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).
Analysis of Kestrel engine connecting rod bearing failures and the effects of oil grooves and bearing materials.
| Identifier | ExFiles\Box 179b\3\ img165 | |
| Date | 7th February 1933 | |
| ORIGINAL To R.{Sir Henry Royce} From Hs.{Lord Ernest Hives - Chair} c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to Rg.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} Hs.{Lord Ernest Hives - Chair}7/WJ.7.2.33. KESTREL CONNECTING RODS. X3859 On the engine on which the big end bearing of the articulated rod type failed when attempting the high power test we machined grooves in the journal bearings. Except for the one connecting rod bearing which was replaced nothing else was altered. Since the oil grooves have been fitted we have completed the two hours test a 900 HP. twice. There has been no sign of trouble with the bearings. We are continuing to run the engine until we have completed ten hours at 900 HP. We do not look upon this as a conclusive test but we think it supplies very good evidence that increased supply of oil to the big ends will protect them. From examination of the engines which have failed we think it is definite that it is not a general deterioration of the bearings which causes the failure, but a very sudden collapse. In a number of cases the rest of the bearings in the engine were in excellent condition. We have records of four Type Tests with a continuous supply of oil to the big end bearings. From the Type Test results, comparing them with four tests without the grooves, there is no outstanding difference. We think the value of the grooves comes in when there is a scarcity of oil and it enables the oil to get back on to the bearings more rapidly. We have had one phenomenally good set of big end bearings. These were white metal lined. They ran on a hardened shaft and they were bearings of the wider type. We cannot say that on other engines bearings of the wider type showed up this outstanding advantage, neither can we say that the hardened shaft is entirely responsible because the last Type Test we ran with hardened shaft with the white metal bearings they were bad at the finish and on the point of collapse. The other feature which may have been a contributory cause of the excellence of the bearings was the fact that the engine was fitted with two piece cylinder blocks. It may be that when we have liners which keep free from distortion the | ||