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 and main bearing measurements, partial seizure damage, and subsequent engine repairs.
| Identifier | ExFiles\Box 114\3\ scan0084 | |
| Date | 30th May 1938 | |
| Sr/VAII/ET.30.5.38 - 2 - 1. 2. 3. 4. 5. 6. 7. Crankshaft: Main Journals max.diameter.. 2.245" 2.244" 2.244" 2.244" 2.245" 2.244" 2.246" min. " .. .242" .242" .242" .241" .243" .243" .245" Ovality...... .003" .002" .002" .003" .002" .001" .001" Crankpins..... 1.998" 1.998" 1.9985" 1.998" 1.998" 1.9975" Main bearings: Sinkage in upper half.... .001" .002" .002" .004" .000" .000" .000" In caps....... .002" .006" .011" .009" .001" .000" .000" Average sinkage of big end bearings...... .002" .0015" .001" .0015" .0015" .0015" Crankshaft: Bow in centre = .012" Remarks: Nos. 2, 3 and 4 main bearings, but especially No4, had picked up due to partial seizure and these, it will be observed, have the biggest amount of sinkage. It is interesting to note that the two main bearings nearest No7 whitemetal bearing are almost O.K. We have carefully examined the engine: all the oil pipes are sound and we cannot account for the damage to Nos. 2, 3 and 4 bearings, unless there has been a shortage of oil. Do you consider that, owing to the state of the crankshaft (ovality, wear and bow), it could have affected Nos. 2, 3 and 4 main bearings? We are surprised at the condition of the crankshaft. We have had the crankshaft tested for Brinell hardness by Messrs. Aubert & Duval, who report that the Vickers/Brinell hardness of case is between 650 and 680. We have fitted a set of new main bearings and a re-conditioned crankshaft. We have also fitted a set of stepped liners to the big ends, to take up sinkage. Up to the time of writing, we have modified about 30 engines and this is the first time we have experienced trouble with main bearings on modified engines. We have now completed the repairs to the engine and have found the car to be very good on test. The engine was quite smooth and free from any sign of roughness or vibration. We shall be glad to have your opinion as to who you consider should pay for the above mentioned work. Sr/VA. | ||