper course is to steer straight for the animal so that the car might pass over it and it is not.struck by the wheels. When mohs "f sheep or cattle are met with the motorist's obligation is to slow down at once, and stop if necessary until the drover has cleared a path for him, and he is also obliged by law and the dictates of common politeness to be specially careful when meeting or overtaking restive horses. MOTOR CYCLING FIXTURES March 4.—Evening pillion run. March 14.—Hill climb. March 17.—Monthly meeting. March 28.—Mystery run April 21.—Monthly meeting. April 26.—Social run. May 9.—Camberfy scramble. May 19.—Monthly meeting. May 23.—Social run. .lune 6.—Petrol consumption test. June 16.—Annua] meeting. CLUB NOTES All motor cyclists are invited to the A.A.O. cycle section's pillion run, the riders and passengers leaving the club rooms at 7.15 next Wednesday evening, with Whare Flat as their destination. Entry forms are now available for tlw Southland Motor Cycle Club's 100-mile beach race, which is to be held at Oreti Beach on March 21. This will bo the Jnvorcargill club's first event of this type, and it is to be hopud that it will be well supported by the Dunedin motor cyclists Another sporting fixture which may be of interest to local riders is the Timaru hill club, which will bo run off next Saturday, March 7. TOLD AT THE WHEEL She: " You shouldn't be ashamed of the second-hand car you got for your ' birthday—why, the ads. say ' Everybody drives a second-hand car.' " Fie: " Yes? This is the one everybody d:m-:\"