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).
Procedure for addressing engine bearing roughness and thumping on 3½ and 4¼ Litre Bentley Chassis.
| Identifier | ExFiles\Box 115\1\ scan0288 | |
| Date | 12th February 1937 | |
| 12th February 1937. DEPOT SHEET NO. Hd.{Mr Hayward/Mr Huddy}333. ENGINE BEARINGS. 3½ and 4¼ Litre Bentley Chassis. Origin of information:- Rm{William Robotham - Chief Engineer}6/R.16.12.36. MAIN BEARINGS. 4¼ LITRE BENTLEY. 1. When there is any complaint of roughness and thumping it will probably be found to be due to hammering of the Hall's metal bearings in their housings. This is usually most noticeable on the rear main bearing, graduating less to the front bearings. The procedure to be adopted in dealing with such complaints is as follows:- Remove the main bearing caps only and measure by clock the amount of sinkage of the upper halves of the main bearings above the joint face of the crankcase. Pressure should be applied to the bearing to make sure that it is bedding well into the housing. This amount of sinkage is then taken up by stepping the shim as shown on the attached drawing No. RM.{William Robotham - Chief Engineer}271. The existing steel shims with Hall's metal facings should be replaced with new ones made in R-R.56 aluminium. Leaving the part of the shim which actually faces on the bearing section, at the standard thickness of .100", reduce the remaining portion which joints between the cap and the crankcase by the amount of sinkage as measured. With regard to the cap half, the sinkage can be recovered by filing off the joint faces of the cap. Following these modifications, the crank and bearings should be oil pressure tested. -continued- | ||