Mainspring steels

[TonyL]

Some excellent posts there, trajectory, with some very useful information and observations.

Thank you for bouncing in.

[Kuyajonathan]

Forgot to mention Krupps spring steel... Had a good reputation, not sure exactly what it was composed of but I think it was a generic name for a range of products for varying purposes.

As to calculating any theoretical values for springs........yikes, modulus, stress, strain, % elongation etc etc there are books with pages of calculations & the mathematical derivations of the formulas. Some of its quite interesting but it's heavy going.


Was once told a helical springs were not what I thought they were. I thought they had a constant coil diameter. Apparently, so I was told, a helical spring has a coil diameter that reduces in one direction over its length. Apparently somewhat like the thread on an old fashioned wood screw, anyone else heard of that?

I have heard of progressive springs used on car & motorcycle suspension, these are in constant movement, intial soft response to compression, then more ' progressively' stiffer as compressed. Coils further apart at one end, closer at other . Never seen or heard of them in Airguns, Probably not comparable situation to our use?

[bighit]

I have heard of progressive springs used on car & motorcycle suspension, these are in constant movement, intial soft response to compression, then more ' progressively' stiffer as compressed. Coils further apart at one end, closer at other . Never seen or heard of them in Airguns, Probably not comparable situation to our use?

Some engine valve springs were progressive but not many .

[trajectory]

I have heard of progressive springs used on car & motorcycle suspension, these are in constant movement, intial soft response to compression, then more ' progressively' stiffer as compressed. Coils further apart at one end, closer at other . Never seen or heard of them in Airguns, Probably not comparable situation to our use?

I believe some automotive springs are truncated conoidal, made with tapering diameter steel. The coils at one end of the spring describe a larger diameter than the opposite end of the spring & the diameter of the wire is different at either end.

[LeeO]

Nowadays, i think supplier is very important,
loads of steel out there, not all equal by some stretch,
Krupp 55 was used for years by a well known Italian sword maker, now i think they use 6150 or 50crv4, would have to double check,
as do a few of the premier English makers,
any sword steel will make a good spring, not the same for knife steel though, a good many yes, but not all,
5160 EN45 -47, etc etc, a lot of the spring steels are interchangeable within both industry's,
heat treat is hugely important,
majority of spring company's really know their stuff, sometimes underthinking it, and letting the company do the spek work is the better option,
or if local, dip the scrap bin and have a play,
if you want super special, there are some impressive smith-metallurgist's out there,
interesting thread,
boing,

[HW777]

How long would you expect an air gun spring to last, retain the power it was designed for and stay the course in consistent fps at the given power you were after ?

25, 50 or a 100,00 shots, it's a bit like Animal spring farm, not all springs are equal.

Given there are lots of OEM replacement springs but only a few after market ones.

Which springs do you rate ?

This would give a good idea of who goes the extra mile and take's their time to spec their springs.

I probably should have done another thread to cover this, I just don't like to bounce one thread off another's idea.

[Geezer]

Couldn’t resist a bit of Googling.

40 cents each in bulk:

https://www.alibaba.com/product-deta...40b821b0JIMoNV


These must be the good ones, as they are $3.08:

https://www.aliexpress.com/item/32801541338.html


Gas struts, from $3:

https://www.alibaba.com/product-deta...5d095aafmlybVL

[trajectory]

Longevity of Springs

It is possible to calculate spring life........but.....

There are formulas to do so & programs/ algorithms to do so, but there are possibly a couple of problems. One that i can think of is that it's more than likely that for an individual case a full set of values for inputting into such a programme is unlikely to be available. Manufacturers would be in a different position as they would have the information required/ data & even if they didn't do the calculations themselves they might go to 'spring maker' & let them know what their requirements were & between them they would be able to sort things out. I think it would be a joint project with both parties contributing their expertise & letting the other party know what was negotiable.

Durability or life prediction is not an easy question to answer, we wouldn't usually expect similar longevity from items from either end of the price spectrum. You have to engineer a safety factor in. That might be fatigue cycles, or tensile strength or whatever is relevant to the application. Springs do break but in an air rifle there's usually a progressive drop in performance as things start to wear. So there's usually some indication that things aren't performing at their optimum.

Some factors are harder to take into consideration & they might effect predictions/expectations.
Perhaps there's a person who cocks & fires their air rifle within 20 seconds & then one that regularly sits waiting for a shot opportunity for 20 min with their rifle cocked.....life expectancy will be dependant on many factors, some of which are beyond the control of the makers. They might be able to predict life expectancy based on best available information under certain conditions of use but I don't recall seeing it in an advertising claim. I seem to recall seeing wear factors being quoted but not shot cycles.

It's interesting though, how many shots can a spring deliver, anyone counted the no. of tins of pellets through an air rifle from new?

[Black Beard]

You can get an estimate of fatigue life off the maximum stress in the spring and a simple graph but it would be very heavily dependent on the heat treatment. Another difficult factor is what is the maximum stress in the spring? If the airgun is properly set up it would be a lot less than if the spring was buckling and the piston was smashing into the end of the cylinder. Springs have inertia (equivalent to adding 1/3 of their weight to the piston) and you can't stop that instantly. Too many variables to work out but I guess with a decent spring and a not over-stressed gun it should be tens or hundreds of thousands of cycles.