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         tems and the high speed of the hoisting lines, the overall
         efficiency of such approaches can be around 55%.
           Certain embodiments of the present technique, however,
         include a hoisting system using one or more single-part
         hoisting lines to reduce the friction and inertia effects associ-
         ated with the conventional approach of adding sheaves and
         increasing the number of parts of the line in the reeving to
         increase the mechanical advantage. It is noted that figures
         14-16 and 18 depict such single-part hoisting line arrange-
         ments, while figure 17 depicts a multi-part hoisting line ar-
         rangement. In one embodiment a 1500-ton hoisting system
         using  a  drawworks  with  a  single-part  hoisting  line,  with
         no mechanical advantage from multi-part block-and-tackle
         reeving, is estimated to have lower friction losses (e.g., ap-  Figure 19: Partially fragmented side view of a zipline.
         proximately 30% lower) compared to a conventional draw-
         works of the same capacity.                          rider. When the brake is engaged to stop the reels’ rotation,
                                                              the brake  line  is  brought  to a stop, thereby arresting  the
                                                              motion of rider.
                                                               Figure 19 depicts a continuous  assist braking and con-
                                                              trol system 10. Rider 32 is tethered to a point on a moving
                                                              brake line 40 which parallels main cable 12. Various ways
                                                              of tethering rider 32 to brake line 40 are described below.
                                                              By controlling the movement, speed and acceleration (or de-
                                                              celeration) of brake line 40, a zipline operator may control
                                                              the movement, speed and acceleration  (or  deceleration) of
                                                              rider 32 and apply appropriate braking force as rider 32 ap-
                                                              proaches landing platform 20.
                                                               Brake line 40 may be an endless loop entrained around
                                                              and tensioned between upper reel 50 and lower reel 52. The
                                                              endless loop may be suspended above main cable  12 in a
                                                              generally vertical plane, so that the endless loop has a lower
                                                              cable portion 46 and an upper cable portion 48 which may
                                                              travel in  opposite directions  as indicated by arrows  46A,
         Figure 18: Fifth example of a hoisting system.       48A. Brake line 40 may alternatively be oriented in a gen-
                                                              erally horizontal plane (not shown), such that two side-by-
                                                              side cable portions thereof may travel in opposite directions.
           This reduction may be of particular use in an active heave
         compensating system where high line speed and accelera-
         tions may often occur to compensate for heaving motion of
         the  floating  vessel  12.  In  addition  to  the  efficiencies  dis-
         cussed above, the single-part hoisting system can eliminate
         the cut-and-slip procedures periodically required for conven-
         tional multi-part block-and-tackle reeving systems. Further,
         multiple single-part lines 20 can be wound from the draw-
         works 22 and used to suspend the load 30 so that there is no
         single point of failure that would allow the load 30 to drop
         from a broken line 20. In some embodiments, the single-part
         reeving can include one or more wire ropes connected direct-
         ly to a live top drive load 30 and anchored to the rotating
         drawworks drum 26.
         Continuous assist zipline braking and control system  Figure 20: Shuttle brake line braking and control system.
         Pat. 9,573,605 U.S. class A63G 21/22 Int. class B61H 9/02
         Inventor: Charles Z. Steele, Whistler, CA., David E. Udow,   Brake line 40 may be made of a strong rope or stranded steel
         Whistler, CA., Robert L. Steele, Winnipeg, CA.       wire cable, and is preferably inelastic. Upper and lower reels
         Assignee: Ziptrek Ecotours Inc., Whistler, CA.       50, 52, may be rotatably mounted on upper and lower reel
           A continuous assist braking and control system operable   frames 51, 53 respectively. Upper and lower reel frames 51,
         to control the movement, speed and acceleration of a zipline   53 may be mounted on supports 14, 18 or on overheard sup-
         rider traversing a zipline. A brake line is entrained around   ports 17, 21 or on other suitable supports.
         first and second reels, and suspended above the zipline. The   Brake line 40 need not be an endless loop. For example, as
         rider is tethered to the brake line. A brake is coupled to at   shown in figure 20, brake line 40 may be a long cable 46B
         least one  of the  reels.  When  the  brake  is  disengaged, the   having terminal ends, each of which is wound around upper
         brake line is pulled along with the rider as the rider tra-  reel 90 and lower reel 92 respectively. Upper and lower reels
         verses the zipline. When the brake is engaged, the reels’ rate   90, 92 may be rotatably mounted on upper and lower reel
         of rotation is slowed, thereby slowing the brake line and the   frames 91, 93 respectively which may in turn be mounted on

         60     Wire Rope News & Sling Technology   April 2017
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