Rigging Hardware — Sling D/d Ratio Derate
Sling D/d Ratio Derate capacity check with the standard derating rules applied.
Bend a wire rope sling around its own diameter and HALF its strength is gone — the D/d curve is rigging's least-known big number. Shackle pins are the everyday case: a 16 mm sling on a 19 mm pin runs near D/d 1.2. Sling ratings already assume a generous bend; tight hardware silently revokes it.
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.
Sling D/d Ratio Derate capacity check with the standard derating rules applied. A free crane load, wind & rigging safety tool — no sign-up, no upload, instant results in your browser.
About Rigging Hardware — Sling D/d Ratio Derate
Rigging Hardware — Sling D/d Ratio Derate computes the governing relationship Wire-rope efficiency vs D/d (WRTB curve: 100% @25:1 → ~50% @1:1) live as you type. Bend a wire rope sling around its own diameter and HALF its strength is gone — the D/d curve is rigging's least-known big number. Shackle pins are the everyday case: a 16 mm sling on a 19 mm pin runs near D/d 1.2. Sling ratings already assume a generous bend; tight hardware silently revokes it. 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 Rigging Hardware — Sling D/d Ratio Derate
- 1Enter your values — Bend diameter D (pin/corner), Rope diameter d (sensible defaults are pre-filled).
- 2Read the live results: D/d ratio, Strength retained.
- 3Check the "with your numbers" line to see Wire-rope efficiency vs D/d (WRTB curve: 100% @25:1 → ~50% @1:1) substituted step by step.
- 4Adjust inputs until the scenario matches yours, then copy or share the result.
Why use Rigging Hardware — Sling D/d Ratio Derate?
- ✓Instant, free and private — every calculation runs client-side in your browser; nothing is uploaded
- ✓Built on the stated formula Wire-rope efficiency vs D/d (WRTB curve: 100% @25:1 → ~50% @1:1) 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.)
- ✓Bend a wire rope sling around its own diameter and HALF its strength is gone — the D/d curve is rigging's least-known big number.
- ✓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 rigging hardware — sling d/d ratio derate use?+
It evaluates Wire-rope efficiency vs D/d (WRTB curve: 100% @25:1 → ~50% @1:1), 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?+
Bend a wire rope sling around its own diameter and HALF its strength is gone — the D/d curve is rigging's least-known big number. 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?+
Sling D/d Ratio Derate capacity check with the standard derating rules applied. A free crane load, wind & rigging safety tool. Shackle pins are the everyday case: a 16 mm sling on a 19 mm pin runs near D/d 1.2. 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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