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).
Bump tests and subsequent fracture analysis on road springs.
| Identifier | ExFiles\Box 119\2\ scan0200 | |
| Date | 30th September 1924 | |
| R.R. 493A (40 H) (SL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} EXPERIMENTAL REPORT. Expl. No. 2628 REF: Hsl/LG30.9.24. Handwritten: X1331, X9410 To R.{Sir Henry Royce} from Hs.{Lord Ernest Hives - Chair} c. to CJ. BJ. c. to RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} c. to DA.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} BUMP TESTS ON ROAD SPRINGS. Below is a list of the fractures we have had on the top plates of the 12 1/4 springs made by Woodheads. An interesting point in connection with these springs is that in every instance the fracture has occurred close to the centre bolt. The fractures have taken place under the sheath which holds the spring to the axle. With the Firths springs, although a percentage of them fractured in this place, the majority of them broke 8" to 12" from the rear eye. Particulars of Woodhead 12 1/4% springs broken on the Bumper. | Position on chassis. | Load Lbs. | Life hrs, mins. | Position of Fracture. | Thickness of top leaf. | Brinnel of Fracture. | | --- | --- | --- | --- | --- | --- | | No.1 Near side | 950 | 23 5 | 1.5" to rear | .282" | 375 | | No.2 " " | 950 | 17 42 | 1.5" to front | .282" | 388 | | No.3 Off side | 1000 | 29 6 | 1.0" to front | .286" | 388 | | No.4 " " | 1000 | 18 5 | 1.5" to front | .293" | 388 | | No.5 Near side | 950 | 20 1 | 1.5" to rear | .293" | 363 | | No.6 Off side | 1000 | 20 58 | 1.5" to front | .300" | 363 | Fractures measured to front or rear of centre bolt. Below is a comparison of the brinnel hardness and thickness of Firths and Woodheads springs. contd :- | ||