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).
Technical description and cutaway illustration of a new 120 m.p.h. model from 'The Motor' magazine.
| Identifier | ExFiles\Box 160\5\ scan0228 | |
| Date | 29th January 1941 | |
| January 29, 1941. 565 The Motor A New 120 m.p.h. Model 2.73, 3.73 and 5.34. Bottom gears, 10.5 and 9.1. New Gearbox Details The cones are of very large size, give a powerful synchronizing effect, and a locking mechanism is fitted which prevents engagement of gears until the relative speeds are correct. In order to reduce power loss and to give a light gear engagement, the box is filled with engine oil (SAE 30 viscosity) and it says much for the skilful design and accuracy of gear cutting that the indirect and overdrive ratios—even with this thin oil—are almost inaudible. The whole engine and gearbox unit is rubber mounted, high at the front and low at the back, so that the mounting axis is above the centre of gravity of the engine. This gives an inherent stability which prevents excessive rock on the engine, such motion also being restrained by rubber buffers, whilst a link also holds the engine in a fore and aft direction. The drive from behind the gearbox is taken to the rear axle through a divided propeller shaft. The problem of propeller-shaft vibration is a very severe one on fast cars and is not ameliorated by the use of overdrive; this reduces engine r.p.m., but not propeller-shaft speed. The difficulty is increased as the length of the shaft goes up; shafts become progressively longer as engines are mounted further forward in the frame for reasons of weight distribution and improved body space. The use of a two-piece propeller shaft with the universal joint mounted in the centre of the chassis reduces the effective length of the shaft. At the same time it introduces noise transmitted from the engine or rear axle up the shaft, through the steady bearing into the frame and then to the passengers. On the Bentley, care has been taken to insulate the centre bearing, this being one of the many points which receive such attention and which result in unusual quietness on the road. The rear axle itself incorporates hypoid gears which lower the centre line of the propeller shaft, the half shafts being fully floating on the Mark V and semi-floating on the Corniche. The rear axle is attached to the frame by semi-elliptic springs hydraulically damped by Rolls-Royce-type shock absorbers. A feature of the rear spring is the use of a tension shackle which has the effect of progressively stiffening the spring as it departs from its normal plane. Reference to springing brings one to the most obvious novelty in the whole car—viz., the use of independent front springing for the first time on a Bentley 417 | ||