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).
Summary on the importance of selecting the correct specialized lubricant for hypoid gear axles.
| Identifier | ExFiles\Box 114\1\ scan0087 | |
| Date | 11th January 1937 guessed | |
| SUMMARY In the foregoing part of this paper considerable effort has been made to explain the nature of hypoid gears and to try to convey some idea of why straight mineral oils are not suitable and that special oils are required. Also, I have tried to convey the idea of how much effort is being made by the axle designer and the manufacturer to attain as nearly as possible perfection in building the axles. I have tried to give you some idea of what more than 10 years of development work directed exclusively to hypoid axles has yielded. And now, I shall try to convey the idea that all of these "pains" and all of the benefit for this work can become an absolute and total loss by the use of an unsuitable lubricant. The aim of the car manufacturer, of course, is to have his product operate in the hands of his public with the nearest approach to perfection that is possible. He is not interested in selling oils and, if it were possible, he would have nothing to do with lubricants. However, when he is faced with the condition which now exists it is necessary for him not only to become vitally interested in lubricants but to exercise every power at his command to see that his product gets the right kind of lubrication. The choice of the car lubricant by the car manufacturer will be based on a rating of the five items listed as follows: 1. EP{G. Eric Platford - Chief Quality Engineer} value 2. Low abrasiveness 3. High stability 4. Low chemical activity 5. Proper flow properties And he will use the method at his command for rating these various items but, more than anything else, he will be influenced by their ability to operate in his automobile. In the choice of a lubricant, mere viscosity has no advantage from a load carrying standpoint. The common notion that the body of the oil determines the load carrying capacity has absolutely no value in judging the load capacity of EP{G. Eric Platford - Chief Quality Engineer} lubricants. Furthermore, heavy or thick oils do not reduce noise and consequently have no value as noise suppressers. What is absolutely important is that the oil must flow readily in the coldest weather and if it becomes thick enough to channel the axle can be ruined in five minutes. On the other hand, the oil must not have the characteristic, like some of them do, of becoming stiff when beat up with entrapped air when the axle is run at high speed. Some of these oils become stiff and will channel just like the white of an egg may be beat up and become stiff. Such oils return to their original state when the air is removed by slight heating and stirring. Some oils simply foam badly which in some cases it builds up sufficiently high pressures within the axle, even when vented, to cause seals to leak and therefore lose oil. Oils which oxidize readily are unsatisfactory. Some oxidize so badly that it is not merely a matter of the viscosity increasing during the course of use, but the oil actually "cokes" in the axle. Such oils cause damage quickly and are totally unsatisfactory. A word about service is pertinent here because with a good stable EP{G. Eric Platford - Chief Quality Engineer} lubricant frequent service is not at all necessary. It is, of course, necessary to keep the axle filled to the proper oil level and it would be desirable simply to add oil occasionally if there were any leaks but oil changes more frequent than once a year are wholly unnecessary. - 12 - | ||