Over thinking sling SWL

[roys]

I am overthinking this, can someone please tell me where my thinking is flawed.

 

I have the sling for example the one in my attached picture, where on a straight lift the SWL is 1 ton, but doubled over is 2 ton, so say we have a load of 2 ton, then surely if we take the exact part of the sling where it doubles back on itself, let's say the 6 o'clock position, at that exact point the fibre of the sling is in effect single and so is rated at 1 ton yet is still subjected to a 2 ton load. How can that be?

 

Sorry if I have not explained it very well, perhaps I should not drink in the afternoon.:)

 

[carlos]

er it just is!! each leg is taking half the load but your right it is still just a single sling, get some string or wool and play around trying to break it in different configurations.

[roys]

10 minutes ago, carlos said:

er it just is!! each leg is taking half the load but your right it is still just a single sling, get some string or wool and play around trying to break it in different configurations.

Yip I get it that each leg is taking 1/2 the load, but at the exact pivot, or half way point there isn't 2 legs, there is only the one point taking all the load.

[Gary Prentice]

It's all about moving or supporting mass. Imagine the u configuration the other way up and the apex is a pulley. A hundred kg mass is tied to one end, and the other end is used to lift the mass. 

 

Each leg leg is supporting/taking 100 kg , but the load at the pulley is 200 kg.

[roys]

Yip get that as well Gary.

My head hurts,  in my head head hypothetically (as I wouldn't do it) it would work if a knot was tied at the bottom of the U as then each leg as well as the exact bottom of U, or half way point is now independent.

Dont think I am explaining myself very clearly, sorry gents.

[Arborist]

It's the same if your winching, if you return the wire cable you have twice the pull as a straight pull.

[openspaceman]

1 hour ago, roys said:

 

My head hurts,  in my head head hypothetically (as I wouldn't do it) it would work if a knot was tied at the bottom of the U as then each leg as well as the exact bottom of U, or half way point is now independent.

Dont think I am explaining myself very clearly, sorry gents.

It's the tension in the sling that is supporting the load and the doubled sling suspension assumes there is no friction so the tension is the same throughout the sling. Put a knot in it to prevent the load moving and then the tension is no longer uniform throughout the sling.

[billpierce]

I get what you mean. If you were lifting a weight with a metal eye with the sling doubled going through the eye, I understand that the sling is doubled and each length is under less stress but at the point that it folds around the eye must be under most strain. I.e where it is single.

That what your on about?

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[roys]

6 minutes ago, billpierce said:

I get what you mean. If you were lifting a weight with a metal eye with the sling doubled going through the eye, I understand that the sling is doubled and each length is under less stress but at the point that it folds around the eye must be under most strain. I.e where it is single.

That what your on about?

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Yes that's what I'm talking about

[billpierce]

Yes that's what I'm talking about [emoji4]

Yeah get one you mean. Can't explain/ don't understand the physics. Obvs less stress if sling round a nice round object like a tree.

Hopefully someone can explain or maybe we're just being thick

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