Bicycle Stability. The stability of the bicycle when cornering is mainly due to the centrifugal force acting on the center of gravity of the machine and rider assembly, and to the gyroscopic effect of the front and rear wheels.
When circulating in a straight line, the action of the gyroscopic effect is also combined with that of the centrifugal force, because although in principle it may seem surprising to us, the trajectory described by the machine is not entirely straight, but forms a neo-sinuous with respect to the direction of advance of the vehicle.
Thus, when driving “in a straight line” we actually describe small curves, alternately to the right and to the left. The reasons for this fact are set out below.
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- 1 Centrifugal forces
- 2 Center of gravity
- 3 Bicycle circulation
- 4 Sources
Centrifugal forces appear in all bodies that move according to a circular path, and the greater the greater the mass and speed of said body, and the smaller the radius of the path described by it.
Thus, for example, if we make a bolus suspended by a thread rotate, then the centrifugal force, the self- weight and the tension supported by the thread act on it ; Under the action of these three forces, the thread tends to be positioned so that its tension is oriented in the same direction (but in the opposite direction) as that resulting from the centrifugal force and the weight.
Similarly, a cyclist riding a curve should lean inward enough so that the resultant weight and centrifugal force pass through the vehicle’s fulcrum.
If its center of gravity is instead lower than it should be, the rider will fall, unless the centrifugal force acting on him is sharply increased; the speed being constant, this is achieved by reducing the radius of the described curve, that is, by turning the front wheel properly.
This action is favored by the gyroscopic effect of the wheels of the vehicle, since when forced to describe a circular path, they tend to tip out of the curve, thus exerting on the bicycle a moment that, like that of centrifugal force , also tends or straighten it.
This gyroscopic moment is constantly acting on both one wheel and the other, so that the rider can actually lean around the corner. In case the cyclist is in danger of overturning, he can then straighten the vehicle by turning the front wheel more to increase the centrifugal force and the gyroscopic moment; said wheel, rotatable in the steering tube, already indicates to him in a certain way “by itself” the direction in which he must deviate.
For example, if the bicycle – and with it the front wheel – tends to tip over to the left, the wheel also deviates if it leaves to the left, due to the gyroscopic effect, and thus goes on to describe a tighter curve; consequently the centrifugal force and the gyroscopic moment are increased, and these in turn prevent the vehicle from overturning.
The effects just described can be greatly enhanced by properly constructing the steering tube and wheel fork .
When driving without hands, e! The gyroscopic moment that appears on the front wheel when overturning the bicycle is enough, traveling at sufficient speed , to rotate the steering tube in the precise direction and angle so that the resultant of the weight, centrifugal force and gyroscopic force pass again for the vehicle support point, thus preventing the latter from tipping over.
When riding in a straight line, the bicycle first describes, for example, a smooth curve to the right; then it straightens, due to the centrifugal force and gyroscopic effect that act on it; then she leans to the left, and describes a smooth curve to this side; it is straightened again by the action of the centrifugal force and the gyroscopic effect; it then turns back to the right , and so on, so that you actually have a winding path .