Español| Home | Our Story | Distributors | News | Contact Us |

| Catalog | Manual | Features | Designation | Warranty | Calculator

Recommended Minimum Diameter Sheave

As you know, Camesa has for years recommended that customers use a sheave of diameter at least 400 times the largest armor wire diameter in a cable.  Camesa makes this recommendation so that the armor wires on the outside section of the cable are stretched minimally more than the wires not on the outside of the curve.

The number 400 is somewhat arbitrarily selected; however it has been an agreed upon industry recommendation chosen based on experience over the years with cables.  It is well known that the larger the sheave diameter, the less the damage to the strain on the outer wires of the cable due to the cable passing over the sheave.

In logging cables the outer armor wires are always equal to or larger than the inner armor wires.  In the case of the 1N32 cable, both inner and outer armor wires are the same diameter -.0445".  400 times this diameter is 17.8".  However, commonly available diameter sheaves are 17" from inside to inside of grove (root diameter).  The pitch diameter of this sheave would be 17" + 0.322" or 17.322" when it is used with the 1N32 cable.  The "pitch diameter" refers to the diameter of a line drawn down the center of the cable.  The portion of the cable along this line undergoes minimal strain due to the diameter of the cable vs. the diameter of the sheave.  The portion on the inside of this line (less than the pitch diameter) is compressed, while the portion of cable greater than the pitch diameter (outside of the curve) is stretched.  A difference of 1/2" or 3% between what Camesa recommends and the closest commercially available sheave (17" root diameter) used is not significant.

However, if the customer were to use a 14" diameter sheave, the difference between recommended and used sheaves becomes significant - approximately 17%. Cable damage due to stretching of the armor-.wires on the outer section of a 14" diameter sheave is likely to occur.

Previous Page | Print Page