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 comparison of piston scuffing in various Wraith, Bentley, and 25/30 HP engines.
| Identifier | ExFiles\Box 9\1\ 01-page13 | |
| Date | 2nd February 1938 | |
| COPY FOR FILES. WRAITH PISTON SCUFFING. In addition to the Wraith engines we have also had scuffed Pistons in the engine of O.B.IV, the Bentley for 10,000 miles, and a comparison is tabulated below of the conditions under which the various Wraith engines, Bentley and 25/30 H.P. engine of a year ago, have been run. | | WRAITH 1 | WRAITH 2 | WRAITH 3 | WRAITH 4 | WRAITH Prod. | Bentley O.B.IV | Bentley Prod. | 25/30 1936/7 | |---|---|---|---|---|---|---|---|---| | PISTON | R.R.Split Skirt | R.R.Split Skirt | R.R.Split Skirt | RR.Split Skirt | RR.Split Skirt | Aero-lite | Aero-lite | RR.Split Skirt. | | PISTON MATERIAL | RR.53 | RR.53 | RR.53 | RR.53 | RR.53 | RR.53 | RR.53 | RR.53 | | CYLINDER MATERIAL | No Chills | No Chills | No Chills | No Chills | No Chills | No Chills | No Chills | No Chills | | OIL | "Arctic" | Mot.C | Mot.C | Castor | De Laval | Arctic | De Laval | Mot.C | | COMPRESSION RINGS | EW1536 High Press. | EW1536 High Press. | EW1536 High Press. | E60820 Std. | EW1536 High Press. | E60820 Std. | E60820 Std. | E60820 Std. | | SCRAPER RINGS | EB3122 High Press. | EB3122 High Press. | E60821 Std. | E60821 Std. | E60821 Std. | EB3122 High Press. | EB3122 High Press. | E60821 Std. | | CONDITION | Seized | Seized | Seized | O.K. | O.K. | Seized | O.K. | O.K. | From this table it will be seen that the high pressure rings have little to do with piston scuffing since we have cases of both types of rings in engine with scuffed pistons. It can be seen, however, that in all cases where there have been no chills in the bores the seizures have occurred when either Motorine "C" or Mobiloil "Arctic" oils have been used. Piston design in itself does not appear to be the cause of the trouble but one thing is common to all engines and that is | ||