Retractable traction system

A system for retractably deploying enhanced traction of a wheel, the wheel having a tread and an axis of rotation, the system comprising:

• a set of grippers, each gripper having a cleat and a radially disposed strut;
• a set of first strut mounts, each first strut mount coupled to one of the struts, the first strut mount configured to support motion of its corresponding strut between a parked position and an engaged position,
• wherein, in the engaged position of such strut, the corresponding cleat is axially disposed and engaged against the tread of the wheel and, in the parked position of such strut, the corresponding cleat is disengaged from the tread of the wheel;
• a faceplate configured to rotate with the wheel, wherein when such strut is in the engaged position, such strut is coupled to the faceplate and moves with the faceplate and the wheel, and when such strut is in the parked position the strut causes the cleat to be withdrawn in a radial direction from the tread;
• and
• a cleat deployment mechanism comprising,
• a circular first raceway defining a center that coincides with the axis of rotation and a set of first sliders mounted for rotational motion in the first raceway, the cleat deployment mechanism being coupled to the struts and configured on actuation to cause automatic deployment of the struts into the engaged position, and
• a set of second sliders mounted for rotational motion in a second raceway concentric with the first raceway, and a set of second strut mounts, each second strut mount coupled to one of the second sliders and to one of the struts.