Fig. 97.—Bridge type suspension.
A method greatly in vogue in America is that indicated by [Fig. 97], known as the bridge type, and a characteristic Wright detail, the rings being approximately two inches wide by two inches long. The fact that very few examples of this system exist in this country may be ascribed to the inferiority of rubber bands compared with the rubber cable.
Axle Fairings.
Fig. 98.—Axle fairing.
It is now the practice to streamline the compression tubes between the vees of the undercarriage with a fairing of aluminium or three-ply. This is so arranged that in flight the axle lies in a slot formed in the fairing, which appreciably reduces head resistance. A typical arrangement is indicated by [Fig. 98]. The axle is usually formed of steel or duralumin tube, and in the majority of undercarriage arrangements is divided and hinged in the centre, a wire or wires from this point to the fuselage accounting for any strain. Duralumin tube is especially suited for this item, as a much stiffer axle is possible for a given weight, although, unfortunately, this is slightly discounted by the fact that duralumin does not form a good bearing surface for the wheel hubs, and it therefore becomes necessary to fit either sleeves or stub-axles of steel.
Undercarriage Brakes.
Additional means for restricting the length of travel after contact with the ground is sometimes found in the employment of brakes of various types. A very simple and widely used arrangement is to terminate the tail skid in a claw fitting, as [Fig. 99], so that in alighting the tail is shoved hard down, bringing the skid into contact with the ground. The disadvantage is that undesirable strains may be carried to the fuselage members.
