[Pslide]

So I was thinking about the latest air shocks for the DH crowd, and the trade off that we often have to make between a lively, poppy bike and a ground hugging, stable race machine.

I had an idea that might make it possible to achieve a lively and uber-sensitive, high traction suspension setup and bridge the gap between progressive and linear suspension.

Could you make an air shock with a shaft-speed sensitive spring rate? In other words, a shock that had a given spring rate for low to medium shaft speeds (for pedalling and popping) and then opened up to a softer spring rate at high shaft speeds (high speed rough terrain and chatter). This has never been possible with a coil spring, but seems doable with air.

I realize that we have damping that does this. The problem with using damping to resist motion at low shaft speeds is that it dissipates energy - our energy - making the bike feel dead. But achieving this through a variable spring rate would not dissipate energy. The suspension would remain lively and poppy.

So I guess you'd use some kind of inertial valve that increases the air can volume instantaneously with high shaft speeds.

I don't know, maybe this has already been done in air forks? I can't believe that someone else hasn't thought of it. We do have low-speed blow off valves, etc. I haven't studied how they work, but I'm guessing it's tied into the damping, not the air spring. I figure some of you suspension gurus will know more than I do...

PS - Someone under 18 ought to submit this to that Pinkbike contest and get Cane Creek / Ohlins working on it.

 

[jonKranked]

would the simplest way to accomplish that be a dual air chamber? one at lower pressure, one at higher, essentially creating a dual rate spring?

 

[Pslide]

would the simplest way to accomplish that be a dual air chamber? one at lower pressure, one at higher, essentially creating a dual rate spring?

Not sure how that would work, not that it couldn't. Not sure how you would disengage the higher pressure chamber at the higher shaft speed.

Makes me wonder what was going on inside of this thing and all its chambers...




Also makes me wonder if something similar was the magic in the Millyard department of defense mystery shock:



"How do you think this shock compares to higher end shocks, such as the Curnutt, or the Cane Creek Double Barrel?
There is no comparison! Any one who has ridden this system on a rough track will be scratching their heads trying to work out what's going on, you have to ride it to believe it. Current damper technology is a compromise, and you as a rider have to pre-empt the track conditions and set to shock and spring so that it won't buck you off the big jumps, but is manageable over the ripples. Our system reads the track and responds to the actual conditions there and then, on the track, while you are riding. It's super smooth over small ripples, stairs and steps, but you can land a 20ft jump to flat with absolutely no recoil from the back end."

 

[IH8Rice]

Makes me wonder what was going on inside of this thing and all its chambers...

View attachment 110377

theres more info out on the Fox DYAD shock spec'd on Cdales. i do believe they are somewhat similar in design.

and what contest are you talking about on PB?

 

[OGRipper]

Interesting idea. Sounds like you would need variable damping too. If your compression and rebound settings work well low psi, you'd have have limited damping at the higher rate. The variable factors would need to work together.

And I'm not sure that you want a lower spring rate at higher speeds. I mean, you want to lower your spring rate for that 20 foot jump to flat?

 

[Pslide]

theres more info out on the Fox DYAD shock spec'd on Cdales. i do believe they are somewhat similar in design.

and what contest are you talking about on PB?

Reality redesigned.

Will check out Fox DYAD, thanks.

 

[Pslide]

Interesting idea. Sounds like you would need variable damping too. If your compression and rebound settings work well low psi, you'd have have limited damping at the higher rate. The variable factors would need to work together.

And I'm not sure that you want a lower spring rate at higher speeds. I mean, you want to lower your spring rate for that 20 foot jump to flat?

If you think about the damping, it might work quite well. You naturally get more rebound at the high speed/lower spring rate for better suspension control, and less rebound at the higher spring rate for liveliness / pop. It's probably not that simple though.

I did think about the huck to flat issue. But then again, it wouldn't hurt to have a softer spring rate in this situation, to soften the landing and reduce the chance of getting bucked. The airspring will increase rate naturally towards bottom out anyway, so bottom out shouldn't be a problem. You just have more air chamber volume to handle the big hit. Or I could be talking out my @ss.

 

[Pslide]

theres more info out on the Fox DYAD shock spec'd on Cdales.

Blurb on Fox DYAD: Developed in collaboration with Cannondale, the dual-travel, dual-personality FOX DYAD RT2 is actually two completely different shocks housed in one package: Elevate – a shorter travel, smaller volume air shock for rolling and climbing terrain, and Flow – a longer travel, high volume linear air shock for aggressive descending.

Activated by a handlebar-mounted lever, each mode has its own dedicated damping circuits, fully optimized for the intended terrain. Rather than try to make one shock handle everything, we were free to create separate suspension responses for different needs – active and super efficient for the flats and climbs, ultra plush and bottomless for the descents.

Switching between the Elevate and Flow modes also changes the bike's sag point and geometry, a feature we call Attitude Adjust Geometry. In Elevate mode, the bike rides higher, resulting in steeper head and seat angles and keeping the rider in a better position for climbing and tight technical terrain. In Flow mode, the BB drops, lowering the center of gravity and making the angles slack and stable, perfect for charging descents.


So not quite what I was thinking, but maybe similar if it was actuated by shaft speed.

 

[4130biker]

In my experience of harsh/flat landings, I think a higher spring rate is more forgiving. Meaning that it's actually compressing instead of slamming into bottom out. Bottoming out has to be hard on frames and parts and it sure doesn't feel good- even on an air shock.
That issue aside- it seems like you would want a similiar spring system up front so you don't wind up stinkbugging all of the hard landings. :0

 

[baca262]

dyad has 2 springs and 2 dampers for 2 travel modes, it isn't what pslide has in mind. but this other thing just might be it...

 

[IH8Rice]

dyad has 2 springs and 2 dampers for 2 travel modes, it isn't what pslide has in mind..

no one said it was what he was looking for

 

[baca262]

i'm a few posts too late.

 

[baca262]

but, if you could somehow rig the dyad to switch springs depending on low or high speed compression, it could achieve what we want here (assuming you have a custom version with 2 equal springs and dampers with different pressures and r/c settings). now how would you do that, i have no idea.

edit - or not, i'm quite stupid atm.

 

[?????]

How about an ORI Strut?

■Dual pressurized chamber design for unmatched body roll stability
■3-stage velocity-sensitive compression damping
■Velocity-sensitive, 7-position externally-adjustable rebound damping
■Internal hydraulic bump stop on compression stroke
■Hydraulic end-of-stroke cushioning at full extension
■Cooling fins dissipate heat

Nitrogen-charged long-travel
dual spring rate strut that can support over 1300 lbs. load.

Hill & side-force sensing, the ORI DP3 strut instantly and automatically adjusts spring forces while you drive to help level the vehicle on hills and in hard turns–a stabilizer without the heavy hardware! Full-stroke soft spring rate for level running and full-stroke hard spring rate for the struts on the down-hill, or load side.

The ORI DP3 strut features external adjustability for both compression and rebound strokes, with position-sensitive compression damping and velocity-sensitive rebound damping.

Compression damping oil is separate from rebound oil, making it possible to run different viscosity oils for compression and rebound strokes.

http://oristruts.com/products/shocksstruts/dp3-strut/

 

[Pslide]

How about an ORI Strut?

...

Jeez, that thing is pimp king of struts. Rock crawling has gone nuts in the past 10 years.

If I was smart enough I could probably learn something from that thing, but it's above my head.

 

[woodsguy]

but, if you could somehow rig the dyad to switch springs depending on low or high speed compression, it could achieve what we want here (assuming you have a custom version with 2 equal springs and dampers with different pressures and r/c settings). now how would you do that, i have no idea.

edit - or not, i'm quite stupid atm.

Not sure why you would want it to switch for you. Does your riding vary that often and that quickly that you don't have time to flick a switch?

 

[baca262]

nope, the idea is an automatic soft spring with more damping for teh gnar, firm spring with less damping for the jumps n stuff.

 

[TWeerts]

isnt this just speed sensitive damping? as opposed to the position sensitive damping systems commonly used in mt. bikes these days.

didnt risse try speed sensitive damping a while back?

 

[baca262]

speed sensitive damping is commonly used, fox propedal is position sensitive and manitou tpc+ is both.