Let's talk springs, part II.- Geometry.

Fascinating stuff Hector.  I had to go back and reread part 1.  I'm sure I'll reread part 2 as well.

Without going too deep down the rabbit hole, I have a question on square-section springs.  OX used to sell a relatively large diameter square section spring for high-powered guns, which was purported to provide increased power, but a (reportedly) somewhat harsh shot cycle in the guns it was sold for.  In contrast, ARH sells the Merlin spring for mid- to low-powered guns, which is also square section, but a relatively narrow diameter.  It is purported to (and based on personal experience, actually does) provide smoother cocking and firing behavior at roughly the same power levels in the guns it is sold for. 

..

@jiminpgh

As in many things in life, the happiest condition is when there is  BALANCE and HARMONY between all components.

While it is true that spring changing is almost a sport in itself to us Americans,  that comes with a price, and that price is that there are TONS of options and very little guidance.

So, the idea of the post was to enable our readers to come up with different combinations of OD and d (wire diameter) that would generate the same force when compressed to the power stroke of the gun they were working on. That should keep more or less the same energy output of the gun.

This would enable readers to then stress either a fast shot cycle (Small OD, medium to high  d, low Na) or to get a more sedate, mellow cycle (larger OD, smaller d, higher Na). It will also have an effect on the longevity of the spring, harsher (faster) shot cycles will fatigue the spring quicker than slower, mellower cycles.

The equations work reasonably well for all spring sections (Round, elliptical or square), but there is a correction that can be made and it applies to what I termed the "apparent cross section" that is the cross section of the spring in a plane that cuts the spring lengthwise. Because the angle of each coil  changes with each mm of spring compression, this cross section also changes. There is a constant that is called the Wahl constant that addresses this.

Now, for OUR purposes, the slenderness of the spring (length to diameter ratio), the guide, the tophat, the compression duty cycle (almost to solid each and every time), and the shock at the end of the spring elongation cycle tend to overshadow all other fine adjustments (like the Wahl correction).

There is no way the cross section of the spring will determine the "characteristics" of the shot cycle, it is the COMBINATION of the key variables what determines this for a given airgun architecture.

In the couple of cases that I have tried square cross-section spring wire, the ONLY thing that has happened is that the spring has added WEIGHT, and that weight adds to the piston weight. If the piston was "light for duty" (as in a 350 shooting 21.1 grs. Baracudas at 24 ft-lbs), then the result was beneficial, but in the case of a 34 that was shooting 8.44 JSB's it was detrimental.

Again, it's a balancing act where the weights of pellet and piston also play a role.

Another thing that limits our imagination is that wires are not produced in every material with every possible diameter, LOL!

So, we need to also balance what we want with what we can get.

Thanks for reading!

HM

@harvey

Do you mean that the post made you drew a blank?

If so, you were laconically eloquent.

😉

Thanks for reading!

HM

@hector-j-medina-g

My comment was moronic.

It was better to appear laconic.

Lacking knowledge to be forensic.

Though the evidence was intrinsic.

At first the idea seemed... cool.

I invoked the measurement "joule".

If maybe a spring could be measuredly thusly,

maybe spring life wouldn't be as fussy.

But I was wrong.  My spring idea had a kink in it.

and that's when I realized it might be better just to quit.

Pause and learn, figure out your direction

Look a little more, before dissection.

But that's good because I'm still on the track, still in the train.

Knowledge, like the moon, will wax and wane.

signed,

the caboose