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Message: [QUOTE="c3hammer, post: 24451, member: 18554"] Getting back to the original question.... Springs will come up against stress/strain limits very quickly when the length, pitch (n) and wire (d) are reduced. All of these can be reduced for any coil spring to achieve the same rate. But..... The strain to failure comes into play very quickly. Effectively what happens is that when the pitch / angle (n) of the coils gets steeper the spring gets stiffer, but the load is being transfered as a combination of compression and shear (twist) rather than flexure. Most materials have lower compression / shear strength than flexural strength and thus the spring breaks too easily / soon. I've worked with carbon fiber springs for McLaren F1. They could never achieve high enough strain to failure numbers. I just built tooling, so I'm not that good with the math though. It was pretty cool to see how they were braiding and winding the carbon over a thermoplastic rod at very specific angles so that when coiled into a spring and cured all the loads would be transfered more in either compression or flexure and not as much in shear. The only carbon spring I've ever seen work was a torsion spring for aircraft doors. They're coiled up to preload the door so that someone could lift it open with one hand. The cross section was about .25" x .45". It was amazing how a 3.4 lb. spring could allow a huge door to be opened with one hand. I think the steel springs that are used in most of these applications weight almost 5 times as much. Carbon is really good stuff if you just flex it! Pete [/QUOTE]

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