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).
Series of experiments concerning piston bedding and cylinder liner distortion on Kestrel engines.
| Identifier | ExFiles\Box 178\4\ img049 | |
| Date | 27th April 1932 | |
| 1. From MR/AEC. c. to JS.{Mr Johnson's Secretary} c. to MR. RM.{William Robotham - Chief Engineer} c. to H.{Arthur M. Hanbury - Head Complaints} IV. c. to LP.{Mr Lappin} KESTREL CYLINDER. A series of experiments have been carried out with the object of producing properly bedding pistons on Kestrel engines. Attention was first directed to the grinding form. Elliptical pistons, barrelled pistons and eccentrically ground pistons were produced but none gave the desired result, and on further investigation the trouble was found to lie in the distorted condition of the cylinder liner. It was therefore decided not to proceed with the question of piston bedding until liner distortion had been satisfactorily investigated. In order to obtain some data as to the actual amount of liner distortion which occurred, a series of static tests were carried out using a single type Kestrel cylinder with a stiff base plate to represent the crankcase. This base plate carried four cylinder studs and liners were fitted and pulled down as on the actual engine and distortion in the bore measured. Using a standard type liner the maximum distortion proved to be .005" across the diagonals formed by the studs, and was found to be most pronounced in the portion of the bore adjacent to the root of the rubber groove. To arrive at some basis, and to ascertain whether with present design it would be possible to entirely eliminate distortion, a plain parallel liner without rubber groove was produced this being as stiff as possible on all diameters consistent with limitations imposed by existing crankcase and cylinder block dimensions (Fig.1). When tested, the maximum bore distortion proved to be .003" thus proving that it was impossible to entirely eliminate distortion with existing design. It was considered that some improvement to standard liners could be effected by modification to the flange and tests were carried out varying the diameter and section of flange but without appreciable improvement (Figs. 2,3,4,7 & 8). A maximum distortion limit of .002" as on the main cylinder liner was aimed at in the next series of tests which consisted of liners with various forms and spacings of fins (Figs. 5,6,9 & 10). As a result the most satisfactory liner | ||