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).
Continuation of a report on engine component testing, detailing failures of valves, plates, and joints under various boost and tightening conditions.
| Identifier | ExFiles\Box 178\4\ img062 | |
| Date | 26th February 1940 | |
| EA/Cov. & Cyl. Heads. Cont'd.{John DeLooze - Company Secretary} rapidly when a low boost was reached which was also sufficient for failure of the shrunk in steel seat. The relaxed plates were in a different cyl. to the other couplings and the temperature values given are probably on the low side for the average. A special test (aero. ported) also gave failure at 41 lbs boost due to a burnt out exhaust valve seat. These tests were on std. service C.T.C.124 fuel. Overhaul boost tests (built at "overhaul") were started at 41 lbs. boost, but had to be reduced to 35 lbs. to get the 100 hours. The final test, did not go beyond 11 hrs. The detonation was, however, very severe and an exhaust elbow was cracked which would result in serious joint leaks. The engine did not fail or give issue however. There is some evidence now the limitation that over-rides all others on the power output that can be reliably obtained out of this engine will from the point of view of temperature attacks and special aero failures arising from these be the exhaust valve, seat, etc. The detail results of these tests will be available shortly. We have not experienced valve seat trouble on the later boiled antifreeze cooled Merlin III. The seat being the same as the "F" modification. A checkup reveals that the seat in the "C" type Glycol cooled Cyl. Head runs hotter than the Glycol "D" or "F" type heads. The reason for the valve being relatively cooled. It seems evident that some of life and time limitations will be necessary to cater for evaporative cooling conditions. Since the majority of all leaks occurred on the end nuts a short time ago we carried out some experiments on the effect of the degree of tightening the cylinders. On all engines we do these tests with 35 lbs/ft. tighten-ing, but due to the size of these tool post joints on these early engines. During these tests we went up to 100 lbs/ft and had no trouble with the studs. It was established from these tests that to close the gap, the joint must vary considerably from front to rear as low as 70 lbs/ft. to be effective. We have had engines run over 300 hours in service with-out leaks until they were brought in for a bulb test and the studs stripped before a point was reached, however, with that degree of tightness they were sent out. | ||