Link Suspensions - Setup / Design - Discuss

Yay!Gurrr

Yay!Gurrr

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Link Suspensions - Setup / Design - Discuss

I know there are a few seasoned link users and builders here and it gets discussed from time to time. I know peoples, ideas and thoughts change over time and as projects grow/change. SO before I run off to Pirate and entertain opinions of the e-experts there, I figured I'd see what you guys have to say....

While my question pertains to my project, this discussion can go where ever it needs to. Background on my project: I'm building a small 2 seater, 4cyl, 36" tires, ~100" WB, 16" air shocks, rear engine buggy. toy axles, front steer only, full hydro. Suspension design/placement is being considered a high priority.

I know lots of people have opinions of what works and doesn't with many opinions contradicting each other. That's fine I'd still like to hear the discussions.

I understand the basics, but if someone wants to post some general points that's fine too..

Rear - I'm considering a wishbone upper. Standard lowers on the sides.
* Lowers - I'm really not confined to a length but really don't see the benefit (for me) to run more than 36" lowers. (I'll be using heims vs johnny/cartridge joints)
* I think my engine will be pulled forward enough to make the wish bone doable if I'll use 2 triangulated uppers centered on the diff.
* Based on my PBB readings that say.....
[On a dual-tri (or wishbone upper):
1) You can tune the height and slope of your roll axis by changing the upper axle mounts
2) you can change your IC by changing the upper frame mounts. Changing one doesn't have much affect on the other.]

From reading, I like this setup for simplicity and tunability
That said, how are you guys that have a wishbone setup building the link ? Large heil, laid flat ? vertical? Is it holding up well? working as planned?

Moving on...
WTF is DSI/AMJ who/what is it referencing ? I have read so much I've forgotten a few things but see this refered to alot on Pbb.

Front - I plan to run longfields so that will give me 45deg turning up front. So the lowers will be angled in as needed to clear the tires. I haven't spent much time trying to visualize much beyond this... I'm not sure what design makes sense for a rear engine setup.. Ideas?


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This weekend I will get my wheels mounted up and be able to put some scale to my parts laying around.
I also hope to get my engine setting on my frame dolly which I will be building off of. The top is 12.5" which is where I want to be sitting at full compression. (shooting for 18" belly @ ride height)...
 
Dono you tell me :) My reading lead me to believe the roll center could be more easily determined/tuned with the wishbone. Will triangulated uppers near the center be close enough to fall into the same category for planing purposes. In my mind even 12" horizontal/width separating to 2 uppers would be a significant difference.
 
on the lowers, make sure that they are parallel or angled at the opposite angle as the uppers...

Also, you typically want to keep your AS/SD ~80%... a lower number doesnt hurt, but the closer to get the 100% the flatter your suspension will be (no dive on braking, & lifting on acceleration)... IIRC, most factory suspensions are 60% or less, mainly to give the feel of accel/decelleration...

you could also consider running a 3 link & panhard upfront to help clear steering...
 
yager said:
Dono you tell me :) My reading lead me to believe the roll center could be more easily determined/tuned with the wishbone. Will triangulated uppers near the center be close enough to fall into the same category for planing purposes. In my mind even 12" horizontal/width separating to 2 uppers would be a significant difference.
Click to expand...

This would raise the roll center, assuming the lower's horizontal spacing remained constant... a higher roll center isn't nessecarily a bad thing though... if it is at the right height, articulation wouldn't affect body roll...
 
yager said:
Dono you tell me :) My reading lead me to believe the roll center could be more easily determined/tuned with the wishbone. Will triangulated uppers near the center be close enough to fall into the same category for planing purposes. In my mind even 12" horizontal/width separating to 2 uppers would be a significant difference.
Click to expand...

I don't see as many wishbone uppers as I used to.

The link gurus on here may have something to correct or add, but I think a wishbone places all the upper link stress on 1 joint versus 2. This would require a super beefy joint. In addition, I think forces are enacted on the single axle-end joint that its not really designed for. i.e., side loads on the joint/joint body, causing pre-mature failure usually resulting in the body breaking at the threads.

I'm no engineer or guru, but seeing the posts in the past and planning my suspension, I've thought about it and it makes sense. I have yet to run my link setup so I may end up eating my words. :)

I like a non-wishbone setup as I can keep all the joints the same and if a link breaks its still somewhat possible to limp off the trail. With a broken wishbone I think it would be much more difficult. I designed my links front and rear to be very close to the same so I can keep 1 or 2 spares with me in case of an emergency where I needed one. More universal.
 
Yes I understand radial loading vs axial loading of the heims depending on how its used/mounted. I think simply stepping up a size or 2 for the heim and/or laying it flat would solve that issue. (keep in mind this thing with be <3000#)

Depending on how far forward I can position the engine straight links might fit, will have more figured out this weekend...
 
On a wishbone, regardless of what joint is used, it's best to mount the joint with the bolt vertical. Use no less than a 3/4 grade 8 bolt.
Try to stick with 4 links if you can.
 
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