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).
Requirements and specifications for sourcing hydraulic jacks.
| Identifier | ExFiles\Box 26\6\ Scan020 | |
| Date | 24th February 1930 | |
| X4080 To Hs{Lord Ernest Hives - Chair}/AJL. From EV.{Ivan Evernden - coachwork} Ev{Ivan Evernden - coachwork}3/24.2.30. COPY TO Sg.{Arthur F. Sidgreaves - MD} (For Sales). X.3175 X.4080 X.3117 RE. HYDRAULIC JACKS. We thank you for your Hs{Lord Ernest Hives - Chair}/AJL/MJE7.2.30. and regret that our letter questioning the figures which you suggested as necessary for the lift and minimum height should have brought forth signs of ill feeling. It is a fact that for a long while Sales have been trying to persuade makers to produce a jack to fulfill your requirements, and at the moment the matter was handed over to me every one of them had said that they could not give us all you have insisted on. In the mean time we have no hydraulic jack to recommend to customers, yet customers have got jacks which they are using with satisfaction, although we have told them that they will not be found to meet all conditions. It therefore occurred to us to review our requirements to see if there could be found something which we might concede to the jack makers to help them. With this point in view we, as the design office, examined the drawings and sent figures to you for your comments. We also sent them to the makers saying, this is the very best we can ever hope to agree to. We agree that we should find a jack to suit if possible both cars, and the P.2 with 21 and 20 ins. rims. We are inclined to agree to not catering for the case of the total loss of cover and the tube as this must be of rare occurance and can be overcome in the case of this emergency by driving the car on to a piece of board 0.500 ins. thick. This not only increases the minimum or shut height of the jack but reduces the hydraulic lift required accordingly. From your figures we have:- Distance from under front axle at spring fixing to ground with tyre fully deflated, 20ins. rims = 6.00". Similar distance, tyre fully inflated and .500" clear of road =10.750". Therefore hydraulic lift = 4.750". With respect to soft ground, we think that to allow for 1.500" as you suggest would be good if we could afford to be lavish. We suggest that 1.000" should be adequate, as on | ||