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).
The Wraith III water pump drive, continued, discussing shaft interference tests and tolerances.
| Identifier | ExFiles\Box 149a\1\ scan0145 | |
| Date | 8th October 1937 | |
| -2- HPS{Horace Percy Smith - Experimental Factory Mgr}/WB.{Mr Brazier/Mr Bell}1/CB.8.10.37. WRAITH III WATER PUMP DRIVE. contd. A range of shafts giving .002" to .004" diametral interference was listed, but only that having .003" interference was supplied for these tests. Since a reasonable tolerance is necessary, if these couplings are to be adopted productionally, we consider it advisable either to repeat the tests with .002" interference, or in view of the information already obtained, fix the minimum interference at .003". Engine conditions are of course vastly different from the "Static" conditions under which these tests were conducted, but we consider that .003" interference (without the pin) will satisfy all normal requirements. The taper pin of course gives additional security and guards against any possibility of failure. Test No.2 was taken as a matter of interest. The difference between the torques registered in Tests 1 and 2 does not necessarily equal the torque required to shear the pin, since the condition of the surfaces, after slippage occured, could not be ascertained. Neither can the difference between Tests 1 and 3 be taken as the shearing torque of the pin, since the drilling and reaming operations naturally bruise the surfaces locally. HPS{Horace Percy Smith - Experimental Factory Mgr}/W.Bell | ||