A snatch block is a pulley in a hinged housing that opens so you can drop the line in rather than thread it. It is the cheapest way to make a winch pull harder, and the least understood item in most recovery kits.
What Does a Double Line Pull Do?
It roughly doubles pulling power and roughly halves line speed. The line runs from the drum, out to the anchor, through the block and back to the recovery point on the vehicle. Two lines now share the load, so each carries about half of it and the winch motor works far less hard for the same result.
Why It Helps More Than the Numbers Suggest
There is a second effect that gets missed. A winch only produces its rated pull on the first layer of rope on the drum, and every layer above that reduces the pull. A double line pull uses twice as much rope, which keeps the drum on a lower layer for longer and holds the winch nearer its rated figure.
You also halve the current draw for a given load, which matters on a machine with a small battery and on any long recovery where the motor has time to get hot.
Setting It Up
- Anchor the block, not the hook. The block goes on the tree strap or the fixed anchor.
- Bring the line back to a rated recovery point on the vehicle, never to a tow ball.
- Use rated shackles. A hardware store shackle is not a recovery item.
- Use a tree saver strap around a trunk rather than the rope itself.
- Check the block is rated above the winch, and that its groove suits your rope.
Match the block to the rope. Synthetic rope wants a smooth, wide groove with no sharp edges, and running it over a block meant for steel cable damages it quietly over several pulls.
Redirecting a Pull
The other use for a block is changing direction. A winch pulls in a straight line, and a vehicle stuck at an angle to the only solid anchor will pull sideways off the drum, which chews the fairlead and stacks the rope against one flange. A block on a second anchor lets you pull the vehicle the way it needs to go while the rope leaves the winch straight.
Doing It Safely
Lay a damper or a heavy jacket over the line before tension goes on. If something parts, the damper drops the energy to the ground instead of letting it travel. Keep everyone out of the triangle formed by the two lines, never step over a loaded rope and take the tension up slowly rather than snatching it.
See winch accessories for blocks, shackles and controls, and synthetic rope winches if you are still choosing the winch itself.