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 to Graham-Paige Motors discussing crankshaft design and torsional vibration issues.
| Identifier | ExFiles\Box 173\3\ img190 | |
| Date | 8th May 1934 | |
| Exptl. Dept. HS{Lord Ernest Hives - Chair}/Rn.{Mr Robinson}4/KW. 8th May, 1934. F.F. Kishline, Esq., Graham-Paige Motors Corporation, Detroit, Michigan, U.S.A. Dear Mr. Kishline, Thank you so much for your letter of April 24th. We send you herewith a formula which we use for the crankshaft computation. We note that you get a torsional period at 5000 revs. We shall be very surprised if you are able to damp this period out with anything but a very large damper. By this we mean that the inertia mass will have to be very considerable. We have also found that when we fitted a damper to the crankshaft to deal with this master period (three impulses per revolution), the engine becomes rough a long way below the critical speed. We have come to the conclusion that we never can satisfactorily get rid of this top period. The only thing to do is to design the crankshaft so that the main torsional is outside the running range, however, we shall be most interested to hear how you get on. We do not know how to design a 6-cylinder crankshaft that will have a master period higher than 5,500 revs. if it is fully balanced - this is for an engine of about 3 1/2 litres. Naturally 6-cylinder engines of smaller displacements have relatively higher critical speeds. We have written to the Michigan Tool Co. of Detroit, as per the attached letter, and anything you can do to get them to help us to produce gears over here will be much appreciated. Yours sincerely, FOR ROLLS-ROYCE LIMITED. | ||