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Aviation History
1920
1920 - 0277.PDF
MARCH 4, 1920 MODEL AEROPLANES NOTE.—All communications should be addressed to the Model Editor. Electric Engine for Scale Models I SHOW herewith a design for an electrically driven rotary motor for scale and show models. In the figure, A repre- sents the case of the electric motor, B the armature shaft, and C the cylinder. The latter may be of any suitable metal fit for show purposes. An imitation crank-case is made to fit over the motor casing and so carry the seven cylinders, SECTION or MODEL GNOME (ELECTRIC) MOTOR thick tin-plate will do for this. It will be necessary to make the crank-case and fix the cylinders in position before attach- ing the electric motor, since the screws holding the cylinders are fixed from inside the crank-case. The propeller is shown by D, and is fixed by screws to a small plate fastened on the end of the motor ; through it passes via two holes, the wires from the motor terminals. The commutator discs should be of red fibre, and are shown by E and F. A Model-Maker's LatheThe illustrations show a simple form of lathe or " turns " that can easily be made at home, and is suitable for makingcompressed-air motors and small turned parts for model Destjn For rtodeimaKer's Lath* aeroplanes. The bed is of extruded section, being filed to that form from a piece of bright drawn mild steel shaft of i-in. diameter. This is sufficiently accurate to be used 3/ide J?est without further machining. The headstock and tailstockor poppet head are brass castings sufficiently high to admit 2-in. diameter stock 6 ins. long between centres. They should first be made in wood, with prints pinned oneach'end, and then submitted to the foundry. The holes for the bed will then be cored out by them. The hand-rest is merely socketed into a split block locked friction-tight upon the bed. As will be seen, the lathe is intended for use in the vice. An auxiliary headstock with cone pulley and .dividing plate (the latter for wheel-cutting and fluting) is shown with an emery wheel capable of small grinding and lapping, while the small slide-rest shown in the further illustration will be useful for compound turning. I have intentionally shown the drawings in patch black style, as it would seem from correspondence that such style conveys more to the man not versed in workshop drawings. I should be pleased, however, to show scale drawings of the lathe, should a general desire for them be manifest. Rubber and Lubricant To preserve the elastic of a model aeroplane, it must be kept in a dark place when not in use. A good lubricant may be made by emulsifying 2 ozs. of soft soap (pure) in £ pint of water, bringing slowly to the boil. A small quantity of salicylic acid should be sprinkled in to kill any of the sub- stances in the soap likely to prove deleterious to the rubber. Before putting the rubber away, it should be washed in a weak soda-water solution and dried in a cotton swab. The life of a rubber motor cannot be defined. It depends, pri- marily, on the quality of the rubber, and secondarily on the number of strands, the number of turns given, the cross- section, length of skein, etc. But from data obtained by the writer, with careful use, a rubber motor should last at least 60 flights. Elastic, I in. by Jj in., is the most suitable section to employ. New rubber should not be wound fully, the result of so doing being " split " edges to the strands. The full number should be gradually approached. An Efficient GliderIn the accompanying sketch a neat and efficient paper glider, with which some hundreds of glides over 50 ft. longhave been made, is seen. The plane is cambered where shown dotted, and is made from 30 S.W.G. piano wire. An fit* EFFICIENT GLIDER adjustable weight, which slides by friction along the main spar, is used to adjust the centres of pressure and gravity. A is a plan view, B a side elevation, and C an end elevation, D being a detail of the rib joint with the plane edges. Notice that the plane has negative tips. Answers to Correspondents " J. C. H. G. (CANTON).—Stretch the silk from end to end and secure with drawing-pins partially pressed home until the glue has set. Small quantities of Cellon dope can be obtained from Messrs. A. E. Jones, 52, High Street, New Oxford Street, this would tauten it. Or varnish diluted with turpentine would suit. R. H. B. (WOOD GREEN).—You could hardly do better than work to the drawings which appeared in FLIGHT ofvjuly 17 last. The parti ulars there given should enable you to make a good scale model of the Vickers-Vimy. If you still find any difficulty you should visit the Science Museum and see the Transatlantic machine on view there. -,-*•/.
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