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Aviation History
1917
1917 - 1303.PDF
• DECEMBER 13, 1917. commercially, entailing, as it does, the separate construction of half the ribs, no two of which are alike from root to tip in one wing. Also, as the spars converge to a point at the tip, they intersect the ribs at varying distances from root to tip, which again means extra work in manufacture. As for the spars themselves, they also taper from root to tip, again more trouble and expense. What, then, are the reasons which have led a designer to sacrifice so much from a manufacturing point of view, in order to obtain his end ? A walk round the machine soon furnishes the reply to the question. When standing in front of the machine one is at once struck by the peculiar bracing of the front spar. Instead of the usual interplane strut there is on the Ago only a single solid wire running from the front lower spar to the front top spar, while no lift or landing cables of any sort are employed between the two front spars. This feature, then, will probably be found to con- tain the solution of the peculiar design. By doing away with the front bracing, a much freer field of firing is obtained; and there can be little doubt that this was the object for which the designer was striving. Owing to the backward slope of the leading edge of the planes, the outer inter-plane struts are farther back than they would be in a machine with straight wings, and also owing to the taper, closer together and therefore obstructing the field to a smaller extent. The narrower chord near the tip will result in a smaller travel of the centre of pressure, hence possibly the twist on the wings may become less, and the absence of front bracing be a less serious defect than one is inclined to imagine at first. When we say absence of front bracing, this is not quite correct, since, as already indicated, a single solid wire runs from top to bottom front spar. As is well known, in biplanes, with top and bottom planes of the same area, and with the conventional spacing of gap about equal to chord, the top plane carries about 30 per cent, more load than the bottom one, or roughly, T and f respectively. By running a wire from the top to the bottom front spar, the latter is therefore made to carry a certain share of the top spar's load, thus relieving, to a certain extent, the enormous bending moment that must be present on a comparatively heavily loaded machine, whose front spars have a distance of some 13 ft. 6 in. be- tween supports. So much for the general design of the Ago. As regards the construction there is much detail work that is interesting and unusual. The fuselage, which is, as in the majority of German aeroplanes, of very, roomy proportions, as regards occupants' accommodation, is covered with fabric except the front around the engine, which is covered in with three-ply. The floor of the fuselage is of three-ply from the stern to the gunner's (rear) cockpit. From there to the nose the floor is three-ply, covered with aluminium. In section, the fuselage is rectan- gular, a light and comparatively flat structure forming a turtle back over the top of the main fuselage frame- work. This turtle back is built up as a separate unit, and is easily detachable by means of a neat and very simple clip. In case of severe stresses being put on the fuselage, it is therefore an easy matter to detach the top covering and examine and adjust the internal bracing. The four longerons, which are of square section, are pine, from the rear cockpit to the stern, while in front they are made of ash. The struts are in the form of steel tubes, and the solid wire bracing is attached to the struts in the manner shown in one of the accompanying sketches. A small socket, apparently machined out of the solid steel bar, has holes drilled in its edges, through which the bracing wires pass. This socket is slipped over the end of the tube, which has small dents in its end to give more room for the loop of the wire, and the socket, with its strut, is secured to the longeron by a bolt passing through it, with the nut and a spring washer inside the socket, as shown in section in one of our sketches. Except for the fact that the longerons are pierced by two holes—the horizontal and vertical fuselage struts are staggered in relation to one another—close to one another, this arrange- ment appears to be very neat, and certainly takes up very little space. In front, the fuselage bracing is in the form of diagonal steel tubes, no wires being employed. The rear cockpit is occupied by the machine gunner, who 'is seated on a small seat built up of a framework of steel tubing, over which is stretched canvas. This seat is so hinged and sprung that immediately the gunner stands up the seat springs into a vertical position out of his way in case he wishes to do his shooting in a standing position. When horizontal, the seat is supported by a slanting steel tube, pivoted at its lower end to the floor, and having its upper end running in a steel guide, bolted to the under side of the seat. The principle will be better under- stood by reference to one of the accompanying sketches. The gun is mounted on a swivelling bracket, which, in turn, is supported on a rotatable gun ring of wood, forming, in effect, a turntable, by means of which the gun may be traversed in any desired direction. To prevent damaging the nose of the machine and the propeller, a stop is provided for the gun in the form of two small frames clipped to the rear legs of the cabane, which prevents the gun barrel from travelling too far inboard. The pilot's seat, which is in the front cockpit, is placed on top of the main petrol tank resting on ihe floor of the fuselage. A service petrol tank is carried in and mounted flush with the top plane just to the left of the cabane. In the corresponding opening in the upper right hand wing, is carried the radiator, and in connection with these two it is interesting to note that the water and petrol is led through the right and left cabane legs respectively, thus saving a certain amount of piping, which would otherwise be exposed to the air. The controls are, more or less, of the usual German type, with a vertical lever terminating at the top in a double handled grip, and mounted—via a uni- versal joint—on a longitudinal rocking shaft, having at its other (rear) end crank levers for the attach- ment of the aileron cables. On the machine in question, no guns were mounted, but from the various fittings it appeared that there were at one time two machine guns mounted above the engine, and with the usual interrupting gear for clearing the propeller blades. The large engine—a 230 h.p. Benz—is mounted on two longitudinal bearers, which are in turn sup- ported from the fuselage by three direct supports— at the rear a sloping panel of ply-wood, in the middle by tubes sloping up from the junction of the rear panel to the lower longerons, and at the front by 1303 H
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