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).
Technical report discussing engine component design, failures, and performance improvements.
| Identifier | ExFiles\Box 179b\3\ img268 | |
| Date | 17th February 1933 | |
| -3- He.7/W.17.2.33. Cont'd.{John DeLooze - Company Secretary} our oil consumption down except by having the ring at the bottom of the piston. We think however that this position could be reviewed in conjunction with the two-piece block. We know that the two-piece block is very much better for pistons. This might therefore allow us to use a shorter piston and still get better reliability than we do with the present cylinders with distorted liners. We have great hopes of this. The other point of course with the two-piece blocks we should be able to keep our oil down better. We might allow the piston to run out a little at the bottom and still retain the same length of piston. It is therefore well worth trying an engine with a standard crank, articulated rods, and two piece block. All these parts are available so there should be no difficulty. The fact, of course, that the articulated rod demands a different width of bearing means that we have upset our interchangeability of crankshafts but we should get a slightly larger capacity for approximately the same weight. Another point which is causing us great anxiety on the engine is the .475 gears. At the moment we cannot say that we have got a satisfactory .475 reduction gear yet this gear is proved to be the most efficient ratio for the aircraft. We have a modified gear which we expect to have on test next week. On the question of valve failures. We have now had failures with both Silchrome and Firths Crown. They both burn away on the seat in the same way. The advantage the Firths Crown has over Silchrome is that it is stronger at high temperature and the valves do not stretch, but although they do not stretch they still burn. We are proposing to try out some valves with the larger stems as you suggest. The powers we are running at of course are much higher than the engine will ever be asked to run at. At the present time I attribute a large amount of the success of the air-cooled engines to the fact that they know just the limit they can work the engine to and they push them to that limit. For instance, the U.S. air cooled engines which we consider are in advance of the engines made here operate the engines entirely by the use of a thermo couple fixed to the hottest part of the cylinder. They do not make use of the boost gauge, they know the limit at which the cylinders will operate and they work right up to that limit. We are not working anywhere near our top limit on temperature. We have never yet seen one of our engines either Schneider Cup, Miss England, or Service engines, which have | ||