Full definition
The internal reinforcement member that carries the full tensile load in a power transmission belt, running along the belt length at the neutral pitch line. Material choices: polyester (standard, low cost, 2-4% elongation), aramid/Kevlar (high strength, minimal elongation <1%, premium), fiberglass (low stretch, excellent fatigue, standard in timing belts), and steel cable (highest strength, used in heavy conveyor belts). The cord material determines belt elongation under load, fatigue resistance, temperature limits, and maximum power capacity. Per ISO 4184 the cord sits at the pitch diameter, which is the reference for length measurement. Proper cord-to-rubber adhesion is critical and achieved through RFL (resorcinol-formaldehyde-latex) treatment.