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).
Pneumatic governors, piston and ring performance, and specifications of a blown Citroen diesel engine.
| Identifier | ExFiles\Box 133\3\ scan0058 | |
| Date | 3rd March 1939 | |
| -5- Pneumatic governors appear preferable to other types, and can be made to operate quite satisfactorily with a blower, a particular case shown us employing a centric supercharger driven by a single V.belt. These results line up fairly well with the information given us by A.E.C. Pistons & Rings. These items were stated to give very little trouble, ring gumming only being experienced when an engine ran for any length of time under steady load and speed, road conditions appeared easier on the rings. Taper rings were stated to be a complete cure for gumming, and if only tapered on one side were an easier production job. Under very severe conditions, however, it should be noted that R.R. have found it possible on air-cooled sleeve valve units to gum even taper rings. Top lands were usually made from .375" to .500" deep if not more, in an attempt to keep the top ring cooler. A heat trap formed between the crown and top ring in the form of a narrow slot was found to affect starting due to the reduction in compression ratio, but this improved as the groove filled with carbon. Oil consumption was also worse. Miscellaneous. (a) Citroen Diesel. At the conclusion of the visit, we were taken for a short run in a blown Citroen diesel car which it was considered would be very suitable for taxi or delivery van work on the score of fuel economy. The specification of the job is as below:- Capacity - 1.75 litres Engine Speed up to 3300 R.P.M. (has been run experimentally up to 4000). Compression ratio 20 : 1. Supercharged to 6 lbs by Centric blower driven @ 1.3 times engine speed. | ||