Block and Tackle - Rigging Methods

Rigging Methods

A tackle may be

• "Rove to advantage" – where the pull on the rope is in the same direction as that in which the load is to be moved. The hauling part is pulled from the moving block.
• "Rove to disadvantage" – where the pull on the rope is in the opposite direction to that in which the load is to be moved. The hauling part is pulled from the fixed block.

While roving to advantage is the most efficient use of equipment and resources ( Roving to disadvantage simply adds an extra sheave to change the direction of the pulling line. This doesn't change the velocity ratio but increases friction losses ), there are several situations in which roving to disadvantage may be more desirable, for example when lifting from a fixed point overhead. The decision of which to use depends on pragmatic considerations for the total ergonomics of working with a particular situation.

The common wisdom prefers a block and tackle "rove to advantage." However, if the load is to be hauled against gravity, then there is a benefit to reeving the block and tackle to disadvantage, because in this case the weight of the individual can offset the weight of the load. On the other hand, if the load is to be hauled parallel to the ground, there is a benefit to reeving the block and tackle to advantage, because the pulling force is in the direction of the load movement allowing the individual to manage obstacles. It is important to notice that the mechanical advantage is different if the block and tackle is "rove to advantage" or "rove to disadvantage." The mechanical advantage will always be one greater when "rove to advantage" than when "rove to disadvantage."