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Learning how spring and damper works from Live For Speed and Colcob's LFS Suspension Analyser
I post this here so we can learn together how to tweak our car better. Even though LFS and GT4 have differences, I think the basic priciple still the same.
You can download LFS here and Colcob's LFS Suspension Analyser here. LFS stands for Live for speed, a car game that is intended to be closer to simulation instead of arcade. Colcob's LFS Suspension Analyser is an excel file that can be use to analize LFS suspension setting.
For this experiment I use LFS alpha version S1H (at writing, newest is S2W), with XR GT car. XR GT info: Rear wheel drive, 1167kg (2572lbs), weight distribution: 54.0 F / 46.0 R. I intent to see what happen when we change spring rate and damper on LFS. As start see this video:
http://d.turboupload.com/d/1760304/LFS_various_spring_and_damper_change.avi.html
First, let's read some explanation about spring and damper:
"The roles of a spring and a damper are multiple. The role of a spring is to carry the static weight of a body and to isolate the chassis of the vehicle from the vibration caused by road excitation and driving manoeuvres, which affect the ride comfort (Sun et al. 2002). On the other hand, the role of the spring is to insulate the wheel from excitation caused by movements of the chassis, which for its affects the handling of the vehicle (Woods & Jawad 1999). The role of a damper is to suppress the vibrations of the chassis as well as the wheels."
Spring
Spring supposed to support the car's weight. A spring too weak can make the car bottoming out even on static position. Enough spring stiffness to prevent bottoming out during static condition can be not enough during other condition like when doing hard braking or cornering.
Colcob's LFS Suspension Analyser can help us see how spring change car behaviour. On suspension page we can see many usefull graph that help us know how the car will behave. For this post I only use some of them, namely Weight Transfer Analysis, Suspension Loads and Travel, and Damping Analysis. As starting point I use this setting:
I use high ride height and minimum spring rate, damper and anti roll.
This will have graphs like this:
On LFS it will look like this:
http://d.turboupload.com/d/1760619/0_lowest.avi.html
According to the Suspension Loads and Travel graph, the car have zero suspension travel left, the car is bottoming out.
To get more suspension travel, we need to increase spring stiffness. Since I use 0.2 m suspension travel, lets adjust to create 0.1 m suspension travel left. This is the new value:
This will have graphs like this:
On LFS it will look like this:
http://d.turboupload.com/d/1760641/1_spring_change.avi.html
It is interesting that in order to get the same suspension travel we need to use different spring stiffness for front and rear. The car has 54% weight at front distribution, heavier front end need stiffer spring rate to get equal suspension travel. If we look at Damping Analysis graph we can notice too that suspension frequency for front and rear now are same at 1.58Hz, where previously at 0.75Hz and 0.70Hz respectively. Also notice that by increasing spring stiffness we increase suspension frequency too. 1 Hz is 60 bounce a minute.
Now let see how the car behave if we add force to it. I change Longitudinal G to 1 (accelerate).
This will have graphs like this:
We now see that there is weight transfer (-2904.8) and there is a change in suspension travel. During this stage, if we use stiffer spring we will have increased weight transfer. For instance, if we increase the front spring rate to 50 it will change weight transfer to -3005.6.
Now let see we add another force to it. I change Lateral G to 1 (turning right) and change back front spring to 30.9.
This will have graphs like this:
We can see that now the left rear spring travel is bottoming out and right front is pulled out to max. We certainly don't want this to happen on track since this can result in sudden tire traction loss. In order to avoid that we can increase spring rate or add anti roll (to fight back lateral force).
Damper
Damper help spring isolating wheel and car body. They do it by stopping suspension movement.
As starting point I use this setting:
This will have graphs like this:
On LFS it will look like this:
http://d.turboupload.com/d/1760656/2_spring_no_damper.avi.html
According to the Damping Analysis graph, the car is currently under damping. So we need to increase the damper value. I adjust the damper to create 50% optimum damping for compression (bound) and optimally damper for rebound. This is the new value:
This will have graphs like this:
On LFS it will look like this:
http://d.turboupload.com/d/1760688/3_spring_have_damper.avi.html
We can notice that we need a stiffer damper to get the same optimum daping ratio for heavier part of the car (front end).
A change of spring stiffness require a change of damper stiffness, or it will change the damping ratio. For instance if we change spring stiffness to:
The car will now under damped.
This will have graphs like this:
On LFS it will look like this:
http://d.turboupload.com/d/1760692/4_stiff_low_damper.avi.html
In order to make the car have better damping, we should stiffen the damper. To make 50% optimum damping, this is the new setting needed:
This will have graphs like this:
On LFS it will look like this:
http://d.turboupload.com/d/1760697/5_stiff_stiff.avi.html
This is a long post, but I hope you all can understand easily. With the help of Colcob's LFS Suspension Analyser, we can use LFS to learn how spring and damper works. If you discouraged by my post very bad video quality, you can download LFS and have 3 car available to play for free. It is hard to find other game with a convenient drop button for our experimenting purposes
.
Some question may arise around compatibility between LFS suspension behaviour with that of GT4, lets discuss it. It would be cool if we can create spreadsheet like Colcob's one for GT4. But is it possible ?
I post this here so we can learn together how to tweak our car better. Even though LFS and GT4 have differences, I think the basic priciple still the same.
You can download LFS here and Colcob's LFS Suspension Analyser here. LFS stands for Live for speed, a car game that is intended to be closer to simulation instead of arcade. Colcob's LFS Suspension Analyser is an excel file that can be use to analize LFS suspension setting.
For this experiment I use LFS alpha version S1H (at writing, newest is S2W), with XR GT car. XR GT info: Rear wheel drive, 1167kg (2572lbs), weight distribution: 54.0 F / 46.0 R. I intent to see what happen when we change spring rate and damper on LFS. As start see this video:
http://d.turboupload.com/d/1760304/LFS_various_spring_and_damper_change.avi.html
First, let's read some explanation about spring and damper:
"The roles of a spring and a damper are multiple. The role of a spring is to carry the static weight of a body and to isolate the chassis of the vehicle from the vibration caused by road excitation and driving manoeuvres, which affect the ride comfort (Sun et al. 2002). On the other hand, the role of the spring is to insulate the wheel from excitation caused by movements of the chassis, which for its affects the handling of the vehicle (Woods & Jawad 1999). The role of a damper is to suppress the vibrations of the chassis as well as the wheels."
Spring
Spring supposed to support the car's weight. A spring too weak can make the car bottoming out even on static position. Enough spring stiffness to prevent bottoming out during static condition can be not enough during other condition like when doing hard braking or cornering.
Colcob's LFS Suspension Analyser can help us see how spring change car behaviour. On suspension page we can see many usefull graph that help us know how the car will behave. For this post I only use some of them, namely Weight Transfer Analysis, Suspension Loads and Travel, and Damping Analysis. As starting point I use this setting:
Code:
XR-GT SUSPENSION
=======================
Rear Suspension Travel (m) 0.2 Front Suspension Travel (m) 0.2
Rear Spring Rate (kN/m) 6.0 Front Spring Rate (kN/m) 6.0
Compression Damping (kNs/m) 0.6 Compression Damping (kNs/m) 0.6
Rebound Damping (kNs/m) 0.6 Rebound Damping (kNs/m) 0.6
Rear Anti-Roll (kN/m) 0.0 Front Anti-roll (kN/m) 0.0
Track (m) 1.51 Track (m) 1.51
Lateral G 0
Longitudinal G 0I use high ride height and minimum spring rate, damper and anti roll.
This will have graphs like this:
On LFS it will look like this:
http://d.turboupload.com/d/1760619/0_lowest.avi.html
According to the Suspension Loads and Travel graph, the car have zero suspension travel left, the car is bottoming out.
To get more suspension travel, we need to increase spring stiffness. Since I use 0.2 m suspension travel, lets adjust to create 0.1 m suspension travel left. This is the new value:
Code:
Rear Spring Rate (kN/m) 26.8 Front Spring Rate (kN/m) 30.9This will have graphs like this:
On LFS it will look like this:
http://d.turboupload.com/d/1760641/1_spring_change.avi.html
It is interesting that in order to get the same suspension travel we need to use different spring stiffness for front and rear. The car has 54% weight at front distribution, heavier front end need stiffer spring rate to get equal suspension travel. If we look at Damping Analysis graph we can notice too that suspension frequency for front and rear now are same at 1.58Hz, where previously at 0.75Hz and 0.70Hz respectively. Also notice that by increasing spring stiffness we increase suspension frequency too. 1 Hz is 60 bounce a minute.
Now let see how the car behave if we add force to it. I change Longitudinal G to 1 (accelerate).
Code:
Longitudinal G 1This will have graphs like this:
We now see that there is weight transfer (-2904.8) and there is a change in suspension travel. During this stage, if we use stiffer spring we will have increased weight transfer. For instance, if we increase the front spring rate to 50 it will change weight transfer to -3005.6.
Now let see we add another force to it. I change Lateral G to 1 (turning right) and change back front spring to 30.9.
Code:
Lateral G 1This will have graphs like this:
We can see that now the left rear spring travel is bottoming out and right front is pulled out to max. We certainly don't want this to happen on track since this can result in sudden tire traction loss. In order to avoid that we can increase spring rate or add anti roll (to fight back lateral force).
Damper
Damper help spring isolating wheel and car body. They do it by stopping suspension movement.
As starting point I use this setting:
Code:
XR-GT SUSPENSION
=======================
Rear Suspension Travel (m) 0.2 Front Suspension Travel (m) 0.2
Rear Spring Rate (kN/m) 26.8 Front Spring Rate (kN/m) 30.9
Compression Damping (kNs/m) 0.6 Compression Damping (kNs/m) 0.6
Rebound Damping (kNs/m) 0.6 Rebound Damping (kNs/m) 0.6
Rear Anti-Roll (kN/m) 0.0 Front Anti-roll (kN/m) 0.0
Track (m) 1.51 Track (m) 1.51
Lateral G 0
Longitudinal G 0This will have graphs like this:
On LFS it will look like this:
http://d.turboupload.com/d/1760656/2_spring_no_damper.avi.html
According to the Damping Analysis graph, the car is currently under damping. So we need to increase the damper value. I adjust the damper to create 50% optimum damping for compression (bound) and optimally damper for rebound. This is the new value:
Code:
Compression Damping (kNs/m) 2.1 Compression Damping (kNs/m) 2.5
Rebound Damping (kNs/m) 4.2 Rebound Damping (kNs/m) 4.8This will have graphs like this:
On LFS it will look like this:
http://d.turboupload.com/d/1760688/3_spring_have_damper.avi.html
We can notice that we need a stiffer damper to get the same optimum daping ratio for heavier part of the car (front end).
A change of spring stiffness require a change of damper stiffness, or it will change the damping ratio. For instance if we change spring stiffness to:
Code:
Rear Spring Rate (kN/m) 148.8 Front Spring Rate (kN/m) 148.8The car will now under damped.
This will have graphs like this:
On LFS it will look like this:
http://d.turboupload.com/d/1760692/4_stiff_low_damper.avi.html
In order to make the car have better damping, we should stiffen the damper. To make 50% optimum damping, this is the new setting needed:
Code:
Compression Damping (kNs/m) 5.1 Compression Damping (kNs/m) 5.4
Rebound Damping (kNs/m) 10.0 Rebound Damping (kNs/m) 10.7This will have graphs like this:
On LFS it will look like this:
http://d.turboupload.com/d/1760697/5_stiff_stiff.avi.html
This is a long post, but I hope you all can understand easily. With the help of Colcob's LFS Suspension Analyser, we can use LFS to learn how spring and damper works. If you discouraged by my post very bad video quality, you can download LFS and have 3 car available to play for free. It is hard to find other game with a convenient drop button for our experimenting purposes
.Some question may arise around compatibility between LFS suspension behaviour with that of GT4, lets discuss it. It would be cool if we can create spreadsheet like Colcob's one for GT4. But is it possible ?
