Gunsmithing/Mechanical Engineering Spring Question

[Dave2]

Is it just me, or are springs in guns always compressed during operation? Are springs not as strong or something when they're operating on an expansion cycle? Is it a matter of being harder to keep the ends attached? It just seems like there are some design options that aren't being explored here.

[Jumping Frog]

Leaving a PROPERLY DESIGNED AND WELL MADE spring compressed WITHIN ITS DESIGN PARAMETERS will not hurt it at all. Not even over YEARS.

Look at cars. Every car suspension is utilizing compressed springs.

Compressed isn't the issue, it is when stresses associated with compression/release cycles exceed the fatigue limit that you are "wearing out" a spring.

[Dave2]

Leaving a PROPERLY DESIGNED AND WELL MADE spring compressed WITHIN ITS DESIGN PARAMETERS will not hurt it at all. Not even over YEARS.

Look at cars. Every car suspension is utilizing compressed springs.

Compressed isn't the issue, it is when stresses associated with compression/release cycles exceed the fatigue limit that you are "wearing out" a spring.

Oh, I know, this isn't about springs wearing out (as far as I know)... I'm talking about compression vs expansion. For instance, let's say that a recoil spring is normally 1ft long, but during operation it's compressed down to a 1/2ft in length. Why not have a recoil spring that's a 1/2ft long and expands to 1ft during operation?

[alvins]

the springs in your car suspention are under constant compression. over compression or pulling apart is what screws up springs the fastest.general use slowly wears them out.

[Carry-a-Kimber]

A compressed spring stores kinetic energy, an expanded spring does not. Other than that I really don't understand your question.

[srothstein]

I am not an engineer, but it seems to me that any spring that is not in a relaxed state would store energy. Whether compressed or extended, it took energy to get them that way and both will want to expend that stored energy and return to their normal (relaxed) state.

As for the original question, I would guess it has to do with the space and motion desired. I cannot see a reason that a spring could not be used in the reverse direction, for example a recoil spring. If it is stored in a relaxed state and attached at both ends, it would still slow the slide motion by absorbing energy as it was stretched and then expend that energy pushing the slide back into battery. In a case like that, attaching the ends of the spring would be the only difference I can see off hand and that should be a simple engineering question.

I must be missing something by not having studied enough engineering but I can see the question as a valid one.

[srothstein]

Thanks George. I had figured that anchoring the ends could be a problem, but had not thought about breakage and its effects.

[Lonest4r]

What they said ^ plus the fatigue life can be improved with the captured compression spring design by adding a preloaded minimum stress. It decreases the range of the stress to which the spring is subjected. The same could be achieved with a tension loaded spring, but in attaching it you may lose the advantages of having squared ground ends to avoid stress concentrations. Also, manufacture of the springs would cost more than compression springs designed for the same stress and duty cycle.