Basic Load per Vibration Isolator Formula

For a rigid base with symmetrical mounting points and a centered load:

[W_i=\frac{W}{N}]

where:

· (W_i) = load per isolator

· (W) = total equipment mass

· (N) = number of isolators

For a 100 kg cabinet supported by four mounts:

[100\div4=25\text{ kg per isolator}]

So 25 kg per mount is a reasonable starting point.

But this assumes reasonably equal weight distribution. A transformer, motor or battery mounted toward one side can change the actual load at each support.

What If the Center of Gravity Is Off-Center?

For a simplified two-support static model, support reactions can be estimated from the center-of-gravity position:

[R_1=W\frac{L-x}{L}, \qquad R_2=W\frac{x}{L}]

where (L) is the distance between the supports and (x) is the center-of-gravity position measured from the first support.

Take a 200 kg machine, with the two supports 1,000 mm apart and the center of gravity 650 mm from the first support:

[R_1=200\times\frac{350}{1000}=70\text{ kg}]

[R_2=200\times\frac{650}{1000}=130\text{ kg}]

The machine still weighs 200 kg. The support loads, however, are 70 kg and 130 kg, not 100 kg each.

For four- or six-point mounting layouts, the actual calculation must consider the mounting geometry in both directions. A basic mounting drawing and center-of-gravity position are much more useful here than total equipment weight alone.

HOAN Case: 400 kg Equipment on Six Wire Rope Isolators

One HOAN transportation project involved 400 kg equipment supported by six JGX-1278S-199A wire rope isolators.

The initial average load was:

[400\div6=66.7\text{ kg per isolator}]

That number helped establish the initial load condition, but the application also involved road vibration and mechanical shock during transportation. Mounting arrangement and dynamic requirements therefore had to be considered before final selection.

This is a good example of why 66.7 kg per mount is a starting value, not a model number.

Why a Higher Load Rating Isn't Always Better

Once the support loads are known, they can be compared with the candidate isolator's technical data.

HOAN's JGX-1278A series, for example, includes models with published maximum vertical static loads from approximately 122 kg to 370 kg, together with different stiffness and deflection characteristics.

These are maximum static-load values, not recommended working loads for every installation.

If the calculated working load is relatively low, jumping directly to the highest-capacity model is usually the wrong approach. More capacity also means different stiffness and deformation characteristics.

An isolator that is too stiff may not provide the expected vibration-isolation performance. One operating too close to its load or displacement limit creates a different problem.

The better question is:

Which isolator works correctly at the actual mounting load?

Not:

Which isolator has the highest load rating?

Static Load Is Not Shock Load

Static load per mount should not be confused with shock loading.

A 100 kg cabinet on four mounts starts at 25 kg static load per mount. If the same equipment must withstand a 30g / 11 ms half-sine shock, the isolator requires a separate dynamic check.

Pulse duration, mounting direction and available travel matter. Simply multiplying the 25 kg static load by 30g is not a complete selection method.

What Does HOAN Need for Model Selection?

For most applications, start with:

· Equipment weight and dimensions

· Number and position of mounting points

· Center of gravity, if known

· Installation direction

· Vibration conditions

· Shock acceleration and pulse duration, if applicable

· Available installation space or displacement

For equipment with uneven mass distribution, sending a mounting drawing can prevent the wrong load assumption at the beginning of model selection.

FAQ

Can I simply divide equipment weight by four?

Yes, as a preliminary calculation when four mounts are symmetrically positioned and the center of gravity is reasonably centered. If the mass is offset, calculate the actual support reactions.

How do I calculate isolator load with an off-center center of gravity?

For a simple two-support arrangement, use the equipment weight, support spacing and center-of-gravity position to calculate the reaction at each support. Four- and six-point systems require the mounting geometry to be considered in both directions.

Should I choose a higher-capacity isolator for extra safety?

Some load margin is necessary, but excessive oversizing can make the isolation system too stiff for its actual working load. Load capacity, stiffness, deflection and dynamic requirements should be checked together.

Start with the Load, Then Check Where It Sits

For centered equipment, total weight ÷ number of isolators is usually the right first calculation.

For anything less symmetrical, check where the weight actually sits.

At HOAN, equipment weight, mounting layout and center of gravity are used together during preliminary model selection. A few dimensions on the RFQ are often more useful than simply choosing the next larger wire rope isolator.