physics of power steering

[mahoutekiyo]

Hello everyone.
I am one of those people who doesn't give up on something until they’ve COMPLETELY understood it. In this case, I am referring to the rotary valve of power steering. I was able to gather the concept behind the rotary valve, but I just don’t know exactly how it functions. For those of you who don’t know what I’m talking about, the rotary valve is what switches the pressure of the power steering fluid in your car. The easiest way to grasp that concept is to examine the power steering on a rack and pinion, although whether you have a rack and pinion or worm gear on your car, the rotary valve will always be located between the steering wheel and, well, everything else. So the valve switches the pressure from none, to the left or right, depending on which way you want to turn. The rotary valve connects the input shaft to the "torsion bar" (NOT THE ONE DEALING WITH SUSPENSION). From what I understand, the torsion bar twists with the input shaft, which does two things. One: it regulates the amount of pressure distributed to either side, and Two: it allows the steering to work off of torque instead of direction, so that the wheels can be powered, even if the steering wheel is not centered.
The first thing is understandable because there are two valves within the rotary valve - an inner and an outer valve, the inner connected to the input shaft and the outer connected to the torsion bar. If the torsion bar twists, then the valves will turn at different rates, thus opening them in proportion to the amount of turning you do.
(That second thing the torsion bar does is a miracle to me. :: shrug :: )
The big question I have is about the flow of the fluid and the sequence of the valves lining up and where the fluid is coming from. The images I've seen so far make the rotary valve look like Swiss cheese, and God knows where the pressure is being maintained.
If anyone knows exactly how this works, please, PLEASE email me at [email protected] and I will get back to you with images that illustrate my problem more clearly. I *greatly* appreciate any assistance and I hope my little shpiel was enlightening to others. Thank you very much!

[Reed]

i dont know if you have already checked out howstuffworks.com but they have a pretty good explaination at http://auto.howstuffworks.com/steering1.htm
you sound like you already have a good idea of how this works so this may not be much help