The relative benefits of a pull rod suspension

[raymondu999]

Haha, trying to turn the page. Ferrari were scared of using it, that's all.

We can't prove you're wrong on that, but you can't prove that Ferrari found pushrod to be better for their car.

[ringo]

Well we can't prove much as onlookers.

I think we should switch from the back and forth arguing and at least look on the interpretations in a constructive manner.

[raymondu999]

So then. To summarise:

Theory A) Ferrari tested the pullrod solution, pushrod solution and their weird franken-pushrod solution. They found franken-push to be the best solution, better than the pullrod, for their car philosophy

Theory B) Ferrari didn't fully understand pullrod, and were too scared to go that route, fearing that their implementation might be more bad than good

[Jersey Tom]

So then. To summarise:

Theory A) Ferrari tested the pullrod solution, pushrod solution and their weird franken-pushrod solution. They found franken-push to be the best solution, better than the pullrod, for their car philosophy

Theory B) Ferrari didn't fully understand pullrod, and were too scared to go that route, fearing that their implementation might be more bad than good

"A" sounds like engineering. "B" sounds like malarkey.

[mep]

This is real silly season
some driver rumors can never top this.

[ringo]

Objectively, what's the difference between the ferrari F150 and the Renault R31?

The monocoque has little to do with the rear suspension choice.

The engine has little to do with it either, suspension is not mounted on it.

There has to be an infrastructural difference with the Ferrari and the Renault for them to come to differing conclusions.

Renault believes the pull rod is their best iteration.

Ferrari never said their choice is the better than pullrod, but they prefer it. It's better for what their goals are.

One has to be more advantageous than the other on the track. Nothing is perfectly equal in reality.

Now what is the "engineering" reasoning to 2 cars adhering to the same regulations coming to differing conclusions?

Ferrari's choice seems purely down to consistency and ability to understand the tyres without having to deal with a different layout.
That is an engineering consideration, but is more to do with ergonomics than unbridled performance. There was no mention of outdoing the pull rod at its game.

Yes in the layman terms they were "scared" of the unknown and rather have less to deal with, as their focus is to continue on their progress from 2010, seeing as though they were the only team on the right track to closing the gap to redbull last year.

There has to be a fundamental difference to the 2 cars for there to be a difference in what the theoretical ultimate combination of parts is for the 2011 regulations.
This difference may be the KERS, tyres and it may be factors outside of the car itself, like the pit crew and their ability to change setups quickly. One has decided to to be conservative and go a step further of the push rod, but not to the extreme of the pull rod, for the sake of continuity and ease of opperation.



Backtracking a moment; from the sounds of things, conventional push rod is inferior?
No one is defending it any more, they are riding on the ferrari franken rod wagon.
Is the general consensus that conventional pre 2011 push rod is an overall disadvantage? No team is using it.

[RacingManiac]

Backtracking a moment; from the sounds of things, conventional push rod is inferior?
No one is defending it any more, they are riding on the ferrari franken rod wagon.
Is the general consensus that conventional pre 2011 push rod is an overall disadvantage? No team is using it.

I think based on the constraint around the 2011 rule and trend(in that no more DDD), that might be the case. Though I don't see what Ferrari's solution as that "franken". Yes it swept forward quite a bit, but that again comes down to packaging to make room for what they need room for, and in this case I'd imagine it being to clean up rear end aero for rear wing to be more effective, the same reason why RBR went pullrod back in 2009, before them knowing the whole DDD debacle was about to start.

I echo what many have said, at the end of the day what layout it is matters very little, as long as you as a designer achieved what you want to achieve when you start out it can be any layout at the end. And its hell of a lot easier to do here since in F1 the layout is open with every components being designed by the team itself, that they have almost complete freedom to do what they wished...

[myurr]

One has to be more advantageous than the other on the track. Nothing is perfectly equal in reality.

Theoretically painting the car black is better than white because it uses less paint and therefore weighs less. We don't have an all black grid because objectively the difference between the two is minute and there are benefits to having a car that is easy to spot out from all the others.

Theoretically the push rod conveys a slight C of G advantage but in practical terms the difference doesn't appear to be that big. Some teams are going for the theoretical optimum others, like Ferrari, appear to be opting for the more practical knowing that the tiny C of G cost isn't going to affect their performance in any measurable way.

Now what is the "engineering" reasoning to 2 cars adhering to the same regulations coming to differing conclusions?

Because the car is a complex overall system of many interconnected parts that calls for many compromises. There will be many parts where performance isn't 100% optimum, but is compromised so as to gain in other conflicting areas of the car.

One of the HUGE disadvantages of the pull rod is that you have to take the floor off the car to change the damper settings. With new tyres that could be a very big compromise for a small C of G gain. Certainly with Ferrari's solution the pull rod doesn't appear to hold any other advantage, so they've come up with a solution that keeps the push rods easy access, gives at least equal aero benefits, but has a slightly compromised C of G.

[ringo]

No disagreement there.

[segedunum]

I can't see what the big controversy is. As usual, people make some nonsensical comparisons. Even if I thought that a pull-rod layout was the right solution, having enough knowledge about the implications is a legitimate factor in whether you'd go for it right now or not. It doesn't make what solution you come up with in the meantime 'right'.

The payoff is that pull-rod has a lower centre of gravity (very important this year when you're carrying more weight in the car) and the space either side of the gearbox is completely free to keep a diffuser in that area unobstructed. The only way of making a push-rod layout work there is to move things forward and/or up, and up is not good. If you start having decks above that, as happened in 2009, then the pull-rod starts to lose its advantage because there isn't the space there. Now those decks above the diffuser are restricted then a pull-rod layout is really where you'd like to be. Now, if I had a lower centre of gravity and completely unrestricted space either side of the gearbox and in front of the diffuser for development then I know what I'd pick, even if access is a bit more restricted. Make something adjustable and it will be adjusted wrong, as Colin Chapman might have said. If you want to add consistent lap time get the right solution on the car for the right circumstances.

However, when Red Bull started with a pull-rod rear suspension they had all kinds of strange reliability problems around the gearbox and the engine, many probably related to cooling. If I were Ferrari or anyone else I might deem going through that pain for longer term benefit to be unacceptable. They just don't have the luxury of having a few DNFs to learn about what's happening. Working out what will happen to the tyres with something you've not tried before is also another problem.

It might be what we've seen from Ferrari is stage one in the reorganisation of the packaging of the rear end of their car that might well result in a pull-rod configuration at some point in the future. If I was them that's probably what I might do depending on what I had available.

[humble sabot]

The CG argument is not very strong because the difference is so small. Keep in mind also that the added weight for kers has a comfortable spot right on the floor, under the fuel cell, so far nobody's put it anywhere else AFAIK.

[myurr]

Not only that but precisely because of the higher weight it has less of an effect on overall C of G than it would have in previous years.

I struggle to understand why you think it's more difficult for Renault to make the switch than Ferrari. The reality is that Ferrari have chosen what they think is the more optimal solution for them.

[ringo]

The CG argument is not very strong because the difference is so small. Keep in mind also that the added weight for kers has a comfortable spot right on the floor, under the fuel cell, so far nobody's put it anywhere else AFAIK.

No, no, never say such a thing. That's submitting to compromise, which is the wrong way to start out. The CG argument is always strong, only aerodynamics can trump that, and the pull rod wins hands down in that department as well.
Don't be fooled, ferrari are very mindful of it. The difference is small but it's still something.
The best compromise i ever saw for CG was in the front of the car with the driver positioning to allow flow to split either side of the car.

Every gram and every cm always counted, don't be changing that for the sake of the argument now. Let's wait until we see what ferrari has under the hood. Something's telling me there is a depression in the top of the gearbox with the parts nestled in it.

Ferrari had cold feet, and with pressure from montezellemo to get off to a very strong start to the season, troubleshooting the pull rod would take away valuable time in the first races. They are using the no nonsense approach, and should be able to hold their own against weak teams that may have pull rod, but poor everywhere else.
Mcalren is the next team that may have something interesting. I have a feeling it wont be pullrod, but rocker arm.

[Jersey Tom]

Disagree. Level of significance is extremely important. Only have so much time for development. When you have ideas X, Y, and Z on the discussion table, you have to be able to say, "Ok, relatively speaking Y is too small to be bothered with right now."

Low hanging fruit.

[humble sabot]

I like a low cg as much as the next guy but I think you'd be surprised to find that a lower cg isn't always objectively better. Suspension dynamics are a funny thing. Of course I can't weigh in directly on whether the car would be better served by having 1kg moved 6 inches lower at the rear axle centerline. Mass centroids and all that.

Engineering is a balance of compromises. Assuming that one can design without compromise is quite possibly as dangerous as, if not the same as, designing with no regard for the consequences. F1 isn't the magic realm of engineering where nobody ever has to compromise.

Try looking at it this way; the design team gets together and says: ["we have Sauber who's going to use this, we're putting some mass (KERS) under the fuel cell, so we've dropped the cg a bit in the middle, we have to keep in mind that the new tyres aren't known, and will have to be accounted for at each track, so accessibility of adjustments is a real concern, and we know we have aerodynamic space to work with under the rear of the box if we keep the components on top"] They probably also took into account the current trend to vent engine compartment air over the top of the box, which means the benefit aerodynamically of moving the parts downwards isn't cut and dried. I think it's safe to assume that gearbox work started before the diffuser design was finished which is important. I'd go out on a limb and suggest the DDD ban probably happened after the box concept had been fleshed out and i don't think it would be much of a risk.

technologically speaking a pullrod isn't anything special. it's a differnt layout of the same parts. which reminds me that the Italian video we saw shows that the Redbull setup actually has a pull actuation on the damper, that's really the more unconventional portion. Then again it wouldn't be the first time one of those renders was done wrong.