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).
Detailed review of chassis design, including suspension, transmission, and engine mounting systems from an article in 'The Autocar' magazine.
| Identifier | ExFiles\Box 160\5\ scan0286 | |
| Date | 31th January 1941 | |
| 98 The Autocar January 31st, 1941. (Left) The automatic lubrication pipe lines to the rear spring shackles are shrouded to protect them against damage from stones. One of the exhaust pipe mountings is also seen; and (right) the intermediate universal joint used in the transmission, which, most interestingly, is mounted in rubber. the big-ends, and the gudgeon pins, the oil supply to the valve gear is at a reduced pressure. Incorporated in the system is a General by-pass filter, made by British Filters, Ltd. The four-speed gear box follows the same lines as on the existing model, fourth speed being indirect and having the high ratio of 3.64 to 1, whilst direct drive is on third (4.3 to 1). Second gear is 6.43 to 1, and first 10.25. The object of the high or overdrive ratio is, of course, to allow sustained high speeds on Continental roads at moderate engine revs. Approximately, the engine is doing no more than 3,500 r.p.m. at a road speed as high as 85 m.p.h. An interesting point is that exceptionally easy operation of the clutch pedal is made possible by the use of centrifugal loading which ensures absence of slip as the car accelerates, although light-acting springs are employed to hold the dry single-plate clutch up to its work. An engineer might spend a week peering into this chassis and taking stock of it, learning much of the methods of achieving certain ends with a scientific disposal of minimum material rather than by “brute strength.” An excellent case in point is afforded by the manner of attaching the steering gear box to the frame side-member. The bracket employed is almost slight in construction; the bolts that hold it are comparatively few and small in diameter. Yet one realises that the stresses involved have been weighed up accurately, and that for a greater mass of material to be employed at this point would merely add weight. Where adequate strength is to be secured only by the presence of more generous areas and sections, there is, of course, no hesitation to employ them, as, for example, in the members of the immensely strong X-braced frame, which is partly of box section. There again, however, there is no wastage. One notices in examining the frame members in side elevation that there are numerous variations in depth. A clearly marked practice on the chassis which is directly connected with the policy of improved quietness, smoothness and flexibility of operation is the use made of various forms of rubberised mounting for components where relative movement occurs between one part and another, or is desirable to encourage. [Image Caption Bottom Left] Cam and roller steering gear is used; the attachment of the box to the frame is shown. Also seen are the fuse and voltage regulator boxes and the neatly conduited wiring. A point of detail is the mounting on the bulkhead, in a suitable cover, of a spare ignition contact breaker spring. [Image Caption Top Right] The hypoid bevel type of rear axle and rearward section of the divided propeller-shaft. Also to be noted are the sharp curvature of the frame members above the axle, and the secondary silencer, flexibly attached to the frame. To start with, the engine and gear box unit is an outstanding example of this practice. In effect, it is carried in the frame only at front and rear—in front on a mounting placed quite high and offset from the centre line of the engine, and at the rear of the gear box on a member attached at two points to the main frame, a form of rubber insulation being interposed. Additionally there is a steady pad about centrally beneath the gear box, resting upon a cross-member. The outcome of this system of engine suspension is to allow the engine a perceptible degree of lateral flexibility in the frame. Other examples of flexible mountings are the attachments of the exhaust system, which incorporates primary A 6 | ||