critique these lower links

[jesusgatos]

I'm designing these lower links for this project. They're kind of unique in that the lower shock mounts are 2" ABOVE the centerline between the pivots. I've designed them this way for improved ground clearance because this is a dual-purpose 4WD vehicle. After doing a bunch of research (here and here), I've decided to use stabilizer links like these to keep the links from flopping around(this image is of a vehicle designed/built by Drew at Poly Performance); except my stabilizer links will be coming from the center of the vehicle out to the links. Target weight for the vehicle is under 4000lbs, but it will have a functional bed and I will carry heavy loads on some of our off-road trips (maybe two dirt bikes plus gear).

The lower links I've designed are 47.75" long, and the suspension will cycle about 26" of travel using 16" coilovers and 18" bypass shocks (mounted 28" & 34" out on the links from the chassis-pivot). I'm planning on using 1" uniballs up front and 1 1/8" heim-joints in the rear. The tubing is 2" x .250-wall. The inner side plates are 3/16" and the outer side plates are 1/8". The interior gussets and top plates are also 1/8". The shock cutouts are based on the actual clearances that I think I'll need, taken from 3D models simulating the shock positions at full extension and full compression. I shouldn't need to provide for more than a few degrees of misalignment from side-to-side. SolidWorks tells me that each link would weight 32.3lbs.

I've included some links to the CAD files (native SW08 assembly file & IGS) in case anyone wants to run them through any type of FEA. I have a copy of COSMOSworks, but have not really gotten that far yet (still getting a handle on SW). I've also included an eDrawing file for those of you that don't use CAD programs, but might want to download a 3D file to check out. You can download a free copy of eDrawings here.







FILES TO DOWNLOAD

SolidWorks (08) assembly

IGS file

eDrawing

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[DUMP!]

Hey Jesse,

Two things,

First, even if you are only using a 35 inch tall tire your shock mounts will live within the radius of that tire so is there really a need for all the extra links for only 2.0 inches of additional ground clearance that should pretty much be covered by the tire dia anyway??

Second, 3/16 plate with a 1/8th doubler seams a bit over kill. I realize you're probably shooting for durability and less maintaince but still. I would think making the main plate 1/8 with a .090 doublers would be more then adequate.

Just my two cents. Solidworks skills seam to be progressing well.

Dump

[Ramsey_ElWardani]

Remove the lower shock uniballs and use solid spacers that will keep the links from flopping. Works great in several apps that we all see at the races.

[jesusgatos]

Solidworks skills seam to be progressing well.

Well, the SolidWorks tutorial that you took me through was one of the things that really helped me get started in SW. So, thanks again.

First, even if you are only using a 35 inch tall tire your shock mounts will live within the radius of that tire so is there really a need for all the extra links for only 2.0 inches of additional ground clearance that should pretty much be covered by the tire dia anyway??

Yeah, I tend to think so. I want this truck to site relatively low for a trail vehicle and I'm sure it'll be sliding and dragging over a lot of stuff as-is. With the wobble-problem solved, I really don't see much of a downside. Do you?

Second, 3/16 plate with a 1/8th doubler seams a bit over kill. I realize you're probably shooting for durability and less maintaince but still. I would think making the main plate 1/8 with a .090 doublers would be more then adequate.

Really? Damn, Drew at Poly just responded to the link that I posted to this thread over on Pirate by saying that his links are pretty similar to mine and they've bent. I wish I knew how to use COSMOSworks. But the other thing that's keeping me from analyzing the links from that angle is that I don't really have any idea what type of forces are involved (at least when it comes to putting them into numbers and terms that I could evaluate mathmatically).

Remove the lower shock uniballs and use solid spacers that will keep the links from flopping. Works great in several apps that we all see at the races.

Chad Ragland's truck is set up like that, right? That is something I considered, but I decided that I didn't want the lower shock mounts to be the only things keeping the lower links from flopping around. Mostly because on trails it's not unusual to drag a link over something and it was a side-load, that would be pretty hard on the shocks. Thanks for the suggestion though!

[partybarge_pilot]

Really? Damn, Drew at Poly just responded to the link that I posted to this thread over on Pirate by saying that his links are pretty similar to mine and they've bent.

I have seen thin cross section TA's like those bend from side impacts, I.E. sliding off a corner and using your TA as a grader blade. The canoe style hold up to that much better.

[jesusgatos]

I redesigned the links based on the feedback I got here and over on Pirate. I was able to keep the weight almost exactly the same (32.13lbs) and I think they're a lot stronger now. I'll still probably end up designing another set of links entirely out of sheetmetal (like the ones Triage designed/posted), but I wanted to try to 'save' this design first.

I haven't put much time into anything more than roughing-out the shape on this version. I'd obviously gusset the uniball cup, but I'd like to talk about where I might be able to add/remove material to maximize strength and minimize weight. All of the sheetmetal is now 1/8" and I'm thinking I could probably punch some holes in the inside side plates, which still run the entire length of the boxed section.

If anybody wants to download the CAD files to play with, I've posted links below.





FILES TO DOWNLOAD

SolidWorks (08) Assembly

IGS file

eDrawing

[1450-ranger]

I' recommend more cross section near the ends

[jesusgatos]

I just realized I didn't post a cross-section of the links, but the vertical side plates (the lower shock mounts) still run the entire length of the boxed section, and the internal gussets between the shocks extend all the way out to the outer side plates. I'm figuring that I'd just make them interlocking pieces. If what I'm saying isnt making sense, please just download the eDrawing file. You can create a cross-section view really easily to see what I mean.

[Mark Newhan]

Chad Ragland's truck is set up like that, right? That is something I considered, but I decided that I didn't want the lower shock mounts to be the only things keeping the lower links from flopping around. Mostly because on trails it's not unusual to drag a link over something and it was a side-load, that would be pretty hard on the shocks. Thanks for the suggestion though![/QUOTE]

My prerunner has the same style ( with delrin bushings at the lower shock eye), I dont think you will have a side load problem. There are lots of trucks built like this in the last several years.

[jesusgatos]

I' recommend more cross section near the bung

Why? To keep the link from bending or to keep the uniball cup from separating from the tubing (2" x .25-wall)? I would use some type of wrap-around gusset to keep it from pulling apart.