The relative benefits of a pull rod suspension

[mep]

Well, what I mean is that the a-arms angle is shallower. It seems clear to me that for the same amount of vertical movement, the rotation the arms go through is smaller, got it? Also, the amount of camber change is smaller too (we discussed elsewhere how camber change in droop or bump influences grip).

Eeeh no you confuse me even more now.
I don't get why you talk about a-arms now. They can be tilted upwards, downwards or be parallel to the ground independent of push/pull rod.
Even if they had to rotate more just let them I don't see why this should reduce suspension travel.

For example, to get the same damper displacement for a given vertical displacement of your wheels, you have to build longer rockers. Am I wrong? Please, retro-feed, mech-guys. thanks.

Yes your pull rod has a shallower angle this causes higher forces inside them.
Possible this easily outweights the gains from buckling (if they even exist).

[Ciro Pabón]

Well, I know those ain't a-arms, but I hope you get my drift. Anyway, here is the best I can do:

Since you'll have a shallower angle between the upper "a-arm" and the pullrod than between a pushrod and the lower "a-arm", you'll have less flexibility in terms of motion ratio (namely, you won't get it as high as you might like, because of the geometry.

[raymondu999]

I am yet to see any performance disadvantages of pull rod to push rod. It is clear as day and has been repeated countless times why 1 is superior.

I would think the hundreds of geniuses designing F1 cars over the years would've caught on to that, not just Newey. The very fact that some cars use pushrods rather than pullrods in 2010 (even when red bull showed that a pullrod can be very effective even with a ddd at the end of 2009) means that some designers think the compromises outweigh the benefits.

[ringo]

2010, the double diffuser was the issue.
And still no one can come up with a performance disadvantage.
Those hundreds of "geniuses" simply never considered the pull rod. In the same way they never considered the f duct or blown diffuser or flexi wings. They're just normal humans like us doing their day job, they can't think of everything.

[ubrben]

2010, the double diffuser was the issue.
And still no one can come up with a performance disadvantage.
Those hundreds of "geniuses" simply never considered the pull rod. In the same way they never considered the f duct or blown diffuser or flexi wings. They're just normal humans like us doing their day job, they can't think of everything.

Don't be so silly - of course they considered it.

An advantage of a pushrod is that the compression in the pushrod creates a tension in the outer wishbone - effectively reducing it's peak loads.

Many cars have run pull rods for packaging and aero reasons; Dallara Indycar, Arrows F1 in the late 90s.

There are positive reasons to use pullrods from an aero and CG perspective but negative reasons from an installed stiffness and component stress point of view.

Just because Adrian Newey incorporated pullrods onto the Red Bull, which won the championship doesn't mean it's automatically the optimum solution.

Ben

[ringo]

can you give me any numbers to demonstrate?
We all know the force in the upper wishbone is higher, so what?
If you tell me by how much, and how it affects the construction of the wishbone, then we have ourselves a disadvantage.

If after sizing the wishbone, there is only any increase in thickness of 1 carbon skin, where's the problem?
You can't just look a design and conclude that becuase it's not popular it must have a disadvantage.
Why were American cars continuing to use push rod 2 valve per cylinder engines? Surely the engineers were aware that 4 valves are better?
Why were the cars all over 4 thousand pounds with ladder frames?
They can't continue to do those things again, the European and Asian competition is simply too strong to be ignored.
In the same way the redbull team cannot be ignored. If you want any hope of competing, you need to analyze the car and compare it to yours and find out what components are making the difference, then re-adapt.

Evidently the engineers never considered it seriously before 2010, you have no proof that they did. I have proof that they didn't; you can't seriously consider something advantageous then toss it away.
All were complacent with the pushrod being the standard for many years and never saw any reason to look outside of that. There is an article in this thread explaining how that happened.

[CMSMJ1]

=D>

Ringo..you should be a politician.

Look...once upon a time, people used rockers and inboard brakes and so on. They stopped using them as other benefits were found that precluded the use thereof.

Do you recall the 2000 Telefonica Minardi (did you watch F1 then?) It had pullrod front suspension and swept the field away with it's breakneck speed and obvious, overwhelming and devastating technology..that no-one else thought of..or maybe it didn't actually sweep anything or anyone away. hmm, maybe Pullrod is not the answer??

Perhaps, just perhaps, the rest of the design was not quite so good as the other cars using pushrod suspension?

Hey..I wonder..maybe the Red Bull has something in the overall, global and complete design that makes it a better package than one single silver bullet?

Can you please retract your position from manic obsession to just somewhere closer to normalcy with regard the wondrous magic of the pullrod? People seem to want to discuss this with you..but you are being fundamentalist about it...the world is not flat you know..we all know it, but you are being stubborn.

[Jersey Tom]

You can't just look a design and conclude that becuase it's not popular it must have a disadvantage.

Likewise you can't just eyeball the pullrod and say "Oh it's so magical, just imagine how it cleans up the airflow!". Can't say "Well Red Bull was successful... and they had a pull rod.. OBVIOUSLY it's the best choice." If you're going to exclude handwaving as a valid argument (which we all should), it works both ways.

Evidently the engineers never considered it seriously before 2010, you have no proof that they did. I have proof that they didn't

Aside from the fact that it has been USED plenty of times before, in anything from FSAE to F1.

Not saying pull rods or push rods are inherently good or bad. Either can work just great in different applications. The thing that drives me nuts is how much people are jerking off to them as if they're the most technically revolutionary idea since man invented fire... when they've been all over plenty before. If inexperienced, exhausted, and potentially drunk FSAE kids can consider the advantages and disadvantages of both types of arrangements, I damn well guarantee professional race team designers do as well. To think that it's been totally forgotten for so long, with zero consideration, is obnoxiously absurd.

[ringo]

So what's wrong if the rear pull rod suspension is hyped?
How many rear torsion bar pull rod suspensions running through the bellhousing are out there?

The exhaust blown diffuser is in the same situation.
It existed before, then it faded in popularity, teams get complacent, ignore it, then someone reinvents it and suddenly everyone scrambles to get it on their car.
The current blown diffusers are vastly different than their older counterparts.

I'll repat, the pull rod is not magical, but it's reinvented and back in circulation, so normally it will be followed by some hype.

It's not hard to believe it was not considered seriously before 2010. Was the exhaust blown diffuser considered seriously after it left F1, not even 10 years ago?

Jersey Tom you are overreacting. Your first paragraph is a gross exaggeration.

It's simply a fresh interpretation of an age old technology that every team is now considering to put on their car. This wasn't the case every year of the last 20 years. They can't be that indecisive.

So once again i am asking for a performance disadvantage that prevented teams from placing this thing on their cars every year that they have "considered it" for the last 20 years; assuming they did. If it's such standard draft, that drunk brain damaged FSAE kids can do it, why is it that this thing never left the drawing board?

It's natural to believe it simply was not taken seriously and was never on the drawing board to begin with, just like how the American auto engineers simply ignored overhead cam shaft technology for decades.
We will see something else in 2011 that is simply an innovation of an old technology and you can bet some will say "yeah, the engineers were thinking about it for 40 years; the pros outweigh the cons, but they never used it, nahh, in this sport you don't need every grain of advantage you can get, not worth it".

[Ciro Pabón]

Sorry for interrupting the cozy chat...

What if you don't have infinite time to consider all options? Maybe teams invest their limited time in what seems worthy. People starts by checking changing rules and says something like:

"Hey, under the new rules, that include foreign competition in the American market, it's worthy of our attention and our money to change all the machines we have to machine blocks in a new way and make engines with four valves".

You know the old adage: "if it works, don't fix it". Ciro's corollary is: "fix something else instead".

I guess the rules about nose dimensions this year have made people to look at a different layout for suspension, something already mentioned in this thread, period.

[Jersey Tom]

It's natural to believe it simply was not taken seriously and was never on the drawing board to begin with, just like how the American auto engineers simply ignored overhead cam shaft technology for decades.

As an engineer, it's really not natural for me to believe that.

Also, don't even begin with American or any other OEM's and the reasoning behind the decisions they make. Unless you've worked for them or with them, it's really not as obvious as some make it out to be.

That kind blanket statement is not too dissimilar to a question my friend asked me when gas prices shot in the US not long ago. "Why haven't manufacturers been working on fuel efficient cars for years?? They're just in it with the oil companies for the money!"

To which I countered with... in reality, there was no reason to. No justification, at least on the business end. People weren't interested in fuel economy until it zapped their pockets, and there would have been no market for these expensive cars with all the associated R&D work.

[myurr]

So what's wrong if the rear pull rod suspension is hyped?
How many rear torsion bar pull rod suspensions running through the bellhousing are out there?

The exhaust blown diffuser is in the same situation.
It existed before, then it faded in popularity, teams get complacent, ignore it, then someone reinvents it and suddenly everyone scrambles to get it on their car.
The current blown diffusers are vastly different than their older counterparts.

I'll repat, the pull rod is not magical, but it's reinvented and back in circulation, so normally it will be followed by some hype.

It's not hard to believe it was not considered seriously before 2010. Was the exhaust blown diffuser considered seriously after it left F1, not even 10 years ago?

Jersey Tom you are overreacting. Your first paragraph is a gross exaggeration.

It's simply a fresh interpretation of an age old technology that every team is now considering to put on their car. This wasn't the case every year of the last 20 years. They can't be that indecisive.

So once again i am asking for a performance disadvantage that prevented teams from placing this thing on their cars every year that they have "considered it" for the last 20 years; assuming they did. If it's such standard draft, that drunk brain damaged FSAE kids can do it, why is it that this thing never left the drawing board?

It's natural to believe it simply was not taken seriously and was never on the drawing board to begin with, just like how the American auto engineers simply ignored overhead cam shaft technology for decades.
We will see something else in 2011 that is simply an innovation of an old technology and you can bet some will say "yeah, the engineers were thinking about it for 40 years; the pros outweigh the cons, but they never used it, nahh, in this sport you don't need every grain of advantage you can get, not worth it".

Push rod vs pull rod is a minor performance improvement from an aero point of view, and a tiny tiny C of G improvement. The downside is all about packaging and space on the car, along with what sounds like a tiny mechanical disadvantage (or could be a tiny advantage depending on who you ask).

The difference is not about adding or removing components, merely where they are placed. Obviously they can't be placed down low without displacing something else, unless in your car design there is an unused gap (unlikely on an F1 car).

Last year the DDD got in the way with some of the car designs, the reason Ferrari gave for not making the switch and I'd imagine McLaren as well. The 2009 cars were all shorter than the 2010 cars and probably didn't have the room. If I remember correctly the Red Bull was one of the longest cars that year which is why they probably had the room.

In 2011 and beyond if the cars remain long then they'll probably all have the room to house the dampers down low so they can use a pull rod. If the cars are shorter you'll probably see many teams switch back to push rods for packaging reasons.

Pull rods are no magic bullet, were likely evaluated by every team on the grid in 2010 after seeing it on the Red Bull, and were rejected for packaging reasons that were more important than any perceived advantage. There is no reason why a push rod based car couldn't win next year if one of the top teams goes that route - the difference between the two solutions is not going to decide the championship.

[ringo]

Ok, so you've admitted a minor performance advantage.
Is it not worth having?
A good analogy is the fuel engineers work on, creating advanced fuels with hardly any advantages to the compositions they replace. Is it not worth it?

I am seeing some hypocrisy here. On one hand the theme is every gram of mass and it's height counts. On the other other hand, maybe for the sake of disagreeing, i am being told a small advantage doesn't matter.

As an engineer, it's really not natural for me to believe that.

Well I can bet you wouldn't seriously consider putting a dry sump system on a lawn mower. It may cross your mind, and you smirk at the absurd idea and nonchalantly put it aside. The competition doesn't have it, and it's generally accepted that the small advantages offered by it are not necessary to compete with existing mowers. Who needs a dry sump lawn mower? just a few performance advantages, who cares!?

But once a competitor puts a dry sump lubrication system on their sit down mower, and it starts to take some of your market share. Hell will brake lose in the R&D department.
Did you consider it before? Yes, but did it move from your head to the design development stage?

Also, don't even begin with American or any other OEM's and the reasoning behind the decisions they make. Unless you've worked for them or with them, it's really not as obvious as some make it out to be.

Well the results of their decisions are quite obvious. Complacency and underestimation lead to their collapse. The cars weren't selling outside of America anyway.

That kind blanket statement is not too dissimilar to a question my friend asked me when gas prices shot in the US not long ago. "Why haven't manufacturers been working on fuel efficient cars for years?? They're just in it with the oil companies for the money!"

To which I countered with... in reality, there was no reason to. No justification, at least on the business end. People weren't interested in fuel economy until it zapped their pockets, and there would have been no market for these expensive cars with all the associated R&D work.

I think we are converging on something here.

To which I countered with... in reality, there was no reason to. No justification, at least on the competition end. People weren't interested in [place revitalized innovation here] until it zapped their [prize money/championships/dominance], and there would have been no reason for these [place revitalized innovation] cars with all the associated R&D work.

[myurr]

Ok, so you've admitted a minor performance advantage.
Is it not worth having?
A good analogy is the fuel engineers work on, creating advanced fuels with hardly any advantages to the compositions they replace. Is it not worth it?

I am seeing some hypocrisy here. On one hand the theme is every gram of mass and it's height counts. On the other other hand, maybe for the sake of disagreeing, i am being told a small advantage doesn't matter.

Talk about selective reading. As I keep trying to point out to you it depends if that minor performance advantage outweighs the disadvantages I also outlined to you. If you have to make the car longer or you have to displace something else to give a non-optimum layout then these disadvantages may wipe out the performance advantage many times over.

[DaveW]

Scarbs views make informative reading...