ALIGNMENT OF SPRING STACKS

Within a spring stack the disc springs do not always move evenly (figure 32). 

This naturally leads to overloading at one end of the stack with consequential reduction in fatigue life. This is also the reason way, with dynamic loads, the first breaks occur at the end of the spring stack in most cases. Therefore, we recommend that the spring stack be aligned on the guide rod with a ‘vee bar’ and then maintained in position with a light preload. After alignment the spring stack should not be completely relaxed. This procedure has been found most satisfactory in practice for minimizing friction in spring stacks. If it is not possible to align the stack for design reasons, the stack should be compressed flat once or twice. This also has the effect of centralising the springs and reducing friction. 

 Figure 32 - click to enlarge

The friction is usually somewhat less in a vertically arranged stack than in the horizontal installation position. It is therefore better to have long stacks arranged vertically rather than horizontally. 

With a dynamically loaded stack there is a running in period during which the friction is reduced, especially with multiple layering. The reason for this is a certain smoothing effect at both the contact edges and the touching spring flanks.