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

[Tomba]

I thought the pushrod should be connected to the lower A arm. Then the lower A arm connected to the upright.


But when I saw lotus T127, I found ..........

On T127, the front pushrod seems to run through the lower arm and connect to the upright directly.

Then when steering, what is the kingpin? There are 3 points.

Does any team else used this type?

[ysyy88]

how to insert pictures?

ok, it works

Here, the pushrod does not connect to the arm, but go through it instead.

[Formula None]

http://farm6.static.flickr.com/5256/5487784299_49549d4c4e_b.jpg

Nice image, man, thanks. Is such an arrangement common in F1? 4 pivot points on a front upright? (2 control arms, pushrod, steering)

[marcush.]

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.
In reality many many designs do not and seem to keep the spring compressed most in straight ahead steering position.
For whatever reason it seems to work even if this seems very counterintuitive as the car would "fall" into a steering effort

[silente]

In my opinion, this solution can have two main good aspects:

1) normally if you connect the pushrod to the upright, your assembly is stiffer and has an higher strength;

2) Maybe you would like to create an inside spring compression effect when you steer, similar to that you can obtain with caster. This effect helps to reduce understeer above all in slow corners, because it works against front weight transfer in a way proportional to the steering angle you are using.
In this way, you should feel it just a little in fast corners, where you like to have some understeer, but a lot more in slow corners where the car tends to be naturally more understeering.

[marcush.]

if you want to compress the spring the distanace of the hub mounting point distance to the rocker must decrease .The hub sviveling due to steering action will increase this distance in xy view if the pushrod is anything near right anles to the x-axis of the car? so in my view this would lead to a digressive spring characteristic in steer...(of course ignoring everything that is happening in the rocker actuation)

[ysyy88]

http://farm6.static.flickr.com/5256/5487784299_49549d4c4e_b.jpg

Nice image, man, thanks. Is such an arrangement common in F1? 4 pivot points on a front upright? (2 control arms, pushrod, steering)

I want to know whether it is common, too.

[Tomba]

I'm not too sure if such an arrangement has any influence on steering at all. I mean it could be arranged that it doesn't. If the pushrod has a 90° angle to the tub when looking from above, and the team connect the pushrod on the upright exactly on the vertical rotational axis of the front wheel, then spring compression will be steer neutral. We'd need pictures from other angles to see if that is the case though...

The advantages I see is that wishbones can be as short as possible (or also as horizontal as possible) while the pushrod can be kept long, allowing for more precise input in and adjustements of the dampers/springs.

[marcush.]

the rotational axis=kinpin axis (usually).To get your mounting point on this axis might be tricky .

A lot of teams separate the lower wishbone from the pushrod ,also in front ,in fact- who does not?

[richard_leeds]

IMHO ......

Yes, it would be neater for the wishbone and rods to align on common node points. Then the forces will nicely resolve as determinate structures (ie triangulated).

As others have pointed out, the offset arms/wishbones increase the possibility of things not lining up leading to secondary forces and difficulties with a consistent set up.

One very good reason for this arrangement is that the push/pull rod is at the steepest angle, from top of nose to bottom of hub. That gives the greatest control, stiffest support, and lowest forces. A system with a rod contained within the depth of the wishbones would not be as stiff.

Meanwhile the wishbones primarily handle forces in the horiz plane (front/back and and sideways), so they have deep sections and wide spacing at the chassis when viewed from above. The forces when viewed from the front only need to deal with torsion due to the camber, relatively small compared to the other forces, hence thin sections in that plane with small lever arm at the hub.

[scarbs]

The car is running with a Pushrod On Upright set up, often termed (POU or PROU). Many teams run with this set up, the offset from the pushrod pickup and the king pin axis is a tuneable set up parameter. I have seen F1 set up sheets with figures of 8mm offset.

I had it explained to me by an ex-f1 designer:
"When the the car turns outside wheel will drop and inside will rise, this helps grip at low-speed. Its often used in conjunction with Anti-Ackermann suspension (meaning that the outside wheel steers faster than the inside), this can then result in an overall reduction in front-ride-height as you add steering lock."

[DaveW]

The car is running with a Pushrod On Upright set up, often termed (POU or PROU).... often used in conjunction with Anti-Ackermann suspension (meaning that the outside wheel steers faster than the inside), this can then result in an overall reduction in front-ride-height as you add steering lock."[/i]

Why is it I just knew there would be an aerodynamic explanation? Thanks Scarbs.

[ysyy88]

the rotational axis=kinpin axis (usually).To get your mounting point on this axis might be tricky .

A lot of teams separate the lower wishbone from the pushrod ,also in front ,in fact- who does not?

I find it's difficult to get some pictures that can show this part clearly. That end of pushrod is usually covered by tires or brake systems in most pictures.

like this. WTF brake air intake....






Can anybody find us some more pictures?

[scarbs]

Check the toro rosso 2010 thread, the upright that broke shows the set up perfectly

[marcush.]

there is some logic in it to lower the car with steering lock but ...
the amount of steering lock on the upright is really low unless you are going into loews....so you might have a lot of lock in a severe undesteer condition....which leads me to the idea that some setups will mask understeer trouble by adding downforce due to geometric lowering of the front..things can quickly get too complicated...

speaking of king pin inclination: itis what you do not really want ,as it adds positive camber in lock and opposite lock....so your camber gain in bump or camber gain through castergain in lock is eaten up by this.Kingpin inclination is only necessary to get the turn axis through or near the centre of the tyre contact patch to reduce scrub