Hello everybody...

We work with a power cable manufacturing firm. We use 4mm x 0.8mm Steel strip / steel wire of diameter 1.40mm for armoring the assembled cable cores. Can anybody explain how to calculate the exact weight of steel, used as armor in a particular cable? It varies as and when lay length varies rite? We used the following formulas, but we are unable to standardize the X factor,do exactly.

Strip: (4*0.8*n*density*X) grams / m
Wire: (0.7857*1.40*1.40*n*density*X) grams / m

where n is number of wires / strips. Any idea on the lay length connection to the value of X shall be greatly appreciated.

Thanks...

Hello alwin18,

When dealing with a multitude of very small metallic wires or strips helically wrapped over a relatively large diameter cable with a smooth and reasonably round outer surface and with "100%" coverage, the gaps between the individual wires or strips may indeed become a relevant factor. This might be what is throwing off your calculations. One way to do this would be to determine a constant experimentally. Another way would be to contact a technical expert in braiding manufacturing and see if they have a set of modified equations or algorithm for multi wire spiral winding AKA as helix winding that you could use. The first name that comes to mind is:

Mr. Frank Knobloch
Product Manager Braiding & Winding
Maschinenfabrik Niehoff GmbH & Co KG
Fürther Strasse 30
91126 Schwabach
Phone: +49 9122 977-240
E-Mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Web site: www.Niehoff.de

If Frank doesn't have the answer, perhaps he can refer to you to someone who has this information.

Please let us know what you found out. Thank you.

Regards
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com
519 641- 3212

To calculate the increase in length due to lay, all you have to do is use Pythagora's theorem i.e. square of actual wire length=square of linear cable length + square of mean diameter of armouring. Mean diameter of armouring= diameter over innersheath+one strip/wire thickness/diameter.

naren kotecha

By length-in both above cases-I meant length of one lay of armour which should give ratio of actual wire length versus cable length

naren kotecha

Hi Peter

thanks for the suggestions...we normally go by the individual wire calculation and not by considering the armour like a metal sheet...