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 overheating of Peregrine engine oil, discussing heat sources and potential reduction methods.
| Identifier | ExFiles\Box 131\1\ scan0071 | |
| Date | 13th May 1933 | |
| X4693 B. from Hs{Lord Ernest Hives - Chair}/En. C. Sg.{Arthur F. Sidgreaves - MD} C. Wdr. C. Ev.{Ivan Evernden - coachwork} C. Hy.{Tom Haldenby - Plant Engineer} C. Ds. C. RG.{Mr Rowledge} Hs{Lord Ernest Hives - Chair}/En.1/AT.13. 5.33. OVERHEATING OF ENGINE OIL. PEREGRINE. HEAT GIVEN TO THE OIL. The first test made was to measure the heat to the oil. The dry sump method was used as when on V.1515. The results therefore do not take account of any heat which was given to the oil and subsequently lost by radiation from the top and bottom half of the crankcase during the test. The B.Th.U's measured, however, may be taken to represent the heat that has to be dissipated on the road by the draught over the crankcase or separate cooler. The curve at once shows that the heat to the oil is not proportional to the piston speed but more nearly to the square of the piston speed. POSSIBLE REDUCTION IN HEAT TO THE OIL. It is undoubtedly possible to reduce the heat to the oil. Halving the oil pressure at once reduces the B.Th.U's to be dissipated under the worst conditions by 20%. Curve En.Pr.50. Previous tests on the 6 cyl. Kestrel showed that about 2/7 of the total heat to oil was due to the pistons, the remainder to the bearings. We measure 30% due to pistons at 70 M.P.H. on Peregrine on dynamometer drums. Therefore, though this proportion may not be quite correct, it suggests that keeping the oil off the pistons might be very profitable, whilst with a seven bearing crankshaft it will certainly be exceedingly difficult to accomplish in practice. Actual results of trying to do this on a 6 cyl. Kestrel are shown on attached curve Hs.{Lord Ernest Hives - Chair}J51. Furthermore it is becoming accepted practice to increase the heat from the piston to the oil by corrugating the underside of the crown, this suggests that a move in the opposite direction is likely to cause trouble. Under the circumstances we have, to begin with, accepted the quantity of heat given to the oil as being a desirable means of cooling highly stressed parts and the result of running a large diameter seven bearing crankshaft at very high speeds, and have concentrated on finding means of dissipating this heat. | ||