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).
Box spanner clearances for the Wraith III crankcase and requesting modifications.
| Identifier | ExFiles\Box 132\3\ scan0090 | |
| Date | 7th March 1938 | |
| 616 SWDE Rules To ~~Da.{Bernard Day - Chassis Design}~~ from HPS.{Horace Percy Smith - Experimental Factory Mgr} c. to ~~HMC.~~ c. to Rm.{William Robotham - Chief Engineer} c. to ~~P/H.{Arthur M. Hanbury - Head Complaints}~~ HPS.{Horace Percy Smith - Experimental Factory Mgr}2/VS.{J. Vickers}7.3.38. WRAITH III CRANKCASE. Further to your memos ref. Da.{Bernard Day - Chassis Design}4/G.2.3.38. and Da.{Bernard Day - Chassis Design}8/G.4.3.38. in connection with box spanner clearances on the above. We would point out that with a spanner as used on production of .795 diameter if the pieces in question accord exactly to the specified dimensions the clearance is only .0025, and if advantage is taken of the maximum adverse limits a foul of .024 will occur; furthermore, we cannot agree that a greater clearance exists on Wraith at this point than on 25/30 H.P. and Bentley II - the conditions are exactly the same. When discussing clearances in terms of thousandths of an inch it should be appreciated that castings of this type produced from wooden patterns vary considerably, and we feel that a minimum clearance of .050 should be given at this point. In view of this we shall be glad if you will cancel the adverse limits on the hole centres and on the 4.875 dimension, and also set back the wall of the lower half as much as possible. HPS.{Horace Percy Smith - Experimental Factory Mgr} | ||