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).
Cylinder wear issues related to Aerolite pistons and lubrication, with a conclusion and suggestions for improvement.
| Identifier | ExFiles\Box 132\5\ scan0166 | |
| Date | 8th February 1944 guessed | |
| - 3 - When Aerolite pistons were introduced in "E" series 3½ litre; records show an immediate increase in rate of cylinder wear. The main difference between this piston and our conventional split-skirt type was running clearance. An increase in power was measurable /same with this introduction, because of this/difference. Later on 4¼ engines this clearance was reduced again, because of cold knocks. Until just prior to the war, production Test Dept. were actually fitting aerolite pistons by selection, with .0005" to a fit in the skirt. The skirt of the cylinder barrel has been lengthened on B.60 type of block, where another half inch has been added. Summarising, we may now list those factors which tend to reduce cylinder lubrication as affecting the B.40 type block :- 1. Small big end bearing clearances. 2. Longer cylinder skirt. 3. Smaller bore. Conclusion. My suggestion for overcoming the cylinder wear problem, is to run big ends with minimum clearance of .002, and chrome plate the bores. For 3¼ bores and less, we should try plating the bores for half their length, from the top. We have listed reasons why we may be getting less oil to the walls of our small fours, compared with the larger sixes. For reasons already stated, the wear results cannot be accepted with any confidence. There is no reason why the existing quantity of lubrication should not ample for a treated bore. Oil consumption is very poor on both engines, being in the region of 1000 M.P.G. and it ought to be between 2000 and 3000 M.P.G. FJH{Fred J. Hardy - Chief Dev. Engineer}/CTS{C. Trot Salt - Carburation} | ||