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).
Comparison of engine designs, piston treatments, and single-plate clutch specifications.
| Identifier | ExFiles\Box 173\1\ img318 | |
| Date | 12th February 1934 | |
| -2- The Lincoln people make the statement that they have changed to the four bearing engine entirely from an engine smoothness point of view and not from price considerations. It is difficult to make any comparisons between the two designs because the car we tried in England had more rubber in the engine mounting and about 5-1 C/R against 6.1 C/R of the new job. Actually I tried two of the latest cars, and whilst they were improved with regard to suspension, front end steadiness, etc. consider the engines were definitely rougher. However, the general impression here seems to be that at present it is the exception to get a smooth engine with 6-1/R or over. Other details of the car of interest are - BOHN ALUMINIUM PISTON OF ALUMILITE WT. Bare 12 1/4 oz. treated by the new oxidizing process, i.e., placed in a solution of (oxalic acid) } 35-40 min. (H2SO4) } at 80°C. (H2O) } and subjected to a reverse plating current. This is the same piston that Cadillacs have adopted and all speak highly of this facing process which obviates scuffing and the necessity for much running in. I will get a set made to suit the Bentley and bring them back with me. SINGLE PLATE CLUTCH. They fit a long clutch. Have gone back to a single plate after having used a double plate. They like the single plate much better for smoothness of engagement and gear change. The change has been made possible by improved mechanical efficiency of clutch gear. Figures they gave me were:- Separation of plate 3/16" Pedal Travel to obtain - 2-3/8" Spring Pressure - 1800 lbs. 12 springs 6 fingers. These figures do not seem very convincing and as it was brought out as a complete unit they did not know much about it. I measured the friction disc, however, fabric on the driven member. Inside dia. 7.00" Outside 11.875" | ||