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 from Overdrive Gears Ltd. discussing licence proposals and the technical merits of their overdrive system.
| Identifier | ExFiles\Box 136\2\ scan0100 | |
| Date | 9th June 1939 | |
| PLEASE REPLY DIRECT TO "ORMIDALE" THE AVENUE, HATCH END, MIDDX. 'PHONE: HATCH END 1221 1153. Overdrive Gears Ltd., DIRECTORS A.C.WICKMAN. WALTER JENKS. C.D.GAY. E.J. de NORMANVILLE. 76, VICTORIA STREET, LONDON, S.W. 1. TELEPHONE AND TELEGRAMS VICTORIA 6291 9th June, 1939 Dear Mr.Robotham, Thank you for explaining the position to me yesterday. Adverting briefly to your letter of the 2nd instant, I want you, please, to be quite satisfied that my licence proposals were (as stated in my letter also dated 2nd instant which crossed yours in the post) "exemplo gratia" figures, to arrive at an acceptable basis for large models - not a quotation of terms. And now I would claim your indulgence for offering one or two further thoughts on the ratio problem, as further investigation of known facts, and consideration of the probable facts in your case, clearly indicate (I think) that the ratio fears we discussed are quite groundless. I enclose you B.H.P. Required Diagram (Snipe) for Top gear and Overdrive. For the speeds primarily concerned, say, the range from 45 to 70 m.p.h., the curves are very instructive, and show (as you suggested must be the case) that, for propulsion, the ordinary Top ratio is "crackers"! I rely on memory when I express the belief that the Studebaker is about 10% worse in this respect. I submit for your consideration that this is the essence of the whole matter viz: the difference between B.H.P. required for Propulsion, and for acceleration or hill climbing, - coupled, of course, with the essential need of having the extra h.p. instantaneously available for urgent overtaking and hill climbing. I venture to say that you would find a step up ratio of 40% for Overdrive completely satisfactory for Propulsion on a long straight road. You have been good enough to express your appreciation of the ease with which we return to Top when any change of road conditions demands any change of B.H.P. available. I/ W.A.Robotham,Esq., Messrs Rolls Royce,Ltd. Derby. | ||