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).
Technical page discussing cylinder bore wear, focusing on blow-by measurement, thermostats, and crankcase ventilation.
| Identifier | ExFiles\Box 132\5\ scan0128 | |
| Date | 1st January 1939 | |
| Plate 2 CYLINDER BORE WEAR 7 (7) Close attention to the type of fuel used to ensure that it is properly vaporized; certain fuels may require special consideration. (8) The metal temperature must be uniform and as hot as possible within reason. This may require special consideration of the water circulation system. (9) The spark advance mechanism should be free from errors in its timing between the cylinders of one engine. The advance or retard should be readily adjustable by competent service people only, not the customer. Above all, the oil film appears to be the most important factor because every engine function attacks this film, either by weakening or destroying it. In group (a) air cleaners must be applied at entry to prevent more contamination, or there will be no means of directly checking the effectiveness of the ventilator, except by prolonged mileage tests. Even after tests have been completed, it is difficult to be certain that any unsatisfactory conditions that might exist may be due to poor ventilation, or because the blow-by is too great for any ventilator. The author finds that group (b) is the more exacting type to develop, but it is more positive. There can be little doubt that, if a depression equal to ½ inch water gauge is measured in the crankcase under running conditions, then no gas exists in this space. Fig. 16. Apparatus for the Measurement of Blow-by Fig. 17. Bypass Type of Thermostat Fig. 5. Flow Curves of Carburettors as Fitted to “Vauxhall” and Two Other Makes of 10 h.p. Engines --- Full throttle. – – – Part throttle. Graph Y-axis: MIXTURE RATIO—LB. OF AIR PER LB. OF FUEL Graph X-axis: AIR CONSUMED—LB. PER MIN. Fig. 8. Typical Blow-by Curve Graph Y-axis: BLOW-BY—CU. FT. PER MIN. Graph X-axis: SPEED—R.P.M. Fig. 18. Water Circulation System to Avoid Cold Operation [I.Mech.E., 1939] Fig. 19. Bleed Type of Thermostat Image labels: VALVE, BYPASS PIPE, BELLOWS Blow-by in Engines. Recently in England, close consideration has been given to blow-by in engines. This type of investigation has been a general practice in America for ten years, where it began seriously with the development of crankcase ventilators. Some engines were difficult to ventilate because the amount of gas passing the rings was greater than that which could be induced to leave the crankcase before it could contaminate the oil. Crankcase ventilators can be roughly divided into two classes: (a) That in which air is blown into the crankcase and arrangement is made for its exit. (b) That in which a slight depression is maintained in the crankcase and oil sump equivalent to ½ inch water gauge. The author favours a maintained crankcase depression, preferably equivalent to ¼ inch water gauge. This can, of course, be accomplished by connecting the carburettor air intake to the case. Past experience with this type of arrangement indicated that the jets sooted up. Further, as the vapour from the crankcase is acid, recirculation of this vapour through the engine is hardly good practice. The crankcase depression is checked at Vauxhall by means of a manometer fixed with one end open to the crankcase and one end open to the clutch housing. It is assumed that the position of the attachment of the manometer at the clutch housing end is such that the flywheel or road draughts will not affect the results. ‘Blow-by’ must be minimized before ventilators of the ejector type can be used. In fact, if the ordinary tubular ejector (Fig. 7, Plate 1) cannot maintain a depression equal to ¼ inch water gauge at 60 m.p.h., then the blow-by is also too much for long ring life and wear will quickly occur. If leakage of air into the | ||