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 investigation of cracks found between the valve seatings on Kestrel cylinder blocks.
| Identifier | ExFiles\Box 179b\3\ img390 | |
| Date | 28th March 1933 | |
| To R.{Sir Henry Royce} From Ha/LBH.{Mr Hall - Aero Design Engineer} c. to Ag. Hor. c. to Rg.{Mr Rowledge} By.{R.W. Bailey - Chief Engineer} c. to SP.{Mr Spinney} Ir. c. to Lp.{Mr Lappin} c. to Mr. Jaques. KESTREL CYLINDER BLOCKS: CRACKS BETWEEN VALVE SEATINGS. Since the completion of the overhaul period of 200 - 300 hours of a number of fully supercharged engines fitted to fighting machines, it is found that the above defect is very common with engines fitted to this type of machine. Approximately 80% of the 11 S. engines returned for overhaul on completion of 200 - 300 hrs. have developed cracks in the cylinder head between the valve seatings. Experimental experience shows that these cracks are not consequence of running water cooled at power above the rated figures. None of the cylinder blocks which have been used on experimental engines running up to 1000 HP. water cooled, have developed any cracks. No trouble has been experienced with the water cooled type test in this respect, including the two 2500 normal R.P.M. tests. When operating under R.C. conditions, however, the tendency to develop cracks becomes serious. Out of the three R.C. type tests, the last two have resulted in cracked cylinder crowns and most of the hangar running has had similar results. The most arduous conditions that have yet been found occurred during the cylinder head temperature experiments when, using a fully supercharged engine with the old standard water rails, cracked crowns occurred after a short period of running under "take off" conditions with the engine boiling; excessive head temperatures being recorded. Additional tests of this nature, but with the engine fitted with the large water pump and top water rails, showed that under water cooled conditions no excessive temperatures resulted. Running R.C. 3 lbs. boost had to be resorted to before excessive head temperatures recurred. Conclusions. As a result of this experience it appears that with the old standard water system, as fitted to all the 11 S. engines returned for overhaul, excessive cylinder head temperatures and cracked crowns will occur if the engine is allowed to run | ||