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 on the Wraith III water pump drive, focusing on the coupling spider and drive shaft torque failure points.
| Identifier | ExFiles\Box 149a\1\ scan0144 | |
| Date | 8th October 1937 | |
| To By.{R.W. Bailey - Chief Engineer} from HPS{Horace Percy Smith - Experimental Factory Mgr}/W.Bell. c. to Rm{William Robotham - Chief Engineer}/Std. 1269 HPS{Horace Percy Smith - Experimental Factory Mgr}/WB.{Mr Brazier/Mr Bell}1/CB.8.10.37. Holden My/STP WRAITH III WATER PUMP DRIVE. Ex.27891 Coupling Spider. Ex.27889 Drive Shaft. The above combination of coupling spider and drive shaft gave a diametral interference of .003" and for these tests, one spider was pinned (.125" dia. taper pin - 1 off) the other being held by the interference only. Test 1. With the pinned spider fixed, a gradually increased torque was applied to the shaft via the unpinned spider until failure occurred. At 45 lbs. ft. the unpinned spider commenced to "slip", and it was found on releasing the torque, that the shaft had also taken taken a permanent torsional set. Test 2. After pinning the previously unpinned spider with a .125" diameter taper pin, the test was repeated, the slipping torque being then 62 lbs. ft., failure occurring at the same end. - Further permanent set of the shaft also occurred. Test 3. Finally an oversize pin (.187" dia.) was fitted into the originally unpinned spider, and the test again repeated. Failure at the spider having initially .003" interference and a .125" diameter taper pin, occurred at 97 lbs. ft. Therefore, a spider having .003" diametral interference will withstand a greater torque than that required to overstress the shaft. continued. | ||