Rope drive tensioned by an idler pulley, but this system was not used in the UK and each loop was tensioned between its two pulleys by one of them being movable. Rope drives were also cheaper than belts, around a quarter of the price. The rope drives were placed in a large diagonal shaft at the side of the building, usually windowless and distinctively visible from outside the building. Rope drives required a larger such shaft than comparable belt or shaft drives. As the open shaft represented a channel for transmitting fires, unlike the narrow holes of a shaft drive, it needed
Fly system used for spot rigging, where they are often equipped with swivel-pivots to divert lines across a large range of angles. Tension blocks are single-sheave blocks located at the lower end of the arbor guide track, beneath the arbor. The operating line is reeved through the tension block from the bottom of the arbor through the rope lock. Tension blocks typically ride vertically along the arbor guide system tracks, instead of being fixed, to allow for variation in the length of the operating line. Counterweights are heavy objects that are used to balance the lineset loads in a fly system. In