Circumferential Pressure on a member from choked wire 1

[Ussuri]

Does anyone know of any guidance for calculating the pressure exerted on a member from a wire wrapped around in a choked arrangement (think lasso)?

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[SlideRuleEra]

A lasso is an excellent way to look at the problem. Assume no friction (reasonable for a static condition) and that the "thing" lassoed is circular (like a post or pipe).

The only way the lasso can apply force is thru tension (hoop stress).

The only way the post can resist "choking" is by a uniformly distributed, radial force directed outward.

For a moment, assume the post is "crushable" and 14 inches in diameter, for example. Pull on the lasso to shorten the noose (the circumference of the post). Say that the lasso is shortened 4 inches - the post diameter is crushed by 4 inches divided by Pi = 1.27 inches.

The tension in the lasso has a 3.14 to 1 mechanical advantage (4 inch/ 1.27 inch) on the total radial force resisted by a "non-crushable" post.

For the hypothetical dimensions given above, assume tension in the lasso is 120 pounds. Then the total "choking" force that must be resisted by the post is 120 lb x Pi = 377 pounds. For a unit length of the noose this would be 377 lb / 14 inches / Pi = 8.57 lb/ inch of noose length.

Notice that the total force resisted by the post (377 pounds on this case) is independent of the post diameter.

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