Sling Tension — Snatch Block Redirect
Resultant force on a snatch-block anchor from line pull and the included angle between rope parts.
A redirect block sees the VECTOR SUM of both rope parts — at a 180° wrap the block anchor carries double the line pull. The included-angle entry makes the resultant explicit; many 'mystery' anchor failures are just this resultant nobody computed.
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.
Resultant force on a snatch-block anchor from line pull and the included angle between rope parts. A free crane load, wind & rigging safety tool — no sign-up, no upload, instant results in your browser.
About Sling Tension — Snatch Block Redirect
Sling Tension — Snatch Block Redirect computes the governing relationship R = 2·P·cos(θ/2) live as you type. A redirect block sees the VECTOR SUM of both rope parts — at a 180° wrap the block anchor carries double the line pull. The included-angle entry makes the resultant explicit; many 'mystery' anchor failures are just this resultant nobody computed. 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 — Snatch Block Redirect
- 1Enter your values — Line pull, Included angle between parts (sensible defaults are pre-filled).
- 2Read the live results: Anchor resultant.
- 3Check the "with your numbers" line to see R = 2·P·cos(θ/2) substituted step by step.
- 4Adjust inputs until the scenario matches yours, then copy or share the result.
Why use Sling Tension — Snatch Block Redirect?
- ✓Instant, free and private — every calculation runs client-side in your browser; nothing is uploaded
- ✓Built on the stated formula R = 2·P·cos(θ/2) 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.)
- ✓A redirect block sees the VECTOR SUM of both rope parts — at a 180° wrap the block anchor carries double the line pull.
- ✓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 — snatch block redirect use?+
It evaluates R = 2·P·cos(θ/2), 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?+
A redirect block sees the VECTOR SUM of both rope parts — at a 180° wrap the block anchor carries double the line pull. 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?+
Resultant force on a snatch-block anchor from line pull and the included angle between rope parts. A free crane load, wind & rigging safety tool. The included-angle entry makes the resultant explicit; many 'mystery' anchor failures are just this resultant nobody computed. 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.
Related tools
- Sling Tension — Winch Drum Dead Wraps
- Sling Tension — Tagline Control Force
- Sling Tension — Two-Point Suspension Share
- Capacity Check — Flat-Top Tower Crane
- Capacity Check — Hammerhead Tower Crane
- Capacity Check — Luffing-Jib Tower Crane
- Capacity Check — Self-Erecting Tower Crane
- Airway Resistance — Decline Ramp (Trucking)
- Mat Cooling Window — Cold-Weather Limit Check
Related Manufacturing tools
Spindle Speed Calculator — Aluminum 6061
Carbide starting RPM for milling Aluminum 6061: n = 1000·Vc/(π·D) with a handbook cutting speed preset.
● LiveSpindle Speed Calculator — Mild Steel 1018
Carbide starting RPM for milling Mild Steel 1018: n = 1000·Vc/(π·D) with a handbook cutting speed preset.
● LiveSpindle Speed Calculator — Stainless 304
Carbide starting RPM for milling Stainless 304: n = 1000·Vc/(π·D) with a handbook cutting speed preset.
● Live