UuVareations

A typical hard drive has two electric motors, one to spin the disks and one to position the read/write head assembly. The disk motor has an external rotor along with the platters; the stator windings are fixed constantly in place. The actuator includes a read-write head under the tip of their very end (near center); a thin printed-circuit cable connects the read-write head to the hub from the actuator. A flexible, somewhat ‘U’-shaped, ribbon cable, seen edge-on below and to the left with the actuator arm while in the first image even more clearly within the second, continues the hyper link from the head to the controller board about the opposite side.

The top support arm is incredibly light, but more rigid; in modern drives, acceleration along at the head reaches 550 Gs.

Opening the Hard Disk drive

The silver-colored structure may be the top plate from the permanent-magnet and moving coil motor that swings the heads to the desired position. The plate supports a thin neodymium-iron-boron (NIB) high-flux magnet. Beneath this plate will be moving coil, known as being the voice coil by analogy for the coil in loudspeakers, which can be mounted on the actuator hub, and beneath what a second NIB magnet, mounted on underneath plate from the motor (some drives simply have one magnet).

The voice coil, itself, is shaped rather like an arrowhead, and made from doubly-coated coppmagnet wire. The inner layer is insulation, and also the outer is thermoplastic, which bonds the coil together after it’s wound on the form, which makes it self-supporting. The portions in the coil across the two sides from the arrowhead (which point to the actuator bearing center) interact when using the magnetic field, having a tangential force that rotates the actuator. Current flowing radially outward along one side from the arrowhead, and radially inward on the other produces the tangential force.. When the magnetic field were uniform, each side would generate opposing forces that would cancel the other person out. Meaning that the surface of the magnet is half N pole, half S pole, with all the radial dividing line in the middle, causing the two sides of the coil to see opposite magnetic fields and produce forces that add as opposed to canceling. Currents along side top and bottom with the coil produce radial forces that wont rotate the top.