Full definition
The operating principle of V-belts, flat belts, and Poly-V belts, where power is transmitted through friction between the belt surfaces and the pulley. The transmittable power is governed by the Euler-Eytelwein equation: T1/T2 = e^(μθ), where T1 and T2 are tight- and slack-side tensions, μ is the effective friction coefficient, and θ is the wrap angle in radians. For V-belts, the wedging action in the groove multiplies the effective friction by 1/sin(α/2), where α is the groove angle (typically 34-40°), increasing effective μ by 3-5x compared to flat belts. Greater wrap angle means greater capacity (each additional degree helps). Minimum wrap: 120°. Advantages over positive (toothed) drives: automatic overload protection (belt slips before damage), lower noise, simpler installation. Disadvantages: inherent creep/slip (1-2%), speed ratio not perfectly constant, periodic retensioning required.