Stresses on wire rope drum 1

[amarks]

I know this has probably been discussed before, but I am looking for the correct equations to calculate the stresses on a drum, drum barrel, and drum flanges as the number of layers of rope increase, and the pulling force increases during operation.

Back story is I am designing a transmission line pulling unit and am looking at designing the drum that will hold the wire rope that will pull the transmission line back through the towers. The drum on the unit will hold approximately 22,000-26,000 feet of wire rope. I need to design the drum adequately so that the barrel wont collapse and the flanges wont flex outward or buckle.

thanks,
Alex

 

[Compositepro]

You would use separate capstan/pull rollers to provide pull force on the rope and wind onto a spool at much lower tension. This avoids the issue of spool diameter changes and cable damage on the spool.

 

[amarks]

Compositepro - I've seen those before and would like to use those on a future design. However the customer is wanting a design where the planetary gearbox will be direct coupled to the drum.

That being said, for the future design, what are the calculations for reduction of force per wrap of a capstan style roller? I've seen them with 3, 4, 5, up to 8 or 12 grooves.

 

[GregLocock]

I vaguely remember that Blodgetts has an analysis for this.

I have measured the effect of of multiple layers of windings on a drum, and have also developed a reasonably good proprietary analytical model. It turns out the ratio of radial stiffness to axial stiffness of the cable is important, as is the coefficient of friction. Do not ignore the lateral bursting pressure on the sides of the reel.

Cheers

Greg Locock


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[amarks]

GregLocock - Interesting, that is good to know about the axial and radial stiffnesses of the cable. Wonder if that concern would be the same on synthetic rope?

The lateral bursting pressure on the sides is a major concern of mine. I just dont know how to measure the force that will be applied to the drum heads.

 

[GregLocock]

Well, you do an FBD of a few layers of cable. I think it took about a day to put a spreadsheet model together and a couple of weeks to validate it physically.

Cheers

Greg Locock


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[amarks]

Greg - you happen to have an example of your spreadsheet?

 

[dvd]

Good luck with this. Designing a drum to hold 5 miles of synthetic rope, winding under tension, does not seem like the right entry point for someone asking for equations on drum design. Do you do this type of design in some slightly different variation, or just seems like an interesting challenge?

 

[amarks]

DVD - Yes sir, the power and distribution industry does this everyday. They also do this with fiber cable. As an example here is a pulling unit that has 24,000 feet on each drum and is a 4 drum puller. T-3DP-200-FT4 Wagner Smith unit.

 

[GregLocock]

No I don't since my employer paid for me to develop and validate it.

Cheers

Greg Locock


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[BEMPE16524]

here some reference you can look at later:
1. BS2573-2
2. BS5500
3. API2C
4. DNV 2.22 (JUNE 2013: PAGE 51) - you may want to see latest version.

you can get detail info regarding the hoop stress and flange thickness at this section.​

R.Efendy

 

[amarks]

BEMPE16524 - The DnV reference is excellent! Thanks for this information.