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More on Compression Springs

Compression Springs, Part II

In designing compression springs the space allotted governs the dimensional limits of a spring with regard to allowable solid height and outside and inside diameters.  These dimensional limits, together with the load and deflection requirements, determine the stress level.  It is extremely important to consider carefully the space allotted to insure that the spring will function properly to begin with, thereby avoiding costly design changes.

Solid Height of a Compression Spring
The solid height of a compression spring is defined as the length of the spring when under sufficient load to bring all coils into contact with the adjacent coils and additional load causes not further deflection.   Solid height should be specified by the user as a maximum, with the actual number of coils in the spring to be determined by the spring manufacturer.
 
As square or rectangular wire is coiled, the wire cross-section deforms slightly into a keystone or trapezoidal shape, which increased the solid height considerably.  The dimensional change is a function of the spring index and the thickness of the material. When calculating maximum solid height, allowance must be made for all the factors which apply, such as material, finish, and manufacturing tolerances.

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How to Determine Rate

Rate which is the change in load per unit deflection, may be determined by the following procedure:
  1. Deflect spring to approximately 20 percent of available deflection and measure load (P1) and spring length (L1).
  2. Deflect spring to approximately 80 percent of available deflection and measure load (P2) and spring length (L2). Be certain that no coils (other than closed ends) are touching L2.
  3. Calculate rate (R) lb./in. (N/mm)
    R = (P2 - P1) / (L1 - L2)
Spring Products International is Houston's premier manufacturer and supplier of high-quality spring products.  At Spring Products International, we understand just how important your projects are - when you need springs that will do the job and that will last, you need Spring Products International.  We have a vast inventory of stock springs to fulfill orders both large and small.  Our engineers can also fabricate custom springs to your specifications.

Call us today to talk to one of our spring experts and find out how we can  help you with your spring needs - 1-800-515-9773.