**1 –** **Determine application load for each spring**

The load of the application will be determined by the machine weight and the maximum weight that the machine will operate with. Therefore, considering that the centre of gravity is equidistant (distributing equally the loads), the load range of each reinforced rubber spring can be calculated the next way:

\text{Minimum load} = \frac{\text{Unloaded machine weight}}{\text{nº of springs}}\quad

\text{Maximum load} = \frac{\text{Unloaded machine weight + material weight}}{\text{nº of springs}}\quad

An upward adjustment over calculated force is recommended for unplanned overloads or weight miscalculations.

**2 – Select the springs that meet the load range**

With the obtained load values, it is recommended to select the reinforced rubber spring placed in the load middle range.

Oria reinforced rubber springs can operate up to 27,5% of compression of their free height. However, it is recommended to select the spring at 25% deflection or less, thus increasing the life and stability of the product.

If more than one reference meets the load requirements, select the one that has the lowest natural frequency, as the isolation percentage will be higher.

**3 – Verify design parameters**

Verify that the selected reinforced rubber spring meets the stroke required by the application (do not exceed recommended stoke) and that there is enough space for the maximum diameter that the unit is going to take during compression.

**4 – Verify isolation percentage**

Verify that the isolation of the transmission is sufficient. For that, use the natural frequency value at the operating height and the next formula:

\% Isolation = 100 - \left[\frac{1}{\left(\frac{f_e}{f_n}\right)^2 - 1}\right]\quad

\text{Where: } f_e = \text{Exciting frequency (Hz), } f_n = \text{Natural frequency (Hz).}

In the next chart is plotted the transmissibility or isolation that will be obtained from the frequency ratio.

Isolation will only happen if the exciting frequency is at least 1,4 times greater than the natural frequency.

f_e > \sqrt{2} \cdot f_n

Amplification and resonance take place when the frequency ratio ^{fe}/_{fn} lies between ^{1}/_{√2} and √2.

The natural frequency is indicated in each individual data sheet in different compression values. Its value for an undamped system is calculated using the following formula:

f_n = 0.5 \cdot \sqrt{\frac{K}{L}}

\text{Where: } K = \text{Spring Rate (kN/m), } L = \text{Load (kN).}

The spring rate, defined as the amount of weight required to compress a spring by one inch, is equal to the slope of the load-deflection curve at the corresponding load. As the reinforced rubber spring load-deflection curve is not linear (in contrast to steel spring), the spring rate varies with deflection.

K = \frac{\text{Load}}{\text{Deflection}}