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).
Piston ring design, focusing on the wedge-shaped oil film, wear characteristics, and scraping efficiency.
| Identifier | ExFiles\Box 178\1\ img143 | |
| Date | 19th May 1926 | |
| - 10 - being uniform, but increasing from its upper edge to a maximum at the lower, results in a wedge shaped oil film between it and the cylinder wall. The ring therefore tends to ride over the oil on the bore during its upward stroke, instead of pushing it upwards, and scrape it off on its downward travel. See sketch:- [DIAGRAM] WEDGE SHAPE OIL FILM. DIRECTION OF MOTION PRESSURE DISTRIBUTION DIAGRAM. SCRAPING OIL. The importance of fitting this ring the correct way up in the groove is at once evident. The trouble experienced with this ring - as one would imagine - is that wear takes place more rapidly on the greater loaded edge - lower edge - and so tends to produce uniform load distribution at the expense of "oil scraping" efficiency. Even with this fault there is no reason why they should not be employed because when worn to the form giving uniform load distribution they are equivalent to plain rings, and then probably better than new plain rings. EFFECT OF PISTONS:- The piston can exert an influence on the oil pumping as contd. | ||