Rear MacPherson Strut

In a rear MacPherson struct suspension, the knuckle and wheel are located by a control arm, strut, and toe link. The coil spring is part of the strut and acts between the strut tube and the vehicle body. The spring’s axis typically is not parallel to the strut, but is offset to minimize the bending moment in the strut.

Model Use

The rear MacPherson struct suspension system can be used in either a rear half vehicle or a full vehicle models. The default geometry and mass approximate that of a passenger car or light truck, but 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 Center location as the center of gravity.
The lower control arm bushings are defined so their axes point at each other act like hinges on a door. If the front bushing is moved, both the front and rear bushing realign so they have the same axis of rotation.
When the Compliant option is set to No (via the Option menu on the System/Assembly panel in MotionView) the lower control arm bushings are replaced with a single revolute joint located at the front bushing, with its rotational axis directed along the line from the front bushing to the rear bushing.

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.

The image below shows the Model Browser view of the systems in a fully populated rear suspension model. The Rear macpherson susp system has five “child” systems.

Figure 2. Browser View of a Rear-Half-Vehicle Model Systems and Subsystems Employing a Rear MacPherson Strut Suspension

Attachments

Attachments determine how the rear MacPherson struct suspension connects to the rest of the vehicle. The rear MacPherson struct suspension has attachments for the lower control arm (LCA) and toe link. The strut rod attachment is set in the strut subsystem.


Entity	Attaches To
Lower Arm	Default: Sub-frame No subframe: Vehicle body No vehicle body: Ground
Toe Link	Default: Rear sub-frame No rear subframe: Vehicle body No vehicle body: Ground
Strut-rod	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 MacPherson struct suspension with a one-piece lower control arm:

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 MacPherson struct suspension is comprised of the bodies shown in the image below:

Note: Only right side bodies are shown (as the left side bodies are symmetrical), and the coil spring has been omitted from the image above for clarity.

The wheel hub body has no associated graphics and therefore is not visible in the image above.

Bushings and Joints

The table below describes the bodies, bushings, and joints for the rear MacPherson struct suspension:

Note: The table omits the joints internal to the strut.


Label	Type	Body 1	Body 2	Point	Notes
Lower Ball Joint	Spherical	Knuckle	Lower Control Arm	Lower Ball Joint
Wheel Spindle	Revolute	Wheel Hub	Knuckle	Wheel Center
Wheel Hub Fix Jt	Fixed Joint	Wheel	Wheel Hub	Wheel Center
LCA Front Bush	Bushing	Lower Control Arm	Subframe, Vehicle Body or Ground	LCA Front Bush	When the Compliant option is set to No, this bushing becomes a revolute joint.
LCA Rear Bush	Bushing	Lower Control Arm	Subframe, Vehicle Body or Ground	LCA Rear Bush	When the Compliant option is set to No, this bushing is deactivated.
Inner Toe Link Bush	Universal Joint	Toe Link	Subframe, Vehicle Body or Ground	Inner Toe Link Bush
Outer Toe Link Bush	Spherical Joint	Toe Link	Knuckle	Outer Toe Link Bush
Strut Tube Bottom Fixed Joint	Fixed Joint	Strut Tube	Knuckle	Strut Tube Lower
Strut Upper Bush	Universal Joint	Strut Tube	Vehicle Body	Strut Upper

The following image shows the location of the joints and bushings in the suspension:

Figure 5. Right Side Joints and Bushings - Rear MacPherson Strut Suspension

External Files

The jounce bumper curve data and the rebound bumper curve data files are stored in the vehicle library and are referred to by this model. A new file should be created and substituted for these files when actual data is available.

Similar Suspensions

Rear Twist Beam

Rear Solid Axle w/Leafspring