What is the principle , the chief principle, on which the wheel is constructed? It is that of a bicycle wheel.... The lower half of the wheel simply hangs from the mighty axle (center bar) and this lower half supports the upper half by means of the steel framework of its two rims (sides) The wheel, though apparently rigid in its construction,has just enough elasticity to make this method of support possible, and yet not enough elasticity to produce and appreciable trembling or slipping effect.