Air Spring Mechanics
I have been trying to understand why this air spring system has such an incredibly soft, flexible ride when compared to my own air spring system that failed miserably in this department.
In studying these air springs and watching how they work I realized their mechanics? are far different then a simple air bag.
In a regular air bag compressed air enters and the bag grows by stretching the bag upwards and outward. Much like a balloon.
In these Firestone air springs the air bag itself straddles and surrounds a rather larger metal piston that forms the lower spring mount.
Think of this as the air bag itself is rolling up and down the outside surface of this piston because that is what it is doing.
As air enters the bag instead of pushing the bag like a balloon in all directions it simply ?unrolls up? the piston. When air pressure is lowered the air bag ?rolls down? the mounting piston.
This same rolling Up and Down occurs when driving the Jeep and hitting bumps.
Here is a simple drawing I did to show what a vertical cross-section of the air spring looks like, showing the air bag rolled on the piston, and what it looks like rolled up when the pressure is high. As the Jeep moves and the air spring manages the ups and down of the suspension travel the air bag is cycling or rolling up and down the piston instead of pressing against the outer walls of the air bag having little place to go..
In playing around with the Jeep and the air springs today I found that it didn?t matter much how many PSI of air I had in the air springs. The ride was still soft. Much softer then with the coil springs. This remained true throughout the entire range upper to lower of the air springs. The ride did not alter very much at all until the upper and lower limits where reach (maxed out.)
I think this softness, and the apparent ability to flex so well can be attributed to the design of the Firestone air springs. By rolling up and down the piston the volume changes dynamically in relationship to the spring air pressure.
I need to explore this farther, but I did want to share this observation.
Frank