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).
Crankshaft wear, bearing materials, and the need for an oil flow testing machine.
| Identifier | ExFiles\Box 146\1\ scan0176 | |
| Date | 26th January 1938 | |
| - 2 - Sr.3/Crn.26.I.38. Another very important point is the question of crankshaft wear and ovalization. Whenever we take an engine down at approximately 30 to 35,000 kilometres (18,642 to 21,749 miles) and sometimes less, we invariably find that the crankshaft has worn as much as 4 thou., and one to one and a half thou. ovalization. We do not go to the extent of having these crankshafts rectified and renitrided, unless they shew more wear and ovalization still, but you will admit that it seems a pity to take great pains to get the right clearances, etc., when carrying out a complete job, when there is obviously going to be an unknown quantity represented by the crankshaft ovalization. I am beginning to wonder whether, in view of the fact of fitting white metal N° 7, and with the improved Brinall of the present day Hall's metal bearings we fit, it would not be advantageous in the long run to the Company, and to the customer, if, when carrying out the big job in conjunction with an R.20, whether it would not be advisable to fit a new crankshaft which we would have in stock - incidentally we have one now - and then at least we would be satisfied that the job is 100% when turned out, which at the present time is seemingly not the case, owing to the above mentioned crankshaft wear. So much for bearings. The next point concerns the oil flow testing machine. Do you not think that we should have one of these ? If so, could somebody please be instructed to make one of these for us, and have it sent over here ? As far as the 4 1/4 litre Bentleys are concerned, we are quite satisfied that it is unnecessary for the time being as an oil flow test on any car over here would only shew, as we already know, that the bearings need taking up, whereas Kingsbury, when an oil flow test dictates the taking up of bearings, remove the engine and carry out the big job. At 10,000 miles we take up the bearings from underneath, so as to carry out the big job later on. But this oil flow test would certainly be interesting for the 3 1/2 litre cars, and also for testing 4 1/4 litres in the future when having carried out all the modifications and fitted white metal N° 7 etc. etc. these cars have covered sufficient mileage to make us uncertain once again of their bearings. At this time, owing to the presence of white metal N° 7, which through experience has shewed an excellent steadying effect on the crankshaft, we will not be in a position to know what the condition of the bearings is, and to what extent they have hammered. ................ | ||