Tech Question - Leaf Liners' Effect on Spring Rate

Hi Mike,

I just read your comment about Delrin inserts and it raised three more related questions I don't believe I have ever seen answered.

The first is, does using a full length insert change the thickness of the spring pack?

Secondly, what effect do full length inserts have on spring rate?

Finally, in general does using full length inserts change the number of springs per pack?

Thanks for the insights you typically offer. It helps me with my end of the industry.

Dale

Dale,

Good questions.

Full length spring liners are available in two designs.

The first being a simple flat strip and the other channeled with lips going up and down, sort of like an "I" beam. The lips help keep the liner from slipping out.

Installing full length liners does increase the spring pack thickness.

Based upon the width of the liner, the thickness varies from .03 to .06 Inches thick. So the overall spring thickness does increase based upon how many full length liners are installed. But the use of liners has no effect on the spring rate.

Spring rate is a result of the width of the spring, the thickness of the steel, the number of leaves and how the ends are finished.

But the use of liners does have an effect on how the spring performs. Due to interleaf friction all multi-leaf springs suffer what is known as "hysteresis".

That is, it takes more force to start the spring to deflect than it does to keep it deflecting.

The use of either full length liners or tip inserts greatly reduce interleaf friction which in turn reduces hysteresis. This keeps the working spring rate close to it's actual rate.

Keep in mind, that in order for a liner to be effective the liner must be as wide as the spring.

While spring liners help in a spring's performance, the liner has absolutely no strength. Even though a liner is used in a spring, the spring still requires all of it's leaves.

I hope this helps with you. Let me know what else I can do to continue your spring education.

-Mike