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TESTING Analytical Propeller there is only one resultant unbalanced moment Balance vector, so these lines just drawn should intersect at one point; if not, the knife-edge should be re- A simple Practical Method in Use in the Propeller Shop of the Central Air checked. Drawing a line between the point of inter Transport Corporation in China section and the centre of the propeller we get the resultant unbalanced moment vector which should be removed from the propeller to make it By S. Y. Tung, M.Sc. balance; this vector is represented by OR. as shown in FIG. 4. OR could be resolved into two Introduction 2. Check the knife-edge alignment auto components as RB and RC representing the matically. moments which should be removed from blade E have used several methods to balance 3. Taking mean values in calculation, so (2) and (3) respectively. propellers analytically in order to avoid eliminating all possible inaccuracies due to knife- Also from FIG. 4, we found RB is 22·2 oz.-in. the cut-and-try method now commonly edge alignment, rolling friction, etc. and RC is 29 oz.-in.; if the distance from the adopted in the practical field. The method des 4. The operator may be interested in his job propeller centre to the blade balancing plug is cribed here has been employed in the propeller and have confidence in propeller balance. 9·8 in., then 2·26 oz. (22·2/9·8) should be re shop of C.A.T.C. in China and found applicable moved from blade No. 2 and 2·96 oz. (29/9·8) in the following cases: Static Balance from blade No. 3. 1. Most values used are constants for a given The static unbalance of the propeller is mainly If we reverse this vector OR to the other side propeller; if a special printed chart is provided, due to the fact that the centre of gravity of the as Oa, then this vector represents the total one will find that this method is quite simple. propeller does not coincide with its centre of moment which should be added to the propeller, rotation; bearing this in mind, then take the so that its components OE and OD represent following example showing how a propeller the moments which should be added to blades could be balanced statically by the analytical (1) and (2) respectively. method. We could also use the combination of sub traction and addition method to get propeller Putting the propeller on the knife-edge with balance, as shown in FIG. 5, but of which detail the position as shown in FIG. 1 we could bring will not be given here. In the case that the vector it to a standstill by simply adding weight to any OA is not large, propeller balance may be ob convenient point, the component of the un tained by adding weights into barrel bolts balanced moment in this particular direction will (Hamilton propeller) or into hub slots (Curtiss be the product of the moment arm and the propeller); the method of distribution of weight weight added, similarly for FIG. 2 and FIG. 3 . into the barrel bolts or hub slots is simple. We tabulate the results below. In short, as we all know that a vector can Referring to FIG. 4 we draw each unbalance be resolved into any number of components, moment component in its proper direction and so, once we find the vector of the resultant magnitude (as Oa, Ob and Oc), then draw lines unbalanced moment, we can resolve it into perpendicular to these vectors as shown, because components in whatever manner we like. Propeller Position Fig. 1 Fig. 2 Fig. 3 Weight required to stop propeller from rotation 3·57 oz. — 1·00 oz . — 2·79 oz. Weight required to rotate propeller in reverse direction alter it has been stopped 3·89 oz. — 1·43 oz. — 3·07 oz. Components of unbalanced moment 3·73 × 6·75 — 25·2 * —1·22 × 6·35—7·75* —2·93 × 6·35—18·6 * In oz.-inch. BOOKS RECEIVED Professional Publications All books received from Publishers arc listed under this heading. Extended reviews of a selection appear later. Inclusion in this list, therefore, neither precludes, Under this heading are given each month the principal articles of aeronautical interest appearing in nor implies, in any particular instance, further notice. A Guide to the Aircraft Maintenance Engineer's the current issues of the Journals of the leading Professional Societies and Institutions Licence Examinations. Fourth Edition. Paper bound, 102 pages. [The Society of Licensed Aircraft Integrally Stiffened Structures. P. Sandorff and G. W. Papen Engineers, Finsbury Circus House, Blomfield Street, The Engineering Institute of Canada Designing for Comfort in Aircraft Scats. S. Lippert E.C.2. 6s. 6d. post free.] THE ENGINEERING JOURNAL (Monthly) Vol. 33, No. 1, January 1950 The Society of Licensed Aircraft Engineers The Soviet Air Force. Asher Lee. 207 pages, illustrated. Design Development of the Avro Jetliner. J. C. Floyd THE TECHNICAL INSTRUCTOR (Monthly) [Gerald Duckworth. 8s. 6d.] Vol. V, No. 2, February 1950 The Society of Automotive Engineers (U.S.A.) Exports to America. Pamphlet, 31 pages. [The Times, Fuel Systems for Gas Turbines. Part II. R. A. Fry S.A.E. JOURNAL (Monthly) Printing House Square, E.C.4. 6d.] Aircraft Hydraulics. Part II. J. Stuart Backhouse Vol. 58, No. 2, February 1950 Summaries: Dollar Sales. 1—Consumer Goods. Paper bound, 63 The Royal Aeronautical Society Practical Conclusions on Gas Turbine Spray Nozzles. F. C. pages. [Dollar Export Board, Thames House, Mock and D. R. Gauger JOURNAL (Monthly) New Appraisal of 1955 Air Transport—Panel Discussion Millbank, S.W.1. Free.] Vol. 54, No. 471, March 1950 Productivity in Industry. Sir Roy Pinsent. Paper Institute of the Aeronautical Sciences (U.S.A.) A Review of Aerodynamic Cleanness. E. J. Richards bound, 19 pages. [Blandford Press, 16 West JOURNAL OF THE AERONAUTICAL SCIENCES The Weight Aspect in Aircraft Design. L. W. Rosenthal Central Street, W.C.1. 6d.] (Monthly) The Reduction in Weight of Structurally Important Aircraft Vol. 17, No. 2, February 1950 Components by Controlled Cold-Working During Manufacture. Aerials for Centimeter Wave-Lengths. D. W. Fry and Application of Simultaneous Equation Machines to Aircraft J. G. H. Brown F. G. Goward. 172 pages, illustrated. [Cambridge Structure and Flutter Problems. P. A. Dennis and D. G. Dill A Note on the Approximate Plane Motion During the Burning University Press. 18s.] The Royal Aeronautical Society of India Period of Rocket-Propelled Missiles Launched at Small Angles of Yaw from Aircraft. R. II. Bolz JOURNAL (Quarterly) A Case for the Independent Air Transport Companies Seventy-Fifth Anniversary of Ludwig Prandtl of the United Kingdom. Pamphlet. [The British Air Vol. 1, No. 3, November 1949 Charter Association Ltd., 19 Park Lane, W.1. Free.] AERONAUTICAL ENGINEERING REVIEW Gas Turbines and Their Maintenance in Civil Aircraft. C. W. (Monthly) Rossiter-Smith Helical Springs. J. R. Finniecome. Paper bound, Vol. 9, No. 2, February 1950 The Damping Capacity of some Indian Timbers. D. Narayan- 61 pages, illustrated. [Emmott & Co. Ltd., 31 King amurti and B. N. Prasad Eye Movements of Aircraft Pilots During Instrument-Landing Street West, Manchester, 3. 2s. 6d.] The Development of the SAAB-90 Scandia. T. Lidmalm Approaches. P. M. Fitts, R. E. Jones and J. L. Milton, April 1950 113
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Apr 1, 1950
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