Axial Magnetic Suspensions

Abstract

A vertical ferromagnetic needle can be supported in macroscopic equilibrium by magnetic forces alone. One method using a variable magnetic field is described and shown to have considerable latitude in details of application. A 6 g rotor having a moment of inertia of about 0.8 g cm² was suspended in this manner. It was spun at about 1200 rev./sec., its behavior indicating that with suitable driving arrangements much higher speeds should be attainable. At 600 rev./sec. with driving torque zero it exhibited a deceleration of about 2×10⁻³ rev./sec.². A suspended element weighing about ¾ g showed torsion constants, depending on adjustments, down to 7×10⁻⁶ dy cm/rad.