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).
Issues with Wraith wheels, including clunking noises and tightening torque calculations.
| Identifier | ExFiles\Box 10\4\ 04-page31 | |
| Date | 16th February 1938 | |
| To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} c. Da.{Bernard Day - Chassis Design} c. Hay. c. Hx. 656 WRAITH WHEELS. In addition to the slip of the tapers in the transmission on which we have already reported, there is also on Wraith cars a clonk from the rear wheels when reversing the torque during manoeuvring. Our tests have shown that it is almost impossible to do up wheels sufficiently tight to prevent this trouble. Brass inserted wheel nuts are an improvement but not a cure. We have therefore done some calculations on the mechanics of tightening the Wraith wheel. These are attached to this memo. It will be seen that owing to the 10° outer cone, assuming that this is un-lubricated, a spanner torque on the Wraith of 3650 lbs.ft. is required to prevent clonking. This is an amount which could never be approached. If on the other hand we were using the Dunlop N. type wheel with a 6 1/2° outer cone the spanner torque would be less than the driving torque and would amount to 1060 lbs.ft. Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} | ||