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).
Torsional deflection and inertia experiments to determine the natural frequency of a crankshaft.
| Identifier | ExFiles\Box 6\1\ 01-page014 | |
| Date | 1st September 1926 guessed | |
| contd :- -11- TORSIONAL DEFLECTION, INERTIA EXPERIMENTS AND DETERMINATION OF NATURAL FREQUENCY. We took torsional deflection measurements of the crankshaft in position in the crankcase by locking the flywheel and applying a torque to the front end. The method employed was by deflecting a beam of light by small mirrors at each end of the crankshaft. In this way great magnification could be obtained and the use of two mirrors, one at each end, we were able to eliminate errors arising through yielding of the flywheel holding device and torque arm mounting. When the actual crankshaft twist is only small the possible errors mentioned above can assume considerable proportions. A sketch of the apparatus employed for this test is appended together with the deflection curves for both the standard and the stiffer crankshaft. The stiffer crankshaft E.51976 had .125 dia. larger journals, .100 thicker webs and the crank pins the same dia. as standard. From the curves we find that these alterations result in an increase in stiffness of 11.8% over standard. This crankshaft raises the critical speed to approx. 3500 to 3600 r.p.m. MOMENTS OF INERTIA. The moments of inertia were obtained for the crank- shaft parts in order to estimate its free period of oscillation. The Bifilar suspension method was employed. The following are the results :- contd :- | ||