Sauber Front Suspension

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Post Thu May 17, 2012 1:18 pm

When you think about it though, the only time I could see this being advantageous would be if you wanted high ride stiffness and low roll stiffness - in which case you can achieve it here by disconnecting the spring contribution in roll.

If you wanted a low ride stiffness and high roll stiffness you could do it just the same by running soft main springs and a beast ARB in a conventional arrangement.

I do seem to recall some pictures floating around here recently of F1 cars this year with pretty low roll stiffness. Not entirely sure why that would be advantageous.

Interesting regardless.
Grip is a four letter word.

2 is the new #1.
Jersey Tom
 
Joined: 29 May 2006
Location: Huntersville, NC

Post Thu May 17, 2012 2:15 pm

GSpeedR wrote:What mechanism will resist roll on this setup?

Edit: I assume something not shown in the pictures(?).


The torsion bars work against each other in heave to create the spring effect, but in roll they rotate & don't add to the roll stiffness.
Crucial_Xtreme
 
Joined: 15 Oct 2011
Location: Charlotte

Post Thu May 17, 2012 2:21 pm

Jersey Tom wrote:I do seem to recall some pictures floating around here recently of F1 cars this year with pretty low roll stiffness. Not entirely sure why that would be advantageous.

You have to direct that question to the aerodynamicists.... They want no vertical movement (apparently), but kerbs demand roll compliance. I think the solution works, up to a point - until the ouside (front) wheel loses contact. At that point the car has no directional control, as Koybayashi discovered in Singapore.
DaveW
 
Joined: 14 Apr 2009

Post Thu May 17, 2012 2:26 pm

Interesting,

However I don't think this decouples roll and heave completely because the torsion bars are still able to twist under roll.
So when there is some force who resists roll like from a antiroll bar the torsion bars connecting the rockers and this bar can twist especially when you use a very strong anti roll bar.


How about connecting the bar with a spring to the chassis?
This would not change anything during heave because the bar doesn't move in that case but in roll the spring would resist the movement of the bar to the side practically generating an antiroll bar.
mep
 
Joined: 11 Oct 2003
Location: Germany

Post Thu May 17, 2012 2:31 pm

mep wrote:Interesting,

However I don't think this decouples roll and heave completely when there is still an antiroll bar placed somewhere else.
The torsion bars connecting the rockers and this bar can still twist during roll when there is some force coming from a antiroll bar especially when you use a very strong anti roll bar.

How about connecting the bar with a spring to the chassis?
This would not change anything during heave because the bar doesn't move in that case but in roll the spring would resist the movement of the bar to the side practically generating an antiroll bar.


You can (barely)see the anti-roll bar in the picture right below the steering rack. It's removed via the silver hole on the side of the tub.
Crucial_Xtreme
 
Joined: 15 Oct 2011
Location: Charlotte

Post Thu May 17, 2012 2:36 pm

Seems to be a strange position for an antiroll bar. I would rather say the pedals are placed there.

But anyways how does the twist of the torsion bars affect roll?
mep
 
Joined: 11 Oct 2003
Location: Germany

Post Thu May 17, 2012 3:35 pm

Jersey Tom wrote:Might have to go up to a 2 5/8" sway bar to get the roll stiffness with zero contribution from the main springs...


8)

But anyways how does the twist of the torsion bars affect roll?


Depending on motion ratio linearity, there could be no torsion bar twist (thus no roll stiffness) with a roll input: the "fixed" end would rotate with its corresponding rocker. Very neat setup, torsion bars really add a lot of flexibility to package these systems.
GSpeedR
 
Joined: 14 Jul 2011

Post Thu May 17, 2012 3:56 pm

GSpeedR wrote:
Depending on motion ratio linearity, there could be no torsion bar twist (thus no roll stiffness) with a roll input: the "fixed" end would rotate with its corresponding rocker. Very neat setup, torsion bars really add a lot of flexibility to package these systems.


Lotus also has a neat system where the torsion bars not grounded to the chassis, hence free rotation which leaves all roll stiffness up to the anti-roll bar. Lotus had the same strut between torsion bars last year.
Crucial_Xtreme
 
Joined: 15 Oct 2011
Location: Charlotte

Post Thu May 17, 2012 4:17 pm

the Renault R31 pic i posted shows the ARB mounting ,and quite a massive piece of engineering ...

guys we all have discussed this back in 2010 ....and we had concluded already it was roll and bump decoupling .

see Renault r31 thread page 57..
marcush.
 
Joined: 9 Mar 2004

Post Thu May 17, 2012 8:43 pm

What happens in a single wheel bump situation with this?
RacingManiac
 
Joined: 22 Nov 2004

Post Thu May 17, 2012 9:21 pm

mep wrote:However I don't think this decouples roll and heave completely because the torsion bars are still able to twist under roll.


To my mind its completely decoupled. In pure roll you have the front ends of the torsion bars rotating in the same direction as each other and the transverse beam follows them. There is no twist imposed on the torsion bars at all.

Then of course in heave we assume the anti roll bar is not working at all and its only the torsion bars.

RacingManiac wrote:What happens in a single wheel bump situation with this?


Single wheel bump is a mix of heave and roll modes of an axle, so it will operate both the torsion bars and the anti roll bar

Tim
Not an engineer at Caterham F1
Tim.Wright
 
Joined: 13 Feb 2009

Post Thu May 17, 2012 9:27 pm

marcush. wrote:the Renault R31 pic i posted shows the ARB mounting ,and quite a massive piece of engineering ...

guys we all have discussed this back in 2010 ....and we had concluded already it was roll and bump decoupling .

see Renault r31 thread page 57..


Sauber use the same type suspension as Lotus:

the torsion bar mounts allow for free rotation . The torsion bars are not grounded to the chassis instead react against each other. This negates their spring effect in roll, so all roll stiffness is provided by the anti roll bar.

Yes decoupled is correct.
Crucial_Xtreme
 
Joined: 15 Oct 2011
Location: Charlotte

Post Thu May 17, 2012 9:41 pm

RacingManiac wrote:What happens in a single wheel bump situation with this?


Single wheel bump is a mix of heave and roll modes of an axle, so it will operate both the torsion bars and the anti roll bar

Tim


Agreed, but RacingManiac should keep in mind that "warp" and "single wheel bump" are different under this definition.
GSpeedR
 
Joined: 14 Jul 2011

Post Fri May 18, 2012 10:48 pm

Jersey Tom wrote:When you think about it though, the only time I could see this being advantageous would be if you wanted high ride stiffness and low roll stiffness - in which case you can achieve it here by disconnecting the spring contribution in roll.


I would think with rather high aero down force and low CoG -and perhaps a small roll couple-, that's what they're doing.
olefud
 
Joined: 12 Mar 2011
Location: Boulder, Colorado USA

Post Tue May 22, 2012 12:03 am

Ok now as the forum starts to settle down a bit with the changes lets come back to this topic one more time.
Tim.Wright wrote:
mep wrote:However I don't think this decouples roll and heave completely because the torsion bars are still able to twist under roll.


To my mind its completely decoupled. In pure roll you have the front ends of the torsion bars rotating in the same direction as each other and the transverse beam follows them.

Yes correct, for a suspensions without an antiroll bar. So when the car goes through a corner the body rolls to the side, causing both rockers moving synchronous as they are linked to each other with that solid bar and the torsion bars which will not twist in that case.

But so far this suspension does not have an antiroll bar. Which might be fine, maybe they don't need one at the front axle. But somebody here said there will be still an additional antiroll bar attached to the rockers and hidden in the picture.
I say it comes down to the design of this antiroll bar. I differentiate between two types of designs. One which allows for relative movement between the two rockers so the rockers are basically connected with a spring. The second one creates a solid link between the rockers and connects them with a spring to the chassis. It seems like the second one is much more common because it was easier to find a good picture for that design but anyways let's look at the first at the U-shaped design:

Image

Uploaded with ImageShack.us
In the picture you see the rockers are connected to the u shaped antiroll bar. The thin bar connecting the two sides is twisted in roll which requires a relative movement of the two rockers in relation to each other. With the Sauber suspension this movement is hindered by the extra bar connecting the rockers so it is only possible when the torsion bars get twisted. In that case there is a interrelation between the antiroll bar and the torsion bars. The stiffness of the torsion bars will add to the stiffness of the antiroll bar.

If we look at the second picture we see a T-shape design where both rockers are connected with a solid bar so they always move in relation to each other. The actual antiroll bar is the torsion bar connecting the t-bar to the chassis. With such a design and the torsion bars of the rockers having no fixed end but being able to rotate synchronous to each other, there is then actually a complete decoupling of roll and heave.


Image
Shot at 2012-05-21
So this design still needs the construction for the anti roll bar whereas this could be prevented in case of the Sauber suspension by linking the connection bar itself with a spring to the chassis. A simple leaf spring would do that job so I wonder why they don't do that. Like I said earlier it might be the case that they just don't use an antiroll bar at the front.
mep
 
Joined: 11 Oct 2003
Location: Germany

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