Cycling

The term bike rides - Cycling - called locomotion on a bicycle. He also referred to the sport of cycling, which is operated as a leisure activity, to maintain health or athletic competition through to competitive sport.

Without intervention by the driver a wheel would fall within a very short time. The driver keeps the system bike / rider with small steering swings in balance. He is supported by the gyroscopic effect.

• 5.1 Determination of the inclination angle
• 5.2 centrifugal forces and impact driver when cornering
• 5.3 superelevation
• 5.4 evasive maneuvers

• 6.1 lag
• 6.2 wheelbase
• 6.3 Wheel size and weight
• 6.4 rolling surface
• 6.5 front wheel setback
• 6.6 sitting position
• 6.7 Frame size

Speeds

The average speeds when cycling are usually at 10 to 20 kilometers per hour (km / h). A bike with pedal assistance limited supports the driver at speeds up to 25 km / h ( pedelec ). Certain models even up to 45 km / h ( S- pedelec ). At the Tour de France, the highest average speed of a driver is 41 km / h Without differences in height it goes faster: The hour record for bicycles is normal since 2005 at 50 km / h with a particularly aerodynamic bikes at 56 km / h

The bike in the unstable equilibrium

A bike touches the ground in two places - the bearing surfaces of the tires. Even a slight inclination of the plane perpendicular to the roadway level framework leads the standing bike to tip over. Once the focus is no longer on the bearing surfaces is the comprehensive and connecting support surface tilts around the wheel.

By extreme turning the handlebars to the support surface for the focus can be increased. Only experienced people can avoid on a stationary bike for a long time a fall. Since these problems when driving straight do not exist, the dynamics for such holes is crucial.

The balance while driving

A tipping in one direction while driving is counteracted that the handlebar deflects in the same direction, a short curve initiates and the bike is now erected by the centrifugal force to the other side. Here, tipping over can hardly avoid, the handlebars turn are directed in the opposite direction and so on.

Therefore, a straight-ahead comes a barely noticeable oscillation about the equilibrium position between tilting and righting the same. At slow speeds, the commuting by strong alternating steering rashes expresses.

For hands-free driving the lateral tilting of the body helps to produce an opposite gravity torque. Hands-free driving is nearly impossible when driving slowly. Only the run described below and the centrifugal forces make this possible, by triggering at a wheel inclination a controllable steering deflection and thus return the wheel back into the straight line of travel, or allow stable cornering.

The impellers as a centrifugal

As speed increases, both steering movements and center of gravity shifts ( balancing ) are of secondary importance. This basically applies to the straight-ahead as for curves. From a speed of 20 km / h, the forces acting on the impeller centrifugal forces are so strong that a stable straight driving and a lot of the maneuvers may be freehand possible. The contribution of the rotating centrifugal impellers as to stabilize the ride is to support the above-described necessary steering rashes or trigger the Freihändigfahren. This will be both small, necessary in a straight line corrections "automatically" triggered and the longer maintained in force steering rashes when cornering.

Centrifugal effects - stabilization and precession

The front depicts a symmetrical nutationsfreien top; the angular momentum, rotation and figure axes are identical. By a lateral tilting of the front wheel, a torque acts, which is perpendicular to the angular momentum. This leads to a change in angular momentum, and thus to a precession movement (see a gyroscopic effect in two-wheel ): The control arm rotates in the direction of inclination. Conversely, rotation of the front wheel about the steering axis of the bicycle to a tilting in the opposite direction due to the precession.

The rear wheel does not precess, but contributes to the gyroscopic effect by its inclination is transmitted to the front wheel, resulting in a reinforcement of the centrifugal effect and the total wheel stabilized.

The driver's decisive contribution to the long-term maintenance of equilibrium

As experiments confirm (see below), a bike can maintain as a an area rolled, narrow car tires to get a straight line without driver action for a while. This bike and its running wheels inherent characteristic can be explained by the centrifugal forces. In single occurrence of disturbing forces and slowing the speed after a certain time, the wheel becomes unstable, the rolled tire begins to wobble, and finally falls. This is due mainly to the delay of the reaction ( see above: precession ). This start opposite, rhythmic inclinations and rotations that soar and eventually become uncontrollable. Through the follow-up (see below) the mutual reinforcement of forces while muted, but it remains a crucial rest of instability.

The driver can compensate by a trained sense of equilibrium, a quiet sitting on the saddle or a clean pedaling even during hard cycling this instability in the straight ahead position. When cornering, it supports stability through its engineering ( see section cornering). He remains the decisive force - without it gets any bike sometime out of control.

Experiments and theories on the importance of centrifugal forces

David EH Jones (* 1938) found experimentally that with a driver, the influence of the centrifugal effects at normal speeds is very small, without a driver, however, they stabilized the was brought forward or down a hill -propelled free-running wheel he mounted just above the bottom of a third wheel next to the front wheel and turned this in the reverse direction, with the goal of eliminating the centrifugal effects of the two front wheels about. However, he could drive normal, even freehand. Without, however, the driver was robbed of the centrifugal effects bike around on the spot.

Felix Klein and Arnold Sommerfeld have delivered in their theory of the gyroscope an exhaustive theoretical and analytical treatise on the centrifugal effects in the bike. They note that a stable range is 16 to 20 km / h in which only the centrifugal effects are able to generate the stabilization, despite the small wheel masses. It is possible for the driver here, Handsfree to drive. Below this range the Steering that causes the gyroscopic effect is not sufficient to elicit a sufficiently large righting centrifugal force; the driver has a conducive. If you go much faster, no centrifugal effects are felt. The rear track approaches so fast the front wheel track that both together behave as a rigid system. The driving experience is like riding in a narrow rail; steering and thus the maintenance Stay difficult.

Klein and Sommerfeld but acknowledge that a bicycle rather designed to conserve energy and ease as to optimize the centrifugal effects and the compensatory movements of a driver's self- stabilization " not just [ ..] required [ ..] is ." Nevertheless pull in conclusion that " [ ..] it hardly be dismissed out of hand [ is ] that the centrifugal effects contribute to the maintenance of equilibrium in the ride, we want to say, contribute in a particularly intelligent way; they are the ones who by virtue of their effect first phase will feel a Raiding the wheel and then tighten the stronger the lot, but a little slow Centrifugalwirkungen in the service of stability. "

Cornering

A curve is not initiated directly by turning the handlebars in the desired direction. Ruts in the snow or sand show that first a slight steering movement in the opposite direction. You smite for a left turn just to the left, then the contact surface of the tire moving away to the left under the center of gravity. This causes an inclination to the right, which is reinforced by the gravitational force in the following. To take a left turn, but a tilt to the left is basically necessary for the wheel does not tilt to the outside.

To initiate a left turn, it must be brought to the left from the vertical equilibrium in an inclined position. This is done by a quick steering movement to the right. Then the skew is stabilized by steering to the left. Thus, a new equilibrium is reached in which balance the overturning moment due to the centrifugal force and the overturning moment due to gravity.

Determination of the inclination angle

A curve can be regarded as part of a circular path. When the driver is in the curve, the inclination angle at which it does not crash, depending on vehicle speed and turning radius. The faster the travel, and the tighter the curve is, the greater must be the inclination angle position to be taken. This can be clearly ascertained: The line connecting the center of gravity and base of support must namely run in the direction of the resultant of the centrifugal force and attraction. Therefore applies to the inclination angle between the resultant and the vertical:

In this case, the speed of the turning radius and the acceleration of gravity.

For a stationary observer acts on the bike a directional center of the circle centripetal force, which is applied by the friction of the wheels. The static friction coefficient now determined the maximum tilt angle, whose excess leads to the slipping of the front wheel and to a fall. Prior to tight corners and on greasy, gravelly or smooth floor coverings so braking is necessary because otherwise the friction is not sufficient to apply a centrifugal force equal amount of centripetal force.

Centrifugal forces and impact driver when cornering

Like when driving straight, so it's here again, the forces of the rotating wheels that support the drive through curves crucial. Have the wheels caused by the precession of the tilt in the straight-ahead a steering lock, who was correcting, so they now support the necessary for cornering impact of the front wheel. The caster (see below) reduces this impact, with shorter lags better cornering characteristics and worse directional stability characteristics, larger wakes cause the reverse characteristics.

The driver is also fine-tuning left without a controlled ride would not be possible. When sporting cycling ( bicycle racing ) are to successfully tackle bends more techniques essential. For example, the driver must build a body tension, which is caused by Pressing the almost stretched outside of the bend leg ( pedals at the lowest point ). In the sport of mountain biking, however, where it comes to more rapid displacement of the body center of gravity due to the soil conditions, a Waagrechtstellung of the pedals has proved to be rather useful.

Camber

The radius of curvature can be substantially reduced when the road surface is not flat, but inclined towards the center of curvature downwards ( exaggerated). These help make both cyclo -cross and mountain bikers as well as track cyclists advantage:

• In cyclocross and mountain sports one uses, for example, be afraid curves thus have a camber to drive through corners faster.
• In track cycling, the cycling tracks basically have in the curves peaks between 30 degrees ( long open-air cement paths with greater static friction ) and usually 45 degrees elevation angle (in exceptional cases even higher: the defunct railways in Münster and Frankfurt had elevations of more than 55 degrees).

Evasive action

For curves, which are driven in the course of brief evasive maneuvers, the technique of counter-steering in order to initiate the tilting is not necessary when the driver wants to continue, then the drive to the original line of travel. Instead of the described technology as the driver steers the bike over the obstacle, while his center of gravity continues to move almost straight. Consequently, this technique is so suitable only for avoiding ground-level obstacles potholes. If they applied in the wrong situation, it leads to serious falls. The driver The decision on the technology meets not consciously but intuitively in tenths of seconds.

Design features of a bicycle, which influence the driving

Caster

As a follow-up, the distance between the front wheel contact point and the point where the imaginary extension of the steering axis hits the ground, the so-called trace point, respectively. Is defined geometrically by the caster wheel radius, the steering head angle ( between the steering axis and the ground) and the fork bending ( perpendicular distance from the hub to the steering axis ). The name comes from the fact that the wheel the track point " running behind " when steering. If the caster is positive, then there is the tracking point as shown in the figure in the direction of travel before the touchdown point. The size of the wake is usually between five and seven and a half centimeters.

The tracking is probably the most important structural support in the effort against the falling down during straight driving. It acts in the following ways:

The tracking results from the steering angle and the Gabelvorbiegung; as it has an impact on driving behavior, always on these two factors depends. A run-down of 60 mm results in about at a steering angle of 74 ° and a Gabelvorbiegung of 40 mm, but also at 71 ° steering angle and 63 mm pre-bending. In the first example ( criterion Road ) results in a agile handling, the second ( touring bike ) the steering is directionally stable, but also more sensitive when meshing in longitudinal grooves.

That a driving with a negative lag is hardly possible, the experiment shows the chemist David EH Jones. He tried to build a bike that is not navigable in 1970. Most developed wheel types, however, were more or less still usable. Only a wheel with negative caster was " very tricky " to control and had negligible self-stabilization.

Wheelbase

A bicycle with two wheels contact the floor in two points. The distance between these points is called wheelbase. In a curve, the wheel tends to curve direction, the focus migrates in the same direction. The greater the wheel base, the greater the path of the center of gravity on the weight shift and hence the time to achieve the necessary for a turn tilt. The somewhat sluggish behavior of wheels with a long wheelbase, about tandems, can be explained by this.

A bicycle with wide-set wheels is less maneuverable, but remains true to the direction. With close-set wheels, it reacts faster to steering movements, but are then adjusted a rather nervous straight. Its agility is used with road bikes.

Especially not distinctly sporty designed bikes have a wheel base of well over a meter, a tandem even two. In competitions using racing wheels are typically on a wheelbase 97-100 centimeters.

To measure the wheelbase, you measure the distance of the wheel centers ( hub axle center ) with straight handlebars aligned, which have the same distance as the Aufstehpunkte on the ground, where the front and rear have the same radius.

Wheel size and weight

Larger in diameter and heavier the wheel, the greater the centrifugal moments. A normal Gebrauchsrad ( wheel diameter: 60 cm, mass of 1 kg), the centrifugal effects are about five times as large as in a child's bike (30 cm, 0.4 kg). Correctly, the gyroscopic moment of course does not depend on the mass of the wheel, but on the distribution of mass in the rotor (moment of inertia with respect to the axis ) from; for example, has an impeller with a "heavy" rim a larger gyroscopic moment than an equally heavy wheel with a "light " rim with a "heavy" hub gear. Be constructed bicycles but rather from the viewpoint of energy saving and therefore as easy as possible.

Roll-off

On straight sections of the shape of the rolling surface of the tire corresponds to a cylinder surface, at a wheel inclination a cone. A rolled cone revolves around its pointed end. Such a tax is possible by slanting position, but the effect is small. Significantly it is, if it is driven by private treaty with " eingeschlagenem " or sticking difficult to move tax warehouse. With sufficient speed can be balanced with hip bend to the side not inclined roadway just sufficient guided and straight with it.

Front setback

A very small influence of the stem and the steering head. In the straight-ahead, he has the highest position and therefore largest potential energy. The state of lowest energy is sought, therefore, steering angles are enhanced by the reduction in the front wheel. At a steering angle of 8 °, this is only 0.15 mm.

Seating position

The driver moves the weight to the rear wheel, smaller steering forces are required. However, this leads to oversteer and flatterigem driving behavior due to further or faster direction corrections. You bend over and loaded the front wheel, greater steering forces are necessary. One among controls and reached a fluctuating driving behavior on account of late and minor corrections.

Example given that a balanced ride is assured when 55 to 60% of the total weight of the bicycle and rider weigh on the rear wheel.

Frame size

The optimal frame size is also critical to driving behavior. For each type of bike There do own guidelines for their own stride length is observed. Highly recommended is a sporty driving style, the choice of a smaller, in tour -oriented procedure, the choice of a larger framework.

Medical aspects

In recent years, the medical aspects of cycling were also examined by increasing the increase of the cycling. Generally cycling as very healthy ( heart and circulation training ) and joints. It is however important to establish a good ergonomics for the entire body. Not all types of cycling accomplish this in the same way. Studies, among other ADFC have shown that the attitude to the so-called touring bike with the right frame size and real saddle is the attitude that most comes to meet the human anatomy. It is important to achieve a uniform load as possible to the driver's contact points when cycling with the bike according to the natural anatomy of man.

It naturally helps the foot to the contact point pedals the largest percentage load of the body weight, the foot is naturally also created to support the entire body weight. To achieve the most ergonomic back posture, the posture should ideally be such that the imaginary line between the shoulder blade and the highest point of the pedal is vertical. In order to achieve optimal care of the feet and minimize the burden of the knee, the seat height should be adjusted so that it still has slightly bent the leg pedaling at the lowest point.

As the second largest load zone of contact between the buttocks and the saddle is to be considered. This contact point can therefore be particularly problematic, as the human pelvis with his ischial tuberosities and the pubic bone (or pubic bone skids, also called pubic crest ) by the tilt of the pelvis affects the bending of the entire spine. Thus, a false pelvic posture (eg, to avoid discomfort due to the saddle ) lead to a strong load on the spine. Equally problematic is a false pelvic angle on the saddle for the entire pelvic area, as this area is heavily streaked with blood and nerves that lie on the inner thighs and have to supply the lower limb. If these supply paths constrained by a contact of the pubic bone, or the pubic bone skids / the pubic crest on the saddle a long time or even bruised, thus damage to the corresponding vessels and power lines may arise Therefore, it is necessary to bring the main burden of this contact point on the seat hump and possible little pressure to the area of the pubic bone skids, the dam, the genitals and the inside top part of the thigh exercise.

Finally, the hands forming with the handlebar the third contact point between cyclists and bike. Here, too, medical aspects to consider in order to ensure optimal blood and nerve supply to the hands and fingers. The removal of the handlebar as well plays an important role as the handlebar shape (bending ) and the height of the handlebars, which should be the same height as the center of the pelvic bone optimally to the buttocks of the rider. Your arms should be not straight but slightly bent to smooth out uneven surfaces better. The distance between both hands (measured from the little finger of one to the little finger of the other hand) should only slightly exceed the distance between the shoulder blades. The hand should form the straight line with the forearm and are bent either upwards or downwards so through the wrist a permanent and unhindered blood supply to the entire hand to ensure.

As a rough guide, the imaginary lines connecting the three contact points of the shoulder blade should be a rhombus whose side lengths should be approximately equal in length as possible.

In addition, from a medical perspective wearing a helmet while cycling a preventive measure against fall injuries are