From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Article on the properties and benefits of colloidal graphite as an additional lubricant for engines.
| Identifier | ExFiles\Box 145\3\ scan0008 | |
| Date | 11th May 1934 | |
| Reprinted from The Autocar May 11th, 1934 COLLOIDAL GRAPHITE What It Is, and What It Does. An Additional Lubricant SOME time ago, in The Autocar of June 9th, 1933, to be precise, I gave an account of the development of Acheson colloidal graphite. Since then many queries have been received concerning this substance and its use for improving the lubrication of engines, particularly during the running-in period and for the benefit of new motorists it is, therefore, proposed briefly to recapitulate the advantages to be derived from its use. Acheson colloidal graphite is practically 100 per cent. pure graphite colloidised by the special Acheson process, which reduces the size of the particles to the colloidal state, and it should not be confused with ordinary graphite powder mixed with oil. The purest forms of commercial carbon are treated in electric furnaces, and when the pure graphite thus obtained has been colloidised and the substance dispersed in oil, or even in water, the particles are so minute that they remain suspended in the liquid and will even pass through a filter with it. When Running-In The most convenient method of utilising colloidal graphite is in the form of a Running-In Compound. In a way this name is unfortunate, as it suggests to some that the compound is of an abrasive nature, while to others it suggests that it should only be used during the running-in period of, say, 500 miles. Actually, of course, these Running-In Compounds are definitely free from abrasive and are purely lubricants. They consist of Acheson colloidal graphite dispersed in a small quantity of neutral mineral oil, so that when the compound is poured into the oil in the engine sump it will mix readily with that oil. Colloidal graphite may also be conveniently used as an upper cylinder lubricant, it being supplied mixed with a suitable oil for this purpose. It may also be obtained mixed with a penetrating oil for the lubrication of leaf springs. It may, perhaps, be emphasised that colloidal graphite is not a substitute for the ordinary lubrication process by a film of oil, but that it is an additional lubricant. The colloidal graphite suspended in the oil is adsorbed to the working surfaces, and the natural lubricating qualities which it possesses are, therefore, in addition to the lubrication afforded by the oil itself. Thus, these working surfaces receive a better degree of lubrication, and when the engine is started up from cold, and the oil is circulating but sluggishly, lubrication is ensured by the presence of these graphoid surfaces. Moreover, oil will spread more rapidly over a graphoid surface than over a dry metallic surface, so that when starting from cold the oil is helped to spread more rapidly over the working surfaces. Value In Later Life Naturally this improved lubrication given by colloidal graphite is of great value to a new engine during the running-in period, but its use need not be limited to the first few hundred miles, and, indeed, it is advantageous to continue to use it after the running-in period, although the quantity of Running-In Compound recommended during the early life of the engine may be halved. As proof of the effectiveness of colloidal graphite as a Running-In Compound it may be mentioned that tests have shown that a new engine will develop its maximum power much more quickly than when an ordinary ungraphited oil is used. This fact has been established by several manufacturers who now use colloidal graphite for assembly and running-in, and recommend its further use, particularly as regards new engines. By giving better lubrication colloidal graphite helps to minimise wear of all working surfaces, but it also has other advantages in that it tends to prevent the formation of carbon in the combustion chamber, is not affected by heat, and is not washed off the cylinder walls by petrol when starting from cold, so that it gives a better seal between piston rings and cylinders, and so tends to reduce fuel and oil consumption. Ball-Bearing Test Doubts have sometimes been expressed concerning the suitability of oil containing colloidal graphite for the lubrication of ball and roller bearings, but recently tests carried out by the National Physical Laboratory showed that such doubts are entirely groundless. After a continuous test of 100 hours with a heavy load which would give the bearing an estimated life of only 200 hours, so that the test represented the first half of the life of the bearing under the chosen conditions, there was no appreciable wear of the running parts, and the conclusion was reached that the graphited oil was a satisfactory lubricant. It is interesting to note that the advantages of using Acheson colloidal graphite have been investigated by independent scientists, some of whom are still engaged on research work concerning it. Thus the Philosophical Magazine of February last contained an account of “Electron Diffraction Experiments with Graphite and Carbon Surfaces,” by R.{Sir Henry Royce} O.{Mr Oldham} Jenkins, A.R.C.S., B.Sc., which proved the existence of an adsorbed graphite film that washing in alcohol and ether failed to remove. Other experiments by investigators have recently proved that the presence of graphite prevents corrosion on piston rings. A.{Mr Adams} G.{Mr Griffiths - Chief Accountant / Mr Gnapp} D.{John DeLooze - Company Secretary} C. | ||