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).
Optimal mileage and methods for servicing the main bearings on 4 1/4 litre Bentley engines.
| Identifier | ExFiles\Box 146\1\ scan0175 | |
| Date | 26th January 1938 | |
| Bentley Motors (1931) Ltd., DERBY. copy to Rm.{William Robotham - Chief Engineer} Handwritten: SWDL{Len H. Swindell} Files, 1245 Reference: Sr.3/Crn.26.I.38. Bentley engine - main bearings. --------------------------- I must apologize for being so late in answering your memo. BY.5/G.3.I.38 which was most clear and very interesting. We have since had occasion to discuss very thoroughly with GWH{George W. Hancock - Head Chateauroux} the question of servicing generally, and the bearing position, and whilst in agreement with GWH{George W. Hancock - Head Chateauroux} on a lot of points, I do not wish to adopt for the Continent the Kingsbury methods entirely, as experience over many months has given us sufficient information to enable us to adopt the following method of servicing bearings on 4 1/4 litre Bentleys :- When carrying out an R.IO at between 16,000 and 20,000 kilometres (9,942 to 12,428 miles), we remove the bottom half and step the liners. I do not consider it necessary, and I feel sure you will agree, to remove the upper half bearings by turning it round the crankshaft, etc., as suggested in your memo., for the following reasons :- What we do at 10,000 miles is to take up the slack in the bearings, and I do not think that it really matters whether this slack is taken up to the last thou. What we are after is to get cars into a condition where we know from experience they can be relied upon, except in exceptional cases, to go to 30 to 35,000 kilometres (approximately 18,642 to 21,749 miles) which is the mileage at which we have gradually taught our customers their cars should undergo a B decarbonize. At this moment, we remove the engine and carry out the big job, fitting white metal No 7 etc. By adopting this method, we are saving the Company considerable expense, as in reality the customer pays for a large amount of the work done in each case, and if we work our profits on these two jobs against the extra expense incurred in carrying out in one case the tightening up job, and in the other case the big job, the actual expense is relatively small. We find, and I have been very thoroughly into the job, that with the experience we have we are quite satisfied that when taking up bearings from underneath, ~~and you will admit,~~ getting down to the last thou. seems somewhat of a myth with the actual bearing metals, as it is evident that before the cars have gone very far after the tightening up operation has been carried out, there is again a certain amount of slack. ................ | ||