When designing a spring it is important to know whether the spring will be subject to just a few load cycles or a great many.
A few means a service life of approx. 20,000 to 50,000 load cycles; most springs are used in situations with a static load. Examples are springs in valves, springs in windows and doors, springs that hold something closed, etc.
The calculations in this website are based upon springs for static applications. A dynamic load exists if the spring may undergo around 10 million load cycles. As a rule of thumb, springs designed for a static load of 100 N are suitable for a dynamic load of 60 N. In other words, the distance the spring may travel under dynamic loading conditions is 60% of the travel under static loading.
There is, incidentally, another option for loading the spring more severely in the above-mentioned example that still results in a spring that can be loaded dynamically. We do this by keeping the spring travel the same, i.e. a travel with a load difference of 60 N and a starting force F1 of 20 N, for example. The final force is thus: 20 N + 60 N = 80 N.
For springs with a dynamic application we advise you to contact one of our technical advisors who can use a special service life program to calculate the correct spring for your needs.