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).
The initial testing of the B.60 cast iron engine, detailing performance curves, reliability, and crankshaft damper issues.
| Identifier | ExFiles\Box 123\5\ scan0199 | |
| Date | 1st December 1938 | |
| 1044 SECRET. By.{R.W. Bailey - Chief Engineer} from Rm.{William Robotham - Chief Engineer} c. Hs.{Lord Ernest Hives - Chair} c. Da.{Bernard Day - Chassis Design} c. Da{Bernard Day - Chassis Design}/Jnr.{Charles L. Jenner} Rm{William Robotham - Chief Engineer}8/R.1.12.38. B.60 CAST IRON ENGINE. We attach the latest horse-power curve which we have obtained from the cast iron engine compared with the B.III unit which has just completed the 15,000 miles' test. These curves are not truly representative of road performance, because the high power engine can develop maximum power up to 2,500 R.P.M. without detonation @ 6.9 c.r., whereas at 6.6 it is necessary to retard the ignition and lose power on the present standard engine. This was demonstrated in the curve given in Rm{William Robotham - Chief Engineer}1/R.26.10.38. The top horse-power is not as high as we expected, but for the time being we are perfectly satisfied to start off at this point with a new engine. We have, therefore, started 100 hours endurance at these horse-powers to demonstrate the reliability of the major components of the engine. At the same time, on a second unit we are developing inductions systems and the simplified crankshaft damper. The crankshaft damper is, of course, one of the outstanding problems on this engine since we have provisionally thrown away the spring drive with its complication. Investigation shows that no six-cylinder in existence that we can locate which has a crankshaft critical frequency similar to our own runs in service above 4,000 R.P.M. We are told from America that the reason for this is that if they do exceed this speed, they suffer from broken timing chains and gears. We believe, therefore, that the reason we have been able to run up to 4,500 R.P.M. on the Bentley in the past is because we incorporate a spring drive. Since, therefore, we can hardly limit our engine revs. to 4,000 it seems probable that we shall have to develop some simplified form of spring-driven crankshaft pinion, and in the interval may have to revert to our previous practice in order not to delay the introduction of the cast iron unit. We will issue a more extensive report when we have completed an appreciable amount of the 100 hours' endurance. | ||