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).
Propeller testing, blade adjustment, and the possible causes of vibration.
| Identifier | WestWitteringFiles\N\July1925-September1925\ Scan85 | |
| Date | 12th June 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT. -2- Expl. No. REF: Hs{Lord Ernest Hives - Chair}/TAG/LMS.8.25. In the case of our tests we were very careful about the engine being perfectly level when adjusting the blades. The angles were checked with propeller in a horizontal position. The blade angle was checked by placing a straight edge on the pitch line (which is painted on each blade by the makers) and using a protractor and spirit level. To check the figure the propeller was rotated half a turn and the angle measured again. Vibration - possible causes. (1) The propeller being out of balance (mechanically) blade gets bent etc. (2) Inaccurate setting of the blades. (3) Inaccurate manufacture of the blade or blades, such as imperfect shaping of the bellied part of the blade. This would have to be counteracted by the adjustment. If the blades are set to a definite figure on the hub scale, without checking the angle of the blades on the pitch line, then if there are any mistakes in the marking of the hub scale, the blade will not be symmetrical and will set up vibrations. We found this to be the case with the propeller that was tested and also the pitch angles of each blade were not the same where we obtained the best results. This latter part may have been due to some peculiarity in the blades themselves. Hangar test. If each blade of this particular airscrew was set at the hub scale marking of 0 & 0, + 1 & + 1 or -1 & -1, -2 & -2 etc. the vibration was tremendous. By increasing the pitch contd :- | ||