No influence in the lap simulation

Figure showing a 3D animation of a dynamic vehicle simulation with the car jumping with four wheels of the ground

The shockabsorber characteristics are only used in the 7 poster dynamic simulation. It does not have any influence in the lap simulation, because the lap simulation is a quasi-steady-state simulation driving on a flat surface.

A lap simulation on an uneven roadsurface would call for a driver model of the car, making it far more complex and subsequently slow.

Printscreen of the LapSim GUI showing shockabsorber graph

Defined by 4 speed points

Per axle you can edit 5 different shockabsorber characteristics, rebound and bounce.

In this manner it is easy to shift the individual characteristics. This can be done by selecting the position in the edit boxes or by clicking on the respective characteristic in the figure.

Each characteristic is defined by the shockabsorber forces at 4 (adjustable) speed points. The chosen speed points are the same for the front and rear shockabsorbers.

The forces at these speed points can be adjusted in the edit boxes or by drag and drop in the figure, with the left mouse button. Just click on the point you want to adjust with the left mouse button, move it and release.

Nothing 'critical' about critical damping

Printscreen of the LapSim GUI showing the top part of the shockabsorber characteristic where the critical damping is plotted as a grey area

In the figure the critical damping is also plotted as a dark grey area. This is the critical damping related to the sprung vehicle mass and the main spring stiffness.

Please be aware that critical damping is just a name, similar like eigen frequency. It supplies a feedback about the amount of damping of a mass spring system, regardless of the used mass and spring stiffness.

In the figure you see a typical example of a shockabsorber characteristic with a shim package which generates a degressive characteristic in combination with a bleed valve used for the adjustment. In the stiffer positions (bleed valve closed), the shockabsorber is over critical in low speed, giving good body control and becomes sub critical at higher speeds to supply compliance over road unevenesses.

Additional support to the vehicle body

Printscreen of the LapSim GUI showing the editboxes where shockabsorber gas pressure and ratio can be specified

In addition, one can add a (constant) gas pressure force to the damper. This supplies additional support to the vehicle body.

The last item to be specified is the ratio between shockabsorber travel and suspension travel. A ratio bigger than 1 means the shockabsorber has a longer travel than the suspension.