How to determine the diameter of a cable

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    Cable Diameter
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Discussion Overview

The discussion revolves around determining the diameter of a cable required to support multiple buckets, considering yield strength, safety factors, and load distribution. The scope includes mathematical reasoning and engineering design considerations.

Discussion Character

  • Mathematical reasoning, Technical explanation, Debate/contested

Main Points Raised

  • One participant calculates the required area and diameter of the cable based on the total weight of the buckets and applies the yield strength and safety factor.
  • Another participant agrees with the calculation method but does not verify the numerical results.
  • Additional participants confirm that the calculations appear correct but raise concerns about the design methodology, suggesting it may be wasteful.
  • Some participants propose that varying the diameter of the cable along its length could be a more efficient design approach, though they note practical complications with joints and attachments.

Areas of Agreement / Disagreement

While there is some agreement on the calculation method, there is disagreement regarding the design approach and efficiency, with multiple competing views on how to optimize cable diameter.

Contextual Notes

Participants express uncertainty about the practicality of different design approaches and the implications of load distribution across multiple points versus a single point load.

packersfan851
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A Cable that has a yield strength of 620 MPa and a safety factor of 3. This cable must be able to support 5 buckets which must be able to carry up 5,429.554 kg each.
Bucket mass is negligible.

Stress = Mass/Area
Area = force/stress

My attempt at a solution:
Total weight 5 buckets must carry = 5,429.554 kg * 5 = 27147.77 kg

Area = 27147.77kg * 9.8ms^2 / 206.667MPa x 10^6
Area = .00128

.00128 = ∏d^2 / 4
.00164 = d^2
.040496m = d
or 40.497mm

I know this is probably all wrong.
 
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That looks correct to me, your method at least, I don't have a calculator right now to check your numbers.
 
Calculation looks ok as well.
 
Wouldn't this methodology be a bit wasteful design wise? In addition to utilizing a specified factor of safety the loading is then taken to be occurring in one specific point as a combined whole when in reality the buckets are five distinct and spaced point loads?
 
I guess you are right. You could use a different diameter for each section of rope. eg getting thicker as you go up and the load increases. Not clear if that would reduce cost though. In practice the joints and method of attaching the buckets would complicate the issue.
 

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