Gas Strut Calculation

Gas Strut Force Calculator

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function calculateStrutForce() { var lidWeight = parseFloat(document.getElementById('lidWeight').value); var lidLengthMM = parseFloat(document.getElementById('lidLength').value); var strutAttachmentDistanceMM = parseFloat(document.getElementById('strutAttachmentDistance').value); var numStruts = parseFloat(document.getElementById('numStruts').value); var maxOpeningAngleDeg = parseFloat(document.getElementById('maxOpeningAngle').value); var resultDiv = document.getElementById('result'); // Input validation if (isNaN(lidWeight) || lidWeight <= 0) { resultDiv.innerHTML = 'Please enter a valid Lid Weight (kg) greater than 0.'; return; } if (isNaN(lidLengthMM) || lidLengthMM <= 0) { resultDiv.innerHTML = 'Please enter a valid Lid Length (mm) greater than 0.'; return; } if (isNaN(strutAttachmentDistanceMM) || strutAttachmentDistanceMM lidLengthMM) { resultDiv.innerHTML = 'Please enter a valid Strut Attachment Distance (mm) greater than 0 and less than or equal to Lid Length.'; return; } if (isNaN(numStruts) || (numStruts !== 1 && numStruts !== 2)) { resultDiv.innerHTML = 'Please select either 1 or 2 for Number of Struts.'; return; } if (isNaN(maxOpeningAngleDeg) || maxOpeningAngleDeg 90) { resultDiv.innerHTML = 'Please enter a valid Maximum Lid Opening Angle (degrees) between 0 and 90.'; return; } // Constants var g = 9.81; // Acceleration due to gravity in m/s^2 // Convert units to meters and radians var lidLengthM = lidLengthMM / 1000; var strutAttachmentDistanceM = strutAttachmentDistanceMM / 1000; var maxOpeningAngleRad = maxOpeningAngleDeg * (Math.PI / 180); // Calculate center of gravity distance from hinge (assuming uniform lid, CG at midpoint) var L_cg = lidLengthM / 2; // Calculate the force required per strut // Formula: F_strut = (Lid Weight * g * L_cg * cos(Max Opening Angle from Horizontal)) / (Number of Struts * Strut Attachment Distance) // This formula calculates the force needed to hold the lid open at the specified angle, assuming the strut acts perpendicular to the lid. var requiredStrutForce = (lidWeight * g * L_cg * Math.cos(maxOpeningAngleRad)) / (numStruts * strutAttachmentDistanceM); // Display results resultDiv.innerHTML = ` Required Force Per Strut: ${requiredStrutForce.toFixed(2)} N (This is the force required to hold the lid open at the specified angle.) `; }

Understanding Gas Strut Force Calculation

Gas struts, also known as gas springs or gas shocks, are essential components in many applications, from automotive bonnets and tailgates to furniture, industrial machinery, and access panels. They provide controlled lifting, lowering, and holding of heavy objects, making them feel lightweight and easy to operate.

Why Calculate Gas Strut Force?

Choosing the correct gas strut force is crucial for safety, functionality, and longevity. An undersized strut won't hold the lid open or lift it effectively, while an oversized strut can make the lid difficult to close, potentially causing damage or injury. Proper calculation ensures smooth operation and prevents premature wear on hinges and mounting points.

Factors Influencing Strut Force

Several key factors determine the required force of a gas strut:

1. Lid Weight (kg): The total mass of the object being lifted or held. This is the primary factor influencing the downward force that needs to be counteracted.
2. Lid Length (mm): The overall length of the lid from its hinge point to its free edge. This helps determine the center of gravity (CG) and thus the leverage of the lid's weight. For uniform lids, the CG is often assumed to be at the midpoint.
3. Distance from Hinge to Strut Attachment (mm): This is the point on the lid where the gas strut connects. The further this point is from the hinge, the greater the leverage the strut has, meaning less force is required from the strut.
4. Number of Struts: Whether you use one or two struts significantly impacts the force required per strut. Two struts distribute the load, reducing the individual force needed from each.
5. Maximum Lid Opening Angle (degrees from horizontal): The angle the lid makes with the horizontal plane when fully open. This angle affects the effective downward force of the lid's weight. A lid held vertically (90 degrees) requires less force to hold than one held at a slight angle (e.g., 30 degrees) because gravity acts more directly downwards on the latter.

How the Calculator Works (Simplified Model)

This calculator uses a simplified static equilibrium model to estimate the force required per gas strut to hold a lid open at a specific angle. It balances the torque created by the lid's weight against the torque provided by the gas strut(s) around the hinge point.

The formula used is:

Required Strut Force (N) = (Lid Weight (kg) × 9.81 × (Lid Length (m) / 2) × cos(Max Opening Angle from Horizontal in Radians)) / (Number of Struts × Distance from Hinge to Strut Attachment (m))

Assumptions:

• The lid is uniform, and its center of gravity is at its midpoint (Lid Length / 2).
• The gas strut acts perpendicular to the lid at its attachment point when the lid is at its maximum opening angle. This is a common simplification for initial sizing.
• The calculation is for holding the lid open; dynamic lifting (initial inertia, friction) might require slightly more force.
• The angle input is the angle the lid makes with the horizontal plane when fully open.

Using the Calculator and Interpreting Results

Input your lid's specifications into the fields provided. The calculator will output the estimated force required per strut in Newtons (N). This value serves as a starting point for selecting appropriate gas struts. It's often recommended to choose a strut with a slightly higher force rating (e.g., 10-20% more) to account for friction, aging, and to ensure a positive lift.

Important Considerations:

• Safety Factor: Always consider adding a safety margin to your calculated force.
• Dynamic vs. Static: This calculator provides a static force estimate for holding. For dynamic lifting, factors like initial friction and acceleration might require slightly more force.
• Strut Mounting Position: The exact mounting position of the strut on both the lid and the frame significantly impacts its performance and the actual angle it makes with the lid. This calculator simplifies that geometry.
• Strut Length: The physical length of the strut (extended and compressed) must be compatible with your application's geometry.
• Environmental Factors: Temperature can affect gas strut performance.

For critical applications, it's always best to consult with a gas strut supplier or an engineer to ensure precise selection and safe operation.