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).
Investigating excessive vibration caused by a Leitner-Watts metal airscrew on a Condor III engine.
| Identifier | WestWitteringFiles\N\July1925-September1925\ Scan84 | |
| Date | 12th June 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT. Expl. No. REF: Eg/TAG/L.G.S.8.25. METAL AIR SCREW. A complaint has been made from one of the Aerodromes about the excessive vibration felt throughout a machine which has one of our Condor lll. engines fitted with a metal Leitner-Watts airscrew (two-blades) installed. We have made some tests with one of these two-bladed Leitner-Watts propellers fitted on a Condor lll. engine mounted on the hangar, and found that the whole secret of the matter is in the setting of the blades. Unlike the wooden propellers, where the blades and the boss are one unit and have a fixed pitch for all time, the metal airscrew is composed of three chief units, in the case of the two-blade propeller, there are the two independent blades and the hub and as the makers say - "The blades are detachable and easily fitted - Each blade is a replaceable unit of its own". It will be seen from the description that if the blades are not accurately set and have the same amount of pitch, the propeller would start to 'flutter' and set up heavy vibrations, which no doubt would be felt throughout the machine. Method of setting the blades. A datum line is marked on the sleeve of the blade and a scale (reading in degrees) on the hub. When the datum line is against zero on the scale, a section at three quarters of the top radius along the blade (max. pitch line) will on standard blades have a pitch angle of 20° to the plane of rotation. contd :- | ||