The end fram that bolts to the com mutator end of the starter housing. It supports the commutator end of the armature with a bushing and often contains the brush holders that support the brushes Operating Principle. The starter motor converts electric current into torque or twisting force through the inter- action of magnetic fields. It has a stationary magnetic field, the field windings, and a current-carrying conduc tor, the armature windings Figure 18-11). When the ar mature windings are placed in this stationary magnetic field and current is passed throu gh the windings, a sec ond magnetic field is generated with its lines of force wrapping around the wire. Since the lines of force in the stationary magnetic field flow in one direction across the winding, they combine on one side of the wire, in. creasing the field strength, but are opposed on the other side, weakening the field strength.