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).
Kestrel engine development tests concerning crankcase and bearing issues at Peregrine ratings.
| Identifier | ExFiles\Box 115\2\ scan0375 | |
| Date | 10th January 1939 | |
| Lp{Mr Lappin}/Lov{Mr Lovesey}/Ply.2/WJ.10.1.39. DEVELOPMENT ON KESTRELS AT PEREGRINE RATINGS. Cracked crankcases were found on engines Exp.5 and Kestrel 8489, the cracks being in the centre main bearing panel - See photo KF.6. attached. These were attributed to excessive load on No.4. main bearing at the higher speeds and powers involved in running at Peregrine rating i.e. 2850 against 2600 rated speed. As will be seen by reference to the blueprint No.1 attached, the loads on the centre main bearing are considerably decreased by using a balanced shaft and so on this account a balanced shaft was advocated. After a test on K.3377 with an S/NCR unbalanced shaft the bearings were found to be good but had considerable wear, this was attributed to the softness of the shaft. No.4. bearing cap was cracked which was again an indication of overload. A further test in favour of balancing was made on K.4329 which had a nitride hardened VCM. unbalanced shaft, both halves of No.4. main were scrapped owing to bad pitting of the lead bronze. The remainder were fairly good - see photo KF.10 attached. So far everything pointed to the need for balancing but there were two variables: balanced or unbalanced shafts and S/NCR soft shafts or VCM. nitride hardened shafts. No balanced VCM. shaft was run in a Kestrel on Peregrine development. K.3377 went through a further 100 hours at Peregrine rating with a soft balanced shaft and the bearings were good at the end of this test. One unusual fact was that No.7. journal was badly worn which may be an indication of the trouble which developed on the first Peregrines. The last two tests on Kestrels were made on K.4329 and 3377. K.4329 was run with an unbalanced VCM shaft which showed slight pitting of pin and journals but the bearings came out very good being an improvement on the last test on K.3377 (see photo KF.12). | ||