Digressive Springs

[Mr.Kennedy777]

So I know there is a digressive lockout stack spring setup, I was wondering if anyone has heard anything about a digressive spring that was made? I'm not sure who manufactured it but I remember reading somewhere that some engineering company had created this type of a spring a few years back. Would there even be any benefit to running something like this as opposed to a digressive stack or a spring pre-loader?

[zeroracing]

The only digressive spring that I have seen was an April 1st, 2014 press release by a spring company... I don't see it being possible with a single spring, the way the spring compresses it will by nature be progressive, no real way around that without a physical lock out like a dual stage stack can give you.

[fastford]

so you would run the softer spring for the spring your on after you hit the lock out?

[Matt49]

A single digressive spring defies the laws of physics.
A digressive stack is possible but it would be setup completely different than progressive stack. The lock nut would need to go below the slider and have a pre-load on the upper spring at ride height so that the lower spring is doing all of the work (your initial spring rate). Then as the "stack" compresses, the upper spring gradually unloads until the slider moves up and away from the lock nut and then you are on the "dual rate" from there on out on compression.
I personally can't think of a good use for it but I could be missing something. Maybe in combination with some sort of linear compression shock on the RR? I don't know...

[Matt49]

so you would run the softer spring for the spring your on after you hit the lock out?

That's still a progressive setup. A single spring in any stack will always have a higher spring rate than that spring combined with any other spring.
Example: 500 on top of 100 (locking out to the 100). The stack rate is 83.3 and then you locked out to 100. So it is still progressive.
The only way to have digressive stack is for one of the springs to be locked out and then become "unlocked" during compression. My previous post explains how to do it.

[billetbirdcage]

I wouldn't say it would defy the laws of physics but would be very unusual metal or way of doing it to make a single spring digressive. Think of it this way: A typically balloon. When empty the rubber has more spring rate and once expanded it gets softer, basically easier to expand it with less force the more it gets filled. Most people are going to think some sort of metal but if you start thinking about other materials, I think many will see it's possible.

If the material was stiffer in it's free state and became less rigid/stiff as the metal started to bend/bow, you could make a digressive single spring. Not sure that metal exists or they are using a different method to get the same effect. But it seems possible to me as there is some pretty amazing stuff out there in alloy's and composite blends. It would likely be way easier to do with some sort of composite material as a spring doesn't have to be metal.

[Mr.Kennedy777]

What about a stiff rate for entry and a soft rate for exit?

[MachineMasters]

What about a stiff rate for entry and a soft rate for exit?

Look into a spring preloader cartridge. This allows you to preload a softer rate spring (usually on the RR) to have a stiff rate for entry and a soft rate for exit.

jury is still out on these in my opinion..

[Mr.Kennedy777]

I'm not really looking for one or to even do this. Just feeding my thoughts.

[fastford]

That's still a progressive setup. A single spring in any stack will always have a higher spring rate than that spring combined with any other spring.
Example: 500 on top of 100 (locking out to the 100). The stack rate is 83.3 and then you locked out to 100. So it is still progressive.
The only way to have digressive stack is for one of the springs to be locked out and then become "unlocked" during compression. My previous post explains how to do it.

yea i realized after i posted that it would still be progressive , also after thinking about it, i cant really find a benefit from it..

[Matt49]

I wouldn't say it would defy the laws of physics but would be very unusual metal or way of doing it to make a single spring digressive. Think of it this way: A typically balloon. When empty the rubber has more spring rate and once expanded it gets softer, basically easier to expand it with less force the more it gets filled. Most people are going to think some sort of metal but if you start thinking about other materials, I think many will see it's possible.

If the material was stiffer in it's free state and became less rigid/stiff as the metal started to bend/bow, you could make a digressive single spring. Not sure that metal exists or they are using a different method to get the same effect. But it seems possible to me as there is some pretty amazing stuff out there in alloy's and composite blends. It would likely be way easier to do with some sort of composite material as a spring doesn't have to be metal.

I guess I should have specified steel/ferrous metal or something with a similar modulus of elasticity. But this discussion is certainly getting interesting.
What about application?

[Mr.Kennedy777]

well if the rate would decrease as it compressed, it would increase as it rebounded. Could be a good 6th coil spring?

[fastford]

well if the rate would decrease as it compressed, it would increase as it rebounded. Could be a good 6th coil spring?

in that case, it might have a positive effect on the 5th coil.

[Mr.Kennedy777]

I was thinking it could be used to simplify the design of a 6th coil and lighten it up. The spring could get mounted onto the frame using a set of clamps that hold the top of the spring securely around the coil. Then the part attached to the bottom of the coil attached to a chain.. and pull the spring instead of push it. No need for a crazy cage with bolts and sliders. Just a top attachment and a bottom. They could use some cotter pins or something to hold the fasteners closed on the bracket around the spring so they don't jump out. A spring can be used to apply a force to resist tension as well as compression.

[Mr.Kennedy777]

Technically a progressive spring would become digressive and a digressive would become progressive in these conditions correct?