Push rod on upright suspension - an examination

[henry]

Given the geometric constraints the change in toe must change the ride height. As @PhilipM points out if the straight ahead line of action of the push rod is in front of the steer axis the response could be arranged to raise the ride height. The change for the small angles involved in toe will likely be very small. However it will have positive feedback, lower downforce from lifting the ride height will extend the springs and tyres increasing the ride height. So I think the DAS system would likely reduce both aerodynamic drag and tyre scrub.

[PlatinumZealot]

In the videos I don't see much ride height change with steering...

The radius of the nub from the steering axis, the angle of turn, and the inclination of the push-rod would suggest quite a bit of ride-height change...

Can someone do some estimates?

[godlameroso]

OK. Never denied it.
I said i had an idea how it would work. Just wanted to see someone say it.

Here goes:
When the steering is straight, the pushrod top joint and the bottom joint has to make a straight line to king pin axis.

This way when you turn right or left it pulls on the push rod. (thinking of a cricular arc, a point going away from the top of the arc pulls on the pushrod shortening the ride height, the top of this arc intersects with another line drawn from the king pin axis to the knuckle to the top joint of the pushrod so that the point is neutral (or in zero position. When your turn left the point moves way. When your turn right the point moves away.

Thats it.


I dunno.. I mean with regular street cars.. We can get a lowering or raising of a corner of the car when you steer. Because of a number of reasons (king pin offset, caster angle camber angle)..maybe you call this the traditional way?

it interesting other teams could be achieving it whout this extended knuckle thing. I really don't know.

I really want to know if this is indeed the primary purpose of doing the suspension like this. Do photos show Mercedes dropping their nose into turns? Maybe with their low rake angle they can afford to be dropping the nose of the car?

I honestly think the extended knuckle is purely aerodynamic, moving the suspension arms out of the way of the barge boards and diffuser. Doing so makes you have awkward angles to get the geometry you're looking for, it is certainly an interesting engineering challenge for a variety of reasons.

[PlatinumZealot]

Interesting....

We know the steering is "anti-ackerman" in F1 where the outside tyres turn more at an angle.

This is to maximise grip (based on what slip angle give the best grip at high loads).

So you steer the outside more.. And this lowers the outside more based on the photo... Then.. Is this what you want in the respective types of turns? I haven't thought about it yet... Do you want a level front wing or lower on one side? I dunno yet.

[godlameroso]

Depends if you want to load the inside tire with aero you'd want to lower the front wing on that side. But that would make the aero forces push the car away from the turn. Remember that the front wing is an upside down airplane wing and when you roll in an airplane the wings will yaw in the direction of roll. So if you roll into the turn the wing will yaw away from it. There's probably a sweet spot between rolling and lowering the suspension that will give the most front axle performance.

[PlatinumZealot]

Trying to find similar shots from the other cars...

There is a very important detail with the lower end of the pushrod. I expected it to be angled out more with the (driver's) right wheel. Need some other shots.

[Tim.Wright]

We know the steering is "anti-ackerman" in F1 where the outside tyres turn more at an angle.

The picture you used looks like normal positive Ackermann to me.

With the steering axis so far inboard I don't see how you can have anti-Ackermann without having the toe link attachment inboard of the brake ducts.

[godlameroso]

We know the steering is "anti-ackerman" in F1 where the outside tyres turn more at an angle.

The picture you used looks like normal positive Ackermann to me.

With the steering axis so far inboard I don't see how you can have anti-Ackermann without having the toe link attachment inboard of the brake ducts.
https://external-preview.redd.it/gcKxoH ... 576849072f

Is this tie rod position known as zero point or center point steering?

[PhillipM]

The picture you used looks like normal positive Ackermann to me.

With the steering axis so far inboard I don't see how you can have anti-Ackermann without having the toe link attachment inboard of the brake ducts.

Depends where exactly that lower wishbone actually pivots but it looks like it could be neutral on the ackerman just from that single photo.

[PlatinumZealot]

The tie rods are infront.. and outboard of the steering axis.

We know the steering is "anti-ackerman" in F1 where the outside tyres turn more at an angle.

The picture you used looks like normal positive Ackermann to me.

With the steering axis so far inboard I don't see how you can have anti-Ackermann without having the toe link attachment inboard of the brake ducts.

I assumed the lower joint was further outboard. Ok.. But lets assume it is positive. (
This is why the naked photos of the hub are important.)

So with that said,

I would expect the in the photo the inside wheel should have a greater angular displacement and that corner a lower ride height because the base of the pushrod would be displaced more. (this assumes the pushrod and the knuckle are colinear in the "zero" position).

Actually both sides will reduce in ride height but the inside will reduce more.

[Zynerji]

Does loading the outboard side of the wing of the inside tyre help load the inside tyre, or does it transfer to both front wheels equally?

I'd assume it would transfer load to the inside pylon, and "tilt" the nose in that direction, but im not sure. Part of my brain says it would, and possibly lift the outside pylon like a lever, but with zero real world experience, I'm simply not sure, and would like some professional input.

[godlameroso]

Does loading the outboard side of the wing of the inside tyre help load the inside tyre, or does it transfer to both front wheels equally?

I'd assume it would transfer load to the inside pylon, and "tilt" the nose in that direction, but im not sure. Part of my brain says it would, and possibly lift the outside pylon like a lever, but with zero real world experience, I'm simply not sure, and would like some professional input.

Yes it would, the wing span is levering against the nose mounts, the load is transmitted to the bulkhead where it's distributed to the front axle. The thing is both sides of the wings generate lift, one side generates more lift if it's closer to the ground than the other. Both sides press the whole axle to the ground because of the way the wing is mounted to the chassis. But the loads are tricky to measure because there's inherent compliance to the suspension and the chassis itself.

[Zynerji]

Does loading the outboard side of the wing of the inside tyre help load the inside tyre, or does it transfer to both front wheels equally?

I'd assume it would transfer load to the inside pylon, and "tilt" the nose in that direction, but im not sure. Part of my brain says it would, and possibly lift the outside pylon like a lever, but with zero real world experience, I'm simply not sure, and would like some professional input.

Yes it would, the wing span is levering against the nose mounts, the load is transmitted to the bulkhead where it's distributed to the front axle. The thing is both sides of the wings generate lift, one side generates more lift if it's closer to the ground than the other. Both sides press the whole axle to the ground because of the way the wing is mounted to the chassis. But the loads are tricky to measure because there's inherent compliance to the suspension and the chassis itself.

Tyvm

[Greg Locock]

4 pages in on F1 'Technical' and nobody has done K&C

Neither have I, it's a busman's holiday

[PlatinumZealot]

4 pages in on F1 'Technical' and nobody has done K&C

Neither have I, it's a busman's holiday

K&C??