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 crankshaft and journal wear, and the results of endurance tests on RR.56 big end material.
| Identifier | ExFiles\Box 115\1\ scan0196 | |
| Date | 15th December 1936 | |
| -8- No.3 & 5 are drilled midway between Nos. 2 & 3 and 4 & 5 throws. No.4. is in line with No. 3 & 4 throws. From this it will be seen that if the wear were due to the driving load and pressure exerted on the throws, then Nos. 2,3,5 and 6 journals would be expected to have the wear continued over a bigger area of the journal than on Nos. 1 and 7. As it is the peak wear in each journal comes at the centre line of the oil feed holes. Several theories could be put forward in respect of the above with regard to the oil feed but as we are running several units with an extra feed hole in the journals, the latter will no doubt give us further information. Bad crank wear comes out at .002" on the maximum diameter and .005" on the minimum diameter. The last 15,000 miles test on 6.B.1V. which had an external Tecalemit filter came out at .0005 on the maximum and .0025 on the minimum diameters. The hardness figures with our standard V.C.W. crank which is nitrided comes out at approximately 640 and further experiments on wear are to be continued with a Kykro crankshaft in which hardness figures up to 900 can be obtained. Bow as measured at the centre relative to the ends is rather bad on some of the Bentleys coming out at .010. This means that there is additional loading on the centre main bearing and regrinds are made more difficult in order to finish with a true shaft. (7) Summary The conclusion from our tests is that RR.56. is the best big end available and is backed by Leylands' experience and also our running on solid rods in RR.56. which ran 25 hours endurance plus 1 hour at 4500 R.P.M. continuous. Although the ultimate failure was due to weakness of the cap the bearing surfaces had been very satisfactory. Adoption of RR.56. solid shims is both cheaper and more satisfactory. continued | ||