Fig. 183.—Joint of Outrigger to Motor Rod
The gearing ([see Fig. 184]) consists of a brass framework (bound to the ends of the motor rods) which provides bearings for the gears. The use of gears is obvious; they eliminate torque on the spars, or the tendency which a single skein would have to twist the spar. Pieces of tube are passed over the shafts to bear between the gears and the gear bearing. In order to counteract the tendency of the rubber hooks to pull out straight when the rubber is in tension, the hook ends are secured as shown at A. When it becomes necessary to detach the skeins, it is only necessary to slide the tubes along the shaft to open the hook.
In [Fig. 185] the kingpost attachment is shown. The spar is mortised, the kingpost forced through, glue having previously been brushed into the slot, and a pin tapped through from the side to secure it. Birch should be used for the kingposts, and their widest cross-section should be ⅜ in. by ³/₃₂ in., tapering off towards the extremities to ⅛ in. by ¹/₁₆ in.
To the ends of each motor rod are attached small No. 22 s.w.g. piano wire hooks, to which the spar bracing is made fast. A suitable length of wire is passed through the spar, and the hooks then formed. The bracing is fastened to the kingpost by a couple of turns being taken round it.
Next, four twin hooks should be made, of the form shown in [Fig. 186]. Sixteen gauge wire is to be used for them, bent tightly to clip the spar ends, to which they are bound. All the hooks should be covered with valve tubing to prevent them from cutting through the rubber when this latter is in tension.
The joint of the cross members of the envelope to the longeron is given by [Fig. 187], from which the bend in the longitudinal, hitherto referred to, will be clear.
To the tail of the machine a pair of superposed surfaces or elevators are fixed. These are fastened at their foremost extremities to the motor-rod outriggers, and at the rear they are supported by the two cross ribs of the rudder. Small slits are to be cut in the fabric with which the rudder framework is covered to enable any slight alteration in the angle of incidence of the elevators to be effected.
Fig. 184.—Arrangement of Gearing
