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 calculation methods for wishbone linkage effects, comparing force polygons with graphical methods.
| Identifier | ExFiles\Box 154a\2\ scan0302 | |
| Date | 17th May 1940 | |
| COPY. Serial No.1. Oy.7/D/May.17.40. Rolls-Royce Inc. Room 2-251. General Motors Building. Detroit, Michigan. May 17, 1940. Mr. Donald Bastow, Rolls-Royce Ltd., Derby, England. Wishbone Linkage. Dear Mr. Bastow: Replying to Ev{Ivan Evernden - coachwork}/DB.{Donald Bastow - Suspensions}10/JH.16.4.40. Your method of obtaining linkage effect by successive force polygons is correct in principle but inherently inaccurate, and fails to show up the effect on the rate of the load itself. If you or Geoff. will consult either Maurice Platt or Andrew Stenhouse at Vauxhall Motors, Ltd., they can show you some assorted notes on linkage which will help. Your approximation terms on page 3 of your memo should include a term for load as well as for rate. I have scribbled sketches on attached sheet. In case I the angular rate is obviously Wr. In case II the angular rate is Wb.{Mr Brazier/Mr Bell} b is the rate of change of a and vice versa. In case III, where a spring is used, the angular rate is Sb{Mr Bull/Mr Bannister}² - Pa.{Mr Paterson} In case IV the angular rate is Sb{Mr Bull/Mr Bannister}² - Pa{Mr Paterson} (l+ a)/l b being the rate of decrease of l, and a/l (l + a) the rate of decrease of b. If, therefore, you want to use graphical methods rather than my analytical method of approximating the link end paths by parabolas, it would be better to use the graphical methods to obtain the offsets, like a and b, which indicate rates of change, and thus get results in terms of rate more quickly and accurately. P.T.O. | ||