Ferrari F2012

[604gtir]

I can see why a leaky diffuser would rob rear df, but why would the lack of rear df LEAD to lack of sealing?

sorry i was just writing everything i had in my head down, you're right
the leaky rear diffuser robs df, not rear df leads to lack of sealing..

[Jersey Tom]

Objectively the geometry of the suspension is a bit strange: chassis high with an horizontal rod... How can it work fine?

Yep, that's exactly what a lot of people have been wondering.

A sophomore year engineering student could answer this, and I thought we had covered it already in this thread. Draw it out:



Conventionally we think of the push/pull rod supporting the vertical load on the car because the control arms are usually more horizontal, and being tension/compression links in the front view are very inefficient at supporting vertical load. However, it is inconsequential what member(s) take up the tire loads - only that they are sufficiently angled or trussed relative to each other to do so.

In the static condition, the control arms being angled means that they can now support a vertical force. However, since the control arms only work in tension and compression, to support a vertical load you will get horizontal reactions at the chassis. The push or pull rod being horizontal, can now resolve that load and keep the car suspended.

Alternatively, if you really want to think of this in a convention manner just squat the car with downforce and you will see that really it's a pretty standard arrangement (as it has to be, this is simple statics) just in a slightly different view than most are used to seeing.

If "members on other teams" are really so baffled by this they need to take a look at some lecture notes from when they were 19. Or, it's entirely possible it's just ancillary personnel without an engineering background just throwing out their own speculation.

Not everyone is Ross Brawn...

[Crucial_Xtreme]

The control arms are angled downwards. As well as helping carry the vertical wheel loading, the geometry of downward angled wishbones aids the deflection of the pull rod. As they wheel travels upwards the control arms move towards a more horizontal position with the consequence that the end is horizontally further away from the hub as well as further from the ground. At the angles Ferrari use, that appears to equate to a horizontal movement of roughly 25% of the vertical displacement although this proportion inevitably decreases as the wheel is displaced higher and the wishbones approache horizontal.

However, at the low pull rod angle of approximately 8°, this horizontal realignment of the suspension becomes more important than the vertical wheel displacement. Less than a seventh of the vertical displacement is transferred to the rocker by the pull rod whereas 95% of the horizontal motion is. In other words, the geometry itself amplifies the deflection. It’s worth noting that the same process occurs with push rod configurations but in this case the effect is detrimental and reduces the compression of the push rod. It’s one reason why McLaren persist with a low nose as it allows them to exploit lower wishbone angles than their rivals.



The upper and lower control arms are not parallel. The problem with any sideways movement at the wheel is that that would tend to increase tyre wear as the tyre moves laterally against the track surface. However, the upper wishbone is angled more steeply than the lower one (roughly 17° compared with 13°.) It’s a small difference but it means the geometry of the system changes shape as the wheel is deflected upwards. The animation below shows the wheel set at zero camber being repeatedly deflected (zero camber was an arbitrary choice for the animation as it shows the change more clearly, it is likely that Ferrari will run with some degree of negative camber depending on the circuit.) You can see that not only does the wheel hub (right) move outwards but also angles out at the top (positive camber). It’s only a small angle change but it helps reduce the sideways movement at the tyre’s footprint. It’s a trick Ferrari appeared to exploit for the first time last year although McLaren also use a similar trick. Furthermore, the effect will help during cornering where the suspension will adjust to keep the footprint of the loaded outer tyre as high as possible in order to maintain mechanical grip.
The overall result is that the deflection of the rockers is actually not that different from if they’d used push rods at 30°. So it seems to me that not only have Ferrari got nothing to worry about with their pull rod suspension


links-> Analysis #1 http://www.vivaf1.com/blog/?p=10173

Analysis #2 http://www.vivaf1.com/blog/?p=10280

[Lycoming]

Pullrod, particularly with such a low angle, does result in greater forces; but these are things that should be taken into during chassis/suspension design. Getting the same stiffness is feasible, though you may compromise chassis/wishbone design to do so. This is one of the things that you would take into consideration BEFORE you decide to go ahead with the decision. So yes, these are legitimate concerns, but they should have been long since dealt with, because the consequences of the switch in terms of loads are things that could show up in a first year dynamics problem.

Honestly, even if they remove pullrod at the end of the year, it does not necessarily mean it was the cause of all their problems. It just means that they feel pushrod is superior. By what margin, it would be impossible for people on the outside to say.

[Jersey Tom]

The problem with any sideways movement at the wheel is that that would tend to increase tyre wear as the tyre moves laterally against the track surface.

If the tire were rigid, sure.

The wheel has lateral migration with vertical travel.

[fritticaldi]

Thanks for posting the Autosprint article. Last year, Ferrari fired their chief designer Aldo Costa (who is now employed at Mercedes-Petronas)on grounds that he had poorly designed the F150 Italia. After reading the Autosprit article, it is safe to say that newly appointed chief designer Nick Tombazis has done an even poorer job.

[bettonracing]

Inboard suspension pickups.

In fact the A-arms are connected to the chassis via so called "flextures" which are actually solid titanium pieces.

Flexures are the type of joint used at the front inboard suspension pickups... If one could justify the practicality you could have flexures at the outboard pickups at the rear of the car as well.


Lateral forces on the contact patch likely hold it relatively fixed compared to the lateral movement of the wheel (think of it as "wheel plunge" within the tyre). I wonder how consistent tire stiffness is during bump as a result of this 'wheel plunge'. Keep in mind we're talking miniscule amounts of "plunge". Any thoughts?

Regards,
Kurt

[xpensive]

Great stuff X2, this is an xcellent visualization of my previous posts, when it discloses the miniscule pull-rod movement.

When energy equals force times distance, pull-rod forces will go through the roof and as a consequence, so will wishbone such.

As every component has a stiffness and every joint has a clearance, those parameters will obviously have much more influence the smaller the movement of the pull-rod is, why I believe it makes the geometry difficult to simulate with much precision.

[bhall]

Great stuff X2, this is an xcellent visualization of my previous posts [...]

For what it's worth, that diagram was created to illustrate the following point: "So it seems to me that not only have Ferrari got nothing to worry about with their pull rod suspension but that their high-nosed rivals at least, if not the low-nosed McLaren, may have missed a trick."

[xpensive]

Great stuff X2, this is an xcellent visualization of my previous posts [...]

For what it's worth, that diagram was created to illustrate the following point: "So it seems to me that not only have Ferrari got nothing to worry about with their pull rod suspension but that their high-nosed rivals at least, if not the low-nosed McLaren, may have missed a trick."

For what it's worth, that ambition backfired big time if you ask me.

[timbo]

Great stuff X2, this is an xcellent visualization of my previous posts, when it discloses the miniscule pull-rod movement.

X, if you swap pull-rod for push-rod you'd see that movement is pretty much the same (not even x2 difference) and also that push-rod has to be much longer.

[bhall]

X, if you swap pull-rod for push-rod you'd see that movement is pretty much the same (not even x2 difference) and also that push-rod has to be much longer.

I was just thinking that. F1 suspensions hardly move at all.

[timbo]

X, if you swap pull-rod for push-rod you'd see that movement is pretty much the same (not even x2 difference) and also that push-rod has to be much longer.

I was just thinking that. F1 suspensions hardly move at all.

Well, the main thing is that push-rod is FAR from being vertical.

[bhall]

Yes. I should have said, "And F1 suspensions..." to make it more clearly an additional point rather than a reinforcement.

(Or my OCD has gone into overdrive.)

[xpensive]

This discussion hardly moves at all and you two should get a room somewhere until Ferrari presents their push-rod front.