MOTORING NOTES.

Digger (Invercargill RSA), Issue 8, 7 May 1920, Page 14

MOTORING NOTES.

CLEANING SPARK PLUGS. Spark plugs require cleaning occaaionally. The proper way is to take the plug apart and get all the black, carbonized oil and dirt away from the junction oi metal and porcelain. The porcelain must not be roughened with sandpaper or a file, as this makes it more likely than before to accumulate carbon. The points should be brightened with emery cloth, and the rest of the plug be treated with petrol and a brush. ATTRIBUTES OF PETROL. Most lnotorists will be surprised to hear that a very l;ght petrol, of, say, .680 gravity, is not necessarily the best. A low specific gravity means ready evaporation, and this involves great difficulties in storage, transport, and safety. Ako the liigher the specific gravity, the higher is the caiorific value; that is, the heat evolved ou burning unit weight of the subslanee. Petrol consists of a number of compounds of carbon and hydrogen, and the higher the gravity, the greater becoines the proportion of hydrogen, but the heat of coinbustion of hydrogen is over four times that of carbon — a fact which may help to explain this phenomenon. CAR-TRACK DRIVING. Oue of the biggest abuses solid tyres are subjected to is the p; actice of cartrack riding, according to an official of a prominent rubb.er company. Aside from the eiement of danger attending skids from contact with the frogs and switches of street car tracks the premature depreciation of a tyre is certain, because of the abnovmal strain on a small section of the tyre. When on the tracks most of the load is concentrated on a limited portion of ihe tread, so that it is overloaded and quickly worn away ; besides a sharp point©d frog may actually cut out a piece of ihe tyre just as a knife would, this action being aggravated when the rails and rubber ara wet.

FREAK HILL-CLIMBING. An amazing variation of methods of negotiating abnormal surfaces and gradients is to be observed in the motor-cycle hill-climbing tests so popular at Home. In one of the tests (says the "Motor Cycle"), the hill concerned was one of sorne severity, with a very loose and moist surface. The majority of the side-car outfits failed through wheel slip, resulting from rushing tactics. One or two old hands climbed steadily, avoiding the loose crown of the road 'and selecting firmer ground at the side. The engine must be kept turning over at a moderate rate, well within its power. Undue acceleration and konking are alike to be avoided. Solo failures mostly resulted from too great a speed. The old hands climbed steadily and slowly, wrists braced, feet on footboaids, and eyes selecting the firm places. FUEL ECONOMISING DEVICE. The chief disadvantage of the majority of extra air inlets is that they leak when closed, sometimes causing erratic running at low speeds, and difficulty in starting. An English inventor now claims to have eliminated air leaks and to have introduced a new methd of control (says the "Autocar"). Such fittings are usually controlled by lever on the steering column, and drivers often fail to get the best results. This new extra air inlet is operated by a pedal, placed adjacent to the accelerator, which is opened by pressing the foot sideways. On removing the foot the extra air device automatically closes, and it is impossible to lea,ve it open. The inner portion is clipped to the inlet pipe, and round it a sleeve ro. tates, carrying the balls and springs, which are displaced from th'eir seatings as the sleeve is moved. These balls, when seated, prevent any leakage of air which may penetrate between the fixed and rotating portions of the device. Very little effort is required to operate the valve, since it has not to work against the suction of the engine. 3-' 1 !)_!_ , . ■ ■ ■'■■IMI.IU.IMI -I