## Spring Rate and Sorbothane

February 02, 2015

Sorbothane is a material that has a number of applications related to spring rate. Spring rate is an important consideration when choosing the size and number of coils in an application. There are several things to keep in mind when working with anything requiring spring rate, including the benefit of a higher or lower spring rate.

Spring rate is defined as the amount of weight that is needed to compress a single spring by one inch. For some coils or springs, there might be two values listed, a smaller and then a larger. In that case, the smaller number that is listed is the amount of weight that is needed to compress the spring for the first inch and the last one will be the amount needed to compress it to its maximum amount. Every spring has a maximum amount of compression before failure, so that final number can be an important one as well.

The lower the spring rate number of the coil, the softer it is with the opposite being true as well, the higher the number, the harder or stiffer it is. Using a coil that has a low start and higher finish number, means that the coil can give a softer or more comfortable ride in the beginning and still bounce back when the load becomes heavy. There are a number of applications where this can be an important consideration including springs used in bike seats or other vehicle considerations.

To determine spring rate, it is important to understand the spring rate formula. You can use an online spring rate calculator so that you don’t have to do the actual math yourself, but you will still need to understand the factors that are plugged into the formula.

• These include k, which is used for the spring constant. This is the number of pounds of load per one inch of deflection in the spring.
• G equals the modulus of rigidity, which is also rated as pounds per square inch.
• D, (d) is the number related to the wire diameter, usually given in inches.
• N is the number of active coils. In any application, there are two numbers related to coils, the total number and the active number. The active coils are the ones that are subject to motion and is always less than the total number of coils. D is the actual coil diameter.

All of these numbers and facts are plugged into the spring rate calculator and then figured for you so that you don’t have to do a number of different steps to determine the spring rate in your project. Most springs will have their spring rate figured for you when you buy them, but you still need to figure the number for yourself so that you can choose the right application for your needs. It is important that you not only understand what the spring rate is but why it is important and why it really matters. 