Rope & mechanism class

→ minimum diameters

Rope diameter d (mm)

Mechanism class (hoisting)

Not sure? Use our Duty Classification Calculator first

Reeving check (optional)

→ max rope tension

Lifting capacity Q (tons)

Reeving ratio a (rope falls)

Reeving efficiency η

How this calculator works

Rope fatigue life is governed by bending around drums and sheaves. Standards set a minimum diameter ratio h = D/d that rises with mechanism class — the harder the duty, the larger the wheel:

D_drum ≥ h₁·d D_sheave ≥ h₂·d D_equalizer ≥ h₃·d · S = Q·g / (a·η)

D measured at rope pitch (center). Equalizers see no cyclic bending, so h₃ is lower. Results round up to standard sizes.

Class	h₁ drum	h₂ sheave	h₃ equalizer
M1	11.2	12.5	11.2
M2	12.5	14	12.5
M3	14	16	12.5
M4	16	18	14
M5	18	20	14
M6	20	22.4	16
M7	22.4	25	16
M8	25	28	18

h-coefficients per GB/T 3811 / ISO 4308-1 / FEM 1.001. Final drum & sheave design to be confirmed by the manufacturer. © Kinocranes.

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Drum min. pitch Ø (h₁ = 18)	—
Sheave min. pitch Ø (h₂ = 20)	—
Equalizer min. Ø (h₃ = 14)	—

Sheave & Drum Diameter Calculator

Rope & mechanism class

Reeving check (optional)

How this calculator works