Fig. 52.—Interplane strut attachment.
Fig. 53.—Interplane strut attachment.
The main body of this clip is a stamping from heavy sheet-steel, bent up to the section of the spar, the bolts, it will be noticed, passing horizontally through it. The anchorage for the wires is formed by lugs, which have a direct pull on the bolts, and is so arranged that a slight clearance exists between lug and spar.
Fig. 54.—Plane strut attachment.
The plane-strut is shod with steel tubing, and connected to the fitting by a bolt, as shown. Of the strut connections described so far, hardly one can be said to conform to the leading principle of the ideal fitting, i.e. the secure attachment to the spar without piercing the latter for bolts. [Fig. 54] gives a fitting which is as good a solution of the problem as is constructionally possible. The basis of this connection is the lug-plate, to which is welded the strut-socket, the whole being fastened to the spar by four bolts, which are let in the flange of the spar just half their diameter, and tighten on a washer-plate on the opposite side. Lateral movement along the spars is thus adequately prevented, although the outer strut-socket might conveniently be bolted right through the spar, without materially reducing the strength thereof. This is made possible by the fact that the wing spars, disregarding the small wash-out at the extreme tip, are generally parallel in depth from root to tip, the amount of material at the point of intersection of the plane-strut being in excess of that necessary for the stresses concerned. Another attachment achieving similar results is shown in the diagram ([Fig. 55]), forming an example of the fitting employed on the pre-war Avro biplane. It will be noticed that in this case two bolts only are used for the connection, the pull of the flying or lift-wires being counteracted by the duplicated wires taken from the washer-plate to a fitting located on the single central skid of the undercarriage.
Fig. 55.—Interplane strut attachment.