4-4.
Block and Tackle.
a. Block and tackle, also referred to as falls, are one type of hoisting equipment used to raise
and lower the platform of a swing-stage scaffold. Falls are made in various combinations of single,
double, and triple blocks. The number of sheaves (pulleys) used designates the size of the block. As the
number of sheaves is increased, the mechanical advantage is increased. To avoid getting dirt into the
operating parts of the blocks, reeve a set of blocks by laying the blocks out on a clean and level surface
other than the ground. Figure 4-33 shows the reeving and threading of single and double blocks.
Figure 4-33. Reeving single and double blocks
b. When the reeving is completed, the blocks are ready to be fastened. Connect one block
securely to the load and the other to a substantial anchor. To move the load, pull on the fall line. When
you use a block and tackle for swing-stage scaffolds, the rope must be first-grade Manila that is at least
3/4-inch in diameter.
4-25
EN0562
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