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).
Technical report discussing engine cylinder wear, oil consumption, and customer liability for 'fair wear and tear'.
| Identifier | ExFiles\Box 107\2\ scan0120 | |
| Date | 26th May 1938 | |
| (b). cont'd.{John DeLooze - Company Secretary} from the start. This will often result in a seized piston when carried to the extreme. Heading (a) gives corrosion wear effects, heading (b) results in an increased cylinder wear over the expected average, but Mr. Grant's cylinder bore wear figures do not seem to place him under either of these. Coming now to facts, the heaviest wear in any cylinder on Mr. Grant's engine was .005 at upper end of cylinder travel for an axial length of five sixteenth of an inch. .002 increase at midstroke with .001 ovality, this with some wear in the piston ring grooves was the cause of his increased oil consumption, which was a perfectly normal condition. The car was sent in to have the oil consumption brought back to normal, this could only be achieved by regrinding, but it was quite unnecessary from the point of view of good running or reliability I have the records of 35 automobile manufacturers and the cylinder wear under optimum conditions for private vehicles varies, for one thousandths of an inch, from 500 to 5000 miles, these are reliable figures supplied by the car makers, if we take the best figures given this means a wear at the upper end of cylinder of .005 (the customers actual condition) in 25,000 miles. For bus work with separate cylinder liners, hardened and tempered the corresponding figure is one thousandths in 2000 miles or .005" in 10,000 miles, the result of starting and stopping continually and getting rather wet mixtures when re-starting. There was nothing wrong with his engine in the first place, nor is there anything wrong now, the only issue at stake is, the owner objects to pay for "fair wear and tear" and he might as justly expect to be retyred free of charge as have a regrind and new pistons at our cost. This comparison is not a foolish one, in wet weather one can get tyre mileages of 8000, in dry weather on the same car with the same driver he will only get 4000, but in each case it is fair mileage for the conditions. I have dealt with this matter at length, as we must not agree to bear "fair wear and tear" charges because a customer makes himself awkward and my last word on this issue is that all customers must pay for regrinding, as there is no difference in the quality of the material or class of finish from engine to engine, and therefore the variations are due to the drivers conditions or idiosyncrasies for which he must be prepared to | ||