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).
Alterations to pistons, including ring stops, ring stiffness, and balancing.
| Identifier | ExFiles\Box 66\1\ scan0031 | |
| Date | 20th March 1925 | |
| X.8040 To R.{Sir Henry Royce} from E.{Mr Elliott - Chief Engineer} c. to CJ. HS.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} S E C R E T E1/M20.3.25. E.{Mr Elliott - Chief Engineer} A.{Mr Adams} C. PISTON. We received your memo. shewing sketches of alterations to pistons, and we believe that Lec.2030 which we had already sent to Derby and to yourself fully covers these instructions. We now send blue print of Lec.2035. shewing 5 rings all arranged for oil retaining as per your original scheme squeezed into this piston. Re. PISTON RING STOPS. We have shewn the .125 dia. ring stop as used on Goshawk, chiefly because it enables us to pin the bottom ring. There should be less liability to leakage of gas pressure with this smaller stop. We should suggest that these stops be made in gun metal or Delta metal instead of steel. It would then be possible to dress them flush with piston surface instead of .002 clear and they would not tend to become loose when the piston got hot, although we have not heard of any trouble in this latter respect. re. PISTON RINGS. We should like to suggest that slightly stiffer piston rings be tried with Lec.2035 than our present standard, with a view to getting better oil scraping at high speeds. The present rings require 1.5 lbs. to close them on the ends, or 3 lbs. average in the middle. The inertia weight of the ring at 3000 r.p.m. is 19 lbs. at the top dead centre. If the average inertia load were 10 lbs. and the co-efficient of friction .05 then there does not seem much interference with the freedom of the ring due to this cause. BALANCE OF PISTON. The heavier diagonal webs on the split side of piston can be balanced by a slight reduction in the thickness of the piston wall behind the rings on that side. Debiting the heavier webs with the material removed by the saw cuts the reduction should not be more than .050". E.{Mr Elliott - Chief Engineer} | ||