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 from S. Smith & Sons regarding the specifications and options for a car jacking system.
| Identifier | ExFiles\Box 26\3\ Scan337 | |
| Date | 28th December 1933 | |
| S.P.81 S. SMITH & SONS (Motor Accessories) LTD. CRICKLEWOOD WORKS, LONDON. N.W.2. CONTINUATION NO1. December 28th, 1933. Messrs. Rolls Royce, Ltd. The jacks have a stroke of 8½ inches and the ground clearance with properly inflated tyre is 7½ inches. The clearance and stroke can be modified to suit your requirements. The pump unit is not the latest model as these will not be ready for a week or so. The difference between the new unit and the one fitted is that the pump delivery is less to the extent of 25% with a correspondingly shorter operating handle or alternatively easier action. The effort on the handle to lift the rear of the car will be, with the newer model of pump, about 15 lbs, and the lifting time for rear or front is 15 seconds or 30 seconds for the whole car. The return of the jacks is automatic when the release lever is turned and the jacks return in a few seconds. You will note that the pump unit is fitted beneath the front floorboards. This is a convenient position for operating the jacks, but the pump unit may of course be located at any other convenient spot. The flexible tubes used for connecting the pipe line to the axles are tested to 4000 lbs per square inch and are capable of withstanding pressures of over 6000 lbs. The working pressure on your car is 1750 (rear.) You will also note that the jacks are arranged to operate in pairs, so that either the whole or rear is lifted. The pump and distributor valve unit can if necessary be rearranged to permit operation of any one jack or all four. The selector mechanism of the newer model of pump is arranged so as to allow considerable latitude in the position of the indicating arrow and the position is not critical. With regard to jacks, we make these in two diameters. The larger ones have a ram area double that of the jacks fitted to your car, but they take twice as long to operate and are heavier, and consequently more rigid. We are of the opinion that the correct size for your car would be midway between the two, weighing 4½ lbs each and operating at a pressure of 1300 lbs. If, therefore, you come to the conclusion that the very convenient Jackall System is what you require we shall be very pleased to design a set specifically to your requirements. | ||