Assembly of the spine robot with urethene washers. The washers are urethane Die stripper material. The durometer at the narrow end shown is 50. The washers get thicker and are of harder 60-70 and 90 durometers as the spine diameter gets larger. The bushings limit travel as well as lock the segments to limit axial rotation during operation. They also prevent the spine segments from rubbing together and reduce shock loads when the spine robot is used to throw objects