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 performance issues including wristpin fits, city driving complaints, and oil suitability.
| Identifier | ExFiles\Box 16\1\ Scan103 | |
| Date | 10th March 1926 | |
| -2- 2. Wristpin fits. Present very tight wristpins are used here and at Derby successfully. Scoring on the wristpin diameter is not general. Seizure is still on the 45° line where it has always been. A tight wristpin should hold the piston back and prevent it scoring on the wristpin diameter, possibly making it tight on the diameter at right angles to the wristpin. 3. Complaints from cities. This is general. We have known for years that pistons tend to tighten up and give "tight knocks" when run gently for long periods when newly fitted. Cylinder bores can be seen to be dry under these conditions. When run hard as in summer time there is little or no trouble. In winter with lower speeds, less use of extra oil, and starting difficulties, there is almost always more trouble than in summer. For the same reason city running is more trying than country use. 4. Oil. The general use of Mobiloil A in New York may cause trouble. The cars are generally in warm garages but stand about outside for long periods. Mobile A is too thick at low temperatures for these conditions. But since we have had such trouble in getting rid of the really heavy oils and substituting Mobile A for all year round use, we believe we should leave this condition alone. We recommend that on our own demonstration cars our depots should make a trial of Mobile A prediluted with not more than 5% of clean Kerosene. This will avoid the prevalent condition of non-lubrication on a cold engine. We are not yet prepared to recommend it for general use by our owners, but first require more experience on cars run by our own organization. From 200 miles on 69-JG can say that prediluted oil greatly facilitates starting and has no evident disadvantages. Engine is smoother than with new Arctic oil. 5. Use of pilot jet. We have not quite got used to the new (L.H.drive) pilot jet with extra oil connection. The new jet produces a finer spray than the old and uses about half the fuel. The connection of the extra oil we know prevents a breakdown of the oil-seal around the pistons, which occurs almost instantly when extra oil is not connected. | ||