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 Cadillac Motor Co. regarding the poor performance and friction issues of tested Marles Steering Gears.
| Identifier | ExFiles\Box 170\2\ img275 | |
| Date | 29th May 1935 | |
| Exptl. Dept. Hs{Lord Ernest Hives - Chair}/PJH.24/KW. 29th May, 1935. M.{Mr Moon / Mr Moore} Olley, Esq., c/o.{Mr Oldham} The Cadillac Motor Car Co., Detroit, Michigan, U.S.A. Dear Sir, We have recently tried on two of our large cars double tooth Marles Steering Gears made to our own designs, with cams and roller followers produced by the English Marles Co. These gears are very bad for transmission of road shocks in comparison with the La{L. A. Archer} Salle steering gear which we have fitted to a similar car, so we are writing to ask if there is any secret of success for these gears. There is no essential difference between the design of our gear and the design of the La{L. A. Archer} Salle and the overall ratio from steering wheel to road wheels is the same. The helix angle in the centre position in the case of our gear is 6°30'. According to our reasoning, any steering gear must have a considerable amount of friction under shock conditions in order not to transmit the shock, and, so far as we can see, the only place in the Marles gear where this friction can occur to any useful extent is between the roller follower and the cam. The friction that occurs at this point would appear to depend upon the length of the line contact between the follower and the cam as it occurs owing to the fact that there can be pure rolling only on the "pitch line". We have noticed that the English Marles Co. have crowned the sides of the cam tracks as shown on the attached sketch and it seems to us that this enormously reduces the length of the line contact and the friction at this point. | ||