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).
Tests of an improved oil system for the Kestrel engine, aimed at preventing connecting rod failures.
| Identifier | ExFiles\Box 179b\3\ img345 | |
| Date | 20th March 1933 | |
| ORIGINAL To: From Hs{Lord Ernest Hives - Chair}/Yng. c. to Sr c. to Mr. c. to Ir. c. to Sp.{Mr Spinney} c. to Mr. Jaques. Hs{Lord Ernest Hives - Chair}/Yng.4/WJ.20.3.33. X2965 X3859 KESTREL CONNECTING ROD FAILURES. REPORT ON TEST OF IMPROVED OIL SYSTEM. Various tests have been carried out on the subject of connecting rod failures using a special invertable rig - photographs attached. These tests will form the subject of a separate report but the information given herein describes the scheme which so far has shown the greatest promise. The object of this scheme is to provide a supply of oil to the engine immediately the aircraft resumes the normal attitude after inverted flight. This has been achieved by using the scavenge oil pump to supply oil to the engine at all times when the pressure put up by the normal supply pump is below a predetermined figure. Diagram No.903 (attached) shews how this is accomplished. In operation, using a conventional oil tank, the relief valve in the scavenge oil line was set to 30 lbs/sq.in. On inversion, with the engine running at 2250 R.P.M. and an oil inlet temperature of 70°C., the main oil pressure slowly fell to zero. When the normal attitude was resumed the main oil pressure almost immediately rose to 20 lbs/sq.in. and fluctuated between this figure and the normal value (60 lbs/sq.in.) until the pressure pump had fully re-primed itself when the main pressure resumed its steady normal setting. Tests were carried out at various speeds and inlet oil temperatures and under all conditions the operation of the scheme was appreciably the same. Some doubt was entertained as to whether the pressure put up by the scavenge pump when supplying the engine was not largely due to air. A check was made therefore of the oil flow through the bye-pass after inversion. At 2250 R.P.M. and 60°C. temperature this was 3.75 galls/min. The pressure pump at the same speed and temperature delivered 3.25 galls/min. which is generally in accordance with the relative sizes of the two pumps. The total amount of residual oil in the engine after inversion is 1/2 gall. when using an oil system approx. the same as the Hawker Fury. In an installation where the oil tank is | ||