Sling Tension — Winch Drum Dead Wraps
Capstan-equation holding force of dead wraps on a winch drum from wrap count and friction.
Capstan math: each wrap multiplies holding by e^(µθ). Three dead wraps at µ≈0.1 hold ~6.6× the anchor-point load — the reason standards demand a minimum of 2–3 wraps remain on every drum at full payout. The anchor clamp alone is never the plan.
Formula
Note: Rigging and crane decisions are life-safety critical. This calculator is a planning aid — the load chart, sling tags, site lift plan and a qualified lift director govern every real lift.
Capstan-equation holding force of dead wraps on a winch drum from wrap count and friction. A free crane load, wind & rigging safety tool — no sign-up, no upload, instant results in your browser.
About Sling Tension — Winch Drum Dead Wraps
Sling Tension — Winch Drum Dead Wraps computes the governing relationship T_load/T_anchor = e^(µθ) [capstan equation] live as you type. Capstan math: each wrap multiplies holding by e^(µθ). Three dead wraps at µ≈0.1 hold ~6.6× the anchor-point load — the reason standards demand a minimum of 2–3 wraps remain on every drum at full payout. The anchor clamp alone is never the plan. Defaults are pre-filled with realistic values for this exact scenario, and the worked example substitutes your numbers step by step so the math is never a black box.
How to use Sling Tension — Winch Drum Dead Wraps
- 1Enter your values — Line tension (load side), Dead wraps on drum, Rope–drum friction µ (sensible defaults are pre-filled).
- 2Read the live results: Force at rope anchor, Holding ratio e^(µθ).
- 3Check the "with your numbers" line to see T_load/T_anchor = e^(µθ) [capstan equation] substituted step by step.
- 4Adjust inputs until the scenario matches yours, then copy or share the result.
Why use Sling Tension — Winch Drum Dead Wraps?
- ✓Instant, free and private — every calculation runs client-side in your browser; nothing is uploaded
- ✓Built on the stated formula T_load/T_anchor = e^(µθ) [capstan equation] with authoritative sources cited on the page (ASME B30.5/B30.9/B30.20 — Cranes, slings and below-the-hook devices; Wire Rope Technical Board — Wire Rope Users Manual, 4th ed.)
- ✓Capstan math: each wrap multiplies holding by e^(µθ).
- ✓SI ⇄ Imperial toggle converts your inputs in place, so you can work in the units your drawings use
Frequently asked questions
What formula does the sling tension — winch drum dead wraps use?+
It evaluates T_load/T_anchor = e^(µθ) [capstan equation], exactly as published. Sources: ASME B30.5/B30.9/B30.20 — Cranes, slings and below-the-hook devices; Wire Rope Technical Board — Wire Rope Users Manual, 4th ed.. The substituted worked example on the page lets you verify every step against the textbook.
How should I read the result — and how far can I trust it?+
Capstan math: each wrap multiplies holding by e^(µθ). Rigging and crane decisions are life-safety critical. This calculator is a planning aid — the load chart, sling tags, site lift plan and a qualified lift director govern every real lift.
When is this calculator the right tool for the job?+
Capstan-equation holding force of dead wraps on a winch drum from wrap count and friction. A free crane load, wind & rigging safety tool. Three dead wraps at µ≈0.1 hold ~6.6× the anchor-point load — the reason standards demand a minimum of 2–3 wraps remain on every drum at full payout. For neighbouring scenarios, the related tools below cover the same engine with different presets.
Does it support both metric and imperial units?+
Yes — the SI ⇄ Imperial toggle converts the values already in the fields, preserving the physical quantity, so you can flip mid-calculation without re-entering anything.
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