A hand force at the crank radius balances the weight moment at a fixed drum radius. The ideal mechanical advantage is the radius ratio.
Windlass Interactive Calculator
Enter load mass and fixed drum/crank radii. Results are static and lossless—not rated capacity or a lifting plan.
Ideal radius ratio
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Ideal balancing crank force
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Mass times 9.8 m/s2
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Static load moment
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Equation Used
W=9.8m; MA=rc/rd; Fin=W/MA; drum torque=W rd.
The calculator uses g=9.8 m/s2. Rope buildup, efficiency and acceleration are omitted.
- Load is static and represented by mass times 9.8 m/s2.
- Forces act tangentially at fixed radii.
- The windlass is rigid and lossless.
- Drum radius does not change with rope layers.
- Structure, bearings, rope, brake, dynamics and safety are omitted.
Ideal Windlass Moment Balance
NASA Glenn defines torque as force times moment arm.
What This Calculator Represents
A static lossless radius-ratio balance.
Static comparison
W=9.8m
MA=rc/rd
Fin=W/MA
tau=Wrd
MA=rc/rd
Fin=W/MA
tau=Wrd
Worked Scenario
For 60 kg, 100 mm drum and 500 mm crank, ideal advantage is 5:1, weight 588 N, input force about 118 N and drum torque 58.8 N m.
Assumptions and Limits
No losses, rope buildup, dynamics, brake, structure or safety rating is included.
Frequently Asked Questions
Is input force actual?
No; it is ideal.
Are losses included?
No.
Does drum radius change?
Not in this model.
Is acceleration included?
No.
Is holding safety checked?
No.
Can this approve lifting equipment?
No.
References
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