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, reprinted from 'The Light Car', discussing the case for using colloidal graphite as a lubricant in automobiles.
| Identifier | ExFiles\Box 145\3\ scan0038 | |
| Date | 12th January 1934 | |
| THE CASE FOR COLLOIDAL GRAPHITE Continued. as to lead to conditions where-by the formation of hard car-bon deposit is always resisted. There are two distinct conditions under which an upper-cylinder lubricant is called upon to operate. First, when the engine has just started from cold and, secondly, during normal running on the road at the full working temperature. Let us consider the two conditions. It will be obvious that a well-formed graphoid surface on the cylinder walls will tend to perform a large amount of the lubrication re-quired when the engine has just started from cold, whilst during normal running the graphoid surface will assist in the easy spreading of the oil thrown up by the crank-case. The valve stems also benefit by the use of graphited upper-cylinder lubricant. It is easy to see how the oil gets to the stems of the inlet valves, but a point not always appreciated is that colloidal graphite is not completely destroyed by the temperatures existing in the cylinder head; it will, there-fore, be present in the exhaust gases, and thus, although the oil may be burned up, the fine particles of graphite itself will provide an efficient lubricating medium for the exhaust valve stems. There are many advantages to be expected from the use of colloidal-graphited upper-cylinder lubricants, but it does not necessarily follow that all of these advan-tages will be obtained at the same time; that is to say, the benefits produced in one engine may be quite different from those observed in another. It may be taken as an established fact, however, that the lubricant will be beneficial in at least one of the several directions. The average quantity of colloidal-graphited upper-cylinder oil recommended per two gallons of petrol is ½ oz. Users should, however, be guided by the instruc-tions of the blender; these will usually be found printed on the container. Not Harmful to Plugs. A word now with regard to the effect of colloidal graphite upon sparkling plugs. It has been suggested that, as graphite is an electrical conductor, a deposit of it on the insulator of a plug will lead to shorting and conse-quent misfiring. This, of course, must be admitted, but the necessary deposit can occur only when an excess amount of oil reaches the plug, and as this indicates a wrong mechanical condition it is hardly fair to blame graphite for its occurrence. In engines of normal type where the plugs remain dry repeated experiments have shown no trace of graphite on the insulators in sufficient quantities to cause current leakage. Conversely, it can be shown that a film of graphite on the plug electrodes themselves can be of benefit from an easy-starting point of view. Many motorists are familiar with the trick of rubbing a lead pencil over the points in order to induce a reasonable spark from a faulty coil or magneto. The graphite has the effect of aiding the ionization of air between the plug points and thus making it easier for the spark to jump the gap. Referring now to the use of colloidal graphite in other parts of a car, experience has shown that it is of distinct advantage in the gearbox and rear axle. Owing to the intensity of pressure between the teeth of the gears it may happen that at certain points even the most tenacious gear lubricant is squeezed out of posi-tion so that momentary metal-to-metal contact occurs. It follows, therefore, that if there be a graphoid surface on the gear teeth metallic contact will be prevented, whilst, furthermore, owing to the affinity of the oil, an immediate covering of the dry spot will take place so soon as the highly loaded teeth com-mence to move out of mesh. Crosshead. It has been shown, recently, by the National Physical Laboratory that colloidal graphite is distinctly suitable for ball or roller bearings, whilst it is also of interest and, indeed, of importance to mention that after tests, the lubricant has been found entirely successful in self-changing gearboxes of the epi-cyclic type, where, it might be thought, the graphite would tend to cause slipping of the friction bands or of the top gear cone clutch. Tests carried out at the National Physical Laboratory on the Lanchester worm gear testing machine have shown that the addition of a small percentage of concen-trated colloidal graphite to the usual gear oil will raise its critical temperature, which means that it will enable the lubricant to work efficiently at higher temperatures than would otherwise be possible. From the foregoing it will be clear that graphite is also highly suitable for wheel bearings, steering king pins and ball joints and, in fact, on all moving parts requiring lubrication. For Dynamo and Starter Bearings. Provided that it is used sparingly and not allowed to find its way on to the commutator, colloidal graphited oil is effective in the bearings of dynamos and starter motors, whilst a small amount in very thin oil will en-sure free action of the Bendix pinion of the starter. The question of leaf spring lubrication is of interest, more especially with a view to discovering how this can be carried out easily and at the same time efficiently. Few owners care to go to the trouble of dismantling their springs or even of separating the leaves whilst the springs are in position, and yet these, hitherto, have been almost the only means of ensuring that the lubricant will find its way to the working surfaces. There are now available, however, penetrating oils containing Acheson colloidal graphite and with these it is only necessary to remove the mud and dirt from the sides of the spring leaves and then to spray on the lubricant. Its penetrating properties ensure that it will find its way between the leaves. The graphoid surface thus formed on the leaves en-sures that not only will lubrication be provided whilst the liquid constituents of the lubricant remain, but after-wards the absorbed graphite will continue to act as a lubricant. Further applications will spread very rapidly over the whole leaf surface owing to the fact that the original supply of graphite will not have been exhausted and will therefore rapidly attract the graphited oil, as already explained. Incidentally, graphited penetrating oils will be found extremely useful for the lubrication of door hinges, locks and so on, whilst applied at the suspected points it will be found effective in stopping body squeaks. The critical may claim from a perusal of the foregoing that all of the advantages of colloidal graphite lubrica-tion have been set out, but that no mention has been made of its disadvantages. This, certainly, is the case, simply because tests by the makers and blenders of the lubricant, by high authorities such as the National Physical Laboratory, by manufac-turers and by users, have failed to show that there are disadvantages. It is not suggested that the lubricant is essential to the correct running of a car, but, as we have endeavoured to show, it can be a very appreciable bene-fit as an adjunct to a good lubricating oil. Reprinted from The Light Car January 12, 1934. THE CASE ... FOR ... COLLOIDAL GRAPHITE "FILTRATE" (Regd.) Running-in Compound, first introduced in 1931 and now stocked by more than 2,500 Garages, and Colloidal Petroyle Upper Cylinder Lubricant contain Acheson Colloidal Graphite. They are manufactured by Edward Joy & Sons Ltd., Filtrate Works, Leeds, pioneers of Acheson Colloidal Graphite Lubricants. Temple Press Ltd., 5-15, Rosebery Avenue, E.C.1. | ||