Fancy a set of "J-Damper" for your F1 car, well now you can...

[Chernaudi]

Well, if the J damper is so good, why'd it kill the Pugs in the rain, and on bumpier sections of the racetrack at LM, especially when it was supposed to increase grip-McLaren's F1 cars have used them since 2005, and Hamilton has had no problems dominating in the rain.

Could it have been Peugeot's lack of knowlege about the J damper and how it would react in the rain/over bumps, or was something else amiss?

[MPME]

Well, if the J damper is so good, why'd it kill the Pugs in the rain, and on bumpier sections of the racetrack at LM, especially when it was supposed to increase grip-McLaren's F1 cars have used them since 2005, and Hamilton has had no problems dominating in the rain.

Could it have been Peugeot's lack of knowlege about the J damper and how it would react in the rain/over bumps, or was something else amiss?

Overly stiff torsion bars for intermediate conditions. Overly aggressive damper settings. Not enough downforce.

[RacingManiac]

Inerter would only help maintaining grip over bumpy condition where tires were not allowed to take a "set" because of the varying force transmitted through it because of surface undulation, it won't help you if you had setup the car for the wrong condition...

[Dartdude]

Are there any speculations on about how much 1 would weight? I am having a hard time visualizing how these actually work, does the fly-wheel inside it keep spinning in one direction regardless to what the suspension is doing?

[RacingManiac]

I don't think so...it spins different direction as the suspension goes into bump or droop. When it spins up, it stores some energy by the suspension movement, and that adds to the inertia of the moving assembly. Now when you hit a bump say mid corner, instead of upsetting the suspension and jerks that corner up or down, that force is counter acted by the spinning of the flywheel, and inorder for the suspension to be disturbed, the impulse from the bump had to be greater than that of the stored flywheel to move it around. The idea is that you "tune" the Inerter for the condition of the circuit you drive on by setting the mass and gearing of the inerter, thus the magnitude of and duration of the bump or curbing on the circuit such that it will only counter act the forces generated by the undesirable bumps, this is likely to be in much higher frequency domain compare to the handling criteria, as the vehicle rolling/pitching movement is much slower compare to the sharp bumps or curb on the track. Thus as long as the friction of the assembly is not too high, it should be able to change direction of the spin as the car roll, pitch, and heave, but resist the disturbance caused by the bump.

Thats my conjecture, at least from reading those paper and presentation thats what I guess how it works....

[Dartdude]

Is there just one J-damper on front and one on back connected to a lever coming off of the sway bar?

[RacingManiac]

I am guessing it runs parallel to the third spring and runs directly between the 2 corners of the car, one on each axle...but I have no idea...

[Initial Z]

Sorry to bump an old topic, but I was wondering if anyone has any updated information on how this inerter works, how it affects cars, etc.. I am kinda confused how it apparently stores energy.. what I'm thinking so far is that as the car goes over bumps, there is a (slight?) difference in the relative position, velocity, and acceleration of the tires/wheels and the car body. This difference causes a flywheel in the inerter to rotate and thus stores energy in the form of rotational motion. Now if the car comes across another bump, some of this stored energy is used to "reduce" the effect of the bump, and thus reduces the tire load, and thus you get better mechanical grip? Is that the jist of how this thing works?

Also.. this may be a longshot, but does anyone have any idea how to model the inerter using Matlab and Simulink? How about just a model in general? I'm working on a presentation of how this thing works, and a working model of it would be nice..

[RacingManiac]

I think that was the idea, and thats how I understand it. The solid information is few and far in between, I think there was something with how it was modeled in that presentation in the last page:

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

Last month's Racecar Engineering(Jan 09) have a pretty indepth article about it in terms of investigating its effectiveness from simulation. So you might want to check that out.

[Chernaudi]

Why not ask Penske Racing-they make inerters now, since McLaren's exclusive license expired at the end of the '06 or '07 F1 season.

[Initial Z]

I think that was the idea, and thats how I understand it. The solid information is few and far in between, I think there was something with how it was modeled in that presentation in the last page:

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

Last month's Racecar Engineering(Jan 09) have a pretty indepth article about it in terms of investigating its effectiveness from simulation. So you might want to check that out.

Thanks. Is there a link to that article? That site seems really slow right now..

[BlueSubaruSTi]

Most of the good bits of the article were just lifted from the presentation. The main point from rce's article was that "once you hit a bump, the next bump must overcome the stored energy inside the inerter before it can displace the bump any further. However it differs from spring in that the load next an be canceled out in effect before it happens." All we really need to know is that it decreases load variation at the contact patch, for more consistent grip and easier to ride the edge of the friction circle. As far as tuning these things, I tried doing some calculations for our fsae car and it's going to take a lot of work to reinvent the wheel.

[Initial Z]

So I have always imagined the inerter being positioned vertically so that when the tire hits a bump the endpoint connections on the inerter would have a difference in relative acceleration which produces the force. Now from this article: J-Dampers in Formula One - F1technical.net from the two pictures of the inerter, we see that it is positioned horizontally between the rockers.. is that how they do it in F1? In the picture it seems that when either tire (but not both) goes over a bump or dip, that's where the force is generated in the inerter.

Now I have another question. So let's say the car hits a bump on the right tire and assume the flywheel in the inerter rotates counter clockwise and energy is stored. So the next bump comes and it also is on the right tire, so in this case the the inerter won't counteract that bump, and instead will be able to store more energy due to that bump.. is that correct? It would only counteract the bump if the bump occurs on the left tire right?

Sorry, but I just want to get a better understanding of how this thing actually works since there is not much info out there on it.

[RacingManiac]

It should work in both one wheel jounce or 2 wheel jounce, but not in roll, I think most teams are using it in place of one of the 3rd spring/damper unit, though I don't see why you can't use it in parallel with a 3rd spring/damper, provided its tuned with it since it seems to be a device that's sensitive to the ride-frequency of the axle.

I don't think you should see it as an alternative to normal damper spring unit, as those will still be dealing with forces of actual bumps on the race track(as well as load transfer and so on), what it does do I think(and that's a IMO), is that it deals with the undulation of certain road features(curb, washboard road surface, uneven pavement...etc) are not effectively dealt with by conventional dampers because of the higher frequency and rapid reversal of direction. On a normal suspension without it, that kind of disturbance is largely dealt with through the tire, as it compresses and expands as it riding through the disturbance. The spring force produce by the tire is undamped and uncontrolled and as it flexes, as the tire response is significantly less than that of the mechanical system, it cannot take a settle state and generate the intended cornering force, thus reduces your grip. Inerter, as stated by that F1technical.net piece's reference to Renault's mass damper, is designed to deal with that unsettled tire force. As I imagined how it will need to work, it spins up CW and CCW and changes between them readily and essentially controls the energy release from the tire spring and thus helps the contact patch to settle more readily to generate grip. You must have seen those TV shots in which F1 car hops over curb at Monza or Spa in slow-mo, tire bounces across the pavement. All that tire movement would be otherwise undamped and uncontrolled ...