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 condition of Con.Rod and main bearings from a Bentley 260.GA, highlighting issues with shims and uneven wear.
| Identifier | ExFiles\Box 131\4\ scan0289 | |
| Date | 11th June 1937 | |
| W/P from Rm{William Robotham - Chief Engineer}/GWH{George W. Hancock - Head Chateauroux} 1130 To Rm.{William Robotham - Chief Engineer} c. to Hs.{Lord Ernest Hives - Chair} KINGSBURY. June 11th.1937 I am forwarding to you the Con.Rod Bearings taken out of Mr. A.Embiricos's Bentley 260.GA after 7000 miles, after attention to them by the Paris Depot. The main bearings were in a similar condition. The acme thread at the flywheel end also of fan pulley were fouling hard in both cases. A quantity of oil had leaked into the clutch pit and out of the fan drive. The stepping of the shims on the main bearings had been badly done, uneven thickness causing an uneven load on the bearings. No. 4 main bearing was picking up due to over tightness. The nuts on this cap were not correctly tightened up even then the crankshaft stuck when trying to turn it by hand. With the cap tightened up in the same manner as the other bearings, the crankshaft was solid. We could not recommend the state of condition the engine was found in. If this is caused by nipping up the bearings with the engine in position, it will not pay. With the use of a pit, probably a better job could be made. I am of opinion that these jobs cannot be rushed. If the job demands attention, it should be done in a thorough manner, and the engine taken out to do it. The stepping of the shims requires investigation so that correct thickness of shims can be supplied. In the case of B.260.GA it was necessary to step to the extent of .015. By having to do this it leaves the shim too thin to obtain the correct bearing dia. consequently a lot of metal has to be scraped out of the top and bottom of the bearing to correct the bedding. Whatever the depth of the step is, that amount is lost on the shim itself. The bearing does not actually wear very much. To sum up, stepping of the shims is not satisfactory. Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux} Enclosed are two shims taken out of No.4 main bearing, which have not been correctly fitted. | ||