An environmentally protected momentum type, electrically controlled torque producing device consisting of a driving member provided with a multiple of driving shoes with friction lining faces, connecting arms constructed in a manner to hold shoes from engagement with driven member except upon energization of the electrical coil which in turn causes armature to force shoes in an outwardly direction into engagement with the inner periphery of the driven member. Contractile springs are provided to retain driving shoes in the disengaged position while the unit is at zero rotation.