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 on piston design, eccentric grinding, performance after dynamometer testing, and service results.
Identifier | ExFiles\Box 148\3\ scan0021 | |
Date | 1st June 1923 | |
- 2 - EP{G. Eric Platford - Chief Quality Engineer}7/Hl.6.23. "By reducing the eccentricity of the eccentric grinding, the join between the eccentric and circular grinding is so gradual that no sharp, hard edge is left at the edge of the bedding portion when the cylinder is blued and the piston worked up and down in it, and there is no tendency to seize on this line. This blend we find far better than can be done by a man with a file. So much for theory. Actually, due to distortion of pistons and errors in setting up, the bedding on perhaps 50% of the pistons does not come central and a little filing is necessary as indicated at A or B to prevent a hard bearing on the 45° diameter of the piston near the top of the skirt, where we find that seizure is liable to occur. Mosedale's hand-work on pistons, is, however, largely reduced. On test after first dynamometer, most of the pistons need filing a little on the 45° line near the top of the skirt or just touching near the bottom to remove hard spots. After second dynamometer, practically none need touching at all. A set of these pistons has run about 24,000 miles and is still in excellent condition. These long pistons have been put in about 400 cars, the first being delivered to the owner just a year ago. None have come back for service yet. We have fitted a number of sets on service to replace older types and have found that, lacking the heating effect of the dynamometer, these have distorted in several cases and given "tight knocking". After easing, they have been O.K. and have given no further trouble". The point I am anxious to bring to your attention is that I feel they have an advantage in the eccentric grinding of their pistons, in so far as the offset is also accompanied with a slight taper which allows the length of bedding surface to be somewhat more at the bottom of the skirt than at the top. Apart from this I do not recommend we should make any alteration to our present procedure. Will By.{R.W. Bailey - Chief Engineer} and Hs.{Lord Ernest Hives - Chair} please note the remarks on the above report as to the "Service" obtained with their long skirt type pistons. EP.{G. Eric Platford - Chief Quality Engineer} | ||