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).
Problem of cylinder bore wear in engines, particularly Bentleys.
| Identifier | ExFiles\Box 132\4\ scan0148 | |
| Date | 6th July 1938 | |
| Hm{Capt. W. Hallam - Head Repairs}/CTS.{C. Trot Salt - Carburation} from Rm.{William Robotham - Chief Engineer} c. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} Rm{William Robotham - Chief Engineer}2/R.6.7.38. CYLINDER BORE WEAR. We believe that at the moment the weakest part of our engines, particularly on the Bentley is the rate at which the cylinder bores wear. With the overdrive gearbox and larger journal bearings, coupled with aluminium tin big-ends, improved lubrication and large oil pumps, we believe that no matter how hard a car is driven our bearings should now last 50,000 miles. It is apparent, however, that from statistics available from Kingsbury many Bentleys are being re-bored at less than 30,000 miles, and the average is little better than this figure. The most disturbing feature of this cylinder bore wear is that we know very little about it. We have proved conclusively that, in customers' hands, the split skirt piston reduced cylinder bore wear by 33-1/3rd% compared with the Aerolite. So far we have absolutely no explanation as to why this should be so, nor have we done any intelligent experiments to find a reason. We have no first-hand information as to the effect of various cylinder bore materials on the type of wear that worries us most, i.e., the sort of wear produced by constant stopping and starting in London traffic. All our information on this source is second-hand. Leylands tell us that Phosphor-Chrome liners give far the best results; in spite of this we are using Sheepbridge Stoke liners in our P.III engines. If Leylands can cast Phosphor Chrome in their Foundry we can do the same thing. We are in the happy position of having a number of Wraith engines fitted with loose liners. These should be exceedingly useful for studying bore wear as they are economical all round. We have gone to the trouble of making a rig which can be run in the cold chamber. So far although the rig has been completed for more than six months, we have not seen a single piece of useful information which has been obtained on it. We do know that many people have said that by starting and stopping an engine repeatedly a very large quantity of wear can be produced in a fortnight. If we can produce measureable cylinder bore wear in a fortnight, we should be well on the way to finding something out about the problem. | ||