A novel climbing robots with the use its own weight is presented. The climbing method is similar to climbing approach of timber jacks in Japan. Main features are that the climbing robot driven by servomotors with worm gear can rest on a tree by using own weight without any energy and move up and down quickly. To realize the method, position of center of mass of the pruning robot is located outside of tree. A basic mechanism analysis for avoiding falling down from a cylinder is presented. Moreover, it is shown experimentally that an experimental climbing robot equipped four active wheels can move up and down a tree by the proposed climbing method.
