Push rod on upright suspension - an examination

[Zynerji]

FRIC suspension is banned (front/rear interconnect), but I'd imagine FFIC could still be used.

Maybe that's how it can "know" which way it's turning, but Im just speculating.

PS: Concerning caster. In sim racing about 2007ish, my friend and I did a ton of setup mapping in rFactor. Now, obviously, it is a game, but we found tons of time with the toe/caster settings. Oddly, whenever I've spoken about going slight negative on caster with high camber and slight positive rear toe, people don't believe it is a good thing. I watched him win the 2007 and 2008 league championships with that setup philosophy. My friend called it the Snap and Hold setup (smooth), as it was a bunch of small, quick steering maneuvers. He disliked it at first, as he was a very "stair step" corner entry driver (choppy), and it took hours for him to adapt, but it was worth 1.3s in the end.

With modern machine learning, we will probably see lots of "rules of thumb" be overturned with "wacky" setups.

F1 cars already run a fair bit of toe out on the front, a hint of toe in at the rear, and as much camber as Pirelli lets them get away with. What is not known to me is caster angles, although I'm guessing looking at some of these pictures that 6-10 degrees wouldn't be out there.

2018 tires had wear marks on the inside of the front tires which is common signs of having tons of toe out. Probably like half a degree.

We were running toe out (half degree) in the rear, -2 degree camber in the rear. Front was -1.5 degrees toe in with -1 degree of caster, and -4.5 degree camber. This was the base that we just massaged from track to track.

I had the Caroll Smith books helping us at the time, and we found that what he recommended was definitely NOT the fastest lap time. We just figured the tyres model simply didn't calc the true wear, so we got away with it, but who knows?

[Greg Locock]

@strad - in a two wheel bump the effect will cancel out. However in single wheel bump or roll there will be a net steer effect as the wheel moves up on one side.

[Tim.Wright]

Sounds like the effects of caster with the centering torque you are talking about. Ok gonna look into this. Caster angle is another
" complication " in this topic but going by photos of mercedes W10 car it is postive caster angle so there is a self centering tendency. So this is the perfect example.
OK so now you say the Mercedes setup of the pushrod is to lighten the steering a bit by counteracting the effect of the postive caster. Fine let's explore.

https://cdn-1.motorsport.com/images/mgl ... t-susp.jpg

You mentioned "negative" steering torque so automatically one will seek to clear up how the geomtery is designed to work whether car is going left or right?

I have an idea how such geometry can still can "know" (and work) whether the car is steering left or right.. But i wanted to see somebody else's take.

I haven't gone in depth into the kinetics of it yet tho.. Just working peice by peice.

Caster gives a self centering due to tyre lateral forces. The pushrod effect (and KPI for the matter) uses vertical tyre loads. And again, it doesn't need to know left or right. It works the same in both directions.

[PlatinumZealot]

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?

[PhillipM]

Yes, your inboard offset away from the steering axis makes the car drop more with increasing steering angle either way - if you went outboard of the steering axis you'd raise the car instead.
Then your longitudinal offset from the steering axis will make the car rise or fall depending upon the direction of the steering, so a rearward offset would lift the outside wheel and lower the inside one for the same forces, for example, or vice versa for a forward offset.

Most cars are running a blend of the two.

[the EDGE]

Yes, your inboard offset away from the steering axis makes the car drop more with increasing steering angle either way - if you went outboard of the steering axis you'd raise the car instead.
Then your longitudinal offset from the steering axis will make the car rise or fall depending upon the direction of the steering, so a rearward offset would lift the outside wheel and lower the inside one for the same forces, for example, or vice versa for a forward offset.

Most cars are running a blend of the two.

That would explain why Mercedes are running the most extreme version of this, the front of the car rides higher than others due to the shallower angle to rake the car is run at, so we therefore have more room to play with

[PhillipM]

It's actually limited in the regulations because Mclaren did a really extreme version way before it ever got talked out much on here and in the press, so how far you can go depends a lot on the rest of your geometery.

[nzjrs]

FRIC suspension is banned (front/rear interconnect), but I'd imagine FFIC could still be used.

Maybe that's how it can "know" which way it's turning, but Im just speculating.

PS: Concerning caster. In sim racing about 2007ish, my friend and I did a ton of setup mapping in rFactor. Now, obviously, it is a game, but we found tons of time with the toe/caster settings. Oddly, whenever I've spoken about going slight negative on caster with high camber and slight positive rear toe, people don't believe it is a good thing. I watched him win the 2007 and 2008 league championships with that setup philosophy. My friend called it the Snap and Hold setup (smooth), as it was a bunch of small, quick steering maneuvers. He disliked it at first, as he was a very "stair step" corner entry driver (choppy), and it took hours for him to adapt, but it was worth 1.3s in the end.

With modern machine learning, we will probably see lots of "rules of thumb" be overturned with "wacky" setups.

F1 cars already run a fair bit of toe out on the front, a hint of toe in at the rear, and as much camber as Pirelli lets them get away with. What is not known to me is caster angles, although I'm guessing looking at some of these pictures that 6-10 degrees wouldn't be out there.

Manor, Barcelona Setup (2016).

[Xwang]

It's actually limited in the regulations because Mclaren did a really extreme version way before it ever got talked out much on here and in the press, so how far you can go depends a lot on the rest of your geometery.

Is this one related?
https://www.motorsport.com/f1/news/fia- ... 1/1384526/

It seems that the concept is the same, but now they seems to be able to obtain greater suspension lowering when on track than the one they obtain when tested stationary by FIA.
Is it so or is this a completely new "system"?

[Tim.Wright]

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

I said it in literally the first reply of the topic.

[PlatinumZealot]

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

I said it in literally the first reply of the topic.

You never explained it.
Over the years I know you are very knowlegabe and experienced in suspension system so obviously i won't discount what you say. I'm no fool.

[Tim.Wright]

I explained it.

Twice even...

[PlatinumZealot]

I explained it.

Twice even...

Do you think it has anything to do with the Mercedes "DAS" system?

[Tim.Wright]

I'm suspecting the primary use of the DAS is not for tyre scrub but to change the ride height down the straights for lower drag.

[PhillipM]

If the pushrod pickup is forward of the steering pivot it could well be doing both.