Magneto-Rheological shocks

[HDS]

What is everyone's opinion of the Magneto-Rheological shocks? They have been described as the technology of the future for 20 years. Now that they are entering production do they have some potential of becoming popular? In addition to GM's current applications like the Corvette Ferrari is putting it into one of their next cars.

Does anyone besides Delphi and Magneshocks make them yet? Does any one have experience with each company and their products?

http://www.magneshocks.com/

http://delphi.com/manufacturers/auto/chsteer/ride/magneride/

http://www.lord.com/tabid/3329/Default.aspx

TIA

 

[CoryPad]

My opinion is that they are expensive, and have competition from other technologies like CDC from ZF Sachs:

http://www.zf.com/defaultz.asp?lang=1&id=4841

It may develop into a sizable market, but not quickly, and it will continue to have competition.

Regards,

Cory

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[Fabrico]

I have heard of accelerated wear in areas of focused fluid flow, at least in off-road applications.

 

[EfiOz]

How fast is the response time of the fluid?

It sounds like a great idea and could be really good dependent on my question above.

 

[GregLocock]

Veyr fast , 1 millisecond from memory

Cheers

Greg Locock

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[RigTest]

It's a great concept and has the potential to see its way into a lot more OE applications and motorsport as well (until it gets banned). However, Lord (the company which holds the patent to MR fluid) charges exorbitant costs. This should have been a project to bring Delphi back from financial problems but the MRs are simply too expensive. I really hope Delphi finds a way around this and can get this on more vehicles because it's a neat technology.

The MR fluid reacts fast but not fast enough for true high speed wheel control. They advertise 1 ms switching time but it is really more like 17-18 ms to switch from a low force to a high force (say 1000lb change). It takes the magnetic coil 2 ms just to get the current change. I am near certain (obviously I don't work for Delphi) that they are only used to control sprung mass motions. If it could be faster then I think it's superior to its competition.

I worked for another supplier which developed an electro-mechanical adaptive damping shock and one very nice thing about the MR damper is that there is no mechnical valve. A semi-active damper must be able to change "on force" meaning that when the damper is under a large rebound velocity it must switch from a low to a high rebound force. Thus a mechanical valve must overcome the high pressure differential across it to move into a "stiffer" position. Pretty difficult to acheieve. If your damper cannot do this then it must wait for a drop in velocity before the valve position can change. If you expect an active damper to control the unsprung mass motion you must be able to switch "on force".

I think Fabrico reffered to this, but the MR damper only causes a local viscosity change about the piston. Fluid far from the piston is unaffected (or less affected I suppose). This makes it more difficult to get a reasonable spread in damper forces (large max with a reasonable low force).

 

[gt6racer2]

MR Fluid is relatively fast, actually fast enough for wheel control and is being adopted by some OE's, but it's way too expensive ( and heavy ) to make broad market. It also has issues with failsafe since it must be safe to drive without any signal - meaning the "low" setting can not be as soft as you would like it for good comfort. The reason for adoption Vs normal semi-active is just the techno factor - it's cool/different.

 

[HDS]

This is turning into a good thread. There is still hope for this board

It seems like heavy vehicle applications are also one of it's strengths. Given the issues with weight and cost that makes sense.

It is supposed to control both sprung and unsprung masses but I don't know how well.

 

[Fabrico]

The response speed and electronic connection might put MR toward the front of the line for active suspension, if and when it ever really gets here. One of the cross-town rivals is an electrically powered linear actuator.

 

[RigTest]

MR Fluid is relatively fast, actually fast enough for wheel control and is being adopted by some OE's, but it's way too expensive ( and heavy ) to make broad market. It also has issues with failsafe since it must be safe to drive without any signal - meaning the "low" setting can not be as soft as you would like it for good comfort. The reason for adoption Vs normal semi-active is just the techno factor - it's cool/different.

Good point on the failsafe, that is definitely true. I never used the Delphi controller supplies for the MRs, but I would be very surprised if Delphi were able to get unsprung mass control based on use with another controller we used (maybe you know better?). They are slightly faster than any other system we benchmarked but achieving ~ 15 ms response time on a dyno is different than acheiving on a car driving on a pot-holed road.

There is another company I saw a presentation for with essentially a hydraulic ram and a mood valve, claiming that it achieves 1 ms switching time with a huge force spread.

 

[GregLocock]

I was vaguely involved with the Lotus/Moog system. In the lab we used a similar setup to give a frequency response of 200 Hz, although it has to be said that that is a bit of an exaggeration of its capabilities, as it has some decidedly non linear characteristics. Anyway the hydraulics are definitely good for 50 Hz which is way in excess of what you need for a suspension.



Cheers

Greg Locock

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[HDS]

Fabrico
Are you talking about the Bose system?

 

[Fabrico]

There's the Bose system and a couple from the U.of Austin, Texas.

I can't remember where now...but there is also someone working on a semi-mechanical friction system. If controllable, a friction system could be faster and simpler, at least at certain things. Similar to their oiled counterparts, the friction can be introduced separetly at low or high amplitudes or frequencies. It can also be combined with other methods. All current damping systems work with friction of some sort.

Truley active suspensions may not use any form of friction because they may no longer control things through the asorption of energy. The best suspensions on earth have no damping.