{"id":100199,"date":"2026-02-15T20:26:20","date_gmt":"2026-02-15T20:26:20","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100199"},"modified":"2026-02-15T20:26:20","modified_gmt":"2026-02-15T20:26:20","slug":"propeller-unbalance","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/nb\/calculators\/propeller-unbalance\/","title":{"rendered":"Kalkulator for ubalanse i propell | Vibrasjon i marin aksel"},"content":{"rendered":"\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"WebApplication\",\"name\":\"Propeller Unbalance Calculator\",\"alternateName\":[\"Marine Propeller Balancing Calculator\",\"Shaft Vibration Calculator\"],\"description\":\"Free online calculator for propeller unbalance per ISO 21940. Computes permissible unbalance, eccentricity, centrifugal force, and per-blade allowance for marine and industrial propellers.\",\"url\":\"https:\/\/vibromera.eu\/calculators\/propeller-unbalance\/\",\"applicationCategory\":\"Engineering Calculator\",\"operatingSystem\":\"Any (Web Browser)\",\"offers\":{\"@type\":\"Offer\",\"price\":\"0\",\"priceCurrency\":\"EUR\"},\"creator\":{\"@type\":\"Organization\",\"name\":\"Vibromera\",\"url\":\"https:\/\/vibromera.eu\/\"},\"datePublished\":\"2025-01-01\",\"dateModified\":\"2026-02-15\",\"inLanguage\":\"en\",\"isAccessibleForFree\":true,\"featureList\":[\"Propeller unbalance per ISO 21940\",\"Per-blade allowance\",\"Centrifugal force calculation\",\"Eccentricity output\",\"Auto-calculation on input change\",\"Preset configurations\"],\"keywords\":\"propeller unbalance, marine propeller, shaft vibration, centrifugal force, balance grade, per-blade allowance\"}\n<\/script>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"FAQPage\",\"mainEntity\":[\n{\"@type\":\"Question\",\"name\":\"Why is propeller balancing important for marine vessels?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Unbalanced propellers generate centrifugal forces at shaft speed that transmit through bearings into the hull. This causes excessive vibration, accelerated stern tube bearing and seal wear, fatigue cracking in shafting, and passenger\/crew discomfort. Proper balancing per ISO 21940 minimizes these effects.\"}},\n{\"@type\":\"Question\",\"name\":\"What balance grade G should I use for a marine propeller?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"G16 is the most common grade for marine propellers. G6.3 is used for high-speed or navy vessels where vibration limits are tighter. G40 may be acceptable for slow-speed workboat propellers.\"}},\n{\"@type\":\"Question\",\"name\":\"How is per-blade allowance calculated?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"The total permissible unbalance is divided equally among all blades. For a 4-blade propeller with 1000 g\u00b7mm total allowance, each blade may have up to 250 g\u00b7mm of unbalance. This assumes blades are symmetrically arranged.\"}},\n{\"@type\":\"Question\",\"name\":\"What centrifugal force does propeller unbalance create?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Centrifugal force F = U \u00d7 \u03c9\u00b2 \/ 1,000,000 where U is unbalance in g\u00b7mm and \u03c9 is angular velocity in rad\/s. Even small unbalances at high RPM create significant forces \u2014 for example, 5000 g\u00b7mm at 300 RPM produces about 5 N, but at 3000 RPM it produces about 500 N.\"}},\n{\"@type\":\"Question\",\"name\":\"Can I balance a propeller on the shaft without removing it?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Yes, in-situ (on-site) propeller balancing is possible using portable balancing instruments like Vibromera's Balanset series. Trial weights are attached to the propeller, vibration response is measured, and correction masses are calculated. This avoids costly drydocking.\"}}\n]}\n<\/script>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"BreadcrumbList\",\"itemListElement\":[\n{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/vibromera.eu\/\"},\n{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Calculators\",\"item\":\"https:\/\/vibromera.eu\/calculators\/\"},\n{\"@type\":\"ListItem\",\"position\":3,\"name\":\"Propeller Unbalance Calculator\",\"item\":\"https:\/\/vibromera.eu\/calculators\/propeller-unbalance\/\"}\n]}\n<\/script>\n\n<link rel=\"preconnect\" href=\"https:\/\/fonts.googleapis.com\">\n\n<link rel=\"preconnect\" href=\"https:\/\/fonts.gstatic.com\" crossorigin>\n\n<link href=\"https:\/\/fonts.googleapis.com\/css2?family=DM+Sans:ital,opsz,wght@0,9..40,300;0,9..40,400;0,9..40,500;0,9..40,600;0,9..40,700;1,9..40,400&#038;family=JetBrains+Mono:wght@400;500;600&#038;family=Fraunces:opsz,wght@9..144,700;9..144,800&#038;display=swap\" rel=\"stylesheet\">\n\n<link rel=\"stylesheet\" href=\"https:\/\/cdn.jsdelivr.net\/npm\/katex@0.16.11\/dist\/katex.min.css\">\n\n<style>\n:root {\n    --vc-bg: #f4f1ec;\n    --vc-surface: #ffffff;\n    --vc-surface-alt: #f8f6f2;\n    --vc-ink: #1a1a1a;\n    --vc-ink-secondary: #5a5650;\n    --vc-ink-muted: #8a857e;\n    --vc-accent: #c85a2a;\n    --vc-accent-hover: #b04d22;\n    --vc-accent-light: #fdf0ea;\n    --vc-blue: #2a5c8c;\n    --vc-blue-light: #eaf1f8;\n    --vc-green: #2a7a4b;\n    --vc-green-light: #eaf8ef;\n    --vc-yellow: #a67c00;\n    --vc-yellow-light: #fef9e8;\n    --vc-red: #b91c1c;\n    --vc-red-light: #fef2f2;\n    --vc-border: #d9d4cc;\n    --vc-border-light: #e8e4dd;\n    --vc-shadow: 0 1px 3px rgba(26,26,26,0.06), 0 4px 12px rgba(26,26,26,0.04);\n    --vc-shadow-lg: 0 4px 12px rgba(26,26,26,0.08), 0 16px 40px rgba(26,26,26,0.06);\n    --vc-radius: 8px;\n    --vc-radius-lg: 12px;\n    --vc-font: 'DM Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;\n    --vc-mono: 'JetBrains Mono', 'Consolas', 'Monaco', monospace;\n    --vc-display: 'Fraunces', Georgia, serif;\n}\n\n.vc-calculator {\n    font-family: var(--vc-font);\n    font-size: 15px;\n    line-height: 1.65;\n    color: var(--vc-ink);\n    max-width: 960px;\n    margin: 0 auto;\n    padding: 20px 16px 40px;\n    -webkit-font-smoothing: antialiased;\n}\n.vc-calculator *, .vc-calculator *::before, .vc-calculator *::after { box-sizing: border-box; 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}\n}\n<\/style>\n\n<div class=\"vc-calculator\" id=\"vc-propeller-unbalance\">\n\n<header class=\"vc-header\">\n    <p class=\"vc-header-eyebrow\">Free Engineering Tool<\/p>\n    <h1 class=\"vc-header-title\">Propeller Unbalance Calculator<\/h1>\n    <p class=\"vc-header-subtitle\">Calculate permissible propeller unbalance, centrifugal force, eccentricity, and per-blade allowance per ISO 21940. Essential for marine shaft vibration control.<\/p>\n    <div class=\"vc-badges\">\n        <span class=\"vc-badge\">ISO 21940-11<\/span>\n        <span class=\"vc-badge\">Marine Propellers<\/span>\n        <span class=\"vc-badge\">Per-Blade Allowance<\/span>\n    <\/div>\n<\/header>\n\n<div class=\"vc-card\">\n    <form class=\"vc-form\" id=\"vc-form\" autocomplete=\"off\">\n        <div class=\"vc-form-grid\">\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-mass\">Propeller Mass <span class=\"vc-label-hint\">(kg)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-mass\" inputmode=\"decimal\" step=\"any\" min=\"0.001\" placeholder=\"e.g. 500\" value=\"500\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-blades\">Number of Blades<\/label>\n                <select class=\"vc-select\" id=\"vc-blades\">\n                    <option value=\"3\">3 blades<\/option>\n                    <option value=\"4\" selected>4 blades<\/option>\n                    <option value=\"5\">5 blades<\/option>\n                    <option value=\"6\">6 blades<\/option>\n                <\/select>\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-diameter\">Propeller Diameter <span class=\"vc-label-hint\">(mm)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-diameter\" inputmode=\"decimal\" step=\"any\" min=\"1\" placeholder=\"e.g. 1200\" value=\"1200\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-speed\">Shaft Speed <span class=\"vc-label-hint\">(RPM)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-speed\" inputmode=\"decimal\" step=\"any\" min=\"1\" placeholder=\"e.g. 300\" value=\"300\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-grade\">Balance Grade G<\/label>\n                <select class=\"vc-select\" id=\"vc-grade\">\n                    <option value=\"40\">G40 \u2014 Workboat propellers<\/option>\n                    <option value=\"16\" selected>G16 \u2014 Standard marine propellers<\/option>\n                    <option value=\"6.3\">G6.3 \u2014 High-speed \/ navy vessels<\/option>\n                    <option value=\"2.5\">G2.5 \u2014 Precision propellers<\/option>\n                <\/select>\n            <\/div>\n        <\/div>\n\n        <div class=\"vc-presets\">\n            <div class=\"vc-presets-label\">Quick presets<\/div>\n            <button type=\"button\" class=\"vc-preset-btn\" data-m=\"500\" data-b=\"4\" data-d=\"1200\" data-s=\"300\" data-g=\"16\">4-blade \u00d81200mm 500kg 300RPM G16<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-m=\"200\" data-b=\"5\" data-d=\"800\" data-s=\"450\" data-g=\"6.3\">5-blade \u00d8800mm 200kg 450RPM G6.3<\/button>\n        <\/div>\n    <\/form>\n\n    <div class=\"vc-results\" id=\"vc-results\">\n        <div class=\"vc-results-head\">\n            <h2 class=\"vc-results-title\">Results<\/h2>\n            <button type=\"button\" class=\"vc-copy-btn\" id=\"vc-copy-btn\">\n                <svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><rect x=\"9\" y=\"9\" width=\"13\" height=\"13\" rx=\"2\"\/><path d=\"M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1\"\/><\/svg>\n                Copy\n            <\/button>\n        <\/div>\n        <div class=\"vc-result-grid\">\n            <div class=\"vc-rcard vc-rcard-primary\">\n                <div class=\"vc-rcard-label\">Permissible Unbalance<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-ubal\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Specific Unbalance (Eccentricity)<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-ecc\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Centrifugal Force at Permissible Unbalance<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-force\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Per-Blade Allowance<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-blade\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Angular Velocity \u03c9<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-omega\">\u2014<\/div>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- Theory & Formulas -->\n<div class=\"vc-section vc-open\" id=\"vc-sec-theory\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"true\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\ud83d\udcd8<\/span>\n            <span class=\"vc-section-title\">Theory &amp; Formulas<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner vc-theory\">\n            <h3>Permissible Propeller Unbalance (ISO 21940)<\/h3>\n            <p>The permissible unbalance for a propeller is calculated using the same ISO 21940-11 formula used for all rotating machinery:<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-1\"><\/div>\n            <p>Where <strong>G<\/strong> is the balance grade (mm\/s), <strong>m<\/strong> is propeller mass (kg), and <strong>\u03c9<\/strong> = 2\u03c0\u00b7n\/60 is angular velocity (rad\/s).<\/p>\n\n            <h3>Centrifugal Force from Unbalance<\/h3>\n            <p>The centrifugal force generated by unbalance at operating speed:<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-2\"><\/div>\n            <ul>\n                <li><strong>U<\/strong> \u2014 unbalance (g\u00b7mm)<\/li>\n                <li><strong>\u03c9<\/strong> \u2014 angular velocity (rad\/s)<\/li>\n                <li><strong>F<\/strong> \u2014 centrifugal force (N)<\/li>\n            <\/ul>\n\n            <h3>Per-Blade Allowance<\/h3>\n            <p>For symmetrical propellers, the total permissible unbalance is divided equally among all blades:<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-3\"><\/div>\n\n            <h3>Typical Balance Grades for Propellers<\/h3>\n            <table class=\"vc-table\">\n                <thead><tr><th>Grade<\/th><th>Application<\/th><\/tr><\/thead>\n                <tbody>\n                    <tr><td>G40<\/td><td>Slow-speed workboat propellers, non-critical<\/td><\/tr>\n                    <tr><td>G16<\/td><td>Standard marine propellers, cargo vessels<\/td><\/tr>\n                    <tr><td>G6.3<\/td><td>High-speed craft, navy vessels, passenger ferries<\/td><\/tr>\n                    <tr><td>G2.5<\/td><td>Precision propellers, low-noise submarines<\/td><\/tr>\n                <\/tbody>\n            <\/table>\n\n            <h3>Practical Example<\/h3>\n            <div class=\"vc-example-box\">\n                <div class=\"vc-example-title\">Example \u2014 4-Blade Marine Propeller<\/div>\n                <p><strong>Given:<\/strong> Mass = 500 kg, Speed = 300 RPM, Grade = G16, 4 blades<\/p>\n                <p>\u03c9 = 2\u03c0 \u00d7 300 \/ 60 = 31.42 rad\/s<\/p>\n                <p>U<sub>per<\/sub> = 16 \u00d7 500 \u00d7 1000 \/ 31.42 = <strong>254,620 g\u00b7mm<\/strong><\/p>\n                <p>Eccentricity = 16 \u00d7 1000 \/ 31.42 = <strong>509.2 \u03bcm<\/strong><\/p>\n                <p>F = 254,620 \/ 1,000,000 \u00d7 31.42\u00b2 = <strong>251.5 N<\/strong><\/p>\n                <p>Per blade: 254,620 \/ 4 = <strong>63,655 g\u00b7mm<\/strong><\/p>\n            <\/div>\n\n            <div class=\"vc-warning-box\">\n                <p style=\"margin:0;font-size:14px;color:var(--vc-ink-secondary);\"><strong>\u26a0\ufe0f Note:<\/strong> Marine propellers operate in harsh conditions. Fouling, blade damage, and cavitation erosion can alter balance over time. Periodic vibration monitoring is recommended to detect developing unbalance.<\/p>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- Related Calculators -->\n<div class=\"vc-section\" id=\"vc-sec-related\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\ud83d\udd17<\/span>\n            <span class=\"vc-section-title\">Related Calculators<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner\">\n            <div class=\"vc-related\">\n                <a class=\"vc-related-link\" href=\"\/calculators\/residual-unbalance-iso1940\/\">Residual Unbalance (ISO 21940)<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/fan-blade-centrifugal-force\/\">Fan Blade Centrifugal Force<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/separator-balancing\/\">Separator Balancing<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/foundation-vibration-from-machine\/\">Foundation Vibration<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/trial-weight-calculator\/\">Trial Weight Calculator<\/a>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- FAQ -->\n<div class=\"vc-section\" id=\"vc-sec-faq\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\u2753<\/span>\n            <span class=\"vc-section-title\">Frequently Asked Questions<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner\">\n            <div class=\"vc-faq-list\" id=\"vc-faq-list\"><\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- Promo -->\n<div class=\"vc-promo\">\n    <div class=\"vc-promo-text\">\n        <strong>Vibromera \u2014 Portable Balancing &amp; Vibration Analysis<\/strong><br>\n        Professional field balancing instruments for marine propellers, shafts, and rotating machinery. Achieve ISO 21940-11 compliance on-site.\n    <\/div>\n    <a class=\"vc-promo-link\" href=\"https:\/\/vibromera.eu\/\" target=\"_blank\" rel=\"noopener\">Learn More<\/a>\n<\/div>\n\n<footer class=\"vc-footer\">\n    <p>\u00a9 2024\u20132026 <a href=\"https:\/\/vibromera.eu\/\">Vibromera<\/a> \u2014 Engineering Calculators<\/p>\n    <p style=\"font-size:12px;margin-top:4px;\">Based on ISO 21940-11. Calculator #240. Last updated: February 2026<\/p>\n    <div class=\"vc-footer-links\">\n        <a href=\"\/calculators\/engineering-calculators\/\">All Calculators<\/a>\n        <a href=\"https:\/\/vibromera.eu\/contacts\/\">Contact<\/a>\n    <\/div>\n<\/footer>\n\n<\/div>\n\n<script src=\"https:\/\/cdn.jsdelivr.net\/npm\/katex@0.16.11\/dist\/katex.min.js\"><\/script>\n<script>\n(function() {\n    'use strict';\n\n    var SLUG = 'propeller-unbalance';\n\n    function $(id) { return document.getElementById(id); }\n    function fmt(n, d) { if(isNaN(n)||!isFinite(n)) return '\u2014'; var f=n.toFixed(d===undefined?2:d); return f.replace(\/(\\.\\d*?)0+$\/,'$1').replace(\/\\.$\/,''); }\n\n    function calculate() {\n        var mass = parseFloat($('vc-mass').value);\n        var blades = parseInt($('vc-blades').value);\n        var diameter = parseFloat($('vc-diameter').value);\n        var speed = parseFloat($('vc-speed').value);\n        var grade = parseFloat($('vc-grade').value);\n\n        if (!mass || mass <= 0 || !speed || speed <= 0) {\n            $('vc-results').classList.remove('vc-visible');\n            return;\n        }\n\n        var omega = 2 * Math.PI * speed \/ 60;\n        var eper = grade * 1000 \/ omega; \/\/ \u03bcm\n        var uper = grade * mass * 1000 \/ omega; \/\/ g\u00b7mm\n        var force = uper \/ 1e6 * omega * omega; \/\/ N\n        var perBlade = uper \/ blades;\n\n        $('vc-r-ubal').innerHTML = (uper >= 1000 ? fmt(uper, 0) : fmt(uper, 1)) + ' <span class=\"vc-rcard-unit\">g\u00b7mm<\/span>';\n        $('vc-r-ecc').innerHTML = fmt(eper, 2) + ' <span class=\"vc-rcard-unit\">\u03bcm<\/span>';\n        $('vc-r-force').innerHTML = (force >= 1000 ? fmt(force, 0) : fmt(force, 1)) + ' <span class=\"vc-rcard-unit\">N<\/span>';\n        $('vc-r-blade').innerHTML = (perBlade >= 1000 ? fmt(perBlade, 0) : fmt(perBlade, 1)) + ' <span class=\"vc-rcard-unit\">g\u00b7mm<\/span> <span class=\"vc-rcard-unit\">(' + blades + ' blades)<\/span>';\n        $('vc-r-omega').innerHTML = fmt(omega, 2) + ' <span class=\"vc-rcard-unit\">rad\/s<\/span>';\n\n        $('vc-results').classList.add('vc-visible');\n\n        var u = new URL(window.location);\n        u.searchParams.set('mass', mass); u.searchParams.set('blades', blades);\n        u.searchParams.set('diameter', diameter); u.searchParams.set('speed', speed);\n        u.searchParams.set('grade', grade);\n        history.replaceState(null, '', u.toString());\n\n        saveHistory({ mass:mass, blades:blades, diameter:diameter, speed:speed, grade:grade,\n            _summary: 'm=' + mass + 'kg, ' + blades + '-blade \u00d8' + diameter + 'mm, ' + speed + 'RPM, G' + grade });\n    }\n\n    \/* Presets *\/\n    document.querySelectorAll('.vc-preset-btn').forEach(function(btn) {\n        btn.addEventListener('click', function(e) {\n            e.preventDefault();\n            $('vc-mass').value = this.getAttribute('data-m');\n            $('vc-blades').value = this.getAttribute('data-b');\n            $('vc-diameter').value = this.getAttribute('data-d');\n            $('vc-speed').value = this.getAttribute('data-s');\n            $('vc-grade').value = this.getAttribute('data-g');\n            calculate();\n        });\n    });\n\n    \/* Auto-calculate *\/\n    $('vc-form').addEventListener('input', calculate);\n    $('vc-form').addEventListener('change', calculate);\n\n    \/* Copy *\/\n    $('vc-copy-btn').addEventListener('click', function() {\n        var text = 'Propeller Unbalance Calculation\\n' +\n            '\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\\n' +\n            'Mass: ' + $('vc-mass').value + ' kg\\n' +\n            'Blades: ' + $('vc-blades').value + '\\n' +\n            'Diameter: ' + $('vc-diameter').value + ' mm\\n' +\n            'Speed: ' + $('vc-speed').value + ' RPM\\n' +\n            'Grade: G' + $('vc-grade').value + '\\n' +\n            'Permissible Unbalance: ' + $('vc-r-ubal').textContent + '\\n' +\n            'Eccentricity: ' + $('vc-r-ecc').textContent + '\\n' +\n            'Centrifugal Force: ' + $('vc-r-force').textContent + '\\n' +\n            'Per-Blade: ' + $('vc-r-blade').textContent + '\\n' +\n            '\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\\n' +\n            'vibromera.eu\/calculators\/propeller-unbalance\/';\n        if (navigator.clipboard) {\n            navigator.clipboard.writeText(text).then(function() {\n                var btn = $('vc-copy-btn');\n                btn.classList.add('vc-copied');\n                btn.innerHTML = '<svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><polyline points=\"20 6 9 17 4 12\"\/><\/svg> Copied!';\n                setTimeout(function() {\n                    btn.classList.remove('vc-copied');\n                    btn.innerHTML = '<svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><rect x=\"9\" y=\"9\" width=\"13\" height=\"13\" rx=\"2\"\/><path d=\"M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1\"\/><\/svg> Copy';\n                }, 2000);\n            });\n        }\n    });\n\n    \/* Collapsible sections *\/\n    document.querySelectorAll('.vc-section-toggle').forEach(function(btn) {\n        btn.addEventListener('click', function() {\n            var section = this.closest('.vc-section');\n            var isOpen = section.classList.contains('vc-open');\n            section.classList.toggle('vc-open');\n            this.setAttribute('aria-expanded', !isOpen);\n        });\n    });\n\n    \/* FAQ *\/\n    var faqData = [\n        { q: 'Why is propeller balancing important for marine vessels?', a: '<p>Unbalanced propellers generate centrifugal forces at shaft speed that transmit through bearings into the hull. This causes excessive vibration, accelerated stern tube bearing and seal wear, fatigue cracking in shafting, and passenger\/crew discomfort. Proper balancing per ISO 21940 minimizes these effects.<\/p>' },\n        { q: 'What balance grade G should I use for a marine propeller?', a: '<p><strong>G16<\/strong> is the most common grade for standard marine propellers (cargo vessels, tankers). <strong>G6.3<\/strong> is used for high-speed craft, navy vessels, and passenger ferries where vibration must be minimized. <strong>G40<\/strong> may suffice for slow-speed workboat propellers.<\/p>' },\n        { q: 'How is per-blade allowance calculated?', a: '<p>The total permissible unbalance is divided equally among all blades. For a 4-blade propeller with 1000 g\u00b7mm total allowance, each blade may have up to 250 g\u00b7mm. This assumes blades are symmetrically arranged around the hub.<\/p>' },\n        { q: 'What centrifugal force does propeller unbalance create?', a: '<p>Centrifugal force F = U \u00d7 \u03c9\u00b2 \/ 1,000,000 (N), where U is unbalance in g\u00b7mm and \u03c9 is angular velocity in rad\/s. Even small unbalances create significant forces at higher RPM \u2014 force increases with the square of speed.<\/p>' },\n        { q: 'Can I balance a propeller on the shaft without removing it?', a: '<p>Yes, in-situ propeller balancing is possible using portable balancing instruments like Vibromera\\'s Balanset series. Trial weights are attached, vibration is measured, and correction masses are calculated \u2014 avoiding costly drydocking.<\/p>' }\n    ];\n    var faqList = $('vc-faq-list');\n    faqData.forEach(function(faq) {\n        faqList.innerHTML += '<div class=\"vc-faq-item\"><button type=\"button\" class=\"vc-faq-q\"><span>' + faq.q + '<\/span><svg class=\"vc-faq-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg><\/button><div class=\"vc-faq-a\"><div class=\"vc-faq-a-inner\">' + faq.a + '<\/div><\/div><\/div>';\n    });\n    faqList.addEventListener('click', function(e) {\n        var btn = e.target.closest('.vc-faq-q');\n        if (!btn) return;\n        btn.closest('.vc-faq-item').classList.toggle('vc-open');\n    });\n\n    \/* History *\/\n    function saveHistory(entry) {\n        var key = 'vc_history_' + SLUG;\n        var arr = [];\n        try { arr = JSON.parse(localStorage.getItem(key)) || []; } catch(e) {}\n        entry._ts = new Date().toISOString();\n        arr.unshift(entry);\n        if (arr.length > 10) arr = arr.slice(0, 10);\n        try { localStorage.setItem(key, JSON.stringify(arr)); } catch(e) {}\n    }\n\n    \/* URL Params *\/\n    function loadParams() {\n        var p = new URLSearchParams(window.location.search);\n        p.forEach(function(v, k) { var el = $(k) || $('vc-' + k); if (el) el.value = v; });\n    }\n\n    \/* KaTeX *\/\n    function renderFormulas() {\n        try {\n            katex.render('U_{per} = \\\\frac{G \\\\times m \\\\times 1000}{\\\\omega} \\\\quad [g \\\\cdot mm]', $('vc-katex-1'), { displayMode: true, throwOnError: false });\n            katex.render('F = \\\\frac{U}{10^6} \\\\times \\\\omega^2 \\\\quad [N]', $('vc-katex-2'), { displayMode: true, throwOnError: false });\n            katex.render('U_{blade} = \\\\frac{U_{per}}{N_{blades}}', $('vc-katex-3'), { displayMode: true, throwOnError: false });\n        } catch(e) {}\n    }\n\n    function init() {\n        loadParams();\n        renderFormulas();\n        calculate();\n    }\n\n    if (document.readyState === 'loading') {\n        document.addEventListener('DOMContentLoaded', init);\n    } else {\n        init();\n    }\n})();\n<\/script>\n","protected":false},"excerpt":{"rendered":"<p>Gratis online kalkulator for propellubalanse og sentrifugalkraft. Skriv inn propellmasse, blader, diameter, akselhastighet og balansegrad for \u00e5 f\u00e5 tillatt ubalanse i henhold til ISO 21940.<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[],"tags":[],"class_list":["post-100199","calculator","type-calculator","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator\/100199","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator"}],"about":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/types\/calculator"}],"version-history":[{"count":1,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator\/100199\/revisions"}],"predecessor-version":[{"id":100514,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator\/100199\/revisions\/100514"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/media?parent=100199"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/categories?post=100199"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/tags?post=100199"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}