Is there someone who can help me figure out how the rear suspension of the pagani zonda is working?
It looks like the top part is pointing to the back and the lower wishbone is pointing straight outwards but I can be wrong.
I think this suspension is adapting toe-in and out when it's moving up and down.
I'm attaching a picture.
Cheers,
Geoff
Rescued attachment paganirearsmall.jpg
i bet it has so little travel that the angles barely change.
I don't know, but I'll check mine, when I remember where I left it
Mike
No, but it's a lovely piece of engineering.
Pat...
Its was a Girraffe
this bit looks a bit flimsy, anyone think?
Zonda weigh in at over a ton doesn't it?
[Edited on 27/11/05 by liam.mccaffrey]
quote:
Originally posted by liam.mccaffrey
Its was a Girraffe
this bit looks a bit flimsy, anyone think?
Zonda weigh in at over a ton doesn't it?
[Edited on 27/11/05 by liam.mccaffrey]
because they can. Its a great car either way 
Carbon for bling, 600+ bhp to make it move
quote:
Originally posted by akumabito
quote:
Originally posted by liam.mccaffrey
Its was a Girraffe
this bit looks a bit flimsy, anyone think?
Zonda weigh in at over a ton doesn't it?
[Edited on 27/11/05 by liam.mccaffrey]
Closer to 1 1/2 ton I believe... what's the point of building an all-carbonfibre vehicle when you're putting such a huge and heavy engine in the back??
[Edited on 27/11/05 by akumabito]
dunno maybe it are high grade ones? or even titanium ones??
anyway its not all realy well in scale..
using an 2M10bolts...but an huge lump of an 'ally' lever???
alse the bracket look like realy thinn material...
Tks
it was specifically the bracket I had reservations about
Those brackets won't be too bad as I never heard from a big crash with a Zonda.
I started this thread because Jeremy Clarkson once said in Top Gear it was one of best handling cars he ever drove.
If there were some of those cars in my neighbourhood I would have checked it already a long time ago but until now I will have to base my information
on pictures.
Cheers,
Geoff
[Edited on 27/11/05 by geoffreyh]
quote:
Originally posted by geoffreyh
I started this thread because Jeremy Clarkson once said in Top Gear it was one of best handling cars he ever drove.
[Edited on 27/11/05 by geoffreyh]
That's true but I think they chose for another type of suspension because of the power / torque and weight combination.
The Atom has a lot of power but no weight.
Cheers,
Geoff
I read somewhere that this car has anti dive, and anti squat geometry, so the strange angles at the back are almost certainly something to do with
that. I dont see much wrong with the mounting bracket, especialy when you look at the Locost bracketry.
I suppose i expected it to look more substantial, i mean it wouldn't look out of place on a locost
My excuse is the type of work i do everything has to be belt braces and bits of string
I'd say its just as likelly that the angle is like that to maximise the wishbone length ie a compromise.
I'd assumed that the wishbone angles help to steer the rear of the car during cornering...
(front)
/ / (rear)
...however, toe-ing out at the rear seems at odds with convention; in a straight line at least.
In saying that, the Pagani is hardly conventional!
it is the main pivot, and it have a secont toe link
my quess is that its to induce some toe in while the suspension compress like when cornering, and some toe out while the rear of the car goes up when
you brake hard before starting to turn in.. may give a feel of a leghter car..
I thought rear toe-out was always a bad thing...
At the moment I have mine set to toe in, in both bump or droop, so I guess I'll see if I've outsmarted myself, considering I really
haven't driven it yet...
it's just my extrapolation.. probably give a little toe out to help steer .. may not have a great range
Convention suggests that toe-in at the rear is peferential as it aids stability when braking, and - when accelerating - the rear wheels want to
toe-out so a touch of toe-in helps counter this.
However, when cornering both sides are doing opposite things (one side in bump the other in droop). If the suspension is designed to give toe-out when
compressed (i.e. the loaded side), then designing the other side to give toe-in when uncompressed generates a wee bit of rear steer, which can
be beneficial.
quote:
Originally posted by Syd Bridge
quote:
Originally posted by Chippy
I read somewhere that this car has anti dive, and anti squat geometry, so the strange angles at the back are almost certainly something to do with that. I dont see much wrong with the mounting bracket, especialy when you look at the Locost bracketry.
I've said this many times, but.....
Have a good think,........ What holds the car up?........the springs. What stops it dropping down? The springs!
Now explain how angling the wishbones changes the way the springs hold the car up. All the angled wishbones do is balls up a perfectly good wishbone setup.
Dive and squat are functions of CoM height and location, leading to weight transfer longitudinally. Changing the wishbone angles cannot affect that in any way, shape or form. If you want less dive or squat, use harder springs, or lower the CoM. See modern racecar designs for confirmation. Wishbone inner pivots all parallel to c/l, and ground.
I'd be looking for a geometry reason for the angles, and leave the anti dive/squat in Mr.Staniforth's book, where it belongs.
Syd.
I wasn't specifically talking about the wishbone angle only that the rocker ratio on it does change the effective spring rate as the speed it
moves the spring increases on compression and thus the top wishbone on this car does effect the spring.
As you say I recon the angle is purelly down to compramise.
You'd need to see what the bottom wishbone was all about to be certain about how the upright will function -- from the looks of it, the toe link
is at the front of the upright so if the bottom inner wishbone pivots are parallel to the chassis c/l the wheel will toe-in under bump (same as the
Porsche Weissach axle or Mitsubishi's, best forgotten, 4ws system from the early 90's), if the bottom wishbone pickups are parallel to the
top it should keep the wheel straight throughout wheel travel.
The anti squat/dive geometries (with apologies to Syd) are all about having the wishbone pivots at different heights fore and aft.
Cheers, Ted
Hi
Anti Squat has nothing to do with "old scool of thinking",but is mainly used on FWD Cars as it gives more traction ,but
makes rear wheel driven cars more difficult to drive at the limit.3° is said to be the useble maximum.The mini is one of the best handling FWD cars,so
have a close look at the front axle.Alec surely was no fool?!
Best regards,Stephan
"Some very outdated schools of thought put the wishbone pivots at an angle to the c/l laterally, to induce the desired anti's."
Ehm, in other words; we're now past the laws of physics?!?!?!? Please come with some better explanation on your thoughts Syd, as your statements
fall into the same category as saying that the earth is flat.
And that only happens when I'm drunk.
Anti-dive and anti-squat do work, and it is ALL in the orientation of the wishbones. Sure you can take a stiffer spring, but that upsets the rest of
the characteristics.
to make anti-dive/squat geometry work only needs a couple of degrees and wouldnt be a visible change. maybe youve seen the diagram in a book some
where and didnt notice that it was exadurated for easy identification purposes.
from what the pic shows of the zonda upper wishbone it is no more than a semi trailing arm. the the upper outer mount appears to be a single ball
joint so if the bottom mount is parralel then toe wont be effected by the upper wishbone. the reason for the trailing arm setup could (as said
earlier) be simply a compromise to make use of available structure, and/or (also as said earlier) to get a longer wishbone for better geometry.
another point is that at an angle the arch the wishbone follows is skewed so that any camber change in bump or droop is slightly less, which would
make sense with short upper wishbones and is one of the problems i had when designing my rear geometry due to having to leave room for the engine.
Ok Sid i'll try:
To make things clear ,it allways helpes to
imagine the extremes .Lets say the inner wishbone axles are mounted at an angle of 45°!!The driven wheel forces the upright to move vorward,this force
is directed at an angle of 45° to the wishbone,which means that half of the force tries to move the wishbone down and therefor the Car up.At the time
of accelerating the tyres have to take a higher load.If Newton didn't die ,he would have put that in a law,I guess.
I haven't seen any existing race car suspension like you,but I got payed for designing car suspension for several years,so I've
"heard" a few things.I didn't
say you should give the Mini anti squat,it already has it.But this is a discussion forum where people just offer opinions and these may differ some
times.
Best regards,Stephan
Good Luck Chaps.
No use arguing with all you experts.
Syd.
i agree with stephant. His description is accurate.
It works by the wishbone pivots pointing up above the centre of mass, so the direction of the change of momentum is below the plane of the wishbone
pivots, and aiming towards it.
sorry sid
Ignoring absolutely everything that charlatan said, the upper rear wishbones may be angled for anti squat, though without seeing the set-up in
its entirety, it's a bit hard to be certain.
I would imagine it's all more to do with bling and "tech-supremacy" than any real world gains or improvements.
There are rarely any truly evolutionary contributions to suspension design now. Most "developments" are re-visited or re-hashed
technologies.
These scenarios and discussions occur as frequently as bowel movements and bore me to further bowel movements which is why this is my first post on
the matter.
quote:
Originally posted by Rorty
without seeing the set-up in its entirety, it's a bit hard to be certain.
quote:
Until then, have a good close look at any modern racecar. If it would be found anywhere, it surely would be there. And just plainly Aint!!!
quote:
.......Will I be able to claim fractions of a degree 'improvement' in camber-gain per degree-of-roll etc compared to some other car? No, because I'll neither know nor care. If it handles abysmally (which I doubt) I'll rework it until it doesn't........
Hi
I didn't want to say,that the pictured suspension setup was made for anti squat.
Of course it takes a lot more than one picture from above, to get an idea of what they wanted to achieve.May be it just suits the frame design and
they have only one type of suspension bracket .I just wanted to commend the "nonexistance" of anti squat.
Best regards,Stephan
Well Syd, in that test you guys seem to have left out the biggest contributing factor; there was no weight transfer due to braking, as the centre of
gravity of the vehicle was not moving. So of course the test results proved disappointing!
I can tell you from my experience in designing AND testing bike anti-dive and anti-squat suspension systems that it does work. So luckily I can still
say that Newton was right all along.
Marcel
Syd
May be we misunderstood each other.
However,I'm not sure if tests with slicks + tyre softener give the right results in that case,but I know that playing with anti squat at 4WD cars
is done to get slightly changes at the ballance , but the top wishbone angle at the picture above surely has nothing to do with anti squat.
Best regards,Stephan
Ok here's my take on this debate we keep hearing between Syd and others.
Point 1
Think of the car as a mass supported by a system of linkages. If this car was supported by very soft springs then it would be free to move about on
its supporting linkages and would move about the geometric roll centres in every direction.
Point 2
Think of the opposite case. Make the springs very stiff or just replace them with rose jointed links. The car's linkages still move but only by
microscopic ammounts. The important thing now is the CoG, the roll centres just drop out of the picture from a practical point of view. The car now
appears to roll about the CoG with the springs just holding it up. This is exactly what I think Syd is describing
Conclusion
In a road car the result will be some way between point 1 and point 2 so the car will tend to roll, in cornering and front to back in squat and dive,
about a point between the geometric RC and the CoG. Given the stiffness of a road spring I would expect this point to be closer to the RC for a road
car and closer to the CoG for a race car.
Comments all!
Especially Syd, is this what you've been getting at?
Hi
Cymtriks:
The forces produced by anti squat have nothing to do with the hardness of springs,they just get added to the spring forces(under acceleration) and are
produced by suspension geometrie.
A look at the rear suspension of Nascars shows a simple example,of how that is achieved.They usually have the rear axle located by three lateral
links (two lower ones and one above in the middle)+panhard rod.There are several mounting holes(vertical) at the axle ,to set anti squat /anti
dive.
If the springs are locked,as discribed in "point two" not only the roll centre gets out of"view",the whole suspension geometrie
doesn't still exist,as there is no movement.In that case you could simply weld the uprights to the chassis,to get the same.As I hope to
understand Syd now ,he just wanted to say,that the "toe out"mounting of the upper wishbone doesn't produce anti squat,something i would
agree, too.
Best regards,Stephan
Stephant,
This is a long running issue which Syd keeps bringing up. I don't think that you have understood my points!
My point 1 and point 2 are the extreme cases. Point 1 is a very soft case, by which I mean "mathematically" soft, a limiting condition.
Point 2 is also meant to be a limiting case, "mathematically" hard. My reference to replacing the springs with solid links was intended to
illustrate the limiting nature of point 2, a solid link is still a spring, only a very stiff one!
Remember that a suspension theory needs to account for both "soft" and "hard" suspension cases. As Syd points out traditional
suspension theory does not do this as it assumes a "soft spring" case, as in my Point 1 case, to apply all the time.
In practice springs are somewhere in between "soft" and "hard" so the true roll centre must be somewhere between the geometric
roll centre and the CoG.
Syd, are you out there!
cymtriks
I still don't understand what you mean by "true" rollcentre.The rollcentre doesn't change it's position with different
springs.
It's influence to the body roll and load transfer just gets lost by locking the springs(or making them hard as discribed)
Best regards,Stephan
Stephant,
The true roll centre is the one that the car actually rolls about.
The geometric roll centre is the one determined by the suspension geometry.
Ask youself this question. How hard do the springs have to be before the car behaves like a solid mass and rolls about the CoG? In my example, point
2, I used an extreme case of a solid bar which locks out the roll centre. But what about a very hard spring? How hard is hard? At some point the
geometric roll centre will be replaced by the CoG as the point about which the car actually moves.
For a road car the springs will have plenty of movement but they not free moving either so the true roll centre is close to the geometric one but
slightly offest towards the CoG.
Please Syd, is this what you mean?
Is whats being disputed whether IRS can produce any antisquat or if antisquat is not actually existant.
Drag cars use antisquat but I've never seen one use an IRS system and I've read that usable antisquat is difficult to active in an IRS.
from the picture of a Zondas' rear wishbones and you can't even see both ends of them ? Does anti squat exist, does Santa Claus exist, do
fish fart?
This is a long topic, click here to review it.
You're not kidding.
Hi Cymtriks
Of course you can define the changes in tyre load and body roll resulting from changes in spring rate as a changed rollcentre in reality,but what has
it all to do with anti squat?
To me,this discussion startet with "anti squat is nonsens,the springs hold the car up".Antisquat is only dealing with lateral forces,which
have no influence to rollcentres etc.
However,we all think the picture above showes almost nothing to discuss about and I just wanted to say,that fishes do fart.
Best regards,Stephan
Thanks Stephan, at last something useful from this thread.
quote:
Originally posted by Stephant
A look at the rear suspension of Nascars shows a simple example,of how that is achieved.They usually have the rear axle located by three lateral links (two lower ones and one above in the middle)+panhard rod.There are several mounting holes(vertical) at the axle ,to set anti squat /anti dive.
Hi
my english isn't good enough to explain properly,(learnt it 25 years ago in scool)I was talking about forces
,working parallel to the middle axle of the car and thought lateral was the right term.
Regards,Stephan
quote:
Originally posted by locost_bryan
iirc anti-aquat in a irs is achieved by angling the wishbone pivots so that they aren't parallel (when viewed from the side of the car).
quote:
Originally posted by Stephant
Hi
my english isn't good enough to explain properly,(learnt it 25 years ago in scool)I was talking about forces
,working parallel to the middle axle of the car and thought lateral was the right term.
Regards,Stephan
Hi
no problem Bryan, this forum
will be a good training.
Regards,Stephan
quote:
Originally posted by Syd Bridge
quote:
Originally posted by Chippy
I read somewhere that this car has anti dive, and anti squat geometry, so the strange angles at the back are almost certainly something to do with that. I dont see much wrong with the mounting bracket, especialy when you look at the Locost bracketry.
I've said this many times, but.....
Have a good think,........ What holds the car up?........the springs. What stops it dropping down? The springs!
Now explain how angling the wishbones changes the way the springs hold the car up. All the angled wishbones do is balls up a perfectly good wishbone setup.
Dive and squat are functions of CoM height and location, leading to weight transfer longitudinally. Changing the wishbone angles cannot affect that in any way, shape or form. If you want less dive or squat, use harder springs, or lower the CoM. See modern racecar designs for confirmation. Wishbone inner pivots all parallel to c/l, and ground.
I'd be looking for a geometry reason for the angles, and leave the anti dive/squat in Mr.Staniforth's book, where it belongs.
Syd.
Amen to that.
Wishbone inclination does influence the dive and squat properties. Whoever says it doesn't, claims Newton was wrong. Nothing wrong with that, but
you're just part of a small selected group that's not right. At all.
OK,
I thought about this (no, really!) and I scribbled some quick and dirty diagrams to try to illustrate the point as I see it.
For the purposes of the argument we have a simple box for the vehicle and wishbone pivot axes represented by simple horizontal lines (to start with).
The arrow on the diagram just indicates forward. We're talking here about the rear suspension and the suspension upright is shown as a red
box.
Susp diag 1
On the left is the vehicle at rest. It's quite obvious that, if the springs were removed (and assuming frictionless suspension pivots etc), the
vehicle would collapse until it rested on the ground. The only thing holding the chassis in that position, relative to the wheels, is the springs.
In the middle, we've hung the chassis on a wall, with the tyres glued to the wall. This removes gravity from acting in the usual direction on
the chassis. Instead, it is acting in the same way braking forces would - the chassis wants to move forward (down in the diagram) but the wishbones
etc allow no movement in that direction as the force is acting perpendicular to their axes. The chassis can still be moved left/right (equivalent to
up/down) but the 'braking force' isn't making that happen. On the right, tilting the chassis back toward horizontal would cause it to
collapse back against the wall as soon as the 'vertical' force (gravity) is able to act again.
Now lets look at a variation.
Susp diag 2
This is basically the same as before but the rear wishbones are inclined down towards the front - crude "anti-dive" geometry. Same
horizontal and vertical layouts as before but now it's possible to see that on the right the angle of the rear arms will cause the chassis to
rise (move right on the diagram) relative to the wheels! Where is this mysterious force coming from! Could it be.... surely not.... anti-dive?!
The forces acting on the suspension are not just those due to gravity (except when the vehicle is at rest). Under braking or acceleration there is a
horizontal component to the forces between the wheel and the chassis and that component of the forces acts through the angled arms resulting in an
upward force on the chassis relative to the wheel. I don't think anyone here is suggesting that it's enough to hold the car off the ground
(except perhaps under 10G of braking!!) but it's non-zero.
When you think about it, the same effect is why KPI assits self-centering in steering. The non-vertical pivot axis for the wheel causes it to try to
fall relative to the chassis when steered. The wheels are trying to lift the car up - not suprisingly, the car (and gravity) resist Admittedly,
a lot of self centering comes from trail (a result of castor not KPI) but the KPI effect is real - and trail is only meaningful when moving.
Syd, I'm getting the worrying impression from your reply that you think there are no forces other than gravity acting on a moving vehicle.
Longitudinal and lateral forces are every bit as important as vertical for a meaningful analysis.
Dominic
P.S. Everyone please excuse the rough and ready diagrams.
Update:
The above message was written about midnight local time. Looking again in the cold light of morning (I wish - it was 22C overnight last night and 75%+
humidity) I think my analysis is hmmm...... imperfect I'm going to think about this a little more and draw some better diagrams.
Frustratingly, Syd has chosen to revise history somewhat by completely removing his message that I was replying to which then leaves my reply somewhat
out of context. Given that I got a PM suggesting that I may not have fully/properly read his message it's frustrating to find it gone Read
into that what you will.
Dominic
This was getting silly, and the site is supposed to be 'LOCOST' after all.
Additionally, I had transgressed a note to myself regarding further posts involving technical design discussion. I am consciously attempting to avoid
confrontations, just for a change!
The wisdom (or otherwise?) of age and experience tells me that we should agree to disagree, and get on with life. There are a lot more important
things to worry about.
Syd.
I'll gladly continue any of this with anyone interested, but only politely on u2u to avoid any heated discussions. Thank You.
[Edited on 9/3/06 by Syd Bridge]
You can angle the wishbones to get antisquat it has been done on many race cars over the years. However the most you can practicaly get is 20% and
dose cause other side effects.
cheers matt