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Aviation History
1920
1920 - 0985.PDF
SEPTEMBER Q, 1920 In all these plants special attention has been paid to the ventilation of the work-benches or painting-compartments a most important matter in connection with high-class paint- work or doping. In one form fumes, dust, etc., are drawn from the bench or cabinets, through a vent in the latter, by means of a suitably-driven exhaust fan ; but the latest form —the invention of Mr. A. Attwood—known as th« hydro- e,xhaust, is a considerable improvement on previous methods. Briefly, it consists of a cabinet containing a series of platesover which flows a film of water. The fumes, dust or other matter are drawn into the apparatus by means of a fan,and are deposited on the plates and carried off by the water which is collected in a trough and led to a tank.This apparatus can be made in various forms to suit different conditions, either, as a permanent fixture orportable. ^ 4 MODEL AEROPL^NfeS •r -- ~ - All communications to be addressed to the Model Editor. A Whirling Arm—(Continued) ONLY two /parts of the apparatus remain to be given in detail, the portion which travels transversely across the end of the arm under the thrust of the screw, and the pan carrying the variable weights for measuring the thrust. In the drawing ab are the upper and lower spars previously shown ; hh are short crossbars about 12 in. length ; ttttn are A stamp should be enclosed for a postal reply further Oetai/s of H/h/r/iiy firm four stout wire radial arms ; j is a hard wood bar 14 ins. long, to which the wire .arms are attached by means of round- headed screws. Eyes are formed in the ends of the wire, and in these the screws should make a running fit with sufficient play to allow the arms to turn about them easily; * is a deep channel secured to the spars ab, the spars being bevelled at their ends to fit respectively on the upper and lower sides of the channel. In this channel the bar j is to slide. On the side of the channel nearest to the centre of rotation is mounted a pulley in the manner shown in the small detail -drawing. This pulley is to take the thread which is fastened off on one of the wire arms and which, passing over the pulley, runs up alongside the spar a, and then divides to pass over the two pulleys on the upper ball bearing, then down again to the weight pan. The full range of movement of the bar j in the channel need not be more than 2 or 3 ins., the amount of such movement being indicated in the drawing by the angle of the wires shown dotted. The wire arms are shown in the position they would assume when the screw is thrusting, and the thread being under tension is raising the weight. The arrow indicates the direction ofmotion under thrust. It now remains to provide means for attaching and detaching the motors and screws it is desiredto test. This is done by means of two small U-shaped plates I. These are bent so that they fit the motor spar kand the bar j, and by means of two movable pins dropping through holes in the plates and bars j and k lock them securelytogether. Thus any motor and any screw can speedily be put on or taken off. The channel i is shown deep enoughto embrace the motor spar k, and a few motor spars of different lengths but of the same cross-section should be made andconsidered part of the apparatus. When it becomes necessary to test the rubber and screw of a model, the rubber is_detachedfrom the model and put on the motor spar which fits it as regards length. . (To be Continued) A Self-contained Geared'Motor I SHOW herewith drawings of a self-contained geared motor —self-contained in so far as it carries with it a light winding apparatus. Such a motor is a decided acquisition with some models. At one end a double bearing of brass is to be provided for the winding crank. Two methods are shown of checking the handle from "returning" or flying back after the turns have been applied. One is by means of a ratchet formed on the end of a short piece of brass tube, and shown in detail at A. The alternative method is to dispense with the ratchet and fit a sliding pin which, by being slipped forward beyond the arm of the handle after winding, engages with the handle and prevents it from turning. This arrangement is shown by B. Of the two the tube ratchet is most convenient, but the sliding wire most effective, especially if a notch is filed in the wire for the handle to drop into and so prevent the wire slipping back. If the ratchet is decided on, the lugs turned down on the plate forming the double bearing C must be large enough to take the tube. The ratchet should be cut in the tube to the shape shown at a. If the sliding-wire bar is used, another double bearing must be provided for it above the motor spar, as shown by b. At the other end of the motor spar two more double bearings are required, c1 and c2, c1 being for the main rubber spindle carrying the gear wheel /, and c2 for the propeller spindle. Both the wheel / and the pinion g can be obtained from the movement of an old clock ; / has 40 teeth and g about 12 teeth. The motor, if such a ratio is employed, would be geared up 1 to 3J. Having drilled the bearings to the centre distances of tBe two gears correctly meshed, slip the wheel and spindle F into place and bend the hook to receive the rubber. The other spindle is to have a piece of plate e. bent to the shape shown at c and drilled on each side for pins. This is to engage with the propeller, to which it is fastened by pins. The spindle should also be put in place and a collar d soldered. Reply to Correspondent F. B. C. S. (H.M.S. Carnarvon).—Many thanks for the detail drawing, which I shall deal with in due course. 987
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