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).
Investigations into main bearing issues and engine thuds in Bentley engines.
| Identifier | ExFiles\Box 146\1\ scan0157 | |
| Date | 3rd January 1938 | |
| c. Rm.{William Robotham - Chief Engineer} BENTLEY ENGINE - RE: MAIN BEARINGS. Referring to Sr.10/Crn.24.12.37. I regret the delay which has occurred in replying to this, but the intervention of the Christmas holidays prevented it getting attention immediately, and I wished to discuss the matter with GWH.{George W. Hancock - Head Chateauroux} before writing you. Taking first of all the matter which arose in connection with Commodore Beaumont's car, I note that when you decarbonized the engine it was checked for 'engine thud' and thought to be satisfactory, but that when K.{Mr Kilner} had the engine in they refused to let it out until the bearings had been attended to. A similar position arose in connection with the car that Mr. Lappin uses, in this case K.{Mr Kilner} did the work, sent me a big end which they considered was at fault, and as a result of examining this I telephoned K.{Mr Kilner} they must immediately get back and examine the main bearings. GWH.{George W. Hancock - Head Chateauroux} got me on the 'phone again, and pointed out that they had checked the engine before, and after dealing with the connecting rod, and was satisfied that there was no thud. I insisted, however, that the appearance of the big ends indicated clearly that the oil was escaping too freely from the main bearings. When the engine was returned and examined it was found that there was as much as .013 slack in the worst case, and anything between .008 and .012 over the remainder. At the same time I suggested a method of checking the slack in the bearing by the amount of oil that they would pass. GWH.{George W. Hancock - Head Chateauroux} at K.{Mr Kilner} has worked this scheme out to a satisfactory issue, and it was on the basis of this that they insisted that Commodore Beaumont's car required attention to the main bearings. They first of all took the caps off and checked for the amount of slack, they found that there was .006 to .009 slack, but when they removed the crank and cleaned the oil from the back of the upper bearing they found that the maximum slack had gone up to .014. It was the use of the oil flow test which put them wise to the real condition of the engine, and information in regard to what has been developed at K.{Mr Kilner} will be supplied to you before long, when I hope that GWH.{George W. Hancock - Head Chateauroux} will come over to demonstrate their method. So much for the general position in regard to Comm. Beaumont's car, and for the information which has been | ||