Why a sway bar, heave spring, and wheel springs?

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jcorsico
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Why a sway bar, heave spring, and wheel springs?

Post Fri May 10, 2019 12:16 am

Aren't some of these springs redundant?

The sway bar adds increasing force in roll. The heave spring adds increasing force in pitch. Why do you need individual wheel springs then? Each wheel spring adds force in both roll and pitch. Can't you ditch the wheel springs and just run a heave spring and swaybar?

I know people have done that in the past. But why didn't it work?

roy928tt
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Re: Why a sway bar, heave spring, and wheel springs?

Post Fri May 10, 2019 9:49 am

Because a sway bar/ anti roll bar is not a spring, it holds nothing up, it only transfers force from one side to the other, typically augmenting one "wheel spring" by connecting it to the one on the other side. Thereby reducing the independence of each wheel and inducing roll dive.

Rest assured greater minds than yours or mine have come to where we are in F1.

jcorsico
jcorsico
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Re: Why a sway bar, heave spring, and wheel springs?

Post Sat May 11, 2019 9:26 pm

roy928tt wrote:
Fri May 10, 2019 9:49 am
Because a sway bar/ anti roll bar is not a spring, it holds nothing up, it only transfers force from one side to the other, typically augmenting one "wheel spring" by connecting it to the one on the other side. Thereby reducing the independence of each wheel and inducing roll dive.

Rest assured greater minds than yours or mine have come to where we are in F1.
You clearly have no idea what a heave spring is. Greater minds than yours, indeed!

roy928tt
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Re: Why a sway bar, heave spring, and wheel springs?

Post Sat May 11, 2019 11:09 pm

Steady up Sunshine.

You asked, why have wheel springs when you have a heave spring, and I tried to illustrate that without wheel springs you would have no roll stiffness. The car would have resistance to pitch but no resistance to roll....er, that would be wrong also...the sway bar would try to pull the opposite wheel upward and the car would pitch onto the heave spring.

Doesn't feel right though, a sway bar removes the independence from your wheels, so doesn't want to be too stiff, heave spring only operates under brakes or acceleration when both wheels on one axle are subject to the same forces and wheel springs are independent of other wheels so give roll stiffness and bump stiffness.

A good illustration of the effectiveness of current suspension is "that photo" of Nico Rosberg Peter Fox Degner Curve Japanese GP 2016. To achieve that degree of articulation and independence whilst also maintaining a solid platform for the aero to work on at high speed is the work of genius.

Just_a_fan
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Re: Why a sway bar, heave spring, and wheel springs?

Post Sat May 11, 2019 11:35 pm

The anti roll bar (sway bar) resists roll - it only works in roll, the heave spring resists heave (pitch) - it only works in the longitudinal direction, and the individual wheel springs keep the individual tyres in contact with the tarmac in response to individual bumps.

It's not difficult.

The trick is designing and tuning the system so that each only does its job and doesn't affect the other bits. Whilst each wheel spring will be affected by roll and heave, the aim is to make the roll and heave elements effective enough so that the wheel springs don't get involved and are free to deal with each wheel's individual motion.
Turbo says "Dumpster sounds so much more classy. It's the diamond of the cesspools." oh, and "The Dutch fans are drunk. Maybe"

PhillipM
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Re: Why a sway bar, heave spring, and wheel springs?

Post Sat May 11, 2019 11:48 pm

jcorsico wrote:
Fri May 10, 2019 12:16 am
Aren't some of these springs redundant?

The sway bar adds increasing force in roll. The heave spring adds increasing force in pitch. Why do you need individual wheel springs then? Each wheel spring adds force in both roll and pitch. Can't you ditch the wheel springs and just run a heave spring and swaybar?

I know people have done that in the past. But why didn't it work?
Some cars do just have heave springs and an arb. Problem is you have to change both then when you want to change the individual wheel rate so it hurts quick adjustments at the track

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JordanMugen
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Re: Why a sway bar, heave spring, and wheel springs?

Post Sun May 12, 2019 4:01 pm

Just_a_fan wrote:
Sat May 11, 2019 11:35 pm
The anti roll bar (sway bar) resists roll - it only works in roll, the heave spring resists heave (pitch) - it only works in the longitudinal direction, and the individual wheel springs keep the individual tyres in contact with the tarmac in response to individual bumps.
So as Roy928TT said, the car would simply fall on the ground if it didn't have wheel springs to hold it up, as you would intuitively expect? :wink:

Xwang
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Re: Why a sway bar, heave spring, and wheel springs?

Post Sun May 12, 2019 4:11 pm

I think that the presence of the heave spring will avoid the car to fall on the ground.
When rolling the sway bar tries to pull the opposite wheel upward with the effect of compressing the heave spring more so the car will reduce its ground height in roll, but it will not fall on the ground.

jcorsico
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Re: Why a sway bar, heave spring, and wheel springs?

Post Tue May 14, 2019 7:54 pm

PhillipM wrote:
Sat May 11, 2019 11:48 pm
Some cars do just have heave springs and an arb. Problem is you have to change both then when you want to change the individual wheel rate so it hurts quick adjustments at the track
Thank you Phillip.

There are only two types of motion of the chassis - either roll or pitch. The anti-roll bar generates a spring force in roll. The heave spring generates a spring force in pitch. The wheel rate is simply a function of those two spring forces.

I guess you are saying that if you have a car with just an ARB and a heave spring, and you want to increase both the roll stiffness and the heave stiffness at the same time, then you have to change both the anti-roll bar and the heave spring (two springs). Versus, if you had a car with wheel springs, ARB and heave spring, you'd have to change each wheel spring (two springs?). :)

jcorsico
jcorsico
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Re: Why a sway bar, heave spring, and wheel springs?

Post Tue May 14, 2019 7:56 pm

roy928tt wrote:
Sat May 11, 2019 11:09 pm
Steady up Sunshine.

You asked, why have wheel springs when you have a heave spring, and I tried to illustrate that without wheel springs you would have no roll stiffness. The car would have resistance to pitch but no resistance to roll....er, that would be wrong also...the sway bar would try to pull the opposite wheel upward and the car would pitch onto the heave spring.

Doesn't feel right though, a sway bar removes the independence from your wheels, so doesn't want to be too stiff, heave spring only operates under brakes or acceleration when both wheels on one axle are subject to the same forces and wheel springs are independent of other wheels so give roll stiffness and bump stiffness.

A good illustration of the effectiveness of current suspension is "that photo" of Nico Rosberg Peter Fox Degner Curve Japanese GP 2016. To achieve that degree of articulation and independence whilst also maintaining a solid platform for the aero to work on at high speed is the work of genius.
Thank you for trying to be helpful, but you're still very confused!

jcorsico
jcorsico
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Location: New York, NY

Re: Why a sway bar, heave spring, and wheel springs?

Post Tue May 14, 2019 8:00 pm

Just_a_fan wrote:
Sat May 11, 2019 11:35 pm
It's not difficult.
Thank you too for attempting to be helpful, but you don't understand how the heave spring and roll bars interact either.

PhillipM
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Re: Why a sway bar, heave spring, and wheel springs?

Post Tue May 14, 2019 8:11 pm

jcorsico wrote:
Tue May 14, 2019 7:54 pm
I guess you are saying that if you have a car with just an ARB and a heave spring, and you want to increase both the roll stiffness and the heave stiffness at the same time, then you have to change both the anti-roll bar and the heave spring (two springs). Versus, if you had a car with wheel springs, ARB and heave spring, you'd have to change each wheel spring (two springs?). :)
Pretty much, problem is if you want to change the heave spring it's generally a stacked disc setup on the 3rd damper and tied into the inerter rates - so you need to change the whole lot to a matching set.
Wheel springs are generally just two torsion bars that can be slid out after undoing 2 bolts and changed in minutes.

Greg Locock
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Re: Why a sway bar, heave spring, and wheel springs?

Post Wed May 15, 2019 4:50 am

"There are only two types of motion of the chassis - either roll or pitch"

Oh. is bounce a figment of my imagination? No.

Roll is RX, pitch is RY and bounce is Z in a commonly used coordinate system. Using these three unique degrees of freedom and the track and the axle distance from the CG you can work out how much each wheel has moved relative to the body.

roy928tt
roy928tt
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Re: Why a sway bar, heave spring, and wheel springs?

Post Wed May 15, 2019 11:37 am

Happy to learn.

So, have we come to the conclusion that having all 3 "springs" is beneficial?

jcorsico
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Location: New York, NY

Re: Why a sway bar, heave spring, and wheel springs?

Post Wed May 15, 2019 3:29 pm

PhillipM wrote:
Tue May 14, 2019 8:11 pm
Pretty much, problem is if you want to change the heave spring it's generally a stacked disc setup on the 3rd damper and tied into the inerter rates - so you need to change the whole lot to a matching set.
Wheel springs are generally just two torsion bars that can be slid out after undoing 2 bolts and changed in minutes.
Ah, got it. Thank you.