This calculator helps you determine the spring rate (stiffness) of a helical compression spring based on its physical dimensions and material properties. The spring rate, often denoted by 'k', is a fundamental characteristic of a spring and represents the force required to compress or extend the spring by a unit distance. A higher spring rate indicates a stiffer spring.
function calculateSpringRate() {
var wireDiameter = parseFloat(document.getElementById("wireDiameter").value);
var meanCoilDiameter = parseFloat(document.getElementById("meanCoilDiameter").value);
var numberOfActiveCoils = parseFloat(document.getElementById("numberOfActiveCoils").value);
var springIndex = parseFloat(document.getElementById("springIndex").value);
var shearModulus = parseFloat(document.getElementById("shearModulus").value);
var forceUnit = document.getElementById("forceUnit").value;
var lengthUnit = document.getElementById("lengthUnit").value;
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(wireDiameter) || isNaN(meanCoilDiameter) || isNaN(numberOfActiveCoils) || isNaN(springIndex) || isNaN(shearModulus)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
return;
}
if (wireDiameter <= 0 || meanCoilDiameter <= 0 || numberOfActiveCoils <= 0 || springIndex <= 0 || shearModulus <= 0) {
resultDiv.innerHTML = "Input values must be positive.";
return;
}
// Ensure spring index is consistent if both D and d are provided
if (meanCoilDiameter / wireDiameter !== springIndex) {
// If springIndex is not provided or is inconsistent, recalculate it
springIndex = meanCoilDiameter / wireDiameter;
document.getElementById("springIndex").value = springIndex.toFixed(2);
}
// Factor for stiffness calculation (simplified, often includes corrections for end coils and spring index)
// Basic formula k = (G * d^4) / (8 * D^3 * n)
// We will use the spring index C = D/d, so D = C*d
// k = (G * d^4) / (8 * (C*d)^3 * n)
// k = (G * d^4) / (8 * C^3 * d^3 * n)
// k = (G * d) / (8 * C^3 * n)
var springRate = (shearModulus * wireDiameter) / (8 * Math.pow(springIndex, 3) * numberOfActiveCoils);
// Display result with units
resultDiv.innerHTML = "Calculated Spring Rate (k): " + springRate.toFixed(2) + " " + forceUnit + "/" + lengthUnit + "";
}
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font-family: sans-serif;
border: 1px solid #ccc;
padding: 20px;
border-radius: 8px;
max-width: 500px;
margin: 20px auto;
}
.input-group {
margin-bottom: 15px;
display: flex;
align-items: center;
}
.input-group label {
flex: 1;
margin-right: 10px;
font-weight: bold;
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.input-group input[type="number"],
.input-group input[type="text"] {
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padding: 8px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box; /* Ensure padding doesn't affect width */
}
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background-color: #4CAF50;
color: white;
padding: 10px 15px;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 16px;
display: block;
width: 100%;
margin-top: 20px;
}
#spring-rate-calculator button:hover {
background-color: #45a049;
}
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margin-top: 20px;
padding: 10px;
background-color: #f0f0f0;
border-radius: 4px;
text-align: center;
}
#result p {
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font-size: 1.1em;
}