magnetorheological damper

[RacingManiac]

MR damper does not work in the principle of magnetohydrodynamic, at least not to my understanding of it. The Fluid is not being propelled through the piston, the piston is moving in the medium of it. MR fluid changes the viscousity because the metal particle in the fluid assumes an alignment when in the influence of magnetic field, effectively makes it more resistant to fluid shear force. All of the commercial application of this(and they are all made by Delphi, uses the same principle, and they are all monotube shocks, FYI). The piston is charged when current passes through the coil and follows the process I described in my previous post. The liquid's "speed" is in reality the speed of the piston moving through it. The charged piston drives the liquid, not the other way around. And I am 100% sure on that. I am sure you can adopt the same process into a rotary damper, but the same issue applies, no current, no adjustment, thus no reason to use MR fluid.

You don't need current to use MR fluid in a damper, permanent magnet will probably achieve the same effect, but the fixed magnetic field will influence the same amount of fluid around it, what benefit can be drawn from that, especially over a conventional orfice/disc valving type arrangement?

[RacingManiac]

http://www.autospeed.com.au/A_110995/cms/article.html

half way down the page:

But of most interest to us is 'valve mode'. This is where there is a flow of MR fluid from one reservoir to another, with the connection being through a small diameter passage. If the passage is subjected to a variable intensity magnetic field, the amount of fluid that is able to flow will be altered. In effect, the fluid will act as if the opening changes in size.