Crab and the Deadman

The crab, anchored by a deadman, pulls the line through a pulley attached to a tree. The line, supported by the shear legs, then raises the massive oak frame.

The crab, or capstan, also trades distance for strength. If the axle where the rope winds is eight inches thick, but the arms are eight feet long, the four people pushing it will have a 12:1 mechanical advantage.

The crab itself has to be solidly anchored. If there is no convenient tree, a deadman anchor will serve. The deadman is just a log buried in an undercut trench dug at right angles to the load—so what could go wrong?

Murphy's law works even as you sleep. Say you're raising a huge oak earthfast barn frame. The cable runs from the crab, under the frame to a tree, through a block, over a pair of shear legs and back to the frame. The blocks and lines are plenty strong, the shear legs well lashed, the snub lines secure. You've thought of everything, but a gentle rain the night before raising day softens the soil around your anchor in the earth. Halfway up with the oak frame, the deadman starts pulling free. Some shouting and some quickly pointed fence rails speared

The crab, anchored by a deadman, pulls the line through a pulley attached to a tree. The line, supported by the shear legs, then raises the massive oak frame.

into the walls of his grave keep the deadman down in his hole. The wall goes up—another close call, and a bad call at that.

It's not as if the battle of Gettysburg hinged on your charging forward with the raising. Wisdom should have commanded the wall to be backed down until you could dig a deeper pit. What might have happened if your improvised fence rail solution failed?

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