THE NEW CAR.

New Zealand Herald, Volume LXIII, Issue 19221, 9 January 1926, Page 10 (Supplement)

THE NEW CAR.

CARE AND TREATMENT. ADVICE TO THE WISE OWNER. Everyone should know that tho brandnew car requires rather special treatment, and that what is quite good and fair for (he car that has covered its first thousand miles may prove disastrous to the car that is put on the road for the first time. Makers and agents all take great pains to impress upon buyers tho importance of their advice on the subject. Nevertheless, many buyers, and especially buyers who have owned and driven cars before —i.e., the buyer to whom this is riot tho first car— aro inclined to disregard those well-meant precepts. They arguo that they have not previously been forced to observe such restrictive rulings as not to exceed 30 miles per hour for the first 500 miles, that their previous cars have not fallen to pieces as a result, and therefore why should they now depart from their long-established precedents T The present notes are intended to apply primarily to cars built down to a price, by which is meant not cars with workmanship unduly skimped, cars of poor material, or anything liko that, but simply cars that do not belong to the expensive class of vehicle. Provided that the owner bo a man of careful and intelligent disposition he niay conduct the preliminary " running-in " of his car just as well as the manufacturer, and he should realise that, as he has not paid tho manufacturer to do it for him, he must be prepared to do it himself. Until tho part 3 of a motor-car have had timo to sottlo down to harmonious working together, the car cannot gi*' o of anything like its ntmost capabilities. And if that settling down or " runningin " process be unduly forced or hastened the car will never be able to do all that it might havo done. Bearings and Bearing Pressures. The technical explanation turps on what are known as bearing pressures. Quite apart from the bearings usually and properly so called the motor-car contains a mass of bearings which are often not recognised as such. Of these perhaps the most important is tho piston working up and down in the cylinder. Then there aire the pinions engaged with others in the timing gear, in the gear-box, and in the back axlo (both differential and actual driving). If tho timing gear is chaindriven, if tho back axle has worm drive, tho general 'truth of the bearing analogy is in no wise affected. The valve stems in their guides and the mounting of the chassis springs on frame and axle are two further and extreme examples of bearings that are often not recognised as such. No matter how carefully the two surfaces of a bearing be prepared in the workshop, they can never be brought to that pitch of perfect fit which is essential for the minimum of friction between them while they are working together or one is over the other. Such smoothness, both literal and metaphorical, can come only from usage. Now, the stress exerted between the two surfaces of a bearing is measured by what is known as the bearing pressure, and every bearing pressure throughout a car is determined by the throttle opening of the engine. Mere speed as such, and except as applied to the road wheels and chassis springs, is of secondary importance. What does matter is tho load imposed on the bearings. If a pair of pinions be designed to transmit a torque of, say, 501b. or 5001b. per foot, if an engine bearing be designed to withstand a pressure of 15001b. per square inch, if » road spring mounting be designed to -stand a shock of half a ton delivered •in the form of a blow at 40 miles per hour—if these things be called upon to take their maxima before they have settled down, and, as it were, given time to realise what they must be prepared for.' they may not be broken, but they may be badly Btrained. Eeduced Speed and Load. Excessive friction between two bearing surfaces will cause tho beginning of wear that .will proceed at an ever increasing rate and' will soon impose thd noec'l for extensive repairs. If thoae loads be kept down until the bearing surfaces have att.-'ned a state approaching perfection, wiien they are imposed they will be received easily and absorbed naturally, because the smoothness of the bearings will have attained a degree where friction is comparatively slight. Henco we get the very useful precept that not only should the road speed of the new car be kept down to strictly moderate limits, but also the load imposed on engine bearings and transmission should bo even more carefully kept down by the avoidance of wide throttle opening. In order to provide tho maximum possible cushioning medium between the bearings of a new engine and. transmission system - lubricating oil thicker than that to be used at a later dato may bo given to the working parta, and this in itself will imppse a further need for modest opening of the throttle. Paradoxical in a way, but true nevertheless. Similarly, the use of an npper cylinder lubricant—a high flash point oil —is to be commended. Ono of those special oils to be fed to the engine mixed with the fuel is always a good thing to rise, but never better than with tho braad new or very old car. BATTERY EXPLOSIONS. Few motorists are aware of the fact that the gases which issue from the accumulators on a car when it is being charged are highly inflammable. These gases, oxygen and hydrogen, the constituents of water, are liberated freely from the ordinary accumulator when tho latter is fully or nearly fully charged so long as the charging current is being passed into it. This fact should always be borne in mind, though one rarely hears of an accident from this causo. Motor-cycling, Pago 12.