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 tensile strength, fatigue resistance, and composition of cast iron crankshaft material with Molybdenum additions.
| Identifier | ExFiles\Box 132\1\ scan0017 | |
| Date | 18th April 1927 guessed | |
| - 4 - U.T.S. Tons per sq. inch. Elongation. No.Gr.{George Ratcliffe}0. ... 11.18 ... 2.0 " 1. ... 11.74 ... 1.9 " 2. ... 12.90 ... 1.6 " 3. ... 14.58 ... 1.94 " 6. ... 16.20 ... 2.0 " 4. ... 16.70 ... 1.9 The effect on the Tensile Strength by the addition of Molybdenum to the two irons investigated is shown plotted on the accompanying blue print, from which it would appear that the tensile strength reaches its optimum and the creep resistance is little improved by additions of molybdenum above 0.85%. From the results of these tests, several crankshafts were cast machined and built up in service engines. The complete composition was as follows:- Total Carbon ... 3.00% Silicon ... 1.80% Manganese ... 1.00% Sulphur ... 0.05% Phosphorus ... 0.20% Chromium ... 0.21% Molybdenum ... 0.78% To obtain some idea of the fatigue resistance of this material, test pieces were out from the centre of each web of a cast iron crankshaft. These specimens were approximately 0.70" diameter x 5.5" long, and were machined to the standard form of the Wohler type test piece as shown in sketch Fig. The method of testing the pieces was to clamp the specimen as a cantilever in a rotating chuck at approximately 1,800 r.p.m. The specimen was stressed in bending at the point shown on the Drawing Figure of test piece. Prior to commencing the fatigue tests, a test to determine Youngs' Modulus was first carried out by applying small increments of load and measuring the corresponding deflections. Youngs' Modulus ... 17 x 10⁶ lbs. per sq. inch. 18.5 x " " " " " 18.5 x " " " " " 17.5 x " " " " " 16.9 x " " " " " Average Modulus on Specimen B ... 17.68 lbs. per sq. inah. | ||