Idea :adjustable rebound and compression on sway bars

[RobertoX]

The problem with totally decoupled roll and bump in most third spring setups is that there is no roll damping. It can be good for aero where heavy rebound damping in in heave is considered a good thing.

I don't think this different rate roll bar would work that well because in roll what you describe as "bump" would be "rebound" but for the other direction... does the linkage switch over as the car rolls over the centre? (ie going from "rebound" into "bump") if so there would be be quite a clunk, or at least a fairly unsettling transition.

[rms]

The problem with totally decoupled roll and bump in most third spring setups is that there is no roll damping. It can be good for aero where heavy rebound damping in in heave is considered a good thing.

The only way you can decouple roll and bump is with a monoshock, it can not be decoupled with a third spring.

Dallara has the option of a shock to control roll on their monoshock setup.

Current damping with aero and third spring is biased more towards bump, to control ride height.

[RobertoX]

ga.... yeah "monoshock"... thats what I meant sorry... I was thinking of 2 things at once, the previous post talking about UWA (they use a 3rd spring in their setup). Even though 3rd spring setups have similarities to monoshock setups you cant really have a 3rd spring with out the other 2

From what I have read and heard, Its not uncommon to run a fair bit of low speed rebound in the monoshock to maintain the height of the wing (the front one) and any diffuser/ skirts. When ground effects come into play a sudden change in height of these can drastically alter aero...

How do Dallara do that btw? Through those radial type dampers or something?

[rms]

I should have said Dallara IRL car, not F3.
They run a 'T' bar setup with just one spring/shock from the 'T' bar. Roll control shock is between the links from the rockers to the 'T' bar.

With zero droop front suspension, wheel rates around 1500lb/in, plus preload, there is virtually no low speed rebound. The aim after a bump is to get the contact patch pressure back as soon as possible.

Rear suspension has some droop (5 - 10mm) and rebound setting is more critical. If the rear 'jacks down', you start to lose aero and the centre of pressure changes.

FSAE cars seem to want to follow current trends such as third springs etc. What is the point of a third spring when there is no aero ? More complex, less understanding and the basics seem to be ignored.

[RobertoX]

Sounds interesting, ta...

The car with the 3rd spring is one of the best out there, they won in 2005 and then went ot the US and came second IIRC. They then came second in 2006 to an aussie team that came first in the US that year. They run an interlinked hydraulic circuit (see Lachies post) and they need the third spring for extra rate in bump becuase roll is done through the hydraulics, they definately aren't just following trends.
What you say is true of some teams but not all, and they are learning after all...

[rms]

Sorry - didn't mean to sound derogatory about FSAE teams or students.

I am probably looking at the FSAE regs more from the competitive side and not taking the academic side into consideration.