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).
Engine test report analysing the performance of grooved bearings and their effect on oil flow, pressure, and temperature.
| Identifier | ExFiles\Box 179b\3\ img185 | |
| Date | 10th February 1933 | |
| -2- Ho/Expt.3/WL/10.2.33. Cont'd.{John DeLooze - Company Secretary} It was then intended to continue the running for a further non stop period to make a total of ten hours, but after a further two hours A.2. cylinder shewed signs of over-heating so the engine was stopped and it was found that the front exhaust valve of that cylinder was burnt at the seating. The tests were discontinued, to avoid further damage. An analysis of the running time with the grooved bearings is as follows:- 6 hrs. at 891 BHP. 20 mins. at 1000 BHP. 2hrs. 30 mins. Light Loads. Making a total of 9 hrs. 10 mins. with no indication of bearing trouble. It is intended to complete ten hours running at 891 BHP. before examining the bearings for condition. It should be noted that on a previous test on this engine, prior to modifying the bearing, No.2 big end bearing failed after two hours running under high power conditions. Summarising the results of the tests, we find the effect of the grooved bearings is to increase the oil flow through the bearings to such an extent that the pump is not sufficiently large to supply the quantity of oil at the required pressure and temperature, the general indication of this being that the relief valve is choc-a-bloc, as noted by the variation of oil pressure with temperature, for when the inlet temperature is reduced to 40°C. the pressure will rise in excess of 90 lbs/sq.in. and decrease to 42 lbs/sq.in. at 70°C. In this respect it was necessary to run with inlet temperature of 65°C. instead of the normal 70°C. in order to maintain the oil pressure above 45 lbs/sq.in., under all conditions the release oil remains at 38 lbs/sq.in. A further effect of the increased flow through the bearings is to increase the temperature rise of the oil across the engine by 50% or from 21°C. as obtained with plain bearings to 32°C. temp. rise with grooved bearings running under same conditions. This is accounted for by the cooling effect of the oil on the bearings taking heat from that source and also by the increased quantity which is coming in contact with the underside of the pistons. This is borne out by the increased oil consumption, plain bearings shew 10.5 pts/hr. and grooved bearings, with increased flow shew 16 pts/hr., which although is an increase of approx. 50% is not excessive, as the specification | ||