Can anyone tell me how a motorcycle mechanical odometer works?

The instrumentation of a motorcycle includes an odometer and a speedometer. There is a drive shaft under the odometer connected to a set of drive gears in the front wheel through a flexible shaft. A circular permanent magnet is fixed on the drive shaft and rotates with the drive shaft. A metal cover equivalent to a set of coils is placed around the outer circumference of the magnet. , they do not contact each other, and there is a certain gap. The lower end of the speedometer pointer is fixed with the metal cover and connected to a hairspring, which can make the pointer swing smoothly and reset in time. When the motorcycle is running, the front wheel drives the speedometer gear to rotate, which is transmitted to the magnet on the instrument drive shaft through the flexible shaft to rotate. At this time, the magnetic lines of force between the magnet and the metal cover are cut, causing the coil to generate an induced current to form a magnetic field. This magnetic field interacts with the magnetic field of the permanent magnet, causing the metal cover to rotate. The rotation of the metal cover is damped by the hairspring. When the torque of the metal cover is equal to the damping torque of the hairspring, the speedometer pointer will indicate a certain value to indicate the driving speed. The higher the vehicle speed, the faster the permanent magnet rotates, the stronger the torque generated, and the greater the angle at which the metal cover drives the speedometer pointer to swing. When the vehicle speed slows down, the rotation speed of the permanent magnet decreases, the induced magnetic field generated in the coil weakens, the torque becomes smaller, and under the action of the hairspring, the swing angle of the speedometer pointer also becomes smaller. If the motorcycle stops, the permanent magnet also stops rotating, the induced magnetic field in the coil disappears, and the speedometer pointer returns to its original position driven by the hairspring.

The counter is composed of three pairs of worm gear pairs and a counter drum. The rotation of the flexible shaft drives the end worm gear to rotate. When the flexible shaft rotates 1000 times, the end worm gear rotates once. A raised claw is installed on the end face of the end worm gear. Every time the end worm gear rotates, the end worm gear rotates. The counter drum for numbers 0 to 9 rotates 1/10 of a revolution. The transmission ratio between the counter drum and the motorcycle is: the wheel travels 1 kilometer, and the last scale on the right side of the counter drum rotates 10 divisions. At this time, the second scale from right to left rotates one grid. This means that the vehicle travels 1 kilometer. When driving 10 kilometers, the second drum on the counter drum turns the scale of the third drum from 0 to 1 through the protrusion, indicating that the vehicle has traveled 10 kilometers. That is, each time the first drum rotates once, the dial turns Turn the second drum to rotate one grid; the second drum to rotate once, and turn the third drum to rotate one grid until it has traveled 99,999 kilometers. When this number is exceeded, the drums will all rotate to 0, and the reading will start from the beginning again, and this cycle will be used.