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 ring flutter, its effect on oil consumption, and blow-by under different engine loads, including a related graph.
| Identifier | ExFiles\Box 132\4\ scan0105 | |
| Date | 19th October 1937 | |
| -19- Ring Flutter - Continued. The reason for this is put down to ring flutter which appears to be a critical radial vibration of the ring, and the explanation why this phenomena does not occur with normally produced block is that although the rings attempt to flutter the vibration is damped out by the irregularities of the bore which we know to be distorted considerably. It is possible therefore, that certain production engines are subject to this phenomena, if so, then there is a possible explanation why the 4¼ litre Bentley is inherently a worse car than the 3½ litre for oil consumption, the same thing of course, applies to the 25/30 HP. etc. From Fig.X we know that the peak of the vibration is approx. 4100 r.p.m., our calculated speed is approx. 4000 r.p.m. the calculated speed for 3½ litre Bentley is 4350 r.p.m., which means that the 4¼ litre car if driven in the region of 4000 r.p.m. for any length of time will give a worse oil consumption, than the 3½ litre car. FIG. XI Fig.XI shows the effect of reduced load on blow-by, it will be seen that blow-by is at its worst under full throttle conditions, this is only to be expected since the pressure and quantity of gas in the cylinder is greatly reduced under part load conditions. Flutter is no doubt there and under 'over-run' conditions would give very poor oil consumption. Whilst referring to ring flutter and in order to prove our method of calculating the approx. speed at which ring flutter takes place we have estimated the flutter speed of both the Merlin and 'Exe' engines. The Merlin ring according to our calculations should [GRAPH] TITLE: BLOW-BY CURVES SUB-TITLE: AEROLITE PISTONS, STANDARD RINGS CYLINDER BLOCK MACHINED ON CRANKCASE LEGEND: ① FULL THROTTLE ② 3/4 LOAD ③ 1/2 LOAD ④ 1/4 LOAD Y-AXIS: BLOW-BY (CU FT / MIN) X-AXIS: R P M.{Mr Moon / Mr Moore} GRAPH ANNOTATION: MTHS{Reg Matthews}/19.3.37 | ||