Asymmetric tensions off-centre
API · /slackline-api
Slackline Tension API
healthy
3,192 Subscribers
Tensioned-line point-load statics as an API, computed locally and deterministically — the line-tension and anchor-force numbers a slackliner, highliner or rigger works out before they weight a line. This is the V a loaded line makes under a person, not a self-weight catenary: the tension endpoint takes the span, the sag and the body load and returns the line tension and the horizontal anchor pull, because vertical balance is 2·T·sin(angle) = the body weight — so the flatter the line (the smaller the sag) the more the tension blows up, which is exactly why drum-tightening a line to kill the bounce can load the anchors to many times body weight. The sag endpoint inverts it: from a known line tension it returns the sag a mid-span load settles to (sin angle = weight ÷ twice the tension), and flags when the tension is too low to hold the load at all. The off-centre-load endpoint handles standing away from the middle, where the two halves carry different tensions: the horizontal pull is equal on both sides (H = weight × a × b ÷ (sag × span)) but the shorter, steeper segment runs at the higher tension and fails first — the reason a highliner near an anchor stresses that leash harder than one in the centre. Everything is computed locally and deterministically, so it is instant and private. Ideal for slackline and highline rigging tools, climbing and outdoor-gear apps, and tension-and-anchor calculators. Pure local computation — no key, no third-party service, instant. Geometric statics — combine with the real webbing and anchor ratings. 3 compute endpoints. For a self-weight hanging cable use a catenary API; for working-load-limit and safety factor a rigging API.
api.oanor.com/slackline-api
API health
healthy- Uptime
- 100.00%
- Server probes · 24h
- Avg latency
- 98 ms
- Server probes · 24h
- Subscribers
- 3,192
- active
- Total calls
- 0
- last 7 days
Pricing
Pick a tier — billed monthly, cancel anytime.
Free
Free
- 6,000 calls / month
- 2 requests / second
- Hard cap (429 above quota, no overage)
- 6,000 calls/month
- 2 req/sec
- Tension + sag + off-centre load
- No credit card
Starter
€7.90 /month
- 58,000 calls / month
- 6 requests / second
- Hard cap (429 above quota, no overage)
- 58,000 calls/month
- 6 req/sec
- Anchor-force & off-centre rigging
- Email support
Pro
€26.40 /month
- 240,000 calls / month
- 15 requests / second
- Hard cap (429 above quota, no overage)
- 240,000 calls/month
- 15 req/sec
- Rigging & gear-app pipelines
- Priority support
Mega
€84.00 /month
- 1,100,000 calls / month
- 40 requests / second
- Hard cap (429 above quota, no overage)
- 1,100,000 calls/month
- 40 req/sec
- Platform & catalogue scale
- Dedicated SLA
Built by
Related APIs
Other APIs with overlapping tags.
Winch Drum API
Winch and cable-drum maths as an API, computed locally and deterministically — the rope-capacity, line-pull and rope-out numbers a winch operator, rigger or recovery driver works a drum with. The capacity endpoint gives the rope a drum holds by exact layer geometry: the sum over every full layer of the turns per layer × π × that layer's mean wrap diameter, where turns per layer = drum width ÷ rope diameter and the number of layers = the flange-to-barrel depth ÷ rope diameter — a 10-inch barrel, 20-inch flange, 12-inch-wide drum on half-inch rope holds about 940 ft over 10 layers. The layer-pull endpoint shows why pull falls as the drum fills: the rated pull is for the bare-drum first layer, and as rope piles on, the growing lever arm cuts the line pull and raises the line speed in the same ratio — pull × (first-layer diameter ÷ this layer's diameter) — so the top layer of a deep drum can pull barely half the bottom-layer rating, which is why you spool off to bare drum for a hard pull or add a snatch block. The length-at-layer endpoint gives the rope wound after a number of full layers, for marking the rope or knowing how much line is out. Everything is computed locally and deterministically, so it is instant and private. Ideal for winch- and hoist-sizing tools, recovery and off-road apps, marine and industrial-rigging utilities, and engineering calculators. Pure local computation — no key, no third-party service, instant. Geometric estimate — allow for nesting and freeboard. 3 compute endpoints. For capstan friction use a capstan API; for block-and-tackle a pulley API.
api.oanor.com/winch-api
Mobile Crane Lift API
Mobile-crane lift-planning maths as an API, computed locally and deterministically — the load-moment, tipping-capacity and outrigger-pad numbers a crane operator, lift planner or rigging engineer checks a pick with. The load-moment endpoint gives the load × its working radius (the horizontal distance from the slew centre to the hook), the single figure a crane's rated-capacity limiter watches: a 5-tonne load at 8 m is a 40 tonne-metre moment, the same as 10 tonnes at 4 m, which is why chart capacity falls steeply as the boom luffs out — moment, not weight, tips the crane. The capacity endpoint gives a simplified tipping balance about the fulcrum: the load that just tips = counterweight × its radius ÷ the load radius, and the rated safe load is a stability fraction of that (~75 % on outriggers, ~66 % on crawlers per the standards) — a teaching/sanity figure that ignores the boom and superstructure, never a substitute for the load chart. The outrigger-pad endpoint sizes the float: required pad area = the outrigger leg load ÷ the soil's allowable bearing pressure (and the side of a square mat), since overloading weak ground is a leading cause of overturns — a 30-tonne leg on 200 kPa wants about a 1.2 m square mat. Everything is computed locally and deterministically, so it is instant and private. Ideal for lift-planning and rigging tools, construction and crane-operations apps, and site-safety utilities. Pure local computation — no key, no third-party service, instant. Simplified — always use the manufacturer load chart. 3 compute endpoints. For sling and WLL loads use a rigging API.
api.oanor.com/crane-api
Pulley System API
Pulley and block-and-tackle mechanics as an API, computed locally and deterministically. The advantage endpoint computes the mechanical advantage of a pulley system — the ideal MA equals the number of rope parts supporting the load, which is also the velocity ratio — and returns the effort needed to hold or raise a load, effort = load/(n·efficiency), the length of rope that must be pulled (n times the lift height) and the work in and out. The friction endpoint models a real block and tackle where every sheave loses a little tension: the mechanical advantage becomes MA = e·(1−eⁿ)/(1−e) for a per-sheave efficiency e (≈0.96 for a plain bearing, ≈0.98 for a ball bearing), so it returns the true MA, the overall efficiency and the extra effort friction costs you. The solve endpoint takes any two of the load, the effort and the number of rope parts and returns the third — for example, how many parts you need so a given person can raise a given load, or the heaviest load a winch can lift. Everything is computed locally and deterministically, so it is instant and private. Ideal for rigging, lifting and hoist-design tools, sailing, climbing and theatre-rigging apps, crane and winch sizing, and physics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is pulley and block-and-tackle mechanics; for lever and moment balance use a lever API and for rope-around-a-drum capstan friction use a capstan API.
api.oanor.com/pulley-api
Capstan & Belt Friction API
Capstan and belt-friction maths (the Euler-Eytelwein equation) as an API, computed locally and deterministically. The capstan endpoint applies T1/T2 = e^(μ·β) — the ratio of the tight-side to the slack-side tension of a rope or belt wrapped around a drum depends only on the friction coefficient and the wrap angle, not the drum diameter — and solves for whichever of the two tensions, the friction or the wrap angle you leave out, with the wrap angle given in degrees, radians or whole turns. The holding endpoint shows the capstan effect: how a small force holds or moves a large load, holding force = Load·e^(−μβ) and pulling force = Load·e^(+μβ) — a few turns of rope around a bollard lets one person hold a ship. The belt endpoint sizes a belt drive: from the maximum tight-side tension, the friction and the wrap angle it gives the slack-side tension, the effective (net) tension T1 − T2 that drives the load and, with the belt speed, the maximum power transmittable before the belt slips. Everything is computed locally and deterministically, so it is instant and private. Ideal for mechanical and marine-engineering tools, belt-drive, winch, hoist and band-brake design, climbing and rigging apps, and physics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is belt and rope friction; for belt length, wrap angle and speed ratio use a belt-drive API.
api.oanor.com/capstan-api
Frequently asked questions
Quick answers about pricing, quotas, and integration.
How do I get an API key for Slackline Tension API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Slackline Tension API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Slackline Tension API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Slackline Tension API cost?
Slackline Tension API has a free tier with 100 calls / month. Paid plans start at €7.90 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Slackline Tension API GDPR-compliant?
All requests to Slackline Tension API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.
Pick an endpoint from the list on the left to see its details and try it.
Code snippets
Sign up to get an API key, then call any path under your slug.
curl https://api.oanor.com/slackline-api/SOME_PATH \
-H "x-oanor-key: oanor_test_..."const res = await fetch("https://api.oanor.com/slackline-api/SOME_PATH", {
headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();$ch = curl_init("https://api.oanor.com/slackline-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);import requests
r = requests.get(
"https://api.oanor.com/slackline-api/SOME_PATH",
headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())Ratings
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