Rear Quad-Link

The rear quad-link suspension derives its name from the fact that it is made up of four links. The rear quad-link suspension contains three individual links in tension compression and a strut. This suspension offers flexibility to the designer when determining individual handling parameters, and it is generally used on cars and light trucks.



In conventional designs, the strut is connected to the knuckle and is load bearing (and carries most of the load). The links on the other hand, help in determining suspension geometry and carry much less load.

Figure 1. Rear Quad-link Suspension

Model Use

The rear quad-link suspension system can be used in either a half car or a full vehicle analysis. The default geometry and mass is that of a passenger car or light truck, however the model and data can be revised to reflect any size vehicle, from a large truck to a scale model car.
Note:
  • The wheel body represents the mass and inertia of the tire and the rim.
  • The wheel hub body represents the mass and inertia of other rotating bodies such as a brake rotor, but not the half-shafts if the suspension is driven. The wheel hub and brake rotor have no associated graphics.
  • The wheel and wheel hub parts use the Wheel CG location as the center of gravity.
  • Each body’s Center of Gravity (CG) is estimated from the body’s geometry. The formulas are coded into the point panel and can be seen via the graphical user interface. If more accurate CG locations are available they should be used.
Tip:
  • A wide variety of combinations of suspensions and subsystems can be built using the Assembly Wizard. You are encouraged to build systems and understand the resulting model using the graphical user interface.

    When building a new suspension model, build the model with all of the optional systems (stabilizer bar, etc) included in the model. Immediately turn off the systems using the Project Browser and run an analysis on the base suspension to ensure it solves properly. As data becomes available for the optional systems; activate those systems and populate them with data.



Figure 2. Rear-Half-Vehicle Model Employing a Quad-link Suspension
The image below shows the Model Browser view of the systems in a fully populated rear suspension model. The Rear quadlink suspension system has five “child” systems.


Figure 3. Browser View of a Rear-Half-Vehicle Model Systems and Subsystems Employing a Quad-link Suspension

Attachments

Attachments determine how the suspension system connects to the rest of the vehicle. The rear quad-link suspension includes attachments for the front lower link, rear lower link, and the tension strut link:
Entity Attaches To
Front and Rear Lower Links Default: Sub-frame

No subframe: Vehicle body

No vehicle body: Ground
Tension Strut Default: Vehicle body

No vehicle body: Ground
You can also set any attachments using the Attachment Wizard, or by selecting the subsystem in the Model Browser and revising the attachments on the System/Assembly panel.

Points

Points locate the joints and bushings that connect the suspension bodies to one another. The image below shows the principal points for the rear quad-link suspension:


Figure 4. Right Side Principal Points – Rear Multi-link Suspension
Note: The image above omits the left side of the suspension, points locating body centers of mass, and points that locate the optional subsystems (springs, dampers, bump stops and stabilizer bar) for clarity.

Bodies

The rear quad-link suspension is comprised of the bodies shown in the image below:


Figure 5. Right Side Bodies – Rear Quad-link Suspension
Note:
  • The wheel hub body has no associated graphics and therefore is not visible in the image above.
  • Optional subsystems may add bodies to the suspension, for example the shock absorber adds two bodies: a shock rod and shock tube. Any bodies added by optional subsystems have been omitted from the image above for clarity.

Bushings and Joints

The table below describes the bodies, bushings, and joints for the rear quad-link suspension:
Note: The table omits the left side joints for clarity.
Label Type Body 1 Body 2 Point Notes
Front Outer Bush Spherical Front Lower Link Knuckle Front Lower Ball Joint When the Compliant option is set to No, the compliance for this joint is turned "Off" and behaves as a pure spherical joint.
Rear Outer Bush Spherical Rear Lower Link Knuckle Rear Lower Ball Joint When the Compliant option is set to No, the compliance for this joint is turned "Off" and behaves as a pure spherical joint.
Tension Strut Front Bush Universal Tension Strut Subframe, Vehicle Body or Ground Front Tension Strut Ball When the Compliant option is set to No, the compliance for this joint is turned "Off" and behaves as a pure spherical joint.
Rear Tension Strut Bush Universal Tension Strut Knuckle Rear Tension Strut Ball When the Compliant option is set to No, the compliance for this joint is turned "Off" and behaves as a pure spherical joint.
Wheel Spindle Revolute Wheel Hub Knuckle Wheel Center  
Wheel Hub

Fix Jt

 Fixed Joint Wheel Wheel Hub Wheel Center When the Spindle compliance option is set to Yes, the joint type changes to universal.
Lower Front Bush Universal Front Lower Link Subframe, Vehicle Body or Ground Front Lower Bush When the Compliant option is set to No, this joint compliance is turned "Off" and behaves as a pure universal joint.
Rear Lower Bush Universal Rear Lower Link Subframe, Vehicle Body or Ground Rear Lower Bush When the Compliant option is set to No, this joint compliance is turned "Off" and behaves as a pure universal joint.
The following image shows the location of the joints and bushings in the suspension:


Figure 6. Right Side Joints and Bushings: Rear Quad-link Suspension

Similar Suspensions

Front SLA (1pc LCA)

Rear SLA (1pc LCA)

Front Multi-Link

Rear Multi-Link

Front Multi-Link