Piston tap issues and revised running clearances.
| Identifier | ExFiles\Box 48\1\ Scan105 | |
| Date | 20th September 1919 guessed | |
| To By. {R.W. Bailey - Chief Engineer} from Bm. c. to WCr. c. to Hs. {Lord Ernest Hives - Chair} c. to Hr. X4190 chassis Bn {W.O. Bentley / Mr Barrington} 6/W22919. RE PISTON TAPS AND RUNNING CLEARANCES. Confirming my conversation with you on the above subject. We believe that there is no complete cure for piston taps available at the moment. That is to say, we cannot instruct a procedure that will ensure that the Test Dept. experience no difficulty as regards piston taps when preparing cars for despatch, and we must expect cases of piston taps when at normal temperature, even when pistons and cylinders are found to be correct within the limits specified on the drawings. The limits specified on the production drawings are such as will give on the fitting portion ( i.e. the skirt) 9 to 10½ thousandths clearance at the top and 6 to 7½ thousandths clearance at the bottom when cold. The desirable clearances found by experiment were 9 thousandths at top and 6 thousandths at the bottom. We have therefore as maximum by these limits 1½ thousandths more clearance if the smallest piston is fitted to the largest cylinder. This increase in clearance is, of course, quite considerable, and must have considerable bearing on piston taps when hot. We think therefore, since it does not appear reasonable or practicable to reduce the manufacture limits given, that it is necessary that pistons and cylinders should be matched by selection and that the clearances between individual pistons and cylinders should fall within the following limits. Clearance at top of skirt .0085" to .0095" and at the bottom of the skirt .0055" to .0065". This new procedure will, of course, entail a modifica- | ||
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).