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).
Oil turbulence in the sump, reduced oil pressure, and a performance comparison with a Bensport model.
| Identifier | ExFiles\Box 179b\3\ img311 | |
| Date | 13th March 1938 | |
| -4- which shows that the heat from the oil to the aluminium is the controlling factor. OIL TURBULENCE IN THE SUMP. In all the road tests and figures referred to in this report, provision was made to ensure the maximum turbulence in the bottom half as shown in the attached photograph. All the relief valve oil was taken through three fishtail shaped jets, one in each compartment. Therefore we think that the ribbed sump has had the best chance without going to considerable complication, or putting ribs on the inside as well as the outside. Some tests carried out on the bench blowing air across the bottom half show, at 100°C, that the gain due to turbulence on the ribbed sump is about 15%, but this becomes less with temp. increase until at 115°C it is negligible, presumably due to the reduced viscosity. (Hs.{Lord Ernest Hives - Chair} 930) REDUCED OIL PRESSURE. We have previously pointed out that reducing the oil pressure to 20 lbs/sq.in. lowers the B.Th.U's to the oil by 20%. This gain is cancelled by the fact that with the reduced oil flow caused by this pressure reduction, the inlet oil temp. must be reduced 15% to ensure that the bearing temp. is no higher than previously. However, one advantage of reduced oil flow is reduced oil consumption (Curve Hs.{Lord Ernest Hives - Chair}954 attached). For this reason only we may prefer to run with lower oil pressure. COMPARISON WITH BENSPORT. The question has been raised as to why Bensport, with a comparable B.H.P. output/litre, appears to be so much better off than Peregrine on the road. One point is that whilst Peregrine can be driven at 4300 R.P.M. for long periods at a stretch, 4000 R.P.M. on Bensport can, as a rule, only be held for a few moments at a time owing to the higher road speeds. It will be recalled that on Brooklands we got 110°C. oil temp. on Bensport with quite low air temps. | ||