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).
Technical report detailing the results of a Wraith crankshaft bending test.
| Identifier | ExFiles\Box 8\5\ 05-page37 | |
| Date | 22th September 1938 | |
| 614 To Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} from HPS{Horace Percy Smith - Experimental Factory Mgr}/W.Bell. HPS{Horace Percy Smith - Experimental Factory Mgr}/WB.{Mr Brazier/Mr Bell}2/CB.22.9.38. WRAITH CRANKSHAFT BENDING TEST. EW.1370 (VCM.7137, Y.869) Crankshaft Details. The crankshaft was supported at journals 1 and 7 on pieces of half-round mild steel to avoid crushing when knife edges are used; a bar, running parallel to and about 4" above the crankshaft was used as an arbitrary zero from which all measurements were taken. Measurements were taken to ascertain the deflections of all the journals when a total load of 400 lb. was equally distributed between crankpins 1 and 6; these measurements were repeated for crankpins 2 & 5 and 3 & 4 and are shown in BL.2207, Sheet VI, TableI. From these results, vector diagrams were drawn to determine the magnitude and direction of the displacement at each journal. BL.2207, Sheet I illustrates the form taken up by the crankshaft when it is loaded to an extent of 200 lb. per crankpin, applied separately to each pair of crankpins. From the vector diagrams (BL.2207, Sheet II) it was found that the displacement at the centre journal for loads of 200 lb. applied simultaneously on all the crankpins was .027" in a direction between crankpins 3 & 4 and 2 & 5 making an angle of 31° with the direction of 3 & 4. The crankshaft was supported with this direction vertical and weights of 200 lb. and 300 lb. hung from the centre journal in order to ascertain the restoring load. It will be seen from Table II, showing the deflections of all journals for these loads, that the restoring load is 300 lb. From this and the preceding tables, BL.2207, Sheet III was drawn; the resultant displacement will represent the relative magnitude of the out of balance forces at each journal. From BL.2207, Sheet III, it will be seen that the restoring load reduces the displacement at journals 3 & 5 in the ratio of 20:1, that at 6, in the ratio of 10:1 and that at 2, in the ratio of 7:1 A further set of measurements was taken to determine the relative bending strength of the crankshaft in various directions. These results are tabulated (Table III) and plotted (BL.2207, Sheet IV) to show the progressive deflection of each journal for each direction of load, applied at the centre journal. Finally, the displacements for loads of 150 lb. and continued. | ||