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).
The design considerations for the Spectre model's permanent, built-in jacking systems.
| Identifier | ExFiles\Box 139\2\ scan0287 | |
| Date | 14th June 1935 | |
| SECRET. AND CONFIDENTIAL. SpectreCodename for Phantom III Permanent Jacking Systems. We have for some little time been considering the question of the design of a built-in jacking system. The modern type of bodywork necessitates a built-in jacking system and it should be of such a design as to require the minimum of effort to operate it in combination with light weight and simplicity of parts. We first of all considered a jacking system which three simple built-in inverted screw jacks were fixed the chassis frame, one under the front crossmember and one on each rear dumb iron. The two rear ones were coupled together for simultaneous operation by a cross shaft passing through the rear tubular crossmember and the minimum of effort in raising was ensured by the use of bevel gearing mounted on simple needle roller bearings with ball thrusts for carrying the reaction of the loads so that only the inefficiency of the screw would remain. The two rear jacks were arranged for operation either from a single point in the centre of the rear of the car by the use of the engine starting handle or at either side. The single jack at the front was to be operated through the centre of the front apron. This system necessitated the use of slings under the rear axle and in addition was not considered sufficiently attractive from an operation point of view when compared with the hydraulic type of jack operated from the driver's seat. An alternative method of front jacking was at the same time investigated in which mechanically operated screw jacks were built into the front wheel yoke pieces, one for each wheel. This had the same disability with regard to ease of operation, as the previous scheme. Owing to the reasonably good results being obtained on Experimental Department and other cars under the firms control, equipped with Jackall hydraulic jacks, it was considered that the hydraulic jack is the ultimate type to go for because of its great advantage with regard to ease of operation as compared to mechanically operated jacks. | ||