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 evaluation of 'Jenks Jacks' for potential use on cars, outlining advantages and disadvantages.
| Identifier | ExFiles\Box 26\3\ Scan066 | |
| Date | 3rd February 1931 | |
| To By.{R.W. Bailey - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Ltd. X311 Hs{Lord Ernest Hives - Chair}/Ltd.3/KT.3.2.31. JENKS JACKS. We have received for test one pair of Jenks Jacks suitable for the rear of 20/25 HP cars, and a second pair for the rear axle of P.II cars; in addition a third jack fitted with an alternative method of fixture to the axle was received. The attached pamphlet describes and illustrates the jack and its method of operation. One pair have been fitted to the rear of a 20/25 HP car (16-G-IV); the fixing employed being round mild steel bar bent in the form of a 'U' clip which is slipped over the road spring at each end of the spring sheath, the jacks are bolted up to these clips. If we decided to recommend this make of jack we should prefer a fixing on the lines of the alternative s supplied in which a plate is inserted between the spring and our 'U' clips, the jack being bolted to this plate. The jacks are moderately easy to operate and are certainly very much handier than the usual type of jack, they also have ample lift to cope with all possible conditions. Against these advantages there are several disadvantages :- (1) Addition of unsprung weight, 11 lbs each jack, the handle 4 lbs 12 ozs. (Total per car 51 lbs 12 ozs) (2) Although leather covers are fitted, water and mud will penetrate to the screw thread and may easily prevent the jacks from working well. (3) There is insufficient locking provided for the closed position of the jack, after only 33 miles one of the two jacks fitted to the rear of 16.G.IV became partially extended owing to axle vibration; this occurrence could have very serious consequences. We should not care to accept the responsibility of recommending these jacks for use on our cars in their present state of perfection. The idea is certainly very attractive, in addition the car is more safely jacked up than when using our own present standard, but the prospect of their dropping down when running counteracts all their advantages. It is also very questionable whether we could accept the addition of nearly 24 lbs in weight on the front | ||