In some examples, a system includes a brake rotor, a brake armature configured to engage with the brake rotor to substantially fix a rotational position of the brake rotor relative to the brake armature, and a mechanism mechanically coupled to the brake armature. The brake armature may be configured to rotate in a first rotational direction and a second rotational direction substantially opposite the first rotational direction. The mechanism may be configured to maintain the brake armature in a fixed rotational position when a torque applied to the brake armature in a second rotational direction is less than or equal to a threshold torque value. The mechanism also may be configured to permit rotation of the brake armature in the second rotational direction when torque on the brake armature in the second rotational direction exceeds the threshold torque value.