THE PETROL TRAIL

Stratford Evening Post, Issue 35, 13 February 1929, Page 3

THE PETROL TRAIL

MOTORS AMD MOTORING MOTOR CYCLE LUBRICATION. Motor cycle engine lubrication involves tlie same broad pri.no. piles that underlie the lubrication of the other classes of motor, engines, though the methods of application may vary considerably. The object of lubrication is to beep separated the moving parts by an effective film of 0.1, the benefits of which are threefold, viz:— (I) more power available for useful work, less power . absorbed by friction; (‘IV. less wear on the moving parts; (3) cooler operation duo *r» the reduction of frictional beat, Tho lubricating oil must perform duties additional to that of merely reducing friction and, further, should fulfil these requirements through :il! conditions of load, speed and temperature. The most difficult problem presented' by engines of this type is cylinder lubrication. Here, more than anywhere else, must the lubricating oil perform additional functions to that of reducing Tricticu and wear.

PISTON SEAL. •The piston must bo scaled by soma fluid, medium, ivhich will not interfere with its movement, and, at the spine time, wifi resist the passage of tlio highly compressed gases. Such a medium is' provided only by the I'ibiicatint oil, which is thus required to maintain piston seal at all times during engine operation. HEAT CONDUCTIVITY. A further requirement of/the lubricating oil is that of conducting and diffusing beat. The motor cycle "engine cylinder is cooled externally by air currents which carry away the beat; but the beat is generated inside the cylinder.and the piston head, which is not in contact with coaling air, is the hottest part of the engine (with, the possible exception of the exhaust Valve head. 1 ) The greater part of the heat acquired by the piston is conducted by the lubricating "oil to the crankcase, and eventually trans-. ferret! to the atmosphere.. It will be seen therefore from this that heat cond.actively is essential to a satis, factory lubricating oil. CLEAR-BURNING OIL. If an oil be thoroughly lubricating an engine cylinder, a certain amount will bo burnt in the combustion chamber. A realisation of this ■ necessary condition is important and explains where the oil goes to when) it is consumed in the engine.. When oil burns, carbon is deposited.. This is the inevitable result, of its decomposition by heat. The quantity and character of the carbon, deposited is, however, largely dependent upon the nature of the particular lubricant concerned. A lubricating of] should, therefore be selected with a view to its clear—burning properties. It should produce only the minimum of carbon when burnt, ami this should be of the least 1 1 a nnf m h J^‘ w .Tter.

DURABILITY. To perform all the foregoing functions dependably and continuously, tbe lubricant must necessarily possess durability. This term is used, to describe its ability to resist chemical change, a quality which is of th 0 greatest importance if an oil is to give satisfactory results. EFFECTS OF TEMPERATURE The effect of varying temperatures upon oils is of importance also. The (viscosity or “body” of an oil is dependent to a great extent upon the temperature to which it is subjected. Oils of different constitution will respond very differently to temperature changes, som© remaining much more fluid under conditions of extreme cold 'than others. On the other bond, some oils will thin out much more noticeably than others in the presence of heat. HOT ENGINE, The effect upon (the Uubric-ant of the beat developed! during operation lias to be considered. As already explained the oil carries away portion of this heat and in doing sop becomes thinner in body.. 'When the engine is working under load, heat generation increases and iu the vicinity of the piston and cylinder walls exceedingly high temperatures are experienced Under such conditions the oil may fail because it has become too thin, and when it h remembered that the highest temperatures are generated when the engine is operating a,fc its heaviest loads, the sen. ionsness of inefficient _ Inberatiin through this cause will bel appreciated. It is, therefore, very essential that the lubricating oil he of such character that it retains sufficient

“body” at the highest working temperatures of tbe ; engine. PRACTICAL APPLICATION. Many motcr cycles have a system of oil supply which depends on the operation of a pump worked by hand. Th,o human element is, in such designs, the controlling factotn in tno lubrication of “the engine, alnd results in a tendency to either nnepr, oil or ovor-oil —more often the latter. Advice, which may well be'followed, is to add a small quantity of “makeup” oil at frequent interval's, rather than a pumpful at a time less frequently. i