Electromagnetic braking System
This is one of the simplest mechanical engineering projects. An Electromagnetic Braking system uses Magnetic force to engage the brake, but the torque required for braking is transmitted manually.
The main parts of an electromagnetic brake are:
1. The coil
2. The armature.
3. The hub.
The hub is attached to the axle of the vehicle. The armature is mounted on the hub and rotates along with it. The coil is mounted on a stationary element attached to the machine frame of the vehicle. Two friction plates are mounted each on the face of the armature and the machine element holding the coil.
Electricity is applied to the coil at the time of braking. This develops a magnetic field around it and the rotating armature gets attracted towards the coil. As a result the inner and outer friction plates placed between the armature and the coil gets squeezed, which develops a torque and eventually the vehicle comes to rest.
The working of electromagnetic braking is similar to that of a disc brake, except that it uses magnetic forces to actuate braking. From a project point of view, it is better to integrate a magnetic system on a disc brake instead of doing everything from scratch. (Note that the materials of the armature and the coil may be different, but it would be enough for producing a braking torque in an experimental set up.)
Links for further references: http://en.wikipedia.org/wiki/Electromagnetic_brake
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