Impact of a Spring Under Compression

[TCLouis]

I just read in my manual for my springer air gun to NOT store it with sping compressed.
Everyone talks about spring problems from storing magazine loaded with ammo.

Enter my educated friend who says there is not a problem as there is not a "T" in the formula to denote time as a factor . . .

What say Ye?

About that

[ph4570]

I have had several auto pistol mags loaded nearly 100% of the time for as long as 20 years. They still work fine, i.e. no feed problems.

I have wondered about airgun springs myself. I have a RWS 52 that I leave uncompressed. I seem to recall the manual instructing thus but not sure.

[Doc Highwall]

What I do is I have several magazines and keep rotating them every so often and serves as a reminder what I have and where they are hidden.

[montana_charlie]

Everybody's heard of sagging springs on beds and pickup trucks, and some guys won't use a BHN hardness tester because'the spring will change over time' (or so they say).

I believe it all depends on how far a spring is compressed, low long, and the quality of the spring. The three factors interact to allow some springs to remain at near full compression almost forever without damage.

CM

[Lee]

sagging springs on p'upks's. Well those springs are not compressed to a con stant steady force. Bubba drives the normal P/U at 80 mph stupidly over the road, His ass don't see the shock and compression/extension that the bubba truck springs do see.But hey that's bubba. Nuff said. Bye, bubba........Lee:evil:

[OeldeWolf]

As a chemist, the springs in our viscometers, and the trip springs on the microswitches for the sample carousel on the vacuuum XRD machine, were made of beryllium bronze. This was loudly stated to be the only alloy that would not lose elasticity over time.

As a mechanic, I have seen auto and truck springs lose their elasticity and ability to return to original specifications. Not only suspension springs, but also in tensioners and valve trains. I have even measured it myself.

Almost all alloys used in springs will loose ability/strength over time.

[redneckdan]

Springs will take a 'set' over time. Its called creep...otherwise know as time dependant deformation. Cycling the spring will cause the spring to take 'set' faster than being left under load. But make no mistake, being under load will cause a spring to deform over time.

[sagacious]

The spring in a piston air-rifle is under constant load, even when the rifle is "uncocked." This pre-compression is critical for the proper operation of the spring during the final stages of the compresion of the air in the cylinder, and to reduce vibration and potential damage to the spring. When the spring is cocked and compressed fully, it is under truly enormous load. It's operating at it's limits.

When the mainspring suffers from compression fatigue, the spring may lose it's ability to remain under pre-compression. During the firing cycle, both the speed and amount of air compression suffers, and the spring can 'bounce' at the end of it's travel. That shock can break the spring. Even on a properly-maintained spring-piston gun, spring fatigue can eventually lead to a broken spring. That's why one does should leave a s-p gun cocked.

A magazine spring operates under much less demanding circumstances, and the geometry of the spring is much different. Fortunately, it's cheap and easy to replace mag springs as they wear, so keeping them under constant compression is not nearly as big a worry. Good luck.

[sagacious]

As a chemist, the springs in our viscometers, and the trip springs on the microswitches for the sample carousel on the vacuuum XRD machine, were made of beryllium bronze. ...
The gravimeters my father used relied on quartz springs. No elastic fatigue over even geological timescales. I have seen the springs themselves, and they are impressive in their precision of manufacture. Such a spring is capable of measuring the gravimetric gradient over a tenth of a meter, or less. That's a spring sensitive enough to easily detect the difference in gravity over each step in a flight of stairs. The springs were only replaced when broken.

[MtGun44]

Montana Charlie has it correct.

The issue is impossible to accurately answer for a particular spring without a detailed engineering analysis.
The issue is how close is the particular alloy at that particular condition of heat treat and work hardening
that happened during the manufacturing process to it's limits. If the alloy is very near it's limits, it can
slowly lose tension as the grains in the metal actually move around. If the allloy is not near it's limits,
it is capable of storing the strain energy in the spring for many decades. Another issue is how close is
the force stored in the spring to the minimum required to do the job? If you have a spring that loses
10% of the force over some long time, but it was designed to provide twice the required force to do
some particular job (like lift cartridges in a magazing in a few milliseconds) then the fact that it only
has 90% of twice what it needs means it will be fine. If it was designed with very little margin, then
the loss of 10% may cause problems.

SO - as I said, for any particular spring the answer is not easily knowable. Most of the time the designer
and the manufacturer both do a good job and you can keep a spring tensioned for a long time. If the
manufacturer had a screwup, then maybe not. A few batches of magazines have been seen with weak
springs.

Another thing to keep in mind - What was the intent of the designer? I would expect that the designer
of a spring air gun was looking to get the maximum possible performance out of his spring, so maybe
he knowingly drove the design right to the limit. My guess is that leaving an airgun cocked permanently
IS likely to cause a loss of spring strength over time. Can I prove it, no way. How about magazine
springs? Well, I would hope that the designer was smart enough to know that the mag might stay
loaded for long periods and design the springs to take that without problems.

I have heard of multiple cases where a magazine has provably remained loaded for 50-80 years and
functioned perfectly when called upon to feed the ammo. I never worry about it when using good quality
magazines. Something to think about when buying bargain basement magazines - reserve them for
practice, not self defense or serious hunting.

Bill

[sqlbullet]

In reality a largely moot point.

If the gun is meant for defense, it should have a range outing at least monthly to validate both the function of the gun and the shooter. Drills should include magazine changes. Magazines should be marked, and stoppage failure tracked by magazine. Any magazine that shows a propensity for a stoppage should be removed from the defense rotation and used only at the range until said issues are resolved.

If the magazine is to be stored for a period of time, it is best to store it unloaded. This is not to preserve the spring, as much as the magazine feed lip geometry. Over long periods of time, the pressure can cause the lips to move which may introduce reliability issues.

Like Bill, I don't lose any sleep over wearing out a magazine spring. I get to the range regularly, and I change the magazine springs and recoil spring in my guns every 5000 rounds.

[sagacious]

My guess is that leaving an airgun cocked permanently IS likely to cause a loss of spring strength over time. Can I prove it, no way.
This is easy to prove! :neutral: Anyone with a spring-piston gun can measure it's velocity before and after leaving the spring cocked for a week (please, don't try this). The spring will be weakened, and velocity will suffer. The risk of damage is such that leaving the gun cocked overnight is bad news.

I've had to send s-p rifles back to the manufacturer twice to have the mainspring replaced, and I never-- ever-- leave the spring compressed for more than several minutes. As I noted before, these springs operate near their limits, and even with proper use, they are well-known to eventually lose strength. This fact has been the impetus for the gas-ram powerplant replacement of springs in air rifles. Aside form being faster and lighter, that gas-rams do not suffer from spring fatigue is their #1 selling point.

Regards, and good shooting. :drinks:

[MtGun44]

Interesting. Clearly they are running RIGHT against/past the limits on the spring designs.
Not being an airgun guy, I had no idea they were that far extended.

Bill

[bigdog454]

A spring is a spring. As Mtgun44 has stated; a spring depending on it's functional design limits, should always be a spring and not loose it's elasticity. If you abuse those limits ie. bending a leaf spring beyond its intended limit, there is a good probability of spring failure. You also have to take into consideration weather or not the spring was manufactured properly, using quality materials and procedures. A good spring made of good materials and properly heat treated should last forever.