No anywhere near my 3door at the moment to look, can anyone tell me what sort of ackermann angle the steerings arms have.

Ie do they meet at the rear diff, or converge somewhere else, or not at all?



Thanks in advance


Chip

 

WTF

Your asking university type questions on a Ford site? ..

..WTF is an ackermann?

 

Phil, I just want to know what way the steering arms point basically mate.

ackermann = german who died 100 years or so ago.

 

...and whats he got to do with steering joints?

 

Its suspension geometry.

If you asked on somewhere that people know about suspension (ok, only forum i know like that is driftworks) itd be no problem.

Just on here race suspension is limited to "fit some polybushes and slam it on konis bruv"

 

Damn, saw stavros as the last reply and thought I might be getting an answer that was useful, lol

Im sure there must be a few people on here that know

 

Ackerman angle is a function of toein/out and steering arm length, the arm length is usually fixed (unless you are making your own parts???) and the ackerman angle will then be dictated by whether you want/need to run toe in or toe out...

This is assuming you are using a normal rack and are not moving it too?!?!?!?! A quick rack will make no difference but a rack with a different throw will, also if the rack is re-positioned it can affect the throw that the steering arms see.

 

Its normally about 7.5 degree iirc

Why are you planning on playing with it?

Alex

 

Yes mate, thats all correct.

My question is simply that on a standard cossie, with standard toe-in settings, what is the angle of the two arms in terms of where would they converge if you were to extend an imaginary line along them.

Ackermann obviously states that they should meet at the rear diff, but theory has moved on a long way since then, so im just interested as to how closely the cossie does or doesnt follow his principles.

 

Im not planning on playing with it at all, I just want it as a well known car as a point of reference.

Cheers for the 7.5 degrees info


If you know it for any other cars that are common (3 series? S14 200sx) that would also be cool

 

As for phil's comment


its a piece of basic car suspension theory.

http://en.wikipedia.org/wiki/Ackerma...ering_geometry

my 16 year old apprentice mechanics learn it in their 1st year of college!

Alex

 

I'll find you a definate on a certain car today Chip

Alex

 

Thanks Alex

 

Cool, Chip...Sorry man i had no idea what it was on a cossie to be honest! But i do now...Cheers AlexF

 

IIRC Mk2 RS2000 is 4degrees.

 

Thanks Steve


dont suppose you can find out what it is on a S14 as these handle very well

 

To what extent do Ackerman's principles get modified when you introduce Passive rear steer into the equation?

.

 

now theres a question

steering geometry is my weakness with cars but im learning all the time

 

...whoosh over my head

 

Ackerman's theory is all very well...but it only really applies at low speed...dial in weight transfer, tyre and bush deflection on a road car and ackerman goes out the window pronto....

Although the principles of drift cars probably do vary dramatically in comparison to cars which need to set fast lap times....

Is is not the acheivement of a dramatic steering angle thats necessary?

 

Absoultely agree that exact ackermann angles are not what most modern road cars use, far more relevant to low speed saving of tyres than performance, in fact in some cases tyre dynamics can actually lead to the use of NEGATIVE ackermann on certain types of car.

 

In what way?

Far as I see a professional drift car has similar settings to a normal circuit car.

Pretty much zero toe front and rear, more camber front than rear but ideally nor a huge amount of either (just enough extra front to stop any severe understeer), and plenty of castor to give good self centering.

Diff settings are about the same too, as are tyre sizes.

More steering lock is usually acheived with steering mechanics mods rather than geometry changes.

 

Steve,

It was actually more an assumption than a statement...never had anything to do with setting up drift cars....and as they spend most of their time on lock I would have assumed more steering angle was important...rather than optimising geometry....

 

Lots of lock is important, but to win anything you need to be able to drift at higher speeds than everyone else (as once in the last 16 its basically a race), so huge amounts of grip are important, so its the same basic principles as a circuit car.

Good example is the Yoshio Factory D1 S15 has done a 59sec lap of Tsukuba Circuit, a McLaren F1 has only managed 1min 4sec at best.

 

That is bloody impressive stuff Steve!

 

about 2 degrees!!!


not 7

just been through a couple of 3 series of diffrent models on the wheel alignment machine....



Alex

 

2 degrees per arm from parellel with the centre line of the car?
Or 2 degrees relative to each other (ie 1 degree per side)

 

the ackermann angle is two degrees



so 2 degrees difference between the arms as you turn.

 

2 degrees when you turn how many degrees?
The more you turn the more it will vary if they arent parellel

That doesnt make any sense just on its own

 

its usually measured at 20 degrees off centre in either direction

 

Ah thanks for that.

Im still going to have to do some trig now to work out what that implies about the arms themselves at rest though, lol, and i will need to know the toe in to start with too.

Fundamentally though, sounds like they must be very close to parellel in the first place which kind of answers my question roughly anyway