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 bearing failures in Phantom III and B.56.BN Bentley vehicles.
| Identifier | ExFiles\Box 83\4\ scan0060 | |
| Date | 9th November 1938 | |
| X766a Bentley Copy HOTEL DE FRANCE. CHATEAUROUX, Indre. France. GWH{George W. Hancock - Head Chateauroux}/S/JAB. 9th November 1938. To. Ha/Rm.{William Robotham - Chief Engineer} From. G.W.H. Failure of Bearings. 31.EX.PHANTOM III. & B.56.BN{W.O. Bentley / Mr Barrington} BENTLEY. PHANTOM III. The failure of the fork bearings of the connect-ing rods was due, in our opinion, to hammering blows and possibly crankshaft vibration, although the latter had not been noticeable whilst driving the car. We do not think the shell is sufficiently supported. The white metal in our opinion, is reduced in thickness too much and will not stand up to the distortion effects. The bearings show very distinctly, that the metal first cracks, on the outer sur-faces. It is then pounded into fine pieces which eventually fill up the lubricating centre hole. This is what had happened with the rod that failed. The assumption that the failure of the oil cooler matrix was the cause, due to rise in oil temperature, can be very definitely dispensed with. The report of oil in the water was correct. The report of the Oil Cooler matrix leaking was correct. The leak of oil however was comparatively small as only one seam of one tube had opened out, consequently as far as the oil cooler was concerned, there was no loss of its efficiency. No water had entered into the oil system, on either occasions when the matrix was leaking. The sudden rise in oil temperature was due to the cutting off, of the supply of oil to No.2 connecting rod bearing, the heat generated being absorbed by the oil passing through the crank pin. It will be remembered that we have had similar failures occur when no oil cooler has been fitted. In our opinion, the bearings have not sufficient thickness of white metal & are not sufficiently supported. BENTLEY. B.56.BN.{W.O. Bentley / Mr Barrington} HALLS WHITE METAL. In our opinion, the failure of these bearings is due to the metal being too brittle. It may be caused by a change in the characteristic of the metal during running, various changes of temperature, which Mr.Hall could verify. The adhesion of the metal to the shell seems to fail and not being solid is broken up by the ham-mering blows. The symptoms however, especially upon the first examination would point to brittleness, also to the fact that as in the case of the Phantom, the shell of the bearings are too thin, but we admit that this should not apply to the jurnal bearings. G.W.H. | ||