Pressure needle: live chest-wall loadJammed cartilage dampers, rib 3 and 4, leftA sternum post drives four pairs of curved rib bands through small hydraulic dampers standing in for costal cartilage. The crank's yoke breathes the frame in and out; pulling the stress lever jams the third and fourth left dampers, lighting them red and locking the crank; turning the thermal dial wraps a copper element around them until the glow fades and breathing resumes.