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 analysis of crankcases, crankshafts, and cylinders from Wright and Pratt & Whitney engines.
| Identifier | ExFiles\Box 27\3\ Scan216 | |
| Date | 15th May 1939 guessed | |
| 10. Crankcase Wrights are using steel crankcases extensively in production. Three patterns have now been produced for the cyclone, the latest one being a beautiful example of simplicity. With the exception of the 9-cylinder faces the whole case is turned, the main diaphragms are only about 3/16" thick. In order to overcome oil leaks a heavy section rubber ring is fitted into a plain chamfer on the cylinder port and rubber rings are fitted in inserts round the cylinder studs. On the old model Cyclone dural crankcase there is a slight relief on the cylinder facing between the groups of studs. Pratt & Whitney are using duralumin crankcases. The main diaphragm is now corrugated to give greater stiffnes. On the later 2-row engines they have adopted a plain centre bearing Crankshaft Crankshafts are not hardened. Wrights have the Menton type of built-up shaft, and they have now dropped the set bolt and are favouring a pinch bolt of the Bristol pattern. As already stated, Pratt & Whitney have adopted a built-up shaft with a special splined crankpin. They are using involute splines and say they are getting no fretting. Messrs Hobbs and Cronstedt, however, were interest in the Bristol Maneton design so that it would appear that the split crankpin is suffering from the troubles which one would expect. Both Wrights and Pratt & Whitney are very definite about the advantages of dynamic balancing, but do not feel that flapping or flexional vibration is a troubb, and do nothing to counteract it. Wrights, in fact, stated that their "floating kidney" dynamic balance weight had given some troubb through vibrating laterally, and they have accordingly designed a new fixing which allows no force and aft freedom. On the 2-row engines both 4. and 9th order dynamic balance is provided. Cylinders The Cyclone cylinder has a cooling area of 2300 sq.in. Fins are beautifully cast - 5½ to the inch, .070" thick. | ||