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 inspection and fitting procedure for Halls metal connecting rod shells after an engine failure.
| Identifier | ExFiles\Box 114\3\ scan0061 | |
| Date | 21th September 1938 | |
| To By.. from Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux} Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux}8/N.21.9.38. I am forwarding a pair of Halls metal shells for your inspection, that were fitted to No.4. connecting rod of B.72.KT. and which have run 4,000 miles. They were taken out when the engine failed after a Mod.B. No.6. rod bearing breaking up see report K.108. These shells were fitted as I have explained to you i.e. the shells as received from the Works are cut in two. The faces are trimmed up, and the shells are placed in their respective housings. The amount of projection to be squeezed up is approximately .012" on each shell. To make this clear, one side is level with the face of the housing, the other side stands proud .012". The other half being the same makes a total of .024" metal standing proud. No shims are used. The bolts are tightened up until the two steel faces of con rod meet. It is left in this condition for an hour or until all six rods have been dealt with, then the first one bolted up is taken apart and so on. The metal flows without any distortion and when the cap is removed there is approximately .001" recovery of the metal. This is filed to make sure of the face being parallel. The shims are then fitted and after thoroughly tightening up they are bored to the correct clearance size i.e. .003" clearance of diameter of pin, max. min. .00250". The works allow a minimum of .00225" on the diameter. In every case we have found this diameter too small and after a small mileage the bearing is tight on the crank pin. The same procedure is carried out with the journal bearing with the exception that only .008 to .010 is allowed for the metal standing proud before being pressed in. We can vouch for these bearings being solid in the housings and we have no evidence of shells coming loose afterwards. GWH.{George W. Hancock - Head Chateauroux} | ||