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).
Gear rattle, bearing performance after endurance testing, and exhaust system comparisons.
| Identifier | ExFiles\Box 97\1\ scan0128 | |
| Date | 22th March 1938 | |
| -4- in action and can detect no difference in either condition in respect of gear rattle. Further confirmation of this result is to be carried out on Wraith with varying degrees of backlash. In the recent daily reports on Wraith (26.G.VI) there is a complaint of gear rattle which incidentally is running without cam balancers. The mileage is so near to completion of the 10,000 that it is not worth refitting the cam plungers until the car returns, but from our previous tests which includes the condition of .010 backlash we do not anticipate that the cam balancer will effect any improvement on these rattles. BEARINGS. In view of the excellent condition of the whitemetal main bearings and the Hall's metal big end bearings on 26.G.VI after 10,000 miles and the result of a recent endurance on Wraith III No.2 unit on the test bed, we consider that this bearing arrangement will be quite satisfactory for Bentley III. We should not be so confident but for the fact that the engine speeds on 26.G.VI have been as high as a normal Bentley and the endurance run on the bed carried out under Bentley conditions up to 4400 RPM. Attached are photographs of the bearings after the test bed endurance and although the intermediate mains are on the point of failure, they have done remarkably well considering the severity of the test, 68 hrs. endurance, 122 hrs. general development and 1700 miles on the road. The Hall's metal big ends which are of thin section and run only the last 46 hrs. endurance are very good, though there are signs of the No.5 big end being short of oil through the cracking up of Nos. 5 and 6 intermediate mains. Similar, thin section bearings with flanges have been adopted for Wraith and are fitted to 26.G.VI. Looking at these pictures one might suggest that some width could be safely sacrificed off the big ends and given to the intermediate mains. We do not propose to do anything until after a 15,000 miles test on B.III indicates the necessity. EXHAUST SYSTEM. In order to obtain some data respecting the comparison of 4 port and 3 port exhaust systems for future design of cylinder heads, the UHC engine has proved extremely useful by having 6 port exhaust and by arrangement of the manifold converted in effect to a 3 port or 4 port head. | ||