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 requirements and difficulties of hydraulic jacks for vehicles.
| Identifier | ExFiles\Box 37\3\ scan 074 | |
| Date | 28th February 1930 | |
| Da{Bernard Day - Chassis Design}/Ev.{Ivan Evernden - coachwork} From Hs{Lord Ernest Hives - Chair}/AJL. c. to C. (For Sales). V3175.X Hs{Lord Ernest Hives - Chair}/AJL.1/MJ.28.2.30. x 3175 x 4089 x 3117 x 4124. HYDRAULIC JACKS. ---------------- Thank you for your EV{Ivan Evernden - coachwork}3/24.2.30. We fully appreciate the difficulties of the jack designer. It is not an easy matter to cater for a low minimum height in conjunction with a large hydraulic lift. At the same time, none of the jacks we have been asked to test have been sufficiently close to our dimensional requirements for us to consider using them. (e.g. Skyhi Model No.163). In consequence of paragraph 2 of your memo we agree not to expect to cater for the case of the complete loss of a tyre, thus increasing our minimum height requirement by 0.500" and the hydraulic lift by the same amount. With regard to your proposal to cut down the allowance of 1.500 for soft ground and cambered roads, we think we should try our utmost to get this dimension. It is not only necessary to consider the distance of 15" between the tyre and the spring, but also the distance the wheel must be moved outwards before it is clear of the hub. Again, when used under the rear axle, the screwed extension must be employed in order to gain full advantage of the hydraulic lift, it is difficult to screw this up in position ( especially in the case of a car fitted with a luggage box and two spare wheels) and consequently hydraulic lift is invariably used unnecessarily. We would prefer to increase the minimum height in order to obtain this extra hydraulic lift if found | ||