5 replies to this topic

[Joe Bosworth]

I have little whiffs of a rules problem with rubber bump stops being used under anti roll bars on 6tthe Indy cars.

What is the deal re rules and what/how are they using the stops to gain lap times??

This is a totally new one to me so I am hopeful of adding a new dimension to my brain cells.

Regards

[DaveW]

In some suspension layouts, a bar will slide without loading the suspension (actually, it rotates, but think translation to avoid confusion) when the suspension is moved symmetrically and will twist, loading the suspension, when the suspension is "rolled". Bump rubbers are often installed on damper shafts to support the springs at larger displacements in "aero" vehicles (e.g. GP2). Bump rubbers used in this way affect both vertical & roll stiffness when they engage. A bump rubber installed on a 3rd "slider", however, will affect vertical stiffness but not roll stiffness. The 3rd slider arrangement will minimize the impact on mechanical lateral balance, & can be an advantage for platform control when "kerbing".

It is sometimes possible to install a bump rubber between the bar & vehicle structure which can, with care, be functionally identical to a slider-installed bump rubber. This might be an advantage if 3rd elements cannot be fitted for any reason.

3rd elements are not permitted in GP2, & one team was quietly asked to remove a bump rubber limiting bar movement not because it was illegal, but because they had effectively circumvented the 3rd element regulation. If your "whiff" is correct, then something similar may have happened in IRL. I can't imagine it would be useful for oval configurations, though.

Edited by DaveW, 06 June 2010 - 08:09.

[Joe Bosworth]

Ahh, the penny drops! Sorry, some days I am a bit slow. This query came about from a phone discussion with a son in St Louis Mo. I thought I would be lazy because any question can be answered by the good minds on this forum.

The Indy guys are more clever than I gave them credit for.

But the answer starts with posts about #36 to 45 in the Red Bull crash thread.

The IRL guys want a lot of pitch resistance when they get out of the throttle or on tracks like Milwaukee where they get on the brakes quite heavily. They want the pitch resistance so that they don´t gain/lose camber with resultant small losses of grip in their never ending search for absolute cornering stability.

If the tracks didn´t have some very bad bumps they probably would be happy to almost run solid front ends. But that puts them in deep stability trouble when one wheel bumps.

Running a three element front end is the answer to them!

Now if someone with an IRL rule book at hand can advise as to the rule issues can clarify things I am happy to say that I have found my answer.

May be others can be wiser as well.

Regards

[GPD]

Ahh, the penny drops! Sorry, some days I am a bit slow. This query came about from a phone discussion with a son in St Louis Mo. I thought I would be lazy because any question can be answered by the good minds on this forum.

The Indy guys are more clever than I gave them credit for.

But the answer starts with posts about #36 to 45 in the Red Bull crash thread.

The IRL guys want a lot of pitch resistance when they get out of the throttle or on tracks like Milwaukee where they get on the brakes quite heavily. They want the pitch resistance so that they don´t gain/lose camber with resultant small losses of grip in their never ending search for absolute cornering stability.

If the tracks didn´t have some very bad bumps they probably would be happy to almost run solid front ends. But that puts them in deep stability trouble when one wheel bumps.

Running a three element front end is the answer to them!

Now if someone with an IRL rule book at hand can advise as to the rule issues can clarify things I am happy to say that I have found my answer.

May be others can be wiser as well.

Regards

The current IRL rule states that the suspension system must only make use of 4 springs and four dampers, and permits the use of ARB at both ends. Its a clear rule but there is scope within the design of the ARB's on the Dallara to create a 3rd element, all be it an illegal one.

[zac510]

Could you have one spring/damper on the front and three on the back?

[GPD]

Could you have one spring/damper on the front and three on the back?

Ha ha No. it does specify 1 per corner.