As previously mentioned, this machine is a device in which two Timken test cups, no. T-48651, are rotated in line contact with each other and in opposite directions, with provision for controlling the speed of rotation, the slipping velocity and the rate of applying pressure at the line contact between the rotating cylinders or cups. To obtain reproducible result, it is essential that the surface finish of the cups used be uniform and that the shafts on which these test pieces are carried be in perfect alignment. Both points are covered in details of the test methods. The total variation in surface finish shall not exceed 10 micro inches and the inside and outside surfaces of the test cups shall be concentric within 0.0005 inch.
With the lubricant tester in good mechanical condition, test shafts true, and the alignment properly adjusted, the test cups of specified surface finish and concentrically are placed on the upper and lower shafts. With the oil box overflowing, an initial load of 15 to 20 pounds is applied. The machine is then started and at the end of a 30 second period the automatic loading device, at the desired rate of loading , is started. The test cups are then observed for signs of scoring. This is most readily detected by observing the lower test cup on the trailing side at a position approximately ½ inch from the contact line. When signs of scoring are detected, the drive motors are stopped and the load removed. After thorough cleaning and with new test pieces and fresh oil the test can be repeated.
The suggested conditions of test are a main shaft speed of 1000 rpm and a rubbing ratio of 14:6:1. The load should not exceed 450 pounds and if no scoring occurs at this point the test is stopped to prevent over heating of the shafts, etc.
