The relative benefits of a pull rod suspension

[raymondu999]

No no, I don't mean mechanical grip in terms of softening the springs. I mean if setup is NOT compromised in terms of having to have a high ride height/soft springs etc, eg if I just put on soft tyres rather than hards, would that increase the speed they can carry through the faster corners?

[myurr]

No no, I don't mean mechanical grip in terms of softening the springs. I mean if setup is NOT compromised in terms of having to have a high ride height/soft springs etc, eg if I just put on soft tyres rather than hards, would that increase the speed they can carry through the faster corners?

As long as the load isn't too high for the tyre to cope with, then yes...

[shelly]

I have seen the discussion has evolved in comparing mostly mechanical aspect of pull vs push.
I would like to post a poll to gather opinions; choices would be simple (and rough):

Do you think that:
-pull is mechanically and aerodinamically better
-pull is better aerodinamically, worse mechanically
-pull is mechanically and aerodinamically worse
-pull is worse aerodinamically, better mechanically
-if tuned properly, pull and push are equivalent

I know this is very rough (there are a lot of consideration besides),but is just to try to sort out basic opinions

[Sayshina]

Raymond, the faster your car is going when it hits a bump the harder it is for your suspension to deal with. A bump in a high speed corner is a lot like getting hit in the stomach with a baseball bat. You got hit, that part's over. Now you're just trying to absorb that energy. It's easier to make improvments in the low speed area, and when you do improve the high speed response you usually improve the slow speed stuff at the same time.

Shelly, the recent trend toward pullrod seems to be entirely a result of the recent and very restrictive rules changes. If it offered a mechanical advantage you'd have to conclude that every F1 designer 4 years ago was just too stupid to see it. That seems unlikely.

[marcush.]

maybe the poll should include packaging,servicing,CofG position,aerodynamc,installation stiffness...benefits .
But is it really true there are only two alternatives-push or pullrod-?

[fastback33]

Just to chime in here. But, why is everyone trying to quantify how good something is? don't we all know that it is how the entire package works, and something is never better than something else, it just might work better in an specific application. This thread is 28 pages of nothing as far as I'm concerned...

[shelly]

@sayahina: agree with you that advantages and disadvantages ae to be seen in the framework of regulation. In the compromise, I think that aerodynamic is prevailing over mechanics, and as a consequence I see the 2009 rule change as the biggest driver for pull rod introduction.

The no-loophole interpretation of 2009 diffuser rules led to design very small diffusers (like 2001 diffusers); this has shifted focus to flow on the upper side of the diffuser and to the beam wing, which is probably better with pull rod setup.
This was rbr intuition in 2009; but it was not important with double deckers, and that's why nobody followed in 2010.
Rbr kept pull knowing that ddd would have been banned in 2011.

As with accessibility disadvantage of pull rod, there are two factors that reduce it by a great amount:
-off-track setting work is well developed, so tems have a very good idea of setup and do not have to make big changes during race weekends
-parc ferme rule bans on grid adjustement

@fastback33: "whole package" calls should not be misused. While for sure it is the whole package that counts, there are some things that have to be analysed with a certain level of detail, and suspension layout is one of those. If we stick to the "whole package" at any level, we could not iscus about anything: we could just read laptime sheets to see which package is faster.

[DaveW]

...off-track setting work is well developed, so tems have a very good idea of setup and do not have to make big changes during race weekends....

Mmm... That is certainly what math modellers (& aerodynamicists, who don't believe anything else matters) would have you believe. However, mechanical set-up is a compromise set by the vehicle, its tyres, the driver & the track. Modelling can, with help from hardware in the loop tests, put set-up in the right ballpark, but cannot usually yield an optimal set-up without some driver & track testing. Only last year one team took the wrong dampers to a race & suffered all weekend from that decision. The dampers were wrong because the track had changed since the team's last visit....

[ringo]

I think Ferrari have that setup change edge on the others. But we can only say that if the suspension setup is the limiting factor when the driver comes in to pit and discus various things such as the engine and the wings etc.
The 2011 pullrods may actually be easier to adjust than the 2009 designs. Maybe redbull made some ergonomic changes around that area of the gearbox?

I think teams do change setups frequently during practice, but after that there are no changes on Saturdays or late into friday night.
The teams using pull rod may not be at a huge disadvantage time wise. maybe a couple minutes or seconds to get the car jacked up and to remove a few panels.
Who knows if Ferrari have to do something similar, we have't seen their suspension as yet, but i believe some of it is in the upper half of the gearbox.

[Sayshina]

If a sudden change in track temp can throw your setup off, and it can, then it follows that teams will always have to make setup changes at the track.

As far as push or pull being easier to make those setup changes, traditionally push is easier and that is in fact listed as one of the reasons teams went away from pull. However, once you start putting components inside your trans housing, I suspect THAT becomes the limiting factor.

One thing is certain. There's no way last years Red Bull could have been as easy to adjust as last years more traditional pushrod suspensions with everything right on top of the gearbox. It didn't seem to slow them down much.

[DaveW]

One thing is certain. There's no way last years Red Bull could have been as easy to adjust as last years more traditional pushrod suspensions with everything right on top of the gearbox. It didn't seem to slow them down much.

I'm sure you are correct, Sayshina. I recall examining RBR's Turkey times & noting (I think) that they were quickest by over 0.5 seconds through sector 2 (turn eight), but only 0.3 seconds quicker over the lap. That suggested to me that the car excelled through medium/high speed corners, but was not so hot otherwise. I'm sure RBR engineers would reply that it didn't need to be. Whatever, I think it is generally accepted that RBR's performance advantage in 2010 came from the effective use (& extended availability) of exhaust energy, rather than suspension layout ...

[riff_raff]

With metered hydraulic systems, like that used in a hydraulic dampener, the greater the metered flow volume the easier it is to accurately control. So the dampener benefits from a long stroke or a large cylinder diameter, since that makes its dampening rate less sensitive to valving variations and more consistent. Locating the dampeners somewhere that limits their size or travel would not seem to be beneficial.

Making changes quickly to a set-up are a big consideration. That's one of the reasons torsion bars became so popular. They could be changed without removing the dampener, like coil-overs required. They could be very finely adjusted for ride height with their splined vernier ends. And the teams could easily manufacture torsion bars themselves, in very small increments of spring rate. Unlike coil springs, which required specialized machinery and long lead times.

[DaveW]

With metered hydraulic systems, like that used in a hydraulic dampener, the greater the metered flow volume the easier it is to accurately control. So the dampener benefits from a long stroke or a large cylinder diameter, since that makes its dampening rate less sensitive to valving variations and more consistent. Locating the dampeners somewhere that limits their size or travel would not seem to be beneficial.

Absolutely, although it isn't necessary to invoke metering accuracy to conclude that a high pressure/(wheel) force ratio is a poor strategy for an hydraulic damper.

In my experience it is not uncommon for F1 designers to ignore the basic laws of physics when pursuing a perceived advantage. Sometimes they are right, but not always. Completely off-topic, I know, but an example was the Renault "flat V" engine (must be good, it lowers the c.g. height). It also had a catastrophic effect on sprung mass bending stiffness - until structure was added above the engine.

[myurr]

@fastback33: "whole package" calls should not be misused. While for sure it is the whole package that counts, there are some things that have to be analysed with a certain level of detail, and suspension layout is one of those. If we stick to the "whole package" at any level, we could not iscus about anything: we could just read laptime sheets to see which package is faster.

Whilst true the reverse is also true - that we cannot analyse individual parts and say that because this teams car was the fastest every individual design decision they made was the best one.

This isn't really directed at you, but it is just as dangerous to say that the pull rod suspension is the best type because Red Bull were the fastest team as it is to say that you can't examine a component in isolation you must look at the whole car. Maybe Red Bull would have been even faster last year if they had used a push rod layout. Newey himself said that they used the pull rod last year more for continuity reasons than because it was the better design.

[marcush.]

one of the keys to being competitive in F1 totdays is setup should not be influeced much by change of mass and change of environmental conditions + setup should not be influenced by change of tyre compounds....as there is not really much you can do to adapt your car to those changes when it counts.
To be able to change suspension /damper settings quickly cannot be high on the agenda as the nature of F1 has changed a lot in recent years .Long gone is the adjustable damper .They prefer to have a choice of 2 or three fixed alternatives preselected at home since a long time.