Mainspring steels

[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.