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).
Engine idling performance and detailed observations on valve gear components, wear, and potential improvements.
| Identifier | ExFiles\Box 123\5\ scan0103 | |
| Date | 30th September 1938 | |
| -3- Idling. The idling though not specifically tried for as yet, appears good and when the unit is reassembled we are by means of the tappet clearance going to determine what the maximum overlap that can be run with, without detracting from the idling. This will be useful information for the new camshafts now being designed. Valve Gear. Regarding the quietness of the valve gear, a definite opinion could not be established owing to the tappets riding on the radius of the camshaft due to the end float of the latter. As far as we could detect, however, the quietness of the remaining tappets was fairly good. The camshaft is located by a pressure spring, but we consider that the end float should be controlled so that it could not have more than say .010 end float irrespective of the spring. The inlet valves, No.1 in particular, shows very bad wear and plucking in theguides. Considering the geometry of the rocker movement, during its lift relative to scrubbing, this is in line with the standard practice of all our engines, i.e. scrubbing or thrust taken all one way. The one difference to standard practice is that the guides continue by approximately .2", nearer to the top of the valve on B.60, which does limit the fore and aft movement of the valve due to the scrubbing of the valve. We consider that the high guide of the B.60 is preferable to a low guide in that it gives more control over keeping the valve square on its seat, thus reducing the tendency to tappets being noisy through seating on a false seat. When the unit is re-assembled we are going to prime the valve stems with oil from the start to assure that the plucking and wear has no connection with lack of oil in the early stages of running. If, despite the above lubrication, the valves still pluck and wear, then we are going to try the experiment of reducing the scrubbing to a minimum, i.e. the | ||