Stretched out coiled steel springs

Spring rate is proportional to the number of active springs, but proportional to the fourth (?) power of spring wire diameter. You need a spring with thicker wire?

Yeah but. :)

I bought coil springs with thicker wire and had to stretch them too. They were junk tho. :/ For two comprssion cycles they -were- stronger but a few cycles later and they were about like the originals cut in half. :/

Overall the original (thinner wire) springs were stronger. They are just plain ol' better made springs. To stretch one of them takes some real pulling and far too. :)

In theory if you have less coils, all else the same, the spring's rate in increased.

Well, that's true right? :)

But the originals after being stretched and a few coils removed, were not stonger, but weaker than before. 28 coils minus 4

What is going on from a metallurgy stand point? :)

Not necessarily a cure to my problem, just would like to understand what's going on inside the wire. :) Maybe that'll lead to a cure?

But I believe the real cure is to do exactly what David said but do it with quality springs that has larger wire and the right pitch.

Just can't find a source for them is all. :/

Thanks for your input, David. :)

Alvin in AZ

within the elastic strain limit, yes. but apparently you're exceeding that.

indeed.

Skipping over my "cowboy engineering" methods... :)

What about the metallurgical aspect of what I'm doing to the springs?

I'm thinking that streching them is slightly improving the wire itself.

Agree? Disagree? :)

Alvin in AZ ps- I've been subscribed to s.e.m for 10 years. pps- I know these are dumb questions but I'm serious about understanding what's going on anyway. :)

depends on the application. if you're looking for fatigue resistance/stress relief, over-stress can help, but if it's a compression spring and you're stretching it, you're making fatigue worse, not better. explaining your intended purpose would be your next step.

Alvin-

I know you've been on SEM for years.

but (& I'll try to be gentle here)

imo you're blaming the spring material, supplier / mfr when it is the designer / specifier who is at fault.

a properly sized & chosen spring will most likely do what you want done IF it id doable.

You're kinda right (but not really) about "improving" the wire by stretching it....depends on the material & material condition.....it might work harden but it might not.

plus the springs operational range will determine its behavior as well

your comments of "weaker" vs "stronger" are too imprecise to be useful......are you talking about higher or lower spring rate OR higher or lower force to fully compress?

as Jim suggested detailing your situation will get you better answers

I'm guessing you've got a compression spring that you're cutting & stretching to adjust the spring rate?

but then you're over-compressing (bringing the spring up solid) & then re-yielding it

your comment about the thinner (smaller diameter) wire spring being "stronger" has me confused???? how can that be? Did spring diameter change?

keep posting we'll get to the bottom of this

from efunda

cheers Bob

Are you pulling which twists the metal or un-coils the metal so the two ways are different and might make a different.

Martin

Mart> Skipping over my "cowboy engineering" methods... :)

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Sure as heck didn't want to make it sound that bad, but yeah. :/

Couldn't agree more. :) Just that I haven't got access to springs in the size I need... and especially in the quality that's needed for the job.

Yes! :)

With spring wire in mind... which materials are weakened by plastic deformation? Does anyone know off hand? :)

I wanted this thread to be more about materials than my dumb design changes. :)

That, I am learning. ;)

Yes! :) After many tests surprisingly some of the thinner wired springs are out perfoming the thicker wired springs.

Yes and the particular steel they were made from is more the determining factor than anything else.

Yeah, weird huh? :)

Thanks Bob, I'm not an engineer (can you tell?:) and don't understand the math but have read quite a bit about springs and some of it from efunda.com. :)

I realize things aren't going as expected and now understand that it has more to do with the different steel wire material manufacturing processes than anything else. Design limits are very important and I'm not reaching out of those limits if the material was up-to-it and-so the results have more to do with the orginal wire's "spring making qualities" that anything else.

What is going on is I'm pushing the weaker spring material way past it's yeild point. And even tho it's made from thicker wire, it ends up exerting less pressure after a few compression cycles than the smaller, higher quality wire.

That's how the thinner wire beats the thicker wire.

And there too is my gripe with the springs I got from McMaster-Carr.

Jim, in a sense I got carried away explaining too much already about the application. I can't word it worth anything but I can see what is happening now that you guys have asked "pointy questions" and got me to thinking more clearly.

Thanks for the effort! :)

If you've got any more ideas on the subject I'll be glad to "hear" it tho. ;)

You've put this much work into it you deserve to know what I'm up to. ;) Modifying Daisy "Red Ryder" and "Buck" BB guns. :)

I have a 22-250 Rem700 that can link three bullet holes together at

100 yards. The BB guns are actually more fun to shoot. ;)

Take the silly sights off them, hand them to kids, women, anybody and everybody and get them to shoot at stuff without looking at the gun ...only looking at the target and/or looking for the BB in flight. :)

If you live in a place where you could do this too, get yourself at least 3 of them and get after it. :)

The weaker they are the harder they are to shoot tho. :/ The older ones were stonger and shoot better. Their springs are interchangable and with it their shooting quality.

I have a pile of BB guns and want to be able to get new ones off the shelf and make them shoot good too.

Not going to happen looks like. :/

So... just like my knife making, the metallugy part of it might turn out to be the most interesting part of it anyway? ;)

Alvin in AZ

It might be worth finding a copy of the now out of print Associated Spring Corporation Design Handbook. It is not available from Associated Spring anymore, but a google search turned up a used copy for $15 in the first few hits. This booklet has a discussion of spring material selection as well as design equations which will allow you to calculate spring rate and material stress using only simple math. They also have a stock spring catalog available for free download from

Alvin-

I might be wrong but in your situtation (imo) spring geometry & travel range are more important than material properties.

I've used lots of springs from McMaster & they worked just fine....it's not (imo) the spring material that failing you

Looks to me like you're over stressing the spring when compressing it (cocking it)

Another poster mentions a spring design manual.....just what you need.

here's a tip.....don't go "solid" in cocked position

cheers Bob

I have one particular old original spring and the wire isn't any bigger than the new factory springs. The coils are spaced farther and the spring's relaxed length is longer even after a few coils fatigued and broke off. LOL :)

...and it's still stronger than any of the new ones. :)

You can feel it in the cocking effort and hear the velocity increase in the shooting. (how long it takes the BB to hit a distant 55 gallon drum)

Stretching the new ones from McM-C is easy-as-pie doesn't take much "work" or distance. Stretching the new "Daisys" "is work" and takes great length before the yield point is reached.

Know this please ;) the new McM-C springs are the same dimensions in every respect -or- made of thicker wire. Very obvious that they are made from different quality wire.

Associated/Richmond Spring looks promising tho. :)

I believe you are right in most situations but in this situation they have designed a gun's strength around what they can get from the best springs made.

I know it's possible to do better than the new guns' springs. Old (half wornout?) original springs do it easily.

For sure! ...and I'm all over that suggestion. :) Whether I fix the dumb ol'BB guns or not I want to understand springs and the material they are made from. :)

I want to walk away with at least something. ;)

I've never gone "solid" or even close, I'm using the same basic design as the "old" originals. In certain situations I'm reducing the number of coils and giving the springs even more room.

(higher spring rate is the result, when all else is equal)

I've read where there -are- different types of wire being used, some have the same chemistry but are given different properties by the wire's processing.

Others have different alloys and processing.

The factory BB gun springs are made of "better stuff" than what I bought from McM-C no doubt about that. :) Ok? :)

The price was rather low. :/ Good for others but bad for me in my situation. :/

Alvin in AZ ps- the "Buck" mechanism is exactly the same as the RedRyder mechanism, only the shorter barrel length makes the "Buck" have lower muzzle velocity

Alvin-

good luck with your "shade tree mechanic" approach, it's not how real design & development is done............

but with enough time you'll eventually come across a solution

dribbling out the operational details puts those of us trying to help you at a distinct disadvantage

designing a "better(?)" spring while working within the geometric constraints of the existing BB guns is a pretty simple process

the best springs made.