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).
The testing of various cylinder heads, cylinder blocks, and an analysis of slow running performance.
| Identifier | ExFiles\Box 134\2\ scan0144 | |
| Date | 23th August 1937 | |
| -6- 23.8.37. (d) Cylinder Heads. Six cylinder heads have been tried, including two twin valve heads, one in cast iron and one in aluminium. These, however, due to complications in valve gear, were considered unsuitable to a main engine and tests were discontinued. Of the other four heads, two were in cast iron and two in aluminium and photographs of the combustion chambers are shown attached. Nos. 1, 2 and 4 heads had different throat areas, and comparative powere curves are shown on Fig. VII. No. 4 head was easily most suitable from all points of view including power, detonation, ignition advance, and cheapness, and is recommended for a main engine. (e) Cylinder Blocks. Three cylinder blocks were used, two of the cast iron type with 1.500 and 1.600 valves respectively, and one an aluminium block with a dry liner, fitted with a 1.500" valve. There was not much to chose between the two blocks from a power point of view, and, though no endurance on the alum. block was carried out to test the efficacy of the liner, no trouble was experienced in nearly 100 hours' running. It is considered, therefore, that either type of block would be suitable for a main engine. Some trouble was experienced with the 1.500 dia. valve due to its pulling into the seat. Shrunk in valve seats are, therefore, to be tried in both high speed steel and Duracrome. (6) SLOW RUNNING. This item, of course, is impossible to demonstrate practically on the single cylinder unit, and all we are capable of doing is to make all provision possible that we have already found advantageous on a main engine. The main points in favour of good slow running on this unit are:- (i) Valve timing with no overlap. (ii) Close proximity of plug points to inlet valve, allowing the fresh charge to blow straight across them. (iii) Consumption curves indicate that a quite considerable drop in power is permissible without the running becoming unsteady due to too weak a mixture. This condition persists even at small throttle openings. | ||