Fig. 12. Single Tube.
The air is confined in two ways:
First, by what is known as the “single tube.” (Fig. 12.)
Second, by the “double,” or inner tube system. (Fig. 13.)
The single tube is well adapted for light vehicles, or where great speed or weight are not considered, and this type is now confined to bicycles. But it has certain disadvantages, namely: That of creeping, due to the impossibility of properly securing it to the rim of the wheel. Sand and grit are also liable to creep in between the tire and rim, and wear the material, thereby ruining it.
The outer casing, or shoe, is split on its inner side, and usually provided with an annular flange on each side of the split, which rests against the rim of the wheel, and is adapted to receive a rim which securely fastens the annular flange of the shoe, to the rim of the wheel.
Fig. 13. Double Tube.
Various ways are provided for holding the shoe to the rim of the wheel; but in the different types shown by the illustrations, Figs. 13 and 14, the shoe has a flange which is held within channels on the rim, or by some form of fastening device.
The inner tube is usually of thin elastic rubber, so made that when properly inflated it will fit the outer tube or casing. The outer part, which can be made of a different rubber compound, and is better adapted to stand wear, whereas, the inner tube, which is made of the best, and more costly material is protected.