THE MOTORIST

Northern Advocate, 29 December 1934, Page 7

THE MOTORIST

'‘RUNNING-IN” PLACARDS. TO HELP REAR TRAFFIC. On popular tourist roads where ordinarily fast speeds might be permissible much inconvenience Is inflicted on following traffic by drivers who insist upon travelling at a slow pace, thus causing a queue of cars to be formed because of the infectious reluctance of motorists behind to attempt to overtake. It should not be forgotten that in many instances the sluggish driver is not deserving of censure, for he may be running-in a new car, and so must refrain from speeding up for long distances, no matter how insistent those behind him might be. It would, however, be very helpful if owners of new models were to follow the practice encouraged by some French manufacturers, and paste a notice at some suitable spot, such as along the bottom of the rear window, to inform other drivers that they should take the first opportunity of overtaking. A conspicuous label bearing the words “Running-in—Pass me” would save many misunderstandings, and possibly this suggestion might prompt car distributing firms to supply such a placard when making delivery of a new model. It should' be needless to add that motorists in charge of “tight” cars should take pains to show every consideration to other road users, not only by signalling them to pass, but also by studiously keeping as close as possible to the left of the road, so as to leave as wide a space as possible free for faster traffic.

- MEASURING ROAD SPEED. AMERICAN DEVICES. Two instruments have been developed at the Massachusetts Institute of Technology to measure accurately the speed of passing cars. They have been designed primarily for use in studies by engineers of the Massachusetts Highway Accident Survey. One of the devices is a “scientific speed cop” which, placed beside the road, stares unblinkingly at two spaced parallel light beams shining across the highway. When a passing car intercepts a beam the watching eye winks and the second eye does the same when the car reaches its line of vision. The time required by the car to cover the distance between the two eyes indicates its speed. The other instrument employs two insulated thin wire road “trips” which are laid across the road several feet apart. As a car passes over the wires, contact is made with an electrical measuring apparatus, the speed of the car being measured by the time it takes to cover the distance between the wire “trips.” > It is said that both devices have undergone severe tests in the vicinity of Boston and have proved their efficiency in measuring the speed of motor vehicles.

A wealthy merchant In China owns a Packard car. In the two years since it was purchased it has been run only a total of 43 miles. He uses it for an annual pilgrimage of 10 miles from his home to the temple containing the tombs of his ancestors. To pay the highest honour to his parents he uses the car for no other purpose.

RULES FOR PEDESTRIANS

SOUTH AFRICAN SUGGESTION. SIGNALS TO MOTORISTS. A highway has been defined as a passage which all the King’s subjects have a right to use, provided that in so doing they do not inflict injury on any other user. A man driving a car or pedalling a bicycle is bound to announce his approach by horn or bell. If he wants to turn a corner, or pull up, or back, he has to make known his intention to other users of the road, or he is held to have been negligent. But a pedestrian may dither or dash when and where he will without any attempt to signal his intention. “No pedestrian shall step off any sidewalk or footway in or upon any public road within the city into such public road unless and until he shall looked in the direction from which other traffic lawfully upon such public road may be expected to come and shall have satisfied himself that he may do so without endangering his own safety or that of any other person in or upon such public road.” So runs the injunction of the regulation for the control of pedestrians issued by the Cape Town City Council. But everything is left to the pedestrian , himself. He is to decide when and where it is safe to cross, and then is free to do so without letting anyone into the secret. How much simpler if there were a code of signals by means of which he could show what he wished or intended to do.

It would be quite easy to devise such a code. Only one or two arm movements would be needed to indicate whether he was willing to wait until an oncoming motorist had passed. The effect of these signals would be twofold. Not only would they act as r warning to the motorist, but the verj fact of having to make them would force jaywalkers to think what they were going to do, instead of acting on the spur of the moment as at present. The Pig-headed Walker. The pig-headed pedestrian who asserts his right to .the highway by stepping in front of a line of fast traffic would have to announce his decision beforehand, and the resultant saving of brake linings would be enormous. In England so much trouble has been caused by people dashing into the roadway to stop trams and buses that local authorities there have been experimenting with a new signalling device. This consists of a switch and globe attached to a lamp-post or tram standard. When the would-be passenger presses a button the globe is illuminated for several seconds, indicating to oncoming drivers that they are required to stop. The globe remains alight just long enough for its purpose, and then is ready for the next user. This is certainly an improvement on the methods of local tramway

passengers, which are a nightmare to motorists by daylight or dark (says a South African writer).

Few people buy a car or even a push-bike without knowing something of the rule of the road. Unfortunately walking is so automatic that few realise there are right and wrong ways of doing it. The municipal traffic regulations enjoin the pedestrian not “to walk, run, move or conduct himself upon any public road within the city in a manner which is or is likely to be dangerous to himself or to any other person or persons in or upon such public road, regard being had to all the circumstances of the case,” and to keep to the left when walking on the footway. The Most Important. But even more important still is that those on foot should keep to the right on roads without pavements, so as to face oncoming traffic. This is the first rule of any pedestrian’s road code, although there still are people who will walk on the left of the roadway because this was the “right” side in the days of horse-drawn traffic. “Got to know the meaning of all road signals” should be the second commandment of such a code. When a driver puts out his hand to show he is going round a corner, it is amazing how many foot passengers stand uncertain as to which way he will turn. Similarly, when a traffic constable is holding up cross-traffic, but allowing a side-stream to continue its way round the corner, old ladies of both sexes glare at him as if he had lured them into the middle of the road by his outstretched arm only to throw them to the Moloch of the motor car. Such misunderstandings arise merely because pedestrians know nothing of

traffic signals, and refuse to lake the trouble to find out. When every pedestrian is supplied with a pocket edition of his very own code of road rules-—still to be written—such things no longer will happen.

BRAKING TESTS

ACCELERATION COMPARED. BRAKEDRUM ENERGY. Rather a novel way of viewing the performance of the modern car was suggested recently by an engineer who had much to do with brake design. Briefly, his suggestion is to compare the acceleration produced by the relatively large, costly and complicated power unit with the deceleration which is obtained from a simple system of brake-shoes, drums and operating gear. The comparison shows that it is much easier to lose speed than to gain it. In one case there is available, in a medium-sized car, an output of anything from 45 b.h.p. to 60 b.h.p., while in the other case the energising influence is merely the limited physical effort of the driver. Yet the deceleration obtainable in such a car is about seven times as great as its capacity for acceleration.

The figures quoted refer to a med-ium-sized six-cyclinder car of about 16h.p., which is capable of accelerating from 10 m.p.h. to 40 m.p.h. on third gear in about 12 seconds. This gear is selected as being the one which the majority of drivers employ when accelerating. A speed gain of 30 m.p.h., accomplished in 12 seconds, represents . a rate of speed increase of 21 m.p.h. per second of elapsed time, this figure being held fairly consistently over the speed range in question. Brake Efficiency.

Turning to the braking system of a car of this type, the conservative figure of 80 per cent, for brake efficiency as being one which is quite commonly attained is assumed. Such brakes, if fully applied, will cause the car to lose speed at a rate of 17-i m.p.h. per second of brake application. In other words, deceleration obtainable is just about seven times as great as the acceleration on third gear.

Acceleration and deceleration can be compared on a gradient basis.' The third-gear getaway of this car, on the same level, is the same as would be obtained by allowing it to roll, in neuti’al down a gentle slope of about eight degrees. The brakes, on the other hand, produce a retardation equivalent to running up a gradient pitched at about 54 degrees. Another way of comparing the powers of braking and acceleration is to take the time required to reach 40 m.p.h. from a standstill, using the gears. This will amount, to about 16 seconds in a car of the type described, in which time a distance of about 470 feet will be covered.

Brakes operating with an efficiency of 80 per cent, will, however, stop a car (travelling at 40 m.p.h.) in 2.3 seconds, representing a distance, measured on the road, of only 67 feet. Here, again, the ration between the time (and distances) required for acceleration and deceleration is in each case about seven to one.

The engineer’s definition of power is the rate at which work is done. a Whether a car is being stopped omaccelerated the work which must be expended depends upon the force exerted upon the vehicle, and the distance through which it acts. Wind resistance can be neglected at moderate speeds, although in actual fact it operates against the engine and in favour of the braking system. Taking an average, the engine power required to accelerate a 30cwt. car from a standstill to 40 m.p.h. in 16 seconds is about 20 b.h.p.; that is, of course, much less than the peak power of the engine because the peak is only attained at a high revolution speed. To stop the same vehicle in a distance of 67 feet the brakes must work at a rate of about 140 h.p. This gives some idea of the immense amount of energy dissipated in the form of heat through the brake drums.

Some motor tourists deliberately under-inflate their tyres when starting on a long drive, assuming that pressure will be increased by highway heat. From every standpoint, the practice is wrong. Be sure on setting out that the tyres carry the full pressure recommended by the maker.

VARYING SPARK TIMING,

WARNING TO AMATEURS. Since the introduction of high-com-pression engines and anti-knock fuels the question of ignition timing has assumed more importance and it is a popular belief among enthusiastic experimenters that better efficiency might be obtained from their engines by advancing the ignition timing slightly ahead of the adjustment advised by the manufacturers. Where there is a manual spark control such a variation need not be harmful, even if inaccurate, since Hie driver can subsequently correct any slight over-ad-vance by manipulating the sparklever; but if the ignition is regulated by an automatic governing device it is not prudent to depart from the advised setting, except that if there is an accessible vernier adjustment experimental variations can be made to ascertain what position gives the best results with a particular grade of fuel. To understand the mistakes which might be made through inexpert tinkering, it must be realised that the purpose of spark timing is to regulate the ignition in such a way that the combustion of the charge occurs just as the piston reaches the top dead centre of its compression stroke. There is a fraction of time between the jumping of the spark and the complete combustion of the charge, which is known as the period of flame propagation. Obviously if the mixture is prematurely ignited, it will begin to exert the force of its explosion on the crown of the piston before the latter has passed its top dead centre, with a result that as a rule ignition-knock will be perceptible. But with some modern engines it is possible to have the spark too far advanced without that fault becoming audible. Conversely, if the spark is late the piston will have moved downwards for some distance on its explosion stroke, and so some of the power of the explosion will be wasted and overheating may arise, because the lower parts of the walls are unduly exposed \ to the effects of the flame. A great deal depends on the nature of the fuel, the speed of the piston, and the general condition of the engine. The rate of combustion of the present highly-refined fuels is very rapid, but thanks to certain constituents is regulated within proper limits. Wear and tear in an old engine can upset the balance of the spark timing, and occasionally it is possible in such circumstances to advance the ignition slightly with beneficial effects, should it happen that slackness in the timing gear, stretching of a timing chain, or general wear have brought about some degree of retard in ignition; but in every case such an alteration should be regarded in the first instance merely as an experiment, and should be carried out by a competent mechanic. As stated above, the familiar “knock” test is not really dependable, although if there is pronounced knocking when the car is climbing a hill slowly on wide throttle it is apparent that the ignition lever should be retarded, or that the automatic timing apparatus is not correctly set. A practical test r’ecommended by a British expert is to note with a stopwatch the acceleration of the car from, say, 10 to 30 m.p.h., before the timing is varied, and to compare the result with a similar test on the same stretch of road after the alteration has been made. It is also advised that a fuel consumption test should be conducted, preferably with a small, auxiliary tank, which will enable an accurate calculation of petrol mileage to be determined. It is seldom that an advance of more than 8 or 10 degrees is permissible, and it is recommended that for a first trial 5 degrees should not be exceeded, and that care should be taken to mark the original setting, so that it can be restored easily if necessary. A warning must also be given against the assumption that an ignition knock is definite proof of overadvance, since that disturbance is frequently due to carbonised cylinders, or overheating attributable to heavy scale in the water passages of the engine. or to a weak mixture.

Owing to the increasing number of cyclists, of whom there are estimated to be 15,000.000 in Germany and a corresponding increase in the number of accidents, the Inspector-General of Highways lias set aside a sum of 1,000,000 marks (£76,923) for the building of roads for the use of cyclists only.

BURGLAR ALARM,

HANDBRAKE ATTACHMENT. Despite gear, ignition, and door locks, a determined and skilful thief can often contrive to remove a car if it has been parked in an unfrequented spot and he has time enough to overcome the various safeguards. A useful fitting which has been patented by an English company is a combined lock and burglar alarm outfit which can be attached to the handbrake in such a way that the brake can be applied and then\ locked in position. Should anyone tamper with the lock and manage to release the brake, an electric horn is caused to sound continuously. , The equipment includes a secret switch, which is turned on when the vehicle is vacated and is in circuit with a concealed “hooter.” Should-the brake be released, the base of the handle beneath the floor boards actuates a contact, which closes the signal circuit. This burglar alarm switch can also be installed in the door of a saloon car, so as to sound the electric horn should an intending thief force the lock and open the door. To prevent a cunning thief from interfering with its operation, all the wiring and connections are encased in steel tubing. Ingenious amateur electricians could doubtless manufacture a device on the lines described, and one which would prove very disconcerting to prospective “joy-riders.”

AWKWARD EPISODE.

ATTACK BY BULL MOOSE,

A French-Canadian lumber jobber describes a thrilling experience while driving with a companion along . a rural trail to his camp in Northern Ontario. Turning a bend in the road, they met a bull moose, which resented their staccato horn blasts, and charged immediately. “I backed up,” said the lumberman, “but he came on, and there was nothing for it but to await events. He hit us head-on, both antlers going through the radiator screen, crashing the lamps and mudguards. Four times hf attacked. I whispered to my companion not to make a sound, lest we might draw his attack on ourselves. In the last charge he swerved to one side, and I threw the car into low gear and pushed ahead. In two bounds he was again ahead of us. We continued to advance, with the moose backing and glowering at us, his antlers hung with the radiator screen and one lamp. The roar of the company’s lumber truck approaching forced him eventually to retire.

WHEN FITTING TYRES

Many owner-drivers who experience difficulty in fitting tyres to well-base rims appear to overlook the fact that the sole purpose of the well is to make fitting an easy, matter. If advantage be taken of this, it will be found that even a new tyre can be slipped., on with very little effort.. The whole secret is to see that the wired edges of the tyre on one side fit properly into the well, so that the side diametrically opposite will have room to pass over the outside diameter oOhe rim. No difficulty should be experienced when the wheel is off the car, but when a tyre has been fitted with the wheel on the axle care must .be taken to jack up the wheel to a height that will lift the tyre; 2 inches, to. 3 inches above the ground, otherwise it will not be possible to push the; lower portion of the tyre into the well. For greatest ease, remember always, to start removing a tyre opposite the valve.