The relative benefits of a pull rod suspension

[myurr]

Ringo, and chance you could show two photos that directly show the difference between the gear boxes sizes in cross section taken from the last 2 years, as like Sayshina I simply don't believe that the push rod requires a more massive gear box for structural reasons.

Your diagram also isn't showing total cooling requirements, and the type of gearbox is not going to dictate total cooling aperture size. For example Red Bull have a massive bulbous tube that cuts right in front of their rear wing causing poor airflow in that region.

Finally whilst your diagram shows aero losses for the push rod above the gear box you are not doing the same thing for the pull rod across the top of the diffuser.

[shelly]

I think that ringo is pointing out that one advantage of pullrod is that the space needed for installation of elastic elements is in a zone other car which is more convenient, because that volume can not be exploited efficiently from an aerodynamic point of wiew.

To appreciate this I think that 2d schemes, like scarbs', are somehow misleading; I think, like myurr, that 3d photos or drawings could give us more insight, especially if we manage to have pictures of cars which have shifted from rear push to rear pull from 2010 to 2011.

[myurr]

@shelly, completely agree. Further to that I would also be interested in seeing how these compare to Ferrari's solution which appears to have similar advantages to the Red Bull layout.

[ringo]

Ringo, and chance you could show two photos that directly show the difference between the gear boxes sizes in cross section taken from the last 2 years, as like Sayshina I simply don't believe that the push rod requires a more massive gear box for structural reasons.

The pushrod gearbox requires more metal for mounting reasons, and for these mountings you need rigid structure. The pushrods can't float in the air.




notice something about this drawing?
Do you see where the actual gear cluster and it's mounting structure is, compared to the mounting structure of the pushrods, which is basically a shell?
This is basically the explanation behind the williams gearbox. The cluster is the same, but the pushrod needs to be located at a certain geometry and it would need proper support, which comes in the form of a bigger casing.

Your diagram also isn't showing total cooling requirements, and the type of gearbox is not going to dictate total cooling aperture size. For example Red Bull have a massive bulbous tube that cuts right in front of their rear wing causing poor airflow in that region.

You mean cooling out the side pods? I didn't put that because judging from all teams using both suspension designs, the side pod outlets don't seem to be affected. The outlet above the gearbox is most affected.

Finally whilst your diagram shows aero losses for the push rod above the gear box you are not doing the same thing for the pull rod across the top of the diffuser.

The diffuser flow isn't affected. The pullrod is way way upstream of the diffuser.
Secondly the top of the diffuser is not as sensitive as the beam wing. We see this from Renault placing their side pod exit all over the top of it.

I was doing a CFD of both the push and pull, i will try get that up for comparison.

[DaveW]

I never said the structure is weaker for the pullrod either. It's simply at the bottom of the gearbox, in a better location. The best place to keep all the weight and structure is at the bottom.

Apologies, Ringo, but I think your statement may be misleading. It is certainly true that a low c.g. can, & usually will, improve performance, but a pull rod layout may, or may not, reduce c.g. height compared with an equivalent push rod layout depending upon what has to be moved, & where, in order to accommodate the suspension hardware. I'm reasonably certain, however, that placing all the structure at the reference plane will reduce chassis torsional stiffness, & that is not necessarily a recipe for success.

Then there are the vexed questions of heat dissipation & the practicality of changing springs, damper settings or even packer gaps.

[ringo]

well i have never looked inside the pullrod side of the gearbox.
but it could be something like this:

red is hydraulics, green transmission, purple is empty space, blue is clutch and actuation, yellow is suspension. They can be whatever it is that's in there; i have no clue really.
All things being equal and shifting the red, hydraulics, out the way up and longitudinally. There is some benefit there since the yellow has been moved down, and nothing else has replaced it.
Red has moved up slightly, but it's definitely not heavier than the suspension mounts, rockers, springs, dampers, and the thick rods. And it hasn't moved as drastically as the yellow mass.

I think the pull rod is wider at the base. But being tucked up in the shadow of the engine and within the sidepods. There's little or no harm of it being there.
The dampers may also be in the middle as well and not on the ground, so i really don't have a clue to tell the truth.

Ferrari is even more mysterious

not related to COG, but before i forget where to find this picture:

vertical cooling solution is fitting for the suspension type. Can't wait to see it without the engine cover.

[shelly]

I think that the scheme posted by ringo (is it from Peter Wright's book?) confirms that the pull rod scheme has a more efficient packaging, and leaves more freedom un the upper part of the gearbox.
Do some others in this thread agree in stating this is the major advantage of pull vs push?

[747heavy]

if this is the main aim, why is the RBR gearbox as high as she is?



gauging by the hole at app. the middle of the gearbox, and assuming (perhaps wrongly), that it is where the inerter &/or 3rd spring/damper goes through, the gain in CoG height does not seem as large as Ringo would like us to believe.
I think, it is reasonable to assume, that you would not be able to cross under the clutch with this parts.

look at the area where, in this photo, we have this mess with the hydraulic lines and quick couplings. It´s in the shadow of the airbox, so if Ferrari and Sauber place some of there suspension components there, I don´t think, they will "pay" much in terms of blocked flow area.





I think, in this respect Ringos sketch is a bit missleading.
Keep in mind we still have an V8 with 90° cylinder bank angle.
The same goes for the position of the top wishbone in his pushrod example (LHS).
Why would there be the need to run this higher and closer to the beamwing?
Other then, that it helps is argument/agenda off course.
The position of the top wishbone is complete independent from the pull/push rod choice.

Sorry Ringo, I think this sketch is a bit too biased/skewed to reflect your opinion. (which is fine - no problem with that)
Looking forward to your CFD analysis.
I hope it is based on a more realistic assessment.

While I agree, that Williams solution/interpretation is interesting and sound from an aero perspective, it remains to be seen, how reliable it is, and what the smaller crosssection of the gearbox means for the torsional stiffness of the car.
Nevertheless, I wish them the best.

[ringo]

just kidding.
Heavy , i draw these things in MS paint in less than 5 minutes. I don't have a mirror function in paint.
The arms can be looked over. Any thing that i don't mention can be ignored. Since teams have freedom to place them anywhere. I think Torro rosso put their rear arm in line with the beam wing to act as a slat.
Like those drawings in exams, unless otherwise stated, all drawings are not to scale.


That circle hole thing is probably not the mounting point. I think that's for the control arm. Though it may in fact be an access to the 3rd spring, which could have a drop link to the rocker.
but you may be right.

we need to see one in the garage the races.

So 747 are you of the opinion that red bull chose the pull rod as a style or fashion?
Just asking. There must be some apparent differences to you.

[Formula None]

Ringo, I think you've been staring at one part of the car too long:



Seriously though, we all admire the RB5, 6, and 7 and its pullrod rear end and have for 2+ years now. Which is why its odd and irritating that you're acting like you've discovered the red bull secret all of the sudden... Anyway, it's always going to be an uphill battle for you advocating: 1.) simply copying and 2.) ignoring the average team's design process. Which continues to be the ridiculous premise that's been driving this thread. For some indecipherable reason you still have a dog in that fight.

As was mentioned by others and myself waaay earlier in this thread and in the RB7 & F150th threads, the more forward positioning (relative to rear wheel centerline) of the bellcranks (ala Red Bull and this year's Ferrari) is the more important factor here, relative to a pullrod vs. pushrod debate. Another way to say it would be: long gearbox vs short gearbox. Long gearbox being the best choice for tapering rear bodywork and considering the lack of any max wheelbase regulations. If there was one idea to cling religiously to, it should have been long gearboxes, not pullrods.

Repeating my previous sentiments in this thread: most of the pullrod suspension setups this year look a little clumsy compared to the the RBs and the F150th due to short gearbox lengths that don't allow for sufficiently narrow bodywork cross sections and shallow taper angles ahead of the rear wings and diffuser. Its almost like they heard "pullrods" and decided to simply copy the idea without fully understanding it, which is basically the design method you've been advocating this entire thread. So Merc, Renault & the others ended up with short, wide gearboxes (this year, with pullrods) instead of short, tall gearboxes (last year, pushrods). The pluses/minuses of one versus the other seems negligible in my mind, when they could have had a long, sweeping RB or Ferrari 'box design.

The small tradeoff Ferrari made for thicker actuating rods and higher CoG you can be sure were made for other reasons than simply being obstinate.

[shelly]

@747 heavy; you wrote "if this is the main aim, why is the RBR gearbox as high as she is?" but the pictures you posted and commented below as if they were of rbr gearbox are in fact of team lotus gearbox.

I think that this way you are just messing up.

[Formula None]

Lotus are using a Red Bull gearbox this year, shelly.

http://en.wikipedia.org/wiki/Lotus_T128

[shelly]

I did not know that this year's lotus gearbox comes from redbull.
Do they keep also the outer carbon casing from redbull or has it been re-engineered by lotus?

[ringo]

Ringo, I think you've been staring at one part of the car too long:



Seriously though, we all admire the RB5, 6, and 7 and its pullrod rear end and have for 2+ years now. Which is why its odd and irritating that you're acting like you've discovered the red bull secret all of the sudden...

Yes i discovered it. Columbus discovered lands with people living on them already. They didn't get the credit.
Anyway, i will post observations, you can't assume everyone sees the details.

Anyway, it's always going to be an uphill battle for you advocating: 1.) simply copying and 2.) ignoring the average team's design process. Which continues to be the ridiculous premise that's been driving this thread. For some indecipherable reason you still have a dog in that fight.

If you think copying is not part of F1, look on this testing period alone. The very same ferrari that you say "have special packaging needs" slapping on redbull's exhaust idea like it was leggo duplo. And there are many more copiers such as Mclaren using the toyota end plates, and so on.
I am very comfortable with knowing that. There is no uphill battle. Just watch as the season progresses, you'll see blatant copying like you've never seen before.

As was mentioned by others and myself waaay earlier in this thread and in the RB7 & F150th threads, the more forward positioning (relative to rear wheel centerline) of the bellcranks (ala Red Bull and this year's Ferrari) is the more important factor here, relative to a pullrod vs. pushrod debate. Another way to say it would be: long gearbox vs short gearbox. Long gearbox being the best choice for tapering rear bodywork and considering the lack of any max wheelbase regulations. If there was one idea to cling religiously to, it should have been long gearboxes, not pullrods.
.

You didn't say anything like that. Don't make stuff up please. This thread is suspension design, not aerodynamic refinement.
The words in bold are an observation i made months ago, and it was rejected becuase it didn't come from a reputed source. So you can't use something i elucidated and then squeeze it into this discussion.

Ferrari F150 push rods were not mentioned by you or anyone else in any technical manner as it relates to the gearbox length. Don't try to change the discussion to gearboxes. That is another aspect of the car, and i can tell you that it isn't 100% consistent with a push rod gearbox anyway. Push rod has a limit to it's angularity because of it's increasing diameter interfering with the control arms as it gets longer.

I can show you why mathematically as well. I think it was said before that push rods are limited by length because of the buckling load. So there is a practical limit geometrically of what you can do with a push rod.

Repeating my previous sentiments in this thread: most of the pullrod suspension setups this year look a little clumsy compared to the the RBs and the F150th due to short gearbox lengths that don't allow for sufficiently narrow bodywork cross sections and shallow taper angles ahead of the rear wings and diffuser.

Is that so?
They are clumsy compared to the f150th?
Something must be wrong with your eyes. The F150th is not narrower because of their choice. It's still wide at the rocker arms. You are letting the refined side pod shape upstream delude you. That's more a combination of the engine, tank, radiators ect, than whether pushrod is used.
Do a visual comparison from the top view with another car.

There is no poor pull rod interpretation out on the 2011 grid (maybe mercedes). Maybe some are not as extreme as redbull, but none of them are clusmier than the F150th. I don't know how you come to that description in a technical manner.

Its almost like they heard "pullrods" and decided to simply copy the idea without fully understanding it, which is basically the design method you've been advocating this entire thread. So Merc, Renault & the others ended up with short, wide gearboxes (this year, with pullrods) instead of short, tall gearboxes (last year, pushrods). The pluses/minuses of one versus the other seems negligible in my mind, when they could have had a long, sweeping RB or Ferrari 'box design.

Ah keep side tracking to gearbox lenght. Funny you haven't mentioned Virgin and HRT with their short gearbox and push rods.

The renault, mclaren, aren't design failures. Weren't you the one talking about "equality of interpretation" and teams are too smart to do this or that?

Only when you think it suits you, you proclaim superiority in design choices, and that teams are impulsive and the simply copy.

The small tradeoff Ferrari made for thicker actuating rods and higher CoG you can be sure were made for other reasons than simply being obstinate

Why not say what the trade off is?
You keep talking about these reasons and you can't say them. I mentioned Torro Rosso using the same engine and KERS, and they slapped on their gearbox and are doing very well.
Ferrari have no major reasons outside of continuity and servicing, the car is not unique.
In fact their car would have been even better with a pullrod suspension.

It's best to watch as the season evolves and witness the "clumsy" pull rods get narrower like the RB7, and as teams copy and develope to the point that the differentiators can't go unnoticed.

[Formula None]

Your confidence continues to amaze and alienate, Ringo. Does anyone here take you seriously anymore? Not that anyone does me, to be clear, its just that you seem to demand respect around here rather than earn it.

I'll be brief by only replying to the portion where you call me a liar and a plagiarist.

As was mentioned by others and myself waaay earlier in this thread and in the RB7 & F150th threads, the more forward positioning (relative to rear wheel centerline) of the bellcranks (ala Red Bull and this year's Ferrari) is the more important factor here, relative to a pullrod vs. pushrod debate. Another way to say it would be: long gearbox vs short gearbox. Long gearbox being the best choice for tapering rear bodywork and considering the lack of any max wheelbase regulations. If there was one idea to cling religiously to, it should have been long gearboxes, not pullrods.

You didn't say anything like that. Don't make stuff up please. This thread is suspension design, not aerodynamic refinement.
The words in bold are an observation i made months ago, and it was rejected becuase it didn't come from a reputed source. So you can't use something i elucidated and then squeeze it into this discussion.

From the Ferrari thread over a month ago, pg 18:

Here's a comparison I made with the other cars (F150 is 4th one down):

http://img715.imageshack.us/img715/5959 ... ioncom.jpg

As you can see the F150 has the straightest shot to the top of the diffuser, no pullrod intersecting the sidepod-to-floor fillet. Flow issues to the beam wing were an issue last year with all the pushrod cars, which had big lumps of suspension components right in front of said beam wing. Ferrari seem to have resolved this by placing the pushrod pickups so far forward and hiding all the suspension components in the shadow of the engine. You can't get past the extra thickness needed on the pushrod though.

From the MGP W02 thread, pg 20:

Compare the pullrod bellcrank location to the RB7. The W02's is much further back. Further back even than the pushrod bellcrank locations we've seen thus far. Doesn't seem ideal for tightening up the rear cross section.

______________________

The small tradeoff Ferrari made for thicker actuating rods and higher CoG you can be sure were made for other reasons than simply being obstinate

Why not say what the trade off is?

Its in the quote you used. Pushrods are thicker. Higher CoG. I'm just saying Ferrari worked with these compromises probably not just to be stubborn and traditional. They very well could have had good reasons relative to their design process. We could both guess what those reasons are, or we could agree that the Ferrari engineering team is not a bunch of hacks.