The relative benefits of a pull rod suspension

[shelly]

Tomabzis has said in the interview that they chose pullrod foraeo reasons and then worked on it to gain mechanical perfomance o par with push rod.

Aero factor being dominant is what has been said by many (including me) on this thread for a year or so; I think this statemnet for tombazis add a lot of weight ot that opinion

[RacingManiac]

The ferrari is also said to have front pull-rod suspension like the 2001 Minardi.

http://scarbsf1.files.wordpress.com/201 ... t_view.jpg

Difference being they don't used to mount the lower ball joint on the front wheel axis of the upright....The Minardi has a relatively normal looking pullrod layout for a openwheel car, the Ferrari is much weirder with very little angle to work with....

[Jersey Tom]

I don't think the angle of the "pull" rod (horizontal-rod? h-rod?) on the Ferrari is a big deal.

If you had more conventional control arms parallel to the ground then yes, it would be. However, really the important thing is in the front view to have an angle between the control arms and the "support" rod so that those elements can resolve the vertical and lateral forces at the tire footprint.

In this case given that the control arms have taken an angle to ground that's more like a conventional push-rod, and that the pull-rod is more aligned like a conventional control arm, there's enough angle there to be able to resolve the forces sensibly. Draw it out in a FBD.

Or you can think of it... imagine that Ferrari front suspension with several inches (maybe half a foot) of jounce. Angles and orientation would look more "normal."

[xpensive]

...
Strange... that's a really shallow pull rod angle.. the motion ratio must be a scarifice.
...

Indeed, when you try and visualize the the pull-rod's movement as the wheel travels upwards, it becomes very small,
as I fail to see how the steep control-arms would have much influence, other than increasing track-with somewhat?

I suspect there's some sort of geometrical amplifier inside the tub.

[RacingManiac]

Its not necessarily like the pushrod issue where you have chances of buckling a control arm or something, but you still are not getting a lot of movement from it....

I guess one way or another its not really different from the pushrod situation was in F1...

Other question though, how are the dampers packaged with that? I am assuming they are still using torsion bars running parallel to the tub, so your rocker movement will be inplane with the axis of the torsion bar. Are they using pull damper inside the tub?

[munudeges]

I must confess, I'm not seeing it. I can see the logic when Red Bull went pull-rod at the rear because of the aerodynamic benefits they were going to get without having to come up with some convoluted push-rod arrangement that Ferrari had last season.

However, I don't see the aerodynamic benefits that they've said this will supposedly bring. The rear, yes, the front.....I don't see it. If you were going to radically lower the nose section then maybe you'd consider it, but that's not the case here.

[Jersey Tom]

However, I don't see the aerodynamic benefits that they've said this will supposedly bring.

Well if you could do CFD by mental math off a model you've generated by aiming your eyeballs at a handful of still photos, I imagine you would be in quite high demand by many motorsport teams.

Mechanically, I don't really see that this is a detriment. Obviously there's some design intent here. Are we going to know what it is off hand? No. Will it work out? Maybe.

[xpensive]

...
However, I don't see the aerodynamic benefits that they've said this will supposedly bring. The rear, yes, the front.....I don't see it. If you were going to radically lower the nose section then maybe you'd consider it, but that's not the case here.

Neither do I, if it allows you to move torsion-bars and dampers lower, I guess it could have CoG advantages?

[shelly]

Aero benefits, not cog benefits, is what Tombazis said.

As JT pointed out, they are quite evident in cfd and quite invisible to the naked eye.
Interaction with front wing vortices and subsequent wake to the pods are the usual suspects; expect to see a specific shape of the inner part of the front wing flap to better appreciate the coupling

[PlatinumZealot]

I think they get better airflow in the circled volume going back over the side-pod and rear.

[xpensive]

Xactly, better feeding of the rearview mirrors with laminar-flow air, creating counter-clockwise vortextes over the sidepod, while avoiding delamination and turbulent stalling entering the rear wing, I can see that too now!

[ringo]

Tomabzis has said in the interview that they chose pullrod foraeo reasons and then worked on it to gain mechanical perfomance o par with push rod.

Aero factor being dominant is what has been said by many (including me) on this thread for a year or so; I think this statemnet for tombazis add a lot of weight ot that opinion

haha sure.

Don't let me dig up the thread for those quotes.

Aero factor was majority of the the support for pull rod suspension. Second to that cooling, weight and COG. It was labeled as a no brainer.
Many others were in disagreement. I'm not sure if it's the fact that Ferrari, a big brand team, used pushrods that you felt it was the right thing to do.

The 2012 car was supposed to be the egg in the face for either hypothesis.
Lo and behold they switched, and i hear nothing from the pushrod die hards.

This goes back to ferarri stubbornness. Now they are over compensating with the front pull rods.

Pushrods are extinct in F1 guys.

[ringo]

Yes i realized, got mixed up with the names of posters and their opinions.

Anyway; these guys know themselves.

I can't wait to revive this dumb thread when the 2012 cars are unveiled

Ferrari are changing next year and you can quote me on that one.

Au contraire, I think you will see more push rods next year, as teams has by now realized that packaging and adjustment of the pull rod is a nightmare, while CoG and aerodynamic gains are minimal.

And you can quote me on that one.

Xpensive i'ma keep the promise.

Ringo, you have to kill this idea of pull rod suspension being the be all and end all or rear axle designs. Its complete BS. Forcing a pull rod axle into the back of any car will not automatically give you an advantage.
....
For some teams, with their own gearbox/diffuser design, these second order effects might actually be negative therefore the pull rod is not the optimal solution there. I can guarentee this is why McLaren/Ferrari are not using it.

Tim

Blind faith because a Ferrari didn't have it. Now they do.

myurr wrote:If they change in 2012 then I'll say that they have re-evaluated their options and come up with a different compromise. When one of the teams switches back to a push rod, as the inevitably will at some point in the future, then what will you say?

compromise scrumpromise, same ferrari lump of iron slapped on to a gearbox like all the other cars on the grid. Nothing changed mechanically or packaging wise but their outlook.

I find the contrary interesting. The fact that so many people are playing up the advantages of the humble pull rod axle to the point where it is seen as some new must have accessory.

=D>

moral of the thread:

ringo wrote:
If the winning car has it, copy it with no second thoughts. Don't think about it just copy it, you wont regret it.

Anyway i was just keeping a few promises made in the past of this thread. The front pull rod is now the focus of this thread. Quite an interesting geometry on the car.

In fact i think it will work better on the Mclaren Mp4 27.

[Pierce89]

Ringo, was pullrod automatically better on the 75% of cars ferrari beat?is t worse now that ferrari use it? The reason peopl trust ferrari over you is because they've won more world championships than you

[RacingManiac]

Are we still on about one layout is better than the other because of the layout, not the reason of why it is used?

If only designing a system is so easy....