THE PETROL TRAIL

New Zealand Times, Volume LIII, Issue 12615, 27 November 1926, Page 18

T HE PETROL TRAIL

FOUR-WHEEL BRAKES ACTION ANALYSED FREAKISH HUMOURS. Driving a car with the behaviour of which I was perfectly familiar (states an English writer), and that, thanks to its excellent front-wheel brakes, I had come to regard as securely defended against the least ; risk of skidding, I got one of those horrid surprises that shatter both faith and mudguards at-the same time. According to the amiable habit of its kind, a motor-’bus came, without'warning out of a side street, and 1 accordingly trod firmly on the brake pedal. 1 had no hesitation in doing so, for in the main tho roads were dry enough. Unfortunately, however, tho patch of surface upou which my deceleration had to be accomplished was I a bit that had managed to escape the sun. Jt was slippery, but 1 should have said, in normal condition, not dangerous. I should have said that, at all events previoiis to what followed. It was as fair and fine and frightful a skid as I have had in a pretty comprehensive driving career. The car, at the time, was going quite straight, but there was never any doubt as to the effect the skid was to have upon it. It. spun round three-quarters of a circle, and fetched up agaiust the kerb with a thump that made one of the wheels look like a discarded and badly disintegrated umbrella. EVIDENCE FROM TYRE TRACKS . The road carried little traffic, and 1 had an opportunity ' to examine the tyre, tracks. From them it was obvious that. the back brakes had locked the wheels, while the front ones w-ete still comparatively free, so that for the moment the car might have been said to have had no front-wheel brakes at all. I was not able to understand that state of affairs, since the whole braking system had been adjusted only a few hundred miles before, and it was not long sinoe, .as a matter cf precaution, all the shoes had been relined. Subsequent consideration, however, has led me' to the belief that this sort of thing is susceptible to a simple explanation, and that as it seems capable of taking place with jany ordinary kind of front-wheel brake it represents a weakness in the system which ought to be eradicated. Jn ,the generality cf designs—l except jthoso in which the hydraulic system of [transmission is adopted—the frontwheel brake shoes are expanded in the same way as those at the back, namely, by a cam and lever. The priu- j cipal fault of a mechanism of that 1 kind is that it is not, so to speak,) symmetrical in its progvessiveness. Under conditions of wear and tear in the linings the ‘‘just off" position of » the cam lever results in a small move- I ment of the shoes. owing to the greater angle which the cam takes up j relative to the anvil of the shoe. Ju \ other word*, a rod stroke of lin only expands the shoes about I.32iji, instead of 1-3-inch. Assume that two .similar brakes, one in front and one ft the back, are linked, cither with or without a compensating device. It' the jjr.tcrinl of the brake lining.* ’r> the sime in each case and other tl'.ngs are equal, it can be assumed that the two levers will continue to move through the same angles indefinitely,'' so that each pair of shoes will open always to the same .amount when the pedal fS depressed. This, however, does not take place in practice. INTERESTING PROBLEM HOW LONG WILL PETROL LAST. One of the chief factors in the success of the automobile in America has been cheap petrol. This year, with n.ore than 20,000,000 motor vehicles in operation, benzine is cheaper than it was five years ago. It is estimated that the total petrol consumption-this year will reach 10 billion gallons in U.S.A.—more than four times what it was ten years ago. Next year, if the present rate of increase is maintained, it will be from 12 to 13 billion; in 1928, possibly lo billion, and so on. At this rate of oensumption, how long will the world’s supplies last presents a most interesting problem. STARTING TROUBLES TAKE CARe'oF THE WIRES. To avoid all ignition, starting and lighting troubles, it is advisable to inspect all wire terminals about once every month or six weeks, and see that they are snug. For those not especially familiar with the electrical system it may be advisable to itemise all tho connections. The generator is connected with the battery, which in turn is connected with the ignition coil, ignition switch, the starting motor and all lights. From the coil the connections lead to the distributor, which is connected with all the spark plugs. Besides snugging up all connections, it is well to examine the battery terminals..lf they are corroded, brighten them ui> ami apply a very little vaseline before reconnecting. CAR OWNERSHIP AMERICAN VIEWPOINT. The use of motor-cars in the United States has resulted, in a great decentralisation of urban life and an extraordinary development of suburban life. There is hardly a city in the United States which does not have suburbs, made possible only because of automobiles. Consequently, housing problems have been solved, and great economic wealth created as a result of increased laud values. It is quite common in the United States for a city dweller to buy a motor-car, which makes it possible for him to move into the suburbs, where lower rentals enable him to have more room and to live better. The motorcar provides him with transportation to and from work. Without the car he probably would have to remain in the city and its congestion. Suburban development means the building of streets and highways, and means more employment. It means the building of homes, the laying-out of sewerage systems, the extension rf electric light, water and gas facilities, all of which provide more employment. The United States has proved that the motor-car is a creator of economic wealth, and consequently the United States believes in making it as easy as possible to own and operate an automobile. In America the automobile is thought of as individual transportation, a necessity, not a luxury, and its use is encouraged iu every way.

LOSS OFJVATER RADIATOR BADLY FITTED MAY HAPPEN~IN NEW GAR. The complaint is often made that the radiator of a new car constantly requires filling up. The trouble may be that water is leaking into one or more cylinders through an imperfect gasketfitting. This happened to the engine in the case of a motorist who experienced recurring trouble after the car was overhauled and refitted, with the result that, when about 20 or 30 miles from home, the water dropped to dangerously low level, and he only managed to get home by taking a can. of water on board and replenishing the radiator every three or four miles. Incidentally, the motor engineer' called in would not take this risk, but towed the car to his garage. This engineer made a good job of it by running the

after-filling the gasket- and before filling the water-jacket. This enabled him to give the bolts an extra turn and ensure an absolutely watertight titling. Since then the owner had no trouble, a few drops of water after many days being sufficient to maintain the level. If water is leaking into a cylinder some will be found in the carburettor or the exhaust. This test should be made. In some cases, however, the radiator may merely be filled unnecessarily full. The radiator having been filled nearly to the top of tlie overflow pipe, note the level to which it has fallen, at the end of a run, and then notice the level to which it falls when the engine is cold. Jf this is a safe level, begin on a run, 'and if there is no defect in the gaskets the water should be,at the same levels hot and cold when the radiator is next examined. The dangers of neglect are that the water may suddenly leak away very rapidly, as in the case mentioned and .if not discovered in time will lead to overheating and seized pistons, and, hi any case, water will get into the sump and convert the oil into a non-lubricating emulsion. If water has got into the cylinders the oil in the sump must, of course, be drained off and fresh oil substituted. BALLOONJYRES DON’T UNDER INFLATE CAUSE OF LOW MILEAGE. To under inflation of balloon tyros most, of the owners’ trouble is attributable. Many men to-dav are running their low-pressure tyres far below the pressures recommended by the makers. This tendency upon the part of car owners to run tyres under inflated may- be due to a certain amount of advertising, which led them to believe that low-pressure of balloon tyres can be run with practically no air. They fail to distinguish between low aitpressure and too low air pressure. The air pressures, ns recommended by the tyre makers, are minimum pressures, and the air should he maintained in the tyres at above these pressures, but never below, it maximum mileage is to be had. .Many low-pres-sure tyres are prematurely ‘worn out, duo to absolute disregard or ’misunderstanding ol this fact; Under inflation, causes verv t-aoid tread wear.' due to the fact ‘that the tyre, .instead, of rolling properly, upon the ground, flattens out entirely "to too great an extent, and this causes a scrubbing and grinding action between the tyre and the road surface as it revolves. The rapidity with which this grinds away the tvre derrends npon the degree of under inflation. A great deal of under inflation causes the tyre to westoff on one or both of the outside edges, leaving the centre rather high. Again, under inflation may cause the tyro- to wear in cups or" odd spots around the circumference of the tyre. Jf such things are occurring, the carowner should watch air pressures more closely. It'is well to remember that it is the average pressuro maintained throughout the life of the tyres which gives the desired results in life, not the pressure you may have any one day. Preventive measures are the employment of a reliable low-pressure gauge, testing the tyre pressure once a week, inflating the tyres to four or five pounds over tbe minimum recommended by tlie tyre inakers, looking well to the air valves that they do not leak, and, if the weekly pressure test shows too rapid a loss of pressure, take the tubes out and examine them thorough-Accoi-ding to a bulletin of the American Research Foundation, the United States, yearly, use. 0.-. o gallons of crude petroleum per person’,’ while the rest, ol the world uses 12 gallons to live persons.

ROAD CONDITIONS HIGHWAYS BOARD REPORT progressTof work. The monthly report presented to the Alain Highways" Board for October contains the following information respecting the work accomplished on the various road sections. On the Wellington-Napier route via Wairarapa a commencement has been made with the construction of the bridge over the Kaikora stream. Good progress is being made on the Whakaruatapu deviation, and it is expected that the Piri Piri section will he available for traffic in about six weeks’ time. The deviation work on Alatahiwi hill is also well in hand. On the main North road to Auckland a largo amount of work is being undertaken, both in resoect to road improvement and bridge work. The Mo-

kau river bridge work is progressing. In Inglewood county surfacing is being done, and portion, of the road in the Pa tea county section is under reconstruction. In the Ngahaurauga gorge considerable improvements have been accomplished, and are being extended. Between Johnsonville and Taw a Plat a section, of the road lias been widened, and a further section is being undertaken. In addition, sixteen chains of new formation have been metalled and roiled. The total length of widening and metalling between Paremata and the foot of the Paekakariki hill is over i lour miles, in addition to which a sea wall has been completed. Sectional work is in progress between Paekakariki and Tokomaru. Preparations are being made between Levin and Tokomaru for bituminous penetration work as well as on the Waikanae-Manakau section, and widening and reforming is in progress on other sections. The improvement made to the Maungaroa and Itimutakn hill roads is much appreciated by motorists, and when the work now in hand in Wairarapa is completed some fine surfaces will have been provided. WHEN THTouTtHINS OUT CHANGE EVERY THOUSAND MILES. AVe all know that alter engine oil has been used for a time it loses its body, and w© sometimes refer to the change as ‘‘breaking down.” Oil does not break down or undergo any permanent thinning out when it is heated in th© average automobile engine. A mixture of oil and motor spirit is naturally thinner than new oil, and this is exactly what wo have in the crankcase w hen the oil is said to have “thinned out.” Cnvaporised motor spirit in the cylinders leaks past the pistons and mixes with the- oil in the crankcase. Whenever there is an excess ot liquid iuel in the cylinders this <$ bound to happen. AN e know* that new oil will separate the moving part belter than thinned oil; although the latter might give us a fair lubrication tinder ideal conditions. To prevent engine wear, we want to separate the moving parts far enough, so that the particles of rend dust, and other abrasives that are carried in the oil film will not touch the metal surfaces and cut them. Much of this road dust and abrasive material is drawn in w*ith the air through the carburettor, to an cxter.t that varies with the driving conditions. For the longest engine wear the oil should not be allowed to thin out too much; and abrasives should not be allowed to accumulate. If the engine is kept at i e proper temperature duvihg operation if it is given an occasional hard run, and if the choke is not used excessively, the body of the od will be kept up for a reasonable time. If the oil is changed at proper 1 intervals, at least every thousand miles, the abrasives, under ordinary conditions, will not accumulate to an extent that will cause damage. Oil which is not used too long, and which is kept reasonably warm while the engine is running, usually clean and of proper body. With this* protection the engine will give many times the service that would be possible othcr- ' wise. streetTatalities MOTOR-CYCLE’S CLEAN RECORD Statistics show that of the 63 deaths caused by road vehicles in Southwark, (London), last year, 23 were by motor vans. 14 by motor-omnibuses/ 3 by trams, 3 by motor-coaches. 3 by taxicabs, 6 hv motor-cars, and 11 pedal cyclists were killed by collisions. Not a single fatal accident was caused by a motor-cycle.

CAR SPRING WAVE LENGTHS RESL'LT OF TESTS. After a short run last week in an experimental ear, says “locus*” in “The J,ighv Car ami Cyelecar.' 5 I whs chatting with the designer about suspension problems, as the car hail impressed me as being very well sprung. I may acid that wo had tested the car over a wide variety ol road .surface. J was Jiauded a stop-f» ateh and told to walk for one minute, counting my steps during that time. The result was SS paces, and tlie designer told me that ho and three' cr four otkor men had carried out this teat and

discovered that their average number of paces was 90. Accordingly the springs of the car had been calculated to give about IK) “waves' 1 per minute at iiO m.p.h. At first 1 could not see the connection between the two {mints, hut it was explained that in walking there i> a slight up-and-down movement, and the hudy naturally ac* commodates itself cr.>ily to this rate, hence the spring design.

At Eastleigh (England’' recently, a police constable boarded a ear and chased a man whom he Mis{>eoted of riding a stntcn motor-cycle: ho then leapt on the carrier ot the machine, and was carr : ed some tnib's liehiro ho could make the rid-r stop. \ crasdl terminated the hectic journey.