Independent single trailing arm suspension w/lateral links

[MRDAGERUS]

Hi,
Could anyone point me in the direction of some paper or analysis of the automotive rear suspension with the following characteristics:
- single independent longitudinal radius arm w/rigidly attached hub carrier (knuckle), (NOT 4-link!)
- upper and lower, un-equal length links, semi-perpendicular to the longitudinal axis of the car
- shock/spring inclined inboard 15 degrees and attached to the knuckle/lower link pivot point

This is a layout of the rear suspension on the Lotus Esprit cars.

As per OEM design, the upper and lower links are non-parallel, see picture.
The top link outboard mounting attachment/pivot to the hub carrier is located rearward of the lower link pivot.
The top link inboard pivot is attached to the chassis forward of the lower link center line, so they form an "X" in plan view.

To reduce bind,WHAT IF, we make the upper link "more parallel" to the lower link?
This can be accomplished by moving the upper link outboard pivot slightly forward and inboard one to the rear (no more than 1/2")?

MY CONCERN: By introducing above described changes, how the anti-squat geometry of the rear suspension may be affected?

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[MRDAGERUS]

Here is a diagram of the links in plan view. (The sketch proportions are exaggerated.)

My initial concern stemmed from the observation that making links "more parallel" reduces the forward reaction at the upper link hub carrier joint (R1<Ro) AND it probably affects rear Caster (?). Question is how...

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[GregLocock]

It's a very simple and effective rear suspension for a RWD car. I don't think diddling around with the plan view angles of the lateral arms will make much odds, particularly to the antisquat, which is controlled by the location of the longitudinal link to body location, and the contact patchwheel centre (late edit).

The Australian Ford Falcon Control Blade IRS has similar properties, albeit with another lateral link and a compliant longitudinal link.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[BrianPetersen]

I resorted to google images to get an understanding of the layout. The antisquat is going to be determined by what is happening in the side view. Because the torque to the hubs is coming through the drive shafts and doesn't involve a torque reaction through the suspension linkage (as it does with a live axle with a differential) the antisquat comes purely down to the fore/aft motion of the hub related to suspension movement. If the trailing arm pivot at the chassis end is higher than the wheel centerline then there will be a little bit of antisquat because a component of the force pushing "forward" on the hub ends up pushing "up" on the chassis-end pivot.

The toe behaviour with suspension movement away from whatever ride height has the lateral links horizontal could be interesting. Toe-out is bad ...

 

[MRDAGERUS]

Thank you for your input.

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