Spool Thickness

[strainstress]

I am trying to find out the thickness of the spool required to wind a 1-3/8" rope with 3000 lbs tension load on it. The diameter of the spool is 15".

Here's my approach :

1. Calculate pressure applied by the rope on the cylindrical spool :

p = 2*2*T/(D.spool x D.rope) = 1828psi (Assuming two rows of rope : one over the other, therefore multiplying by 2)

2. Selecting thickness of the spool to ensure that hoop stress on the cylindrical spool due to this pressure is lower than the code allowed value.
t = p*D.spool/(2*AllowableStress)=~1"

1" seems excessive for a spool whose function is to wind and unwind the rope. Am I making a mistake in my approach.

Can someone shed some light on spool design principle ?

Thanks

 

[desertfox]

Hi

Look at page four of this link

http://www.bridon.com/x/downloads/steel_technical.pdf

 

[strainstress]

Thanks desertfox,

The link reaffirms the approach I took. However, I am surprised that the reference formula is independent on the number of times the rope will be would on the spool. I would assume that the contact pressure should be multiplied by the number of times the rope is wound.

 

[strainstress]

Ignore post above, few typos. See below

Thanks desertfox,

The link reaffirms the approach I took. However, I am surprised that the reference formula is independent of the number of times the rope will be would on the spool. Should'nt the contact pressure should be multiplied by the number of times the rope is wound.

 

[ornerynorsk]

A 15 inch spool for 1-3/8 rope???

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[strainstress]

Sorry it's a 7/16" rope, my bad.

 

[desertfox]

Try page four of this link it does exactly what your looking for

http://www.bgisl.com/Hoist_and_Haul_2010_Rebel_Radial_Pressure_Rev_C_from_GR_2010-06-09.pdf

 

[kingnero]

This has already (at least one time) been discussed on this forum. There wasn't a definite answer back then. One of the members on here made a spreadsheet with an iterative method. Google may be your friend...

 

[GregLocock]

Note that the coefficient of friction of the rope is important, as is the ratio of radial to axial stiffness. If mu is low then the inner layers will not detension as the outer layers are wound on.


Cheers

Greg Locock


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