Aeroplane construction

by Sydney Camm

Streamline Wires.

Although in the quest for increased speed the number of exposed wires were reduced to a minimum, the aggregate resistance still remained considerable, this leading to the development of the swaged streamline wire, the introduction of which is generally ascribed to the Royal Aircraft Factory; and these wires are now generally used for all exposed wiring. The points in favour of them are that, properly fitted, a considerable reduction in resistance is obtained, there is a lessened liability to slacken after some use, this rendering rigging a more certain operation, and the nature of its connection obviates the use of turnbuckles.

Figs. 113–116.—Methods of forming wire connections.

They have been variously criticized as being expensive to produce, that the resistance may be increased if improperly aligned in the machine, and also that any fracture or flaw is less liable to be detected before complete failure during flight. In manufacture the solid rod is rolled to the section shown by [Fig. 112], a certain length each end being left for the right- and left-hand thread. Two of the connections mostly used are shown by [Figs. 113] and [114], the latter being preferable, as the universal joint permits of movement in two directions, which reduces the tendency of the wire to crystallize as a result of excessive vibration. To prevent wear at the points of intersection it is usual to fit acorns of fibre or aluminium, a popular form being shown by [Fig. 115]. Some designers still prefer to use the wire cable for interplane bracing, a fairing of wood being bound to the cables by tape at intervals, this also preventing excessive vibration.

Some years ago various attempts were made, mostly on French monoplanes, to utilize flat steel ribbon for exposed wiring, but, owing to the difficulty of successfully forming a terminal, its use never became extensive, although it may possibly be regarded as the precursor of the modern streamline wire.

It is notable that, so far, the wiring of all German aeroplanes is effected by cable, so that apparently the merits of the streamline wire are not recognized. It is also surprising that no attempt has been made to streamline the cable. A device for tying the wires and preventing friction at the point of intersection, found on nearly all enemy aeroplanes, is indicated by [Fig. 116], and there are also instances of quick release devices, these being popular in this country about 1912, and now obsolete.

Although determined attempts have been made of late to entirely eliminate exposed wiring, examples of this occurring in the recent German Fokker triplane, it appears that the various alterations engendered by this procedure in the structure of the machine more than counteract the saving in head resistance.

Moreover, with modern methods of construction the ultimate strength of a wireless wing structure leaves considerable room for improvement, and the price paid for the saving is too great.

The arrival of the all-steel aeroplane would entirely alter the condition of things, as with this construction much better chances exist for the production of a reasonably strong wing structure without exposed wing bracing.

CHAPTER XIV.
ENGINE MOUNTINGS.

The mounting of the engine and the general arrangement constitute one of the most important and interesting sections of aeroplane construction, and perhaps a brief outline of the various engines in use will suitably preface a consideration of the mountings of the different types. Although there are signs that certain revolutionary engines may eventually come into use, the types in use on modern aircraft are the stationary air and water-cooled, the radial air and water-cooled, and the air-cooled rotary. The greater variety occurs with the stationary type of engine, which may be sub-divided into those in which the cylinders are arranged vertically in line, and those where the cylinders viewed from the front form a V. Engines typical of the former class are the Beardmore, Green, Mercedes, and Benz, all of which are water-cooled; and of the latter class, Rolls-Royce, Sunbeam, Hispano-Suiza water-cooled, and the Renault and R.A.F. air-cooled. The types of radial engines which have been extensively used are confined to two, these being the air-cooled Anzani and the water-cooled Salmson. There is another radial engine of comparatively recent production; but mention of this while present conditions obtain is not permissible. Rotary engines of note are the Gnome, Le Rhone, and Clerget, all of which are necessarily air-cooled.