[djf]

Wasn't the whole idea about the Winchester drive that a cushion of air prevented the heads from ever touching the surface?

[RightWhale]

the whole idea about the Winchester drive that a cushion of air prevented the heads from ever touching the surface

Yeah. The head can bounce anyway if the harmonic mode is out of balance, and it can happen even if the box is stationary.

[LibWhacker]

Yes, check out that link I posted. The problem is that the heads are "flying" only a couple of millionths of an inch off the surface of the platter that's spinning at 10,000 rpm. So any vibration, or even any slight current fluctuation, could conceivably cause the head to come into contact with the platter.