How to Set Up a Double Pulley System

Rigging your own block and tackle takes some thought.

Reeving blocks to set up a double pulley system requires a little thought. A double pulley system, also known as a "block and tackle," consists of the pulleys, or blocks, and the tackle, the ropes riven through the blocks. You must decide if you will use a double pulley system with one sheave--the roller in a pulley--in each block, which will give you a mechanical advantage of 3 to 1, or a double pulley system with two sheaves in each block, which will give you a mechanical advantage of 5 to 1.

Things You'll Need

• 2 blocks, each either two-sheave or three-sheave
• Line, natural or synthetic fiber

Instructions

Rigging Two Single-Sheave Pulleys (Gun Tackle)

1. 

   Lay the blocks on the deck, 2 to 3 feet apart, with one block on its side and the other on its face. The hooks should point away from each other. The block lying on its side will be the upper block of the tackle; the bottom block will attach to the load.

2. 

   Reeve the line from the left, through the sheave of the block lying on its side.

3. 

   Reeve the rope through the sheave of the block lying on its face.

4. 

   Bring the rope up to the becket of the block lying on its side and secure it to the becket with a becket bend or an eye splice.

5. 

   Use the block that has the rope belayed to its becket as the uppermost block in your tackle to gain the best mechanical advantage.

Reeving Two Double Pulleys (Twofold Purchase)

1. 

   Lay the blocks on the deck, 2 to 3 feet apart, with one block on its side and the other on its face. The hooks should point away from each other. The block lying on its side will be the upper block of the tackle; the bottom block will attach to the load.

2. 

   Reeve the line from the left, through the sheave nearest the deck on the block lying on its side.

3. 

   Reeve the rope through the one sheave of the block lying on its face.

4. 

   Reeve the rope though the empty sheave of the block lying on its side.

5. 

   Reeve the rope through the remaining sheave of the block lying on its face.

6. 

   Pass the rope up to the becket of the block lying on its side and secure it to the becket with a becket bend or an eye splice.

7. 

   Use the block that has the rope belayed to its becket as the uppermost block in your tackle to gain the best mechanical advantage.

Tips & Warnings

• Until riven through a block, it's called "line." After being riven through a block, it becomes part of "tackle" and is called rope.

• Always ensure that the line and blocks chosen have a sufficient safe working load for the task you are attempting.

References

• "Handbook of Rigging"; Joseph A. MacDonald, W. E. Rossnagel, Lindley R. Higgins; 2009

Resources

• "The Art of Rigging"; George Biddlecombe; 1990