Speedometer magnets for the motorcycle are one of the biggest users of AlNiCo magnet over the past decades, and most speedometer magnets are exported to India or Vietnam nowadays.
The drive shaft of speedometer connects with driving gears inside the front wheel through a flexible shaft. AlNiCo magnet is fixed on the drive shaft and rotate with the shaft. A metallic cup cover AlNiCo magnet which serves as coils, and there exists a certain gap between AlNiCo magnet and cup. Low end of speedometer’s needle fix together with metallic cup while connect with a hair spring. Hair spring will ensure needle swing’s steady and reset timely. The front wheel drives the gears rotates during motorcycle is running, then turn AlNiCo magnet on the drive shaft. At this point, lines of flux between AlNiCo magnet and metallic cup will be cutting, thus generate an induced current and magnetic field. The metallic cup will rotate due to interaction between the induced magnetic field and AlNiCo’s magnetic field. The damping effect of hair spring will affect the rotation of the metallic cup, and the needle will rest on the certain speed when cup’s torque is equal to damping torque of hair spring. The higher speed leads to stronger torque and thus obtains more wide swing angle. The counter is composed of three pairs of worm gears and drum. The rotating flexible shaft will drive end worm gear, and gear will turn a circle when flexible shaft turned 1000 circles, then raised claw will stir digits on the drum. Speedometer magnets are fabricated by casting process, and both AlNiCo 2 and AlNiCo 3 can be served for this application.
