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).
Test report and analysis of a Dunlop Jack, detailing its dimensions, failures, and potential improvements.
| Identifier | ExFiles\Box 48\1\ Scan023 | |
| Date | 1st February 1927 | |
| To EY. from Hs. {Lord Ernest Hives - Chair} Hs {Lord Ernest Hives - Chair} 3/LG9. 2.27. DUNLOP JACK. Below are given particulars of the latest Dunlop Jack received for test purposes. (This jack has no identification No. or name.) Minimum height ................ 6.325" Hand adjustable initial lift ..... 3.00" 1st. stage mechanical lift ..... 3.675" 2nd. " " " ..... 3.35" Total mechanical lift ............ 7.025" Maximum height ................. 16.35" The above dimensions barely fulfil all conditions required. The mechanical lift is ample, but the hand adjustable initial lift could be increased by 1.5" to considerable advantage; this would make the max. height 17.85" and would enable full advantage to be taken of the large mechanical lift when lifting the rear axle of a car, where over 10" initial jack height is required. If the adjustable initial lift were increased to 4.0" the jack would meet all requirements comfortably. N.B. Adding 1.5" at the base of the jack will not meet the case, this would prevent the jack going under the front axle; the additional 1.5" must be on the adjustable hand lift. This jack failed mechanically after it had been used a very few times. The cause of the failure is due to there not being a sufficiently substantial stop to limit the maximum movement of the 2nd. stage of mechanical lift. It is possible to keep on turning the jack until the 2nd. stage lift is screwed completely out of its worm; this is what happens when the jack breaks down. The jack is also difficult to operate, requiring excessive effort to lift a car.(a thrust race should be provided in the base of the jack; also at the top - see sketch.) The main casing could be made in alum. to effect a considerable saving in weight. Hs. {Lord Ernest Hives - Chair} | ||