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).
Test report on the alteration in fit, wear on tracks, and reduction in ball diameter of a bearing.
| Identifier | ExFiles\Box 115\2\ scan0595 | |
| Date | 14th December 1937 | |
| REPORT ON TEST NO. 785. B. Ransome & Marles. OBJECT OF TEST: To note the alteration in fit, wear on tracks and reduction in ball diameter of a bearing having .005" preload on the outers when subjected to the usual Rolls Royce Bevel Pinion conditions of service. BEARINGS: 6/MDJT.30. SPEED: 3000 r.p.m. LOAD: 1050 lbs. Journal. 1420 lbs. thrust. LUBRICANT: Wakefield "E.P." Pump feed. DURATION: 440 hours. MAXIMUM TEMP. RISE: 104°F.{Mr Friese} NORMAL TEMP. RISE: 93°F.{Mr Friese} ATMOSPHERIC TEMP: 72°F.{Mr Friese} GENERAL REMARKS RE TEST: A 6/MDJT.30 was fitted up to have .005" gap between the outers. Tested on the universal rig by means of clocks on the outer rings it was found that a load of 1280 lbs. was required to bring the outers together. The balls were measured and weighed before the test and at each examination. A master set of balls was obtained in order to check track wear at each examination. The bearing was mounted in the usual Rolls-Royce rig and tested for 440 hours before heavy pitting was found in the tracks taking the thrust load. Examinations were made after 130, 240 and 340 hours. The following measurements and observations were made: Duration: 130 hours 240 hours 340 hours 440 hours Reduction in preload: .00275" .00275" .00275" .0028" Track wear: .0009" .0009" .0009" .0001" Reduction in ball diameter. Journal track: .0005" - .0006" .0005"-.0007" .0006"-.0007" .0006-.0007" Ditto Thrust track: .0005" - .0008" .0006"-.0008" .0006"-.0008" .0006-.0008" Loss in wt. of BALLS. Journal Track: .154 gms. .180 gms. .210 gms. .219 gms. Ditto Thrust. track: .212 gms. .236 " .246 " .246 " Remarks: Brg. in good condition. Brg. in good condition. Brg. in good condition. Tracks pitted. CONCLUSIONS DRAWN FROM TEST: The test run was equivalent to a life of 37,840 miles at 86 m.p.h. It is of note that the change in preload ceased completely after 130 hours, and as this change was limited to .00275" it would appear that an initial preload of .003" to .004" should give the stability required in service. The loss in weight of the balls accounts for wear equivalent to approximately 50% in the actual reduction in diameter measured. The remainder of the reduction may therefore be attributed to ball shrinkage and this test confirms our previous experience with regard to this phenomenon of ball shrinkage in bearings subjected to heavy loads at high temperatures. | ||