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).
Report on crankshaft torsional fatigue testing and its findings.
| Identifier | ExFiles\Box 132\1\ scan0149 | |
| Date | 20th September 1939 | |
| 116 COPIES TO R.{Sir Henry Royce} Rg.{Mr Rowledge} By.{R.W. Bailey - Chief Engineer} Wd.{Mr Wood/Mr Whitehead} Bn.{W.O. Bentley / Mr Barrington} The Wardell, Detroit, Mich. Sept. 20th. 1939. To Rm.{William Robotham - Chief Engineer} re. Crankshaft Torsional Fatigue Test. Mr. J.H.Hunt, with special permission from the management, yesterday showed me a report on the Torsional Fatigue Testing of Crankshafts, which is so important (or so it seems to me) that I am sending my notes along to you. A request from yourself or Hs.{Lord Ernest Hives - Chair} would undoubtedly extract a copy of the report. It might even be arranged that sample crankshafts of Merlin engines could be tested in the research laboratories, or an 'Exciter' could be made up and shipped to you. It has never previously been possible to test crankshafts under resonance conditions without running them on the resonance frequency in the engine. Consequently engines have been wrecked every time a break occurred. Also there has never been a satisfactory determination of the importance of small longitudinal streaks or slag-inclusions, and many cranks have been scrapped because of these. A situation arose on Diesel "6-71" Trucks with electric drive where sudden acceleration would boost the engine up above the governed speed, so that it would run momentarily in a torsional period. Many cranks broke after a few thousand miles. It was determined to do some constructive fatigue testing. This series of tests on 19 cranks has - (1) Shown importance of location of oil holes in c'pins. (2) Shown importance of smooth chamfers on oil holes. (3) Developed new heat treat, alloy shafts, and Tocco" hardening, and shown benefit from this. (4) In no case has a longitudinal streak either caused a break or shown any increase during test. (5) Placing each crankpin at the top and calling top of pin 12 o'clock, oil holes had been drilled at 3, 6, and 9 o'clock. The 6 o'clock holes, i.e. on inside of pins, were found fatally apt to cause cracks and were discontinued, with great improvement. (6) Various cracks and deep flaws showed up in the webs. These all showed in magna-flux inspection conducted before each test, but their importance does not seem to have been realized until after test, when another | ||