Page:Popular Science Monthly Volume 38.djvu/790

770 larger the radius the smaller the centrifugal force. If the radius of curvature becomes infinite—i. e., the curve becomes a straight line—the centrifugal force becomes infinitely small, or zero.

So long, therefore, as the bicyclist does not turn corners—keeps in a straight course—the centrifugal force gives us no assistance whatever in understanding why he keeps his seat so securely. But yet it may be thought that this force, if supplemented by skillful balancing, is sufficient. It keeps the bicycle from falling when turning corners: will not good balancing account for the stability when moving in a straight course? We are all familiar with the phenomena of balancing one's self. We know the help a heavy pole gives at such times; how a person's legs and arms move with startling rapidity in the opposite direction to that in which he feels himself falling. There is nothing of this on the wheel. If the stability was due to balancing, it would not be so very difficult for a bicyclist to sit upon his machine when not in motion., and when its wheels both point in the same direction. I have never seen one that could do it. I suspect, however, that it is not impossible, any more than to stand on the top round of an unsupported ladder. But the ordinary bicyclist can not do it; and yet, without apparent effort, he rides securely. That his stability is not due to his balancing and to his rapid forward motion combined, is evident when we reflect that if the handles are made immovable, so that neither of the wheels can be turned to the right or left, it is impossible for any ordinary rider, no matter at what speed he may move, to keep from falling for any considerable time after he once begins to tilt.

Apparently the fact that some can ride "hands off" on a safety wheel contradicts this, for, however it may be on an "ordinary" on a "safety" the rider can not guide it by the pedals, and as he does not touch the handles of the steering-wheel or the wheel itself, it would seem that his not tilting must be due to good balancing. Experiment, however, proves the contrary. Let the steering-wheel be fixed by tying the handles, or by a clamp on the spindle, so that it can not turn to the right or the left, and then let the 'cyclist try to keep it erect. Balancing won't help, except possibly to delay his fall a few moments. And worse than that, he can't ride hands off at all if he tries to do so only by balancing. The explanation of such riding is not very difficult, but requires some other matters to be treated first. At present all I desire to establish is that in this kind of riding, as well as in all others, the rider's ability to keep from falling to one side for an indefinite time while traveling in a straight line is not due to balancing.

I think you will agree with me that the reasons thus far assigned for the stability of the bicycle cast little or no light