COLLOIDAL GRAPHITE.

COLLOI A L GRAPHITE. SOME NOTES ON ITS BENEFICIAL EFFECTS DURING THE ” RUNNING-IN ” PERIOD, AND AS A GENERAL AID TO EFFICIENT LUBRICATION.

MOTORISTS, like other sections of the community, are thoroughly conservative at heart. No matter how obvious the advantages to be derived from a new feature of design or operation may be, many years always elapse before that feature receives their whole-hearted support. Sometimes this is the fault of the manufacturers, but in the main it is the motoring public itself which is to blame, for so sceptical is it of revolutionary improvements that manufacturers dare not risk financial failure through lack of support. Front-wheel brakes and self-changing gear-boxes were invented and perfected years before they became universally adopted, to cite but two examples.

Among those improvements which have not yet been fully recognised by the motoring public, but are rapidly becoming so, is the use of colloidal graphite in engine lubrication. In view of its growing popularity the following notes will assist readers who are not conversant with its properties to obtain some idea of the immense advantages to be derived from its use.

Running-in.

Sports car owners will not need to be reminded of the vital effects of the manner in which an engine is run during the first thousand miles or so of its life. No matter how good the workmanship of its constructors the working-surfaces of cylinder ‘ walls and big-end bearings are rough, and the usual tightness of the engine when first assembled is gradually lost as the ” high-spots ” of this roughness are worn down. A certain amount of efficiency is naturally forfeited by this process, and it is here that the presence of a percentage of colloidal graphite in the lubricating oil has its first use. The colloidal graphite fills up the microscopic irregularities, bringing the bearing surface to a high degree of smoothness. In addition, a process of adsorption takes

place, that is to say, the graphite becomes integral with the metal to which it has adhered, so that it cannot be dislodged by washing the surface with liquid—in fact nothing short of scraping or filing will remove it. The result is that the working parts have freedom of movement with the minimum clearance. It is important to distinguish between adsorption and “building-up.” The latter cannot occur with colloidal graphite, so that there is no danger of blocked oilways.

When the Oil-Film is Broken. “

More particularly during the ” runningin ” period, but also at any time during an engine’s life, there is always a risk

of a piece of dirt or grit forming a local “high-spot,” which causes great pressure on a very small area, thereby breaking the oil-film at that point and allowing a metal-to-metal contact to take place. Here again colloidal graphite comes to the rescue. In the first place there is less likelihood of there being any dirt to get into the bearing if graphite has been used, for the reason that there is minimum working clearance, as already stated. But more important still, even if the oilfilm be broken, and over a large area, the graphite adsorbed in the metal tends to prevent metal to metal contact and provides lubrication for sufficient time to allow the oil-film to re-form. The penetrating and creeping qualities of oil impregnated with graphite are far superior to those of ordinary lubricating oil, so that local ruptures of the oil-film are quickly remedied. Furthermore, the graphite film enables the oil to spread more rapidly.

27 Hours Without Oil I

The finest test of the lubricating qualities of the graphite adsorbed in the metal of working surfaces is that made by the National Physical Laboratory. For the purposes of the demonstration a 2 inch

shaft was run at a constant speed of 500 r.p.m. in a normal white-metal bearing, under a load of 230 lbs. per square inch. After a reasonable period to allow an oil-film to be formed the oil supply was cut off, and the bearing allowed to run dry. Using ordinary lubricating oil the bearing seized after 36 minutes, but when a shaft in which colloidal graphite had been thoroughly adsorbed was used, no trace of seizure was apparent for 27 hours, when the test was stopped. Sudden failure of the oil-pump, or breakage of an oil-pipe, are therefore guarded against by the use of lubricating oil plus colloidal graphite.

Its Invention.

Although graphite was used for years as a lubricant for wood, it was impossible to use it in conjunction with oil as a lubricant for engines owing to the inability of scientists to reduce its particles to small enough dimensions. Invariably the graphite would form a sediment, leaving the lubricating oil in its original state, while larger particles had a certain amount of abrasive action which was detrimental to engine bearings. Finally, Dr. B. G. Acheson found a means of producing abrasive-free graphite which is subjected to a special colloidaLising process to obtain such fine particles that individually, they are microscopically invisible. Then came the introduction of ” Oildag ” by Messrs. B. G. Acheson, Ltd., a colloidal graphite in which. the graphite particles are in perfect suspension in oil, and cannot be filtered. As an example of its complete suspension, it is interesting to note that colloidal graphite is the only known liquid which can be used satisfactorily for filling the windpipes of mosquitos for X-Ray photograph purposes, even aniline dyes becoming filtered owing to the minute diameter of the insect’s orifice.

How to use it.

any way

form a substitute for ordinary lubricating oil, its function being to give the latter smoother bearing surfaces to lubricate. This being so, it is only natural that certain large-scale manufacturers of lubricating oil are now turning their attention to the sale of special compounds containing a percentage of colloidal graphite. The best results are obviously obtained if a preparation such as Filtrate Runningin Compound, or lienzell Running-in Compound, is added to the first supply of oil put into the sump of a new

car. A preparation of such undeniable ad vantages in prolonging the life of a car cannot be ignored indefinitely, and there is every indication that any prejudice with which colloidal graphite may have

been regarded by the motoring public will shortly be turned into an insistent demand.

H. N.