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).
Letter discussing ongoing tests on crankshaft stiffness and torsional frequency, including related calculations.
| Identifier | ExFiles\Box 25\3\ Scan333 | |
| Date | 19th April 1933 guessed | |
| contd :- -2- We are continuing with our tests on the effective stiffness of the crankshaft when twisted right through from the propeller hub to the tail of the crankshaft. In this case we correct our results so as to eliminate the reduction gear. We imagine it replaced by an extension of unknown flexibility on the nose of the crankshaft. We then say that if Tp = torque applied to prop. hub. θp = twist measured at hub. Tc = equivalent torque on nose of crankshaft extension. θc = equivalent twist in crankshaft plus extension piece. .55 = reduction ratio in gear. Then Tc = .55Tp θc = θp / .55 We then find that the stiffness of the crankshaft and imaginary extension piece as given by Tc and θc is almost half that of the crankshaft alone. We are hoping to trace this drop in stiffness which is at present incalculable. The effective inertia of a propeller on the nose of this extension piece is its actual inertia multiplied by (.55)2. We also hope to verify the torsional frequency of a complete aere engine by exciting vibrations electrically, but we shall not commence this experiment until we have compared notes with Mr. Constant at Cambridge. We have written to him asking when it will be convenient to pay him a visit, and await his reply with interest. We hope the above information contains what you required to know. We are preparing some further information for you in accordance with requests you made at Farnborough, and shall send it off in the next few days. Yours faithfully, | ||