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 conditions, bearing failures, and oil consumption analysis for cars 93 NK and 9 G.III.
| Identifier | ExFiles\Box 71\4\ scan0263 | |
| Date | 22th June 1925 | |
| 48840 Hotel de France, Chateauroux, Indre. France. To: "HS{Lord Ernest Hives - Chair}" From: G.W.Hancock. ------------------ Conditions under which temperatures are given for 93 NK, on the 21st inst., are as follows :- Bonnet shutters closed, with following wind, speed 70 m.p.h., distance four miles. Water temp. 91°C. Air temp. 26°C. Oil temp. 91°C. With wind - water temp. 87°C. Oil temp. 87°C. Air temp. 24°C. Car turned round and run over course again for this test. Conditions for 9 G.III., on 21st inst., :- Five miles run. Full throttle - approx. 60 m.p.h. Cross wind. Radiator shutters in either case full open. Water temp. 98°C. Air temp. 24°C. We wired to you to-day, as follows :- " Ninety three NK Number three conrod bearing " " seized Number five metal cracked Number six " " badly scored These will run We have one " " spare rod here stop Wire instructions ' " " Hancock. " This has occurred on the morning's run; engine pulling up through tightness, but freed itself in a few minutes. Car returned to garage at moderate speed, and bottom half was taken off, and rods taken out, for examination. No. 3 rod had seized. The metal has partially run. All the other conrod bearings give the appearance of being on the tight side. There are hard marks on all of them. We can say definitely that these rods were not put up tight. It gives one the impression that these are tightening up during the run, although we have never noticed this. One peculiar thing is that the oil pressure never fails, or gives any sign or warning, when these rods go. In the present instance, the engine was 3/4 full of oil, the oil pressure being 15 lbs. A remarkable thing is that on yesterday's run, the oil consumption had dropped some 200 miles to the gallon, and on this morning's run the oil consumption dropped to 260 m.p.g. This, as far as I can say, is due to an increased oil spray from conrod bearings, and is being flung up on to the pistons, and thereby being thrown out, or burnt. We cannot see any other explanation for this. We are taking this opportunity to dismantle clutch, for investigation purposes. | ||