Series 991C / Series 991N Tee Guide Double Purchase Arbors
Double purchase rigging is used when arbor travel is restricted. For each foot of arbor travel, the batten travels two feet. In order to balance the load on the pipe batten, two pounds of counterweight must be added for each pound of load on the pipe batten. The efficiency of this style of arbor is diminished, resulting in more effort required to raise or lower a balanced set.
Model 991C and 991N double purchase counterweight arbors are designed to be captured and guided between tee or jay bar. Each arbor is fabricated from heavy steel shapes to provide a sturdy frame in which to load counterweight. Arbor rods are spaced 10" on center. They are available in increments from 6 to 12 feet. Ball Bearing Roller Guides and Arbor Guide Shoes are sold separately.
The arbor top is outfitted with a sheave assembly to reeve the lift and purchase lines back toward the head block. The arbor bottom is outfitted with a sheave assembly to reeve the purchase line from the tension block back toward the floor. Provisions must be made for a separate tie-off of the lift and purchase lines at the head block and the purchase line at the floor area