Lubrication

Manawatu Times, Volume LVI, Issue 7063, 24 January 1933, Page 3

Lubrication

COLLOIDAL GRAPHITE. In the early days of tho automobile, vegetable oils were considered the only oils suitable for engine lubrication, but this idea soon changed. Mineral oils have now for the last thirty years or so been universally used for engino lubrication, and with modern methods of refining crude oils the present quality of first-grade motor oils leaves little to be desired.

However, changes often come about, and eventually graphite will play an important part in automobile lubrication, including tho engine, transmission, differential and chassis. Up to the present the use of graphite as a lubricant has had ' sevoro limitations, but scicuce has recentlymarched ahead and conquered these.difficulties. Graphite is either flake or colloidal, and is capable of withstanding the high pressure exerted by heavy bearing loads where an oil film will break down and cause seizure of the bearing. Its action may toe compared to that of a pack ol cards. Direct pressure from above will not displace the cards, but tho lateral pressure produces eliding. That is exactly how graphite works. The minute “flakes’' of graphite can resist tremendous bearing loads, and, because they can slide easily, friction in a graphited bearing is far less than in an oil-lubricated bearing. Flake graphite cannot be used, however-. Only colloidal graphite in suspension in oil can toe used for engine lubrication, and it is only recently that, this method has been perfected. Previously tho drawback was the gradual settling of the graphite in the oil. Tests have been made with graphite in bearings which, were called upon to support heavy loads. When ordinary lubricating oil was used and tho supply cut off it was found that tho bearing seized iu about three-quaTters of an hour. With the same bearing and load (2301 b per square inch) using graphited oil as a lubricant, the bearing seized alter 27 hours’ running, so H, N. Bassett in a treatise on the properties of graphite, tolls us. In oil colloidal graphite is used, but if the oil is at all acid or alkaline precipitation of the graphite occurs. In a perfectly natural oil colloidal graphite does not settle out, but if an oil contains acids (Which are sometimes used in order to increase “oiliness”) eoldoidai graphite is precipitated. Instead of oil as a vehicle, water may be used for colloidal graphite, and machines have been known to run for several hours using such a method of lubrication. A Feed Difficulty. Oil develops a film over a bearing surface very quickly, but graphite is much slower, and may take several weeks or months to produce a “graphoid’’ surface. Such a surface consists of a film of graphite which cannot be rubbed off or removed otherwise than by filing or scraping. Hardened steel, engino parts have been found to contain graphite embedded within the surface of the steel. In automobile engine lubrication colloidal graphite in suspension is most valuable, and it can be used wherever oil is employed. Furthermore, colloidal graphite is of submicroscopic structure, and goes where ever the oil goes —and. even further. Graphite, so Mr Bassett states, increases the “oiliness’’ of an oil, and is therefore of great value in the runningin of a new engine. Bearings and cylinders take on a smoother surface, and friction is reduced to a minimum. Graphite is not affected by temperatures, and is therefore useful for reducing tho friction in engine cylinders. Moreovci, a graphited surface shows very little wear.

Dr. Acheson, the discoverer of the suspension of colloidal graphite in oil, states that .35 per cent is a sufficient quantity. Oilless bearings in modern cars are often of the graphite type in that graphite is in the bearing surface (incorporated during maanufacturc). Top steering column bearings arc usually of this type, as also are the bearings of

many American self-starter motors. Flake graphite is used for the lubrication of spring leaves, but it will not penetrate rust. On the other hand, colloidal graphite in oil does penetrate rust on springs, etc., and is therefore useful.

At present one of the difficulties to be overcome in respect to the use of a colloidal graphite in oil is the risk of blockage of the oil delivery pipes in the engine. The graphite is liable to collect ■in these small pipes and passages and restrict the flow of oil. Until this hazard is eliminated the use of graphited oil is not likely to become a practice. However, the benefits of using a natural oil containing colloidal graphite in suspension are too great to allow a temporary difficulty to stand in the way. Science will soon find a positive method of lubricating by graphited oil.