Steek Breaker vs. Fabric Breaker
Having read the various comments regarding rip and impact resistance we agree with the position that a low stretch bekaert steel cord is not a resilient as a heavy duty nylon cord construction.
We do however not agree with the concept of nylon breakers being preferable to the proprietary SFBT Sempertrans (ex-Michelin) high stretch steel cord breaker.
Unlike the fleximat cords, it has 3.25% stretch at 10% of its tensile (similar to nylon) and a 1.6mm diameter. This makes it very shock absorbant and capable of bunching up when placed at a pitch of 8mm or less.
As mentioned by Peter Alderson the fleximat transverse steelcord lies against the longitudinal cords and can result inboth abrasion and fretting corrosions, whereas the SFBT transverse steelcords are produced in a calendared layer with rubber surrounding them. This is placed on top of the rubberized longitudinal cords in one, two or even three layers to create termendous impact resistance and excellent puncture resistance and rip resistance.
The superior rubber to steel adhesions also offer better resistance to the risk of delamination.
With regards to impact resistnce, a "double-density" two layer Metalcord version has currently been operating over three years accepting lumps of copper ore (160PCF) 24" x 24" x 48" (610mm x 610mm x 1219mm) dropping over 10 feet directly onto the belt.
From the point of view of troughability, we have successfully used two transverse layers of the steel cords in a 30" wide belt troughing 35 degrees in northern Quebec.
The transverse cord construction on its own has no affect on transition distance, pulley diameters, or vertical-horizontal curves.
The longitudinal cords, unlike conventional steelcords are not dependent upon size (especially diameter) for load support and impact resistance because tansverse forces are absorbed by the transverse cords, not the rubber surrounding the longitudinal cords. The result is an ability to use 3mm cords placed closely together to further increase flexibility around pulleys and reduce the chances of punctures.
Mechelin technology also provided SFBT Sempertrans with the ability to provide E-type 7x7 longitudinal cords with similar modulus to conventional cords (0.2% stretch) as well as M-type 4x7 longitudinal cords of very low modulus with 0.6% stretch capable of replacing fabric belts, accept shorter transitions, tighter curves, and accept crowned pulleys.
We have sold this product for thirty years and can attest to its unique abilities.
To see a picture of Metalcord follow this link:
345 Marwood Drive
Canada L1H 7P8