double triangulated 4 link for offroad / street rig

[Kail]

I wanted to discuss double triangulated 4link for front and rear on my bronco.

My background is hot rod fabrication. It is what I do for a living. I am fairly new to off road.

I was reading how a double triangulated 4 link allows more travel with less bind then a standard triangulated 4link. It would allow me to use a bushing on the frame side and heim joints or johnny joints on the axel side. To allow a slightly less harsh ride.
So how does this setup fair on the street / freeway? Is there a build on here that has used this?

I want to build a well rounded adapt to all truck. I don't want to spend to much on parts especially since I can make nearly everything my self. I have very good fab skills, cad capabilities and access to a cnc plasma cutter.
I have done several normal triangulated 4links on cars with great success. And I am looking forward to this new challenge.

Thanks, Kail

 

[Quick & Dirty]

Triangulating the lowers alters the roll axis geometry and amount of roll steer. The roll axis is from the intersection of the lowers to the intersection of the uppers. Triangulating the lowers brings the intersection closer and lower.

A proper four link shouldn't bind if the lowers are triangulated or not.

A triangulated 4 link on the front needs hydraulic steering. A regular drag link will move in a different arc causing bump steer. If you are keeping regular steering, then go with a 3 link and panhard bar.

 

[Dude seriously]

Triangulating the lowers alters the roll axis geometry and amount of roll steer. The roll axis is from the intersection of the lowers to the intersection of the uppers. Triangulating the lowers brings the intersection closer and lower.

If I read that right, then increasing the distance (I know this is next to impossible with the narrow Bronco frame) left to right between the upper and lower links will increase the roll resistance?

In Washington state I think there is a law on the books that requires anti-roll bars on coil sprung rear suspensions. But I have been too lazy to look it up. It is much easier just to repeat silly things I’ve heard.

 

[Quick & Dirty]

If I read that right, then increasing the distance (I know this is next to impossible with the narrow Bronco frame) left to right between the upper and lower links will increase the roll resistance?

It changes roll steer, no effect on roll resistance.

As the axle articulates, or the body rolls side to side, the wheels move forward and back, as well as up and down. The more the wheels move forward/backward the greater the steering effect. Like a skateboard steers by leaning side to side. Ideally you want your suspension design to minimize this effect, so cornering or wind gusts don't make it squirrel all over the road.

 

[Dude seriously]

It changes roll steer, no effect on roll resistance.

Ok, I followed that. Thanks.

And I also learned I have much to learn before tackling a 4 link.

 

[Kail]

Triangulating the lowers alters the roll axis geometry and amount of roll steer. The roll axis is from the intersection of the lowers to the intersection of the uppers. Triangulating the lowers brings the intersection closer and lower.

A proper four link shouldn't bind if the lowers are triangulated or not.

A triangulated 4 link on the front needs hydraulic steering. A regular drag link will move in a different arc causing bump steer. If you are keeping regular steering, then go with a 3 link and panhard bar.

So to make sure I am clear. The panhard makes it so the axle follows the same arc as the steering eliminating bump steer.

 

[Quick & Dirty]

The rock crawlers call it flex steer.
Here is a example of a poor design. Notice how the rear axle is twisted up driving the rear to the side.

Here is a pic of how roll axis is layed out. Intersection of lowers to intersection of uppers (B to A). Ideally the roll axis should be near flat to minimize roll/flex steer.

 

[Quick & Dirty]

So to make sure I am clear. The panhard makes it so the axle follows the same arc as the steering eliminating bump steer.

Yes. You want the drag link and panhard parallel so the axle and steering linkage swing in the same arc.

 

[Kail]

Diagram clarified a good deal thank you

 

[Kail]

So at this point I am thinking 3 link front and standard triangulated 4 link in rear

 

[Quick & Dirty]

Some triangulation of the lowers is generally good, depending on how far from horizontal they are.

Here is an online 4 link calculator; Punch your design in and see how the geometry works.
http://mysite.verizon.net/triaged/4linkcalcv15html/index.html

This thread on pirate has downloadable files if you have Excel on your computer.
http://www.pirate4x4.com/forum/showthread.php?t=204893

 

[Kail]

Some triangulation of the lowers is generally good, depending on how far from horizontal they are.

Here is an online 4 link calculator; Punch your design in and see how the geometry works.
http://mysite.verizon.net/triaged/4linkcalcv15html/index.html

This thread on pirate has downloadable files if you have Excel on your computer.
http://www.pirate4x4.com/forum/showthread.php?t=204893

That link just made you my new best friend. ;D