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).
Whirling of propeller shafts and the formula used for its calculation.
| Identifier | ExFiles\Box 148\4\ scan0004 | |
| Date | 15th August 1932 | |
| X 434 E.{Mr Elliott - Chief Engineer} FROM DA.{Bernard Day - Chassis Design} DA{Bernard Day - Chassis Design}1/M15.8.32. Copy to HS.{Lord Ernest Hives - Chair} WHIRLING OF PROPELLER SHAFTS. With reference to our conversation over the telephone, we have not yet had an opportunity of discussing this point with R.{Sir Henry Royce}, but will do so at once. We note that you give the theoretical whirling speed of the Peregrine shaft as 67 MPH. According to our calculations this represents approximately 4100 RPM., and is the critical speed of a 2.750" shaft, 57" long, if solid. Hollow shafts whirl at a very much higher speed; in this case we make the critical speed 5450 RPM., increasing the diameter to 3" and reducing the thickness of the gauge to .064 the theoretical whirling speed is 6000 RPM. The Peregrine gear ratio being what it is, 5000 RPM. represents 80 MPH., so that it would appear / to increase the diameter to 3" would materially improve the whirling. /that The formula we use is: S = 4705000 X D² d² / L² DA.{Bernard Day - Chassis Design} | ||