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Aviation History
1923
1923 - 0171.PDF
MARCH 29, 1923 Finally, the spar forms, with the three-ply covered leading edge, a member that is particularly good in torsion. It might be added that breaking tests have shown the moment of resistance to be such that the spar successfully withstands bending loads which impose a maximum fibre stress of 6,2001 bs./sq. in. In torsional tests the spar withstood a torque resulting in torsional shear stress of 800 lbs./sq. in. In both cases the moment of resistance was calculated on the total area of the cross section of the spar. As regards details, the three corner strips of the spar are of spruce, and are tapered towards the tip in such a way that, while the overall size of the spar remains the same, the corner strips taper considerably. The same applies to a certain extent to the ply-wood covering, which is about 5/32 inch thick at the point of maximum bending moment, and only 1 mm. thick at the tips. The ply-wood is, of course, put on in panels, successive ones of which become thinner as the tips are approached. The ply-wood panels are attached to the corner strip by glueing and tacking. The ribs are built up of grooved flanges of spruce, into which are let narrow strips of thin three-ply, the shape being main- tained by distance pieces, having saw-cuts in their ends where these fork over the ply-wood web strips. The arrangement is shown in one of our sketches. This form of spar construction would appear to be parti- cularly applicable to metal construction, and we hope that the wider scope offered in this direction will be made full use of. We might add that the triangular spar construction has been patented by the Air Navigation and Engineering Company. The fuselage is composed of a light framework covered with thin three-ply wood. The bulkheads are, in most cases, skeletons with gussets of three-ply wood where two or more members meet. Where local considerations demand, the bulkheads are of more solid construction, with internal struts and a covering of ply-wood front and back, thus forming a box. This is the case where the wing tubes attach and in similar places. At the rear of the fuselage these bulkheads are built up to form the vertical fin, which is thus virtually integral with the fuselage. The pilot is placed in a low hammock seat, and a hole in the middle of the wing serves as a means of entering and leaving the cockpit, as well as for giving a better view. Reference has already been made to the fact that the sloping rear surface of the wing spar improves the view in a direction obliquely upwards and forwards. The " hollow-ground " deck of the fuselage facilitates looking directly forward of the machine, and altogether the view is probably as good as it is humanly possible to make it in a tractor machine. The undercarriage, as already indicated, consists of twowheels mounted on the usual tubular axle, but the rubber cord shock-absorbers of which are supported from the free ends oftwo tubular cantilever beams projecting laterally from the floor of the fuselage. On their ends these beams carry fish-plateshaving slots for the axle to work in, as shown in our drawings. The whole will be enclosed in a streamline fairing. The wheels call for a somewhat detailed description, as theyare of very unorthodox design. Mr. Shackleton frankly The all-wood wheel of the A.N.E.C. Light Aeroplane under test. The load supported when this photograph was taken was over 1,000 lbs., and the wheel showed no sign of breaking. The weight of the wheel is 5 lbs. admits that they are not his own invention, as wheels of this type have been made and tested in Germany. He has, however, improved on the construction, and has produced a wheel which, for a weight of 5 lbs., will support a tremendous load. On the day of our visit to the Addlestone works one of these wheels was being tested, and the accompanying photograph, showing the wheel under test, was secured by our photographer on this occasion. The load sustained when the photograph was taken was considerably over 1,000 lbs., and it is thought that the wheel will carry probably nearly THE A.N.E.C. LIGHT AEROPLANE : Some constructional details of the wing. The spar is of triangular section, and is built up of three corner strips of spruce, joined under each rib by an internal triangle formed of thin spruce strips. The whole is covered with ply-wood. The entire leading edge is covered with ply-wood. 171
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