Wheels.—Wheels are now in a transition state. The ultimate wheel has not yet appeared; but whatever its form or construction, certain things are essential.
Flexibility.—In the ordinary wagon or carriage wheel, there is but little, if any, flexibility; but in automobiles, where speed is a consideration, elasticity, either in the rim, or in some other part of the wheel, is necessary.
One of the reasons for this is, that on account of tire expense, motor wheels are smaller than carriage wheels. Making them smaller, however, produces certain disadvantages. One is that in going over the inequalities of the road, the axle on the small wheel has a greater vertical movement than on a large wheel, and the jar on striking an obstruction is more pronounced, also. These disadvantages, however, are more than counterbalanced by the elasticity of the invention.
Large vs. Small Wheels.—Fig. 9 shows a large wheel A, passing over a depression B. The large arc of the wheel does not permit the rim to go to the bottom. On the other hand, the small wheel C goes to the bottom of the depression, and the vertical distance which the axle of this wheel must travel, is three times as far as in the case of the wheel A.
In Fig. 10, where the large wheel strikes an obstruction D, the angle of its upward movement, as designated by the line E, is much less than the impact force of the small wheel, as shown by the greater slope or incline of the line F.
Fig. 9. Crossing Depression.
Fig. 10. Striking Obstruction.
Minimizing Shocks.—It is obvious, therefore, that if part of this shock can be taken up by the tire, the difference due to the smaller diameter of the wheel, will not be so apparent.