# B Combined Stress of Cable Around Pulley

1. Aug 10, 2016

### formula428

I have an application where I'm trying to lift an object by using a pulley and pulling on the cable. We were forced to use a pretty small pulley and thin cable, so my question is how to analyze the total stress of the cable? I should be looking for axial stress, bending stress (cable around pulley), and bearing stress (cable onto pulley)?

I did some initial calculations and they didn't seem to make sense. Note the cable we are using is a McMaster multi-strand flexible cable, so I know it's pretty easy to physically bend it around. How would I go about calculating these?

2. Aug 10, 2016

### nasu

I think the main factor (about the cable) is the tensile stress in the cable. This will tell if it can hold the load.
There is also the stress in the bar or cable that supports the pulley. And if the pulley is really flimsy you may bend its axis so you may need to look at the bending stress in the axis too..

3. Aug 10, 2016

### sophiecentaur

4. Aug 10, 2016

### formula428

I'm not concerned about the pulley or bolt/pin that supports it, those are easy checks and I'm plenty good there.

My question is how to actually calculate the combined stresses in the cable. What methods are used?

5. Aug 10, 2016

### Staff: Mentor

It is usually assumed that the bending stresses in a cable are negligible. Take the cable and see what kind of bending stresses you calculate based on the radius of the pulley and the thickness of the cable.

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