The "J-damper" is an inerter designed by the University of Cambridge and used by McLaren and now licensed to Penske..

http://www.eng.cam.ac.uk/news/stories/2008/McLaren/

http://www-control.eng.cam.ac.uk/~mcs/lecture_j.pdf

A little more info from the same person, although not in racing terms.

Great links!! Thanks a lot!

Great posts, thank you.

After several years conversation about 'J' dampers, factual information. An explanation that offers clarity. The Inerter changes linear energy/movement to rotational energy/movement. When I was a child, and still wearing shorts pants I had a handheld toy with 2 lever/grips, when you squeezed them a disc at the end would rotate faster and faster(you could get them once a year at the Fun Fair) so I can understand this Inerter. The inspiration came from electrical engineering ...ahh. A mystery explained. Brilliant work and welcome information. Thanks for the most excellent links.

A link to another article on the inerter / J-Damper. Not much different than the Cambridge article, but has links to Penske Shocks website.

http://www.theengineer.co.uk/Articles/307759/Shock+tactics.htm?nl=TE_NL&dep=webops&dte=030908

Also useful links on the top right hand side here

http://www.admin.cam.ac.uk/news/dp/2008081906

I'm am trying to fully understand how the Inerter eliminiates vibration. Under road load the inerter will transfer liner displacement to rotational, storing the energy in a flywheel.

Does the slow release of this energy (by rotating back to its original position) coupled with the damper create less chance of further oscillation?

Can I assume the flywheel does transfer the energy back to the suspension somehow? Adding another spring to do this seems it would only create more vibrations, which is what the J-damper is trying to eliminate... Is the stored energy just lost?

It sounds like it might be a bit more linear in its ability to store energy (relative to the force being input). Not that I know anything about suspension damping really but I've been trying to work out this device for quite a while!

repaf1 wrote:Can I assume the flywheel does transfer the energy back to the suspension somehow? Adding another spring to do this seems it would only create more vibrations, which is what the J-damper is trying to eliminate... Is the stored energy just lost?

To understand inerter function you should concentrate on electrical analogy. In RCI network you are flexible to tune each component to get desired characteristic, suspension is similar oscillating system and you also must optimize its frequency response.

timbo wrote:
To understand inerter function you should concentrate on electrical analogy. In RCI network you are flexible to tune each component to get desired characteristic, suspension is similar oscillating system and you also must optimize its frequency response.

But that's constantly changing: slow, medium, fast corners, pitch, yaw, roll..

The main advantage of it (the mass dampener) on the Renault system was in controlling the wheel oscillations riding over the curbs and I think the purpose of the inerter is the same. As timbo suggested it deals with frequency, the quick spike of movement going over curbing. The movement of the wheel accelerates the flywheel (via a screw) and the inertia of the flywheel consumes the added energy of the quick movement of the wheel over the abrupt change. That's my story and I'm sticking to it.

See if these don't help:
http://en.wikipedia.org/wiki/Moment_of_inertia
http://en.wikipedia.org/wiki/Rotation_a ... fixed_axis

that's my understanding of it as well, though there is a detailed presentation about it...

http://www-control.eng.cam.ac.uk/~mcs/lecture_j.pdf

I'd imagine the implication of this is pretty huge, not just in F1 but in regular cars as well...

The thing I cannot get my head around is the fact it was banned as a moveable aero device.

The details on here are great, thanks for finding them guys.

The J-damper was not banned as a MAD. The mass-damper was. That's the beauty of the J-damper; the mass damper was just a mass on a spring, whereas the inerter behaves differently. hence the electrical analogy to understand how it works.