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).
Tests carried out on serrated/pressed fit levers comparing knurled shafts with serrated ones.
| Identifier | ExFiles\Box 6\6\ 06-page152 | |
| Date | 2nd June 1937 | |
| COPY. To E.{Mr Elliott - Chief Engineer} from HPS.{Horace Percy Smith - Experimental Factory Mgr} G.{Mr Griffiths - Chief Accountant / Mr Gnapp} to E/De. HPS.{Horace Percy Smith - Experimental Factory Mgr}2/VS.{J. Vickers}6.E.37. SERRATED/PRESSED FIT LEVERS. We give below W. Bell's report on tests carried out in connection with the above. Wraith II LeC.5375. In the previous tests, the shafts were knurled, and pressed into plain bores. In these tests both the shaft (Ex.25164) and lever (Ex.25165) were serrated as shown in LeC.5375. Three models were tested, the fit at the effective diameter of the serrations in each case being :- Test 1. .005" Clearance. Test 2. .005" Interference. Test 3. .015" Interference. The attached graphs illustrate that the serrations proved to be capable of withstanding more torque than the shaft, which in each case began to take a permanent set between 500 and 600 lbs. ft. - the shafts were hollowed to represent the axle pads as shown on the scheme LeC.4995. It will therefore be necessary to stiffen up the shafts, and we propose to repeat tests with the clearance lever and a solid shaft. It was unfortunate that in the previous series of tests, the torques at which the larger interference knurling grips failed, coincided with the elastic limit of the shafts, thus the weakness was not fully revealed. Nevertheless, it is evident that serrating both pieces very considerably increases the torsional strength of the assembly. The loads required to press the levers on to the shafts - as recorded on the press - were :- .005" Interference, 5 tons. .015" Interference, 8 tons. Also in the latter case it was found that the bore of the shaft decreased by approx. .009", whilst the lever expanded .012" diametrically, after the pressing operation. continued. | ||