THE choice of a suitable lubricant for a given mechanism involves a study of the relation between the various factors of design, operation and lubricant characteristics. One of the most important phases of the extreme-pressure-lubricant problem is the development of laboratory apparatus and test methods for the determination of the characteristics of a lubricant that are significant measures of its service performance.
During the last year the U. S. Bureau of Standards has undertaken a comprehensive study of the problem of extreme-pressure lubricants in cooperation with the S.A.E. Lubricants Research Subcommittee. Since the primary requisite for an extreme-pressure lubricant is that “it lubricate under high load,” it was decided that a start on this program be made with an investigation of the load-carrying capacity.
The preliminary tests are described, the effect of speed and temperature is considered, and the apparatus and procedure are explained. Following a discussion of the results, five specific conclusions are stated.
For any satisfactory apparatus, it is desirable to have the ratio of the applied load to the actual pressure remain constant throughout each run. To this end a machine is being developed at the Bureau of Standards in which this ratio will remain essentially constant during each run.
An additional feature of interest in this machine is that, not only may the speed and temperature be changed over wide limits, but also the action between the surfaces under load may be changed as desired from pure sliding to pure rolling with various intermediate steps of combined rolling and sliding.