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).
Unsafe low oil pressure in Chassis 93 NK due to worn crankshaft bearings.
| Identifier | ExFiles\Box 71\4\ scan0280 | |
| Date | 7th July 1925 | |
| +8940 Hotel de France, Chateauroux. Indre. France. GWH.{George W. Hancock - Head Chateauroux}1/Crn.7.7.25. To: "HS{Lord Ernest Hives - Chair}" From: G.W.Hancock. Re Chassis 93 NK. We consider, after careful investigation, that it is unsafe to run this car at any high speed, or even at low speeds. When the oil becomes hot, our pressures are :- High speed ....... 15 lbs. Low speed ........ 5 lbs. The reason we give for this is that owing to the main crankshaft bearings being worn so much, the oil leak from these is so excessive that there is not sufficient pressure left to keep the conrod bearings oiled. We believe that owing to the good fit of the conrod bearings, the oil will not force its way through these whilst it has got the easier path to main bearings. The oil pressure we are getting is the difference between the amount the oil pump is delivering and the leak. By this I mean that if all oil supplies were blocked up we should not get any more pressure. You will see by this that practically no oil is being fed to the conrod bearings. I have proved this on the road. Before starting a run, the engine is perfectly free, and will bounce back off compressions. After a three mile run at 60 m.p.h., the engine becomes so tight that it is almost impossible to move it. I am certain that this is the cause of the last failure of conrods, we could, any time we like, run the present metal out of conrods. It is such that we shall be very fortunate if we do not run any bearings out when returning to England. In the meantime I have stopped all mileage tests. I am endeavouring to obtain data re steering with different tyre pressures. G.W.Hancock. | ||