MOTORS & MOTORING

Dominion, Volume 14, Issue 171, 15 April 1921, Page 9

MOTORS & MOTORING

(By

"Clutch.")

The Art of Reversing. Most drivers are aware of the danger of trying to drivei s ear quickly in reverse gear, owing to the difficulty in etoering the desired course. They attribute this, as a rule, either to inexperience pr to the apparently greater effect which movement of the steering wheel has when the car is being driven backwards. The latter idea is a fallacy, since when the steering is fully lockedi over, the car may be driven either forwards or backwards, and will obviously travel on. an arc of the same circle in both cases. The real danger of driving backwards lies in the tendency of the steering to suddenly fly over or to full lock on one side or the other unless a tight hold ie kept on the wheel. This tendency is caused by the inclination given to the pivot pins on which the stub axles turn. If lines are drawn through the centre of these pins and produced they would touch the ground lin. or more in front of the point of contact of the front wheels with the ground. Hence, when the car is driven forward the front wheels tend to keep straight because they are in ef-. feet being trailed behind the pivot pins, and have what is known as "castor action." When reversing, however, the opposite effect it experienced. The wheels are being pushed in front of the pivot pins, and directly anything causes them to deviate the smallest amount from the straight path, they tend to •wing over to the full extent on one lock or the other. This has been the cause of many serious accidents in the past, for if a car is reversed quickly either on the level or downhill, the force tending to turn tho front wheels becomes large, and may momentarily take tho control of the’ steering out of the driver’s hands. A golden rule is, therefore, "Never drive a car at all quickly in reverse gear, especially on the camber of the road or downhill, and in every case keep a tight grip of the steering wheel when driving backwards. A Simple Snark Tester,

If one suspects a eparking plug of being faulty, it is convenient to have somtJ handy method of ■ whether the high-tension current is reaching the central electrode of the plug. The following description is of a small tester recently devised. To a piece of fairly stout vulcanite two brass horn pieces are screwed, each horn being connected to a small grub screw. The ends of these grub screws can be made to approach! pne another or actually to touch, any gap that is required . being easily attainable. The pointe of the grub screws can be observed through a small hole drilled through three-quarters of the thickness of the vulcanite block. The regular recurrence of a spark across the grub screw points shows, ab any rate, that the current is arriving safely at the plug, but it is not necessarily an indication that the plug itself is functioning correctly. four Wheel Brakes.

Although no British car manufacturer is now fitting brakes to front wheels as well as to hack ones, four-wheel braking was standardised for a while on certain British ears a few years before the war. But its use was discontinued for various reasons, and it devolved upon two or three Continental makers to reintroduce front wheel braking in an efficient and reliable form. Other things being equal —as they can be —brakes on the front wheels are considerably more effective ih retarding a car than hack wheel brakes. The latter are liable to skid the wheels when they are forcibly applied, for ,the act of retarding the car "throws the weight forward," so that tho rear wheels do not bear so heavily on the ground. But what the rear wheels lose or are relieved of in this respect, the front wheels gain or have added to them; they press more heavily on the road. Therefore, it follows that by braking on the front wheels as well as on the back ones, the car can be retarded far more rapidly—the brakes can be applied far more forcibly—without the' occurrence of skidding. Not only so, but the possibility of side slips is reduced to a minimum, for a skidding 'wheel slips sideways much more readily than docs one that is rotating at its normal speed in rela«*on to that of the car. Cleaning the Plugs.

To clean a sparking plug.—Unscrcsv the bushing which holds the porcelain in the shell, remove the porcelain (or mica) and soak the shell and porcelain in paraffin or petrol. Clean the carbon oft' each. Do not scrape porcelain, ns it will roughen the glazed part and cause-that part to retain tho carbon If oil is burnt on the porcelain, muriatic acid will remove it. In placing the porcelain back in the shell, be sure tho copper washer is placed back and (bushing screwed tight to prevent leaking. A Curious Radiator.

A number of concentric cups,, the walls of which are hollow, form the cooling •lenient of a na-wly-devised radiator. These cups are arranged one inside the other with a suitable’ air space between them, and are connected to the top and bottom tanks so that the water flows through them. The middle one has its interior surface polished, and is adapted to received an electric lamp which constitutes the head light, and others may form trumpets for a horn. Brake-Cooling.

To prevent deterioratfop of the brake linings through excessive heat, which is particularly likely to occur with -small brakes arranged side-by-side, a recent inventor causes an air current to bo driven automaticajly through the brakes In. the side of the brake drum’ are for-.ied apertures, and" each is fitted with ,a. small scoop which collects air as ths drum rotates, and drives it through tho drum and out through a number of outlets in tho dust cover. The brake shoes are ribbed so that the amount of heat absorbed by the air should be considerable. British Magnetos.

Some interesting facts are coming to light in connection with the supply of magnetos prior to and in the early stages of the war. Three months before the outbreak of hostilities. Germany, which practically controlled tho magneto trade of tho world, stopped shipping supplies of magnetos to England, and shortly after the war started, held up deliveries by the Bosch Coy in America, which firm drew up a legal document binding the purchases under pain of enormous penalties not to transfer any magnetos to any of the Allies. Despite this embargo six other- American firms supplied England with 1+7,000 magnetos, but for which’ Britain’s effort wherever tho automobile or aeroplane was in evidence would have been seriously hampered. Eventually British manufacturers surmounted all difficulties, and were able to supply the most efficient magnetos In tho world before the war was half through. It is said that this trade is now doomed unless the British Government comes to its rescue with some form of protection, as German magnetos are now flooding tho English market at. 4:0 each wholesale, while the actual cost ot production is about <£l2 10m Lighting-up Time.—To-day, 5.22 p.m.; next Friday, 5.12 p.m.