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).
Cup leather failures in EAC engines due to high oil temperatures and oil viscosity.
| Identifier | WestWitteringFiles\M\2April1925-June1925\ Scan19 | |
| Date | 21th April 1925 | |
| R.R. 493a (50m) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. -4- Expl. No. REF: Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}1/LG21.4.25. particular spot. Whenever a cup leather failed it was found twisted over to the top side of the piston at the point in question. It is therefore apparent that the temperature of the oil alone is insufficient to cause the leather to fail, but that when the leather is crushed between the piston and cylinder and the oil squashed out, the leather will rapidly perish. The dimensions of the cup leathers have not been adhered to by the makers and this may account for these failures. We have tried one cup leather in chrome made to drawing which we have given an intensive test with the oil above 90°C but so far it has shewn no signs of failure on an engine. High oil temp. of EAC. engines. Up till recently we have always expected (from 40/50 figures) the temperature of the oil to the relay to be between 50°C and 60°C as a maximum. Recent tests in France shew that in the warm weather the temperature of this oil may be expected to be from 80°C to 90°C. As will be seen from the attached viscosity curve of Prices motorine 'C'. The viscosity of the oil at 85°C is but little above 1/3 that at 55°C. This means that the cup leather must be a very good fit to cope with such thin oil, more especially as the relay has been given 50% more work to do owing to the fitting of the stronger return spring previously described. If the cup leather is made too good a fit, there may be a tendency for it to gum up in the cold weather, or it may perish due to heat of contact. It would be a very great advantage from the point of the relay if the maximum temperature of the oil in the EAC. could be brought within measureable distance to that on the 40/50. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||