Shackle Basics
Part 1 In a Series By Andy Slater

How many of us think about the condition of our pulling hardware before we use it.  Or how that hardware is supposed to be used.  I cant count the number of times I have seen shackles misused on the trails.  People put a lot of trust in a piece of hardware that if misused can cause a catastrophic incident.  In the next few paragraphs I will discuss how to determine the size and capacity of shackles and how to rig them properly before pulling either yourself or someone else.

Size
The size of a shackle is determined by the diameter of the beam (A).  It is not determined by the diameter of the pin.  Most shackles have the diameter stamped on them.  If not, use a tape measure to estimate the size

Screw Pin Shackles

Dimensions-Inches

Max. Load Tons

Size Dia.

Pin or Bolt Dia.

7/16

1/2

1

1/2

5/8

2

5/8

3/4

3

3/4

7/8

4

7/8

1

6

1

1 1/8

8

1 1/8

1 1/4

9

1 1/4

1 3/8

12

Capacity

When tested all shackles are pulled at a uniform rate of speed in a direct tension.  Any deviations such as angular lifts, shock loads, modification of the basic forging etc. will result in drastically reduced maximum loads.  In many cases, if a shackle is not pulled with even pressure on the pin and the upper portion of the shackle the capacity can be reduced by as much as 70%.  In other words, if its not used correctly a shackle rated for 6 tons can be reduced to less than 2 tons.

 

Rigging

So what is the correct way to use a shackle?  In most cases you want to have the strap applying even pressure to the pin.  The object is to keep from applying point pressure to any part of the pin.  The only reason you should turn the shackle around is if your shackle mount is wide enough to apply even pressure to the pin.

Summary
When choosing a shackle make sure it will fit your application.  It is unlikely that a winch would rip a shackle in half.  But put that shackle in a situation where that vehicle is stuck behind a rock with the shackle not properly positioned and you could be looking a missile.  Most 3 and 4-inch straps have higher capacities than a 7/8-inch shackle.  So use caution when using shackles or any other pulling hardware.  If a shackle is misused, it will happen sooner or later.  Next month I will talk about straps.