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).
Notes on American aero-engine design, specifically Pratt & Whitney and Wright Cyclone blowers and connecting rods.
| Identifier | ExFiles\Box 27\3\ Scan215 | |
| Date | 15th May 1939 guessed | |
| 9. performance above 15,000 feet. Mr Hobbs regrets not having for taken this up earlier, and he now has under development 2-speed and 2-stage blowers. He said that the 2-stage blower had agreeably surprised them by exceeding expected efficiency and it was giving results within 3% of the exhaust turbo. The Pratt & Whitney Blower has a cone clutch and oil is used only during the acceleration stage, after which the clutch is locked mechanically. Pratt & Whitney use a single shrouded impellor, and they are adopting plain bearings on their later types. Pratt & Whitney have overcome blower flooding by fitting a small sump and a leak to the induction system fitted with a light valve which is closed by engine suction. The leak is open when the engine is stopped and serves to prevent any build-up before the engine is started. Connecting Rods The Wright Cyclone Master Rod has been stiffened appreciably and now has no drilled or tapped holes in the main flanges. The flanges are nonagonal in outline with recesses milled between the wrist pin holes for lightness. The shank is H section (i.e. at right angles to our normal practice). The wrist pin holes and the main and gudgeon pin bores are chromium plated to overcome fretting. The outside of the fixed big end bush is shot blasted before fitting and it is now retained by a serrated flange and jacking plate very much on the lines of the Bristol main bearing housing. Gudgeon pin bushes are made from solid bronze strip spun into a chamfer at each end of the gudgeon pin bore. Pratt & Whitney still have the solit master rod on the Twin Wasp but they have gone to a solid rod and built-up shaft on the '2180' and '2800' engines. The '2800' engine has floating wrist pins. Pratt & Whitney have had considerable trouble through wrist pin fretting; they use solid gudgeon pin bushes. | ||