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).
Laboratory examination report on failed rear road springs from a Bentley Bumper Chassis.
| Identifier | ExFiles\Box 119\1\ scan0201 | |
| Date | 11th May 1939 | |
| M.1840. Laboratory. from Hl./EJW. c. Rm{William Robotham - Chief Engineer}/FWK. c. Library. Hl./EJW. 3/JM.{Mr Morley} 11.5.39. Bentley Bumper Chassis - Rear Road Springs. Your ref. Rm{William Robotham - Chief Engineer}/FWK. 8/JH. 31.3.39. Two main leaves from the rear road springs of the above chassis were submitted. These had broken in similar positions i.e. through the eye, and had run 9.hrs. and 13.hrs. respectively. Examination of the fractures of both springs shewed that failure had occurred through fatigue, starting from the inner surface of the eye. See photographs M.1840/1 and M.1840/5. The starting points of the fracture are indicated with an "X". Pickling tests which included part of the fracture of each spring, shewed that the inner surfaces were very rough. Photograph M.1840/2, shews this in the spring which had run for 9hrs. This does not appear to be due to corrosion, but rather to heavy scaling. Spring which failed after 9hrs. Micro Examination. A longitudinal section through the fracture and the rough surface, revealed decarburisation on the inner and outer surfaces and shewed that the pits in the rough area were approximately .007/.009" deep. An example of the pitting is shewn in photomicrograph M.1840/3. The depth of decarburisation on the inner surface of the eye was .004/.006" and on the outer surface .006/.009". Part of the fracture was polished down, and decarburisation was found to a depth of approximately .006/.009" on the inner surface, .010/.011" on the outer surface and .007/.009" on the extreme edge of the leaf. Photomicrograph M.1840/4 illustrates the decarburisation found on the inner surface of the eye. Hardness Tests. Core - 444/451 - H.2/120 Cont'd . . . | ||