Stacked airbags

[jeromio]

I've been searching all over for this and I've come up completely empty. It seems (to me) like an obvious solution to the problem(s) of airbag suspensions: the less air pressure, the lower the ride height AND the lower the spring rate. So, super low, you're either on the bump stops (not good), or you're warbling all over with no control (also not good). And then the reverse: max ride height is also max spring rate (jacked up but way too stiff).

So, I'm wondering why you can't just stack 2 airbags, meaning individual airbags each with their own separate air inlet (one on top and one on the bottom). So with one bag completely aired out, the ride height drops, but the 2nd bag provides a relatively usable spring rate. One spring maxed out for lift would leave the 2nd to provide some compliance.

Why is this not something that you can just order off the shelf? Am I missing some important detail?

[PDW HOTRODS]

Wouldn't stronger shocks and a sway bar fix the problem? get taller air bag or position it so it is not maxed out at the highest you want the truck. Stiffer shock and sway bar should keep it from moving around too easy and feeling like riding on a marshmallow.

[SCOTI]

Originally Posted by jeromio

I've been searching all over for this and I've come up completely empty. It seems (to me) like an obvious solution to the problem(s) of airbag suspensions: the less air pressure, the lower the ride height AND the lower the spring rate. So, super low, you're either on the bump stops (not good), or you're warbling all over with no control (also not good). And then the reverse: max ride height is also max spring rate (jacked up but way too stiff).

So, I'm wondering why you can't just stack 2 airbags, meaning individual airbags each with their own separate air inlet (one on top and one on the bottom). So with one bag completely aired out, the ride height drops, but the 2nd bag provides a relatively usable spring rate. One spring maxed out for lift would leave the 2nd to provide some compliance.

Why is this not something that you can just order off the shelf? Am I missing some important detail?

They probably don't make such an animal because of lack of demand. How many people would need the set-up to creep 1" off the ground @ optimal pressure & then later that day need it @ stock right height again @ optimal pressure? It wouldn't be just the springs.... You'd also have to dial in shock travel heights. And, you can't align it for both. Which height would you be aligning it for??

Beyond that, the end-plates of the bags would have to be built so they can be stacked some how or an adapter made allowing two to mount together. Bags @ normal lowered ride height & optimal pressure are typically 5" minimum up front so x2 would be 10" of spring you'd have to figure out how to fit. Some sort of crossmember mods would be required which would possibly lead to other required mods.

They make triple bellow bags but again you'd have to build the vehicles mounting set-up to work within the range of the air spring. Then those shock & alignment concerns would need to be addressed as well.

There is a set-up that allows you to build @ a 'lowered' height & then switch to 'dummy-low' @ the touch of the finger w/the exact same ride quality. Alignment configurations can be built so the impact is minimal. The problem is the price of entry to the club as it's exclusive from the perspective of the blue collar builder.

[Ziegelsteinfaust]

On Finnegans garage a couple years back. They put hydraulic coil overs on his 67 truck.

The hydraulics controlled ride height, and the coil over portion controlled spring rate with dampening.

That's probably the closest thing to what you described.

[SCOTI]

Originally Posted by Ziegelsteinfaust

On Finnegans garage a couple years back. They put hydraulic coil overs on his 67 truck.

The hydraulics controlled ride height, and the coil over portion controlled spring rate with dampening.

That's probably the closest thing to what you described.

This is exactly what I described. Bring your big checkbook to the table though....

[Ziegelsteinfaust]

Originally Posted by SCOTI

This is exactly what I described. Bring your big checkbook to the table though....

Sure it is expensive, but compared to an all-in top shelf air ride kit. Not that much more.

Is it better? Depends. As anything this does is not something I am looking for.

I have had a air ride for a minute, and the way I use my vehicles. This is the optimal choice for me.

[SCOTI]

Originally Posted by Ziegelsteinfaust

Sure it is expensive, but compared to an all-in top shelf air ride kit. Not that much more.

Is it better? Depends. As anything this does is not something I am looking for.

I have had a air ride for a minute, and the way I use my vehicles. This is the optimal choice for me.

Hhmm.... I've seen that the shock set-up alone was over $4k (the 4 shock/coil-overs). Then you have to get the control management & hydraulics (unless that was included in the cost but not communicated). I've yet to see a price tag for the control side of the Hydroshox set-up.
*EDIT* The Hydroshox set-up includes the pump & management systems w/prices starting @ $5k ($4995.00).

JRI's version starts @ $6k for non-adjustable shocks.

The Accuair set-up was what I would consider top-tier & was around $2k which included management & electronics. Bags & shocks can be obtained for under $1500.

[Richard]

Remember seeing something a while back about a rear high lift fad with bags. Yes, you can double the lift from the bags. The ones I saw used a wishbone link to a coupler piece in-between the stacked bags. This would be needed because the setup would want to fold out in the center.

[Richard]

Would think that stacked bags would act the same as the separate coils on my coil over shocks. Each spring (or bag) sees the same amount of weight. For example my stacked 250 lb springs would compress 1" for each 250lb of weight. 1000lb weight each spring will compress 4". Total spring height for both springs will reduce by 8". This method effectively reduces spring rate by half. Have a 125lb spring rate. Changing spring rate in one spring will just raise or lower the effective spring rate (raising or lowering pressure in one bag). Some coil over shocks such as mine have stops for one spring. I can set the point my spring rate changes from 125lb to 250lb by stopping movement of one spring. You would need to stop movement of one bag at a point to increase spring rate. Bottoming out one bag would accomplish this. FWIU stacked bags would decrease spring rate not increase it.

[jeromio]

No, that is true: stacked springs will be "softer". Which does make sourcing the correct bags even more difficult, as Scoti points out.

I think what I'm probably more likely to do is bag + spring bc I'm for sure not gonna get custom bags made.

[Richard]

Should still work with standard type bags. Coils are linear and fairly predictable as they compress. Air bags increase in pressure as they compress, a progressive spring. Finding the correct separate pressures to run for a smooth transition from two bags to one will take trial and error. Using a coil in place of one spring will still make things unpredictable as the air bag compression relates to pressure.