Idea for air suspension programming

[Bryce]

i was thinking about the advantages of an airride setup. If you run minimal compressors and tanks the whole system would be lighter than springs and the progressive spring rate is nice.

So I started thinking about the advantages of air control. This would be a programming issue. So you could have a fast reacting system (air solenoid and fill and empty times). So i was thinking about removing sway bars to lighten up the car even more and using a program to stiffen up the outside air spring to limit body roll. Theoretically you could completely limit body roll.

Anyway, i just wanted to here some pros/cons about this idea. ANd maybe get input from the airride programmers to see if this is possible. And also some discussion on CFM needed to fill up the air bag to stiffen that side and then air it down after the corner. What hardware modifications would be needed if any.

I am interested in this sytem to lighten the car.

[LowBuckX]

My friend did and air set up along time ago and he had to run a compressorless system using a nitrogen tank and regulator to get the speed he needed. As you can imagine getting the tank filled was a PITA. Im sure todays compressors and valves would keep up.

[Bryce]

I was thinking a higher pressure system would be the best idea to increase CFM and a lighter tank might be used. I would need to do some calculations to figure the amount of air storage required to make an active air suspension.

Does anyone know the Volume of an airbag. A quick guess is a 5" diameter bag and a 7" Length when fully extended with a 2" diameter shock running through the middle. So this is approximately 120 cubic inches.

[Rhino]

Technically this would work with the limiting factors being processor power and valve size/speed. In the real world there are a few examples of somewhat active suspension. Such as the Magnetic ride control on the Corvette. My guess is that in the real world an active system built purely on air would prove overly complex for the small weight savings. It would be interesting to see what other things could come of this, such as corner weighting a car for a left or right hand turn.
To do it properly you'd probably need pressure sensors and ride height sensors on each wheel and accelerometers to determine what the vehicle is currently doing. Maybe a steering gear position sensor as well.
You'll need the sensors to be able to determine the difference between differing events such as a single wheel bump, an off camber run up a hill, and corner. It would really start getting interesting when you're turning on a banked corner.
You'll need the system to react lightning fast. As such you'll need an extremely high sample rate, a fast algorithm to decision what changes to make, and large valves to allow a quick fill/release of gas volume.
It would be interesting to determine the pressure differences bags go through in a corner. Due to the weight transfer, and roll, the pressure has to increase on the outside corner. I just don't know of what magnitude it is.
I just received another suspension book today that does hint at some previous development of active suspensions. I'll have to browse through it to see if it has any details.

[MonzaRacer]

Honestly this would be a never ending crap shoot for handling, way to complicated. You going to be cycling a solenid many times a second, and have a compressor running nearly all the time and its just not as feasible as you think.
and your still needing a physical link from control arm to frame to eliminate body roll.
Now with a 4 "channel" system your not going to get the body roll you would in say a 2 or 3 channel set up.
With appropriate valving in Double adjustable shocks and a 4 corner system you would not even need to think about active control and the complex setup you envision.
Honestly 4 way Big Red set up from Ridetech, use the aluminum tank and your in, and double adjustable shocks from them will do pretty much everything you need.
Honestly my 71 Monte had rear CoolRide had better characteristics than the stock front end with a sway bar.
It had individual lines that I filled manually at rear bumper.
Some of the bouncing guys were blowing nitrogen into 1 in fittings but that was to bounce.
Honestly beyond auto leveling , you really dont need active control as the spring rate goes up very fast as you load the spring.
Man the amount of hardware, and software and development would be enormous over tried and true Air Ride.
Sound like several thousand dollars to develop and Air Ride is already done, it works and heck some extra tuning might let you leave a sway bar off.

[BillyShope]

Something else to think about: You could partially fill the air bags with a liquid (antifreeze?) and use a liquid reservoir and an interconnected pump system to control wheel rates and wheel loads.
http://www.racetec.cc/shope

[Derek69SS]

Something else to think about: You could partially fill the air bags with a liquid (antifreeze?) and use a liquid reservoir and an interconnected pump system to control wheel rates and wheel loads.
http://www.racetec.cc/shopeThat would significantly increase the rate of the spring, as the fluid wouldn't compress like air does.

[MonzaRacer]

Honestly I have seen more air ride setups without sway bars and 4 way control and zero handling issues. In fact after relating this thread to a friend of mine with Air Ride and my FlexFI setup and he told me that his Camaro and his Chevelle have 4 way control and no sway bars as the control arms he bought had no provisions for them and he said he honestly doesnt really feel it need them. With the compression set a little firmer than his brothers car that does have sway bars it does ride rougher in his wifes words but she loves the car none the less.
I also agree using any type of liquid inside an air spring would really degrade the springs performance. Also prett ymuch anything you put in inside it would damage the spring. Heck even methanol air brake antifreeze isnt really liked by Firestone or any of the other spring manufacturers but they say short term exposure in allowed.
Honestly I believe automatically controlled shock valving MIGHT be more useful, similar to the Magnetic Ride Control previously mentioned which I do believe was controlling the shocks.
Honestly you would need atleas 1 or possibly 2, 5 gallon tank, 2 if not 4 compressors and running say Ridetech Big Red Solenoids, most likely 1/2" lines, and some serious cooling/drying for the air generation.
in other words I really do believe it would be out of the scope of a one off setup as it wouldadd hardware and complexity to a system that requires so little to function at a level far and above the standard steel/fiberglass/carbon fiber spring.

[MonzaRacer]

Another thing to think of is a certain amount of roll set is required to make a car go through a curve. Friend I went through a driving school just reminded me of this term/phrase. It means a car center of gravity side to side does effect how it goes into a curve.
I keep rereading your post and it seems your looking to remove weight yet you looking at multiple compressors, and tanks, even in aluminum are not light, extra hardware and honestly I see actual negative return on the expenditure of funds and time.
We were given a formula to achieve this factored movement from CG, suspension mounting points, and a multitude of other factors Ihad forgotten about. It would have bubbled to the surface but its been 20+ year since that class!
I figured my 71 Monte like 11 yrs ago and without a bunch of info I needed I plugged in as much as I had and figured the car needed to "set" around an inch with coil springs and after installing rear CoolRide I honestly think the set was around 1/2 or less as the rear just didnt roll like it used to with worn out springs and shocks.
Think of it this way your going to need at least 10 t o12 active control circuits, at least 24 (rough guess in my minds calculator)sensing circuits, all the wiring and bracketry involved and some serious compressor(s) capacity to maintain steady pressure.
Most systems run in the 50 to 150 psi range, and most springs while naever fail over that according to Ridetech, upping the pressure gives a exponentially harder/harsher ride and will conversely seriously degrade your ride. Unless you seriously increase the spring size, then you get into cost,weight,function.
Sounds like little gain for way too much effort.

[Bryce]

In response to the sensors and complexity of the programming, I was thinking only a shock travel indicator would be neccessary. This would stiffen the right spring when the right side compresses more than the left or vica-versa. I have seen ready made shock travel indicators. I think edelbrock makes one of these. This would almost be like a self leveling system when one side compressed more than the other.

[Bryce]

I agree with the added weight of compressors and tanks there is less benefit. I was trying to make it as simple and light as possible. This may not even be possible.

[gkring]

http://v8tvshow.com/content/view/821/1/

the new shocks from ridetech that are coilovers, but electronically adjustable valving for different setings.

[MonzaRacer]

Thats why I was recommending adjustable shocks over active suspension if that didint come through clearly.

[BillyShope]

That would significantly increase the rate of the spring, as the fluid wouldn't compress like air does.
Somewhere between one drop and one gallon could be what you need. Of course, it's going to increase the rate. That's the idea.

As for a compatible liquid: There most certainly exists a liquid which would be compatible. It's silly to dismiss the idea out of hand. Working with a liquid would have some advantages.

And, a fluid is either a liquid or a gas.
http://www.racetec.cc/shope

[Rhino]

Today I did a preliminary read through Competition Car Suspension by Alan Staniforth. It does have a full chapter dedicated to the principals of an Active system developed by Lotus for use in Formula One.
Thinking this through, I would prefer to mimic their approach. It was a 100% hydraulic system, with nothing more than cylinders at each wheel. A central controller would bleed or add pressure at each wheel.
You would be building the system to remove unknowns, you might as well go all the way and remove the variable volume of gasses from it as well.

This system went as far as over-reacting and tilting the car toward the inside corner. With our cars I think this would be counter productive, but it is an interesting read.

[bret]

Interesting thread...still listening...

Though many of these ideas may have no CURRENT commercial viability, the best ideas are nutured by passionate individuals.

I have vowed to not repeat the advice I was given in 1995 concerning air suspension for hotrods.

Let me know how I can help!

[bret]

That would significantly increase the rate of the spring, as the fluid wouldn't compress like air does.

Another way to infuence the spring rate is to play with the profile of the lower piston that the airspring rolls down over. I have seen airsprings that use an adjustable [inflateable] piston to allow a changable spring rate.

The tough thing here is to determine the real goal...what to change, when to change it, why to change it.

Carry on!

[BillyShope]

I have seen airsprings that use an adjustable [inflateable] piston to allow a changable spring rate.
Clever idea!

Assuming sufficient durability, I have, for years, considered the use of air bags...for oval track and road course cars...to be a logical evolutionary step towards the full hydraulic approach. This would seem an absurdity when today's airbag applications are considered. It would never be practical for manufacturers to supply the range of rates required with different bags, but, with tricks like that quoted above or with the injection of a liquid, it becomes possible to have essentially infinite rate variability available to either the driver or the pit crew.

On the other hand, it could destroy the commonly perceived connection between a "soft" ride and air suspension, which could reduce sales in the much larger market segments.
http://www.racetec.cc/shope