Rear Trailing Arm

The rear trailing arm suspension is an independent rear suspension system in which the wheel is attached to the trailing end of an arm that pivots on a bushing (this allows the wheel to move up and down). The suspension design requires a trailing arm that is flexible in order to work. A flexbody is normally used to simulate the trailing arm body.



Figure 1. Rear Trailing Arm Suspension

Model Use

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


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

Attachments

Attachments determine how the suspension system attaches to the remainder of the vehicle system. The rear trailing arm suspension includes attachments for the trailing arm, the upper link, and the lower link:
Entity Attaches To
Trailing Arm, Upper Link, Lower Links Default: Sub-frame

No subframe: 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 in the suspension. The image below shows the principal points for the rear trailing arm suspension:


Figure 4. Right Side Principal Points – Rear Trailing Arm 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 trailing arm suspension is comprised of the bodies shown in the image below:


Figure 5. Right Side Bodies – Rear Trailing Arm Suspension
Note:
  • The wheel hub body has no associated graphics and therefore is not visible in the image above.
  • 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.

Bushings and Joints

The table below describes the bodies, bushings, and joints for the rear trailing arm suspension:
Note: The table omits the left side joints for clarity.
Label Type Body 1 Body 2 Point
Wheel Spindle Joint Revolute Wheel Hub Trailing Arm Wheel Center
Wheel Hub Fixed Joint Fixed Wheel Wheel Hub Wheel Center
Trailing Arm Bush Ball Trailing Arm Vehicle Body Trailing Arm Bush
Lower Link Outer Bush Ball Lower Lateral Link Trailing Arm Lower Link Outer Bush
Upper Link Outer Bush Ball Upper Lateral Link Trailing Arm Upper Link Outer Bush
Lower Link Inner Bush Universal Lower Lateral Link Ground Body Lower Link Inner Busy
Upper Link Inner Bush Universal Upper Lateral Link Ground Body Upper Link Inner Bush
The following image shows the location of the joints and bushings in the suspension:


Figure 6. Right Side Joints and Bushings: Rear Trailing Arm Suspension