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).
The rig testing of standard and redesigned levers, analysing failures and proposing design modifications to improve strength and reduce cracking.
| Identifier | ExFiles\Box 38\1\ Scan054 | |
| Date | 30th September 1919 | |
| R.R. 235a (500 T) (S.D. 408. 28-4-17.) Bm. 2/156/13. Contd. -2- Bnl/W30.9.19. The present standard lever, C.565 ran on the same rig in 5 cases, breaking at 1 hr. 32 mins, 12 mins., 6, hrs, 39 mins, 10 hr. 43 mins, 22 hrs. 33 mins; and in one case ran without failure for 31 hrs. 25 mins. The report remarks that the results are very irregular and may be due to errati c heat treatment. The oval section lever was then re-designed and F.4272 resulted in which the oval section is flatter and wider and runs into the heavy flange surrounding the boss. The first sample broke in the same way as the original design i.e., tore through the boss in 23 hrs. 25 mins. Further samples of the same design broke on the bumping rig after 49 hrs. 10 mins. with 3" bumps, and 53 hrs. 30 mins. with 2" bumps both at 105 revs. per minute. The bumping rig has been run about 12 or 15 hours since the war, but without breaking the standard pendulum lever, C.565. We have had great trouble on the bumping rig owing to the breakage of so many parts on the chassis as reported in EH2/LG18819. The above is a summary of practically all the information we have at our disposal. We feel that although some of the failures of our standard lever are doubtless due to faulty material, or forging flaws yet the present design, C.565, is weak, and should be strengthened. We think the oval section lever, is not only of considerably improved strength but is also a preferable section, as the forging is likely to be more free from faults. We would prefer to change over to the oval section lever as soon as possible but perhaps you may wish to have the tests repeated as they were carried out so long ago. If you decide that the tests shall be repeated before standardising the oval section pendulum lever, then we propose to add metal ti the existing lever as we consider that this would improve the present job both as regards increasing the resistance of fatigue and reducing the risk of forging cracks. We would propose thickening the f langes and web, and not increasing the width of the flanges. Since writing the above the Test Dept: have handed me the boss of lever from chassis no: 2622 Reid, Newfoundland. The boss is of the old type-lever before strengthened up and the fracture is a fatigue fracture extending more than half way across the lever from the front and about 1" down from the centre of the boss. Bn.{W.O. Bentley / Mr Barrington} | ||