How is the front suspension's pushrod connected to upright?

[747heavy]

Do you mean this small link on anti roll bar? This is a Mustang GT500's front suspension.
http://farm6.static.flickr.com/5056/549 ... c1_b_d.jpg

It is connected to a very hight point of the strut, which is equal to the knuckle, I think.

I noticed may cars did so, such as VAG PQ35, BMW325, Mitsubishi lancer and so on.

yes, in a nutshell something along these lines.
It did look a bit different on the race cars, I have seen, and the offset was adjustable, but in principle it´s similar.
You would preload/twist the ARB while steering, thereby creating a sort of "mechanical load transfer"

I did´nt found any good photos of a version used on a race car, but here is another shot of a similar system you found.

SEAT Leon

[747heavy]

possible graphic for the above shown solution.



If, as shown in the graphic, the pushrod connection point is exactly on the steering axis, there is no effect from the steering in terms of load transfer.

As for the Lotus example, which started this thread , the point T and G in the graphic, could be interchanged. With the lower wishbone joining the upright above the pushrod. As long as the pushrod joins on the extentsion of the steering axis, there will be no adverse effect.
As others pointed out, the pushrod angle would be "steeper" and thereby the motion ratio more direct/benefical in this case.


On reason for such an arrangement can be, to reduce bending loads on the (normally lower) wishbone, and that the pickup points of the wishbones onto the chassis don´t need to carry the wheelload/cornerweigth of the car.
Therefore they can be ligther/smaller.

IIRC - BAR in 1999 was one of the first to pioneer/use such a layout at the front, other teams, including Ferrari, followed for the 2000 season.

If the point is offset from the steering axis, then the loadtranfer and change in ride height effects, mentioned and described earlier in this thread are taking place, and can be used to tune the handling of the car.

[mep]

Ahhh very good picture 747heavy. You are really the best.

Would be just nice to have pictures of a upright with a steering effect.
What I notice in the picture is that the pushrod position can't even be adjusted there and the lower wishbone mount is in single shear. Furthermore the lower wishbone mounting bolt is directly screwed into the metal, possible aluminium. This area is likely to cause trouble.
Then the kingpin inclination angle seems to be quite high which should also have an effect on ride high during steering.

Caster changes a car's corner-weights as a function of steering angle. The steering angle into a turn puts more static weight on the front-inner to rear-outer diagonal, and this typically increases weight transfer across the rear causing the car to turn/rotate more in the direction of the steering input. Great.

I think what you mean is caster angle not caster.

If, as shown in the graphic, the pushrod connection point is exactly on the steering axis, there is no effect from the steering in terms of load transfer.

You both mention load transfer or corner weight.
This seems strange to me because I think it’s just raising the ride height of one side. Even when you load the spring in case of the pushrod on upright layout, is this force coming from the steering rack and not from the tire!?

[riff_raff]

I would agree that putting the pushrod attachment below the lower wishbone attachment is beneficial from a loads standpoint. Putting less compressive load through a composite pushrod structure seems like a very good move. And less load on the pivots and rockers also means less friction.

[hyperneel]

to keep the pushrod(spring) neutral to steering effort it would be best to have the lower pushrod joint coincidend with the king pin axis.

Correct me if I am wrong, but if the front geometry has certain positive caster angle included, then there will be jacking effect when the wheels are steered; which will reduce the load on the front springs (thus raising the nose of the car higher), no matter the location of lower pushrod joint.

I myself am designing kinematics of a RWD sports car and recently came across this concept of coinciding the lower pushrod joint with the kingpin axis. I am not sure as to how it will make the jacking effects go away.

Can someone list all the pros and cons of attaching the lower pushrod joint to the upright?