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).
Limitations of chassis engine pistons with spring skirts and proposing design improvements.
Identifier | ExFiles\Box 15\3\ Scan063 | |
Date | 11th May 1933 | |
To Sg.{Arthur F. Sidgreaves - MD} } from E.{Mr Elliott - Chief Engineer} Wor.{Arthur Wormald - General Works Manager} } X/040 E.8/HP.11.5.33. X.4553. X.7040. X.5040. X.4027. c. to Hs.{Lord Ernest Hives - Chair} By.{R.W. Bailey - Chief Engineer} CHASSIS ENGINE PISTONS. From the results we have obtained with running engines at high speeds on Bensport, Phantom 2 and Peregrine, it seems fairly clear that we have reached the limitations of our present type of chassis piston with the spring skirt. There is evidence of the skirt collapsing due to the excessive side thrust of the inertia loading at high speed, and it is likely that the "bucketing" about of the pistons in the cylinder bores has something to do with the failure of the ring stops. We have recently explored all possible ways of improving the design of the piston to meet the more arduous conditions arising out of the latest developments, and our efforts have been directed towards limiting the extent to which the piston can close up under load. If the piston were always at the normal working temperature, there is no doubt that the non-split skirt would do all we wanted, but some provision must be made to eliminate piston slap when the engine is cold. This therefore, suggests a design in which the piston is provided with certain portions which are not split, and others which are, so that both conditions can be met, the distribution of the non-split portions being such as to fully control the movement of the piston at high speed. We have just about to go on test a piston of the normal pattern having a longer skirt from which we expect some improvement, and we now propose to make up another set of these pistons from the same pattern, but machined in such a manner as to provide the dual control that we suggest. The increased length of the cylinder bores that we have recently added on the bottom end of the cylinder block gives us an opportunity of trying a piston of this type, as the lower horizontal slot we propose to add in the skirt must not be allowed to run out of the bore. E.{Mr Elliott - Chief Engineer} | ||