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).
Design considerations for hydraulic jacking systems, comparing the 'Jackall' system to a new confidential 'D.W.S.' system.
| Identifier | ExFiles\Box 139\2\ scan0288 | |
| Date | 18th June 1935 guessed | |
| - sheet 2 - A considerable amount of design work has, therefore, been done in this connection. A scheme was considered in which the hydraulic rams for both front wheels were built into the wheel yokes. This, however, was not found to be entirely satisfactory because owing to the position of the jacks having to be near to the road wheels, there was a possibility of the jack head trapping a flat tyre. The alternative scheme is to use either one jack built into the front crossmember or two jacks attached to the front ends of the side members. In both cases a jack with a very large lift (14") is necessary to cater for the wheel rebound movement. It was found difficult to install a Jackall unit for either of these schemes because the unit became very bulky in consequence of the large range of movement required. The rear axle problem was easier and did not present any appreciable difficulty. We had heard that the D.W.S. Co. were developing a hydraulic jacking system which they hoped would be superior to the Jackall and we asked Mr Donald Sessions if he would care to discuss it with us. He was very pleased to do this and gave us in confidence quite a number of details of his system. Briefly it is similar in principle to the Jackall except that the motive power is provided by a very small pump driven by the engine and controlled by a key on the instrument board. The whole mechanism is extremely simple and the jack units themselves are superior to the Jackall in many respects. Owing to the fact that they are smaller we have been able to fit them in very nicely at the front ends of the sidemembers. Mr Sessions is not yet in a position to let us have a sample set for test, but he hopes to do so in a few weeks. We think this system is superior to the Jackall and we are, therefore, going ahead with the design work necessary to accommodate it. It is realised that this system cannot be tested and perfected in time for the first production SpectreCodename for Phantom III cars so we have completed designs for using the D.W.S. Mechanical Jack as fitted to the Phantom II. We can use the same jacks on the rear as we use at present on Phantom II, but the new type of front suspension demands a jack having a much greater range of lift. Fortunately there is a suitable jack available which fits on to the front crossmember quite simply. The D.W.S. hydraulic system has not been announced at all and we are the only people who have been informed about it. We have been asked by Mr Sessions to treat the whole matter as being strictly confidential. F/Lid.{A. J. Lidsey} | ||