ISO 4184 V-Belt Drive Calculator — Belt Selection, Tension & Wrap Angle
ISO 4184 — Belt drives — Classical and narrow V-belts — Lengths in datum system
ISO 4184 is the international standard for classical and narrow V-belts in the datum-length system. It specifies the cross-section designations (Z/10, A/13, B/17, C/22, D/32, E/38 for classical; SPZ, SPA, SPB, SPC for narrow), their datum dimensions, and the standardised datum lengths that determine how a belt is catalogued and selected. It is the geometric foundation underpinning every V-belt drive calculation: the section designation fixes the groove angle, cross-section area, and permissible tension for a given drive duty, while the datum length governs centre-distance selection and stock availability.
In engineering practice ISO 4184 is used alongside DIN 7753 (which tabulates rated power per belt by speed and pulley diameter) and the Euler–Eytelwein capstan equation (which gives tight- and slack-side tensions from design power, belt velocity and wrap angle). Together these three elements form the complete V-belt design method. MechanixCalc implements this method for classical V-belts, flat belts and synchronous (timing) belts — computing wrap angle, belt length, design-power-adjusted tensions and service-factor guidance — and generates a branded PDF engineering report suitable for design handover.
Calculators that implement ISO 4184
What ISO 4184 covers
- Classical V-belt section designations (Z, A, B, C, D, E) and narrow section designations (SPZ, SPA, SPB, SPC) with datum dimensions
- Datum-system belt lengths: the standardised preferred lengths that govern centre-distance selection and stock availability
- Groove geometry: included groove angle (typically 34°–38° depending on sheave diameter) and the effective-friction amplification it produces versus a flat belt
- Belt velocity and wrap angle computation for open, crossed and tensioner-idler drive configurations
- Design power (nominal power × service factor Ks) and section selection guidance based on design power and small-sheave speed
- Minimum wrap-angle threshold (120° on the small pulley) below which rated capacity must be derated or an idler added
Governing formulas
T₁ / T₂ = e^(µ_eff · α) where µ_eff = µ / sin(β / 2)where T₁ = tight-side tension (N); T₂ = slack-side tension (N); µ = friction coefficient between belt and sheave material; β = included groove angle of the sheave (rad; ≈ 34° for standard V-belt sheaves); µ_eff = effective (wedge-amplified) friction coefficient; α = wrap angle on the small (driver) sheave (rad)
α₁ = π − 2 · arcsin((D₂ − D₁) / (2C)) [rad]
L = 2C + π(D₁ + D₂)/2 + (D₂ − D₁)² / (4C)where α₁ = wrap angle on the small (driver) pulley (rad); D₁ = driver pulley diameter (mm); D₂ = driven pulley diameter (mm); C = centre distance (mm); L = belt pitch length (mm). Multiply α₁ by 180/π for degrees.
P_design = Ks · P ; Fe = P_design × 1000 / v ; v = π · D₁ · n₁ / 60 000where P_design = design (service-factored) power (kW); Ks = service factor (≥ 1.0 for smooth load; 1.2–1.6 for shock/reversing duty); P = nominal transmitted power (kW); Fe = effective (tangential) pull at the belt (N); v = belt velocity (m/s); n₁ = driver sheave speed (rpm)
Frequently asked questions
What is ISO 4184 used for?
ISO 4184 defines the dimensions, section designations and datum lengths for classical and narrow V-belts. Engineers use it to select the correct belt cross-section and standardised length for a drive, and to establish the groove geometry needed for accurate tension and slip calculations. It is the geometric foundation of every V-belt design calculation.
What is the difference between ISO 4184 and DIN 7753?
ISO 4184 specifies V-belt geometry — the cross-section designations, datum dimensions and standardised datum lengths. DIN 7753 tabulates the rated power per belt as a function of sheave diameter and belt speed, giving the designer the capacity curves needed to determine how many belts a drive requires. In practice the two standards are used together: ISO 4184 for belt selection and geometry, DIN 7753 for capacity verification.
Does MechanixCalc implement the full ISO 4184 method?
The Belt & Pulley Calculator computes the geometry defined by ISO 4184 — section-selection guidance, wrap angle, belt pitch length and datum-length selection — and combines it with the Euler–Eytelwein tension analysis (DIN 7753 / classical V-belt practice) to give tight-side tension T₁, slack-side tension T₂, effective pull and shaft bearing load. The full method and all inputs are shown in the generated PDF engineering report.
How does a V-belt groove increase drive capacity compared with a flat belt?
The V-groove wedges the belt sideways, creating a normal force much larger than the radial belt tension alone. The effective friction coefficient becomes µ_eff = µ / sin(β/2), where β is the included groove angle (≈ 34°). For a typical µ = 0.35 and β = 34°, µ_eff ≈ 1.20 — roughly 3.4× higher than a flat belt — which exponentially increases the Euler tension ratio and allows far more power to be transmitted before slip.
Is the ISO 4184 V-belt calculator free?
You can use it during a free 30-minute preview with no sign-up, and a free 14-day account trial unlocks every calculator with no credit card required. The branded PDF engineering report and saved calculations are part of a paid plan.
Related standards
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