It's An OCD Thing, You Wouldn't Understand

[inVERt'D]

You made a lot of work of it though.

Oh, and you ain't seen nothin' yet

[inVERt'D]

Lower control arm axle bracket mockup. I wanted to use 3/8", but didn't have enough. What I did have was some 1/2"x3" strap. Mitering these was a fair amount of work. I couldn't do 1/2" thick brackets without a good, properly beveled miter. I'm not that sort of redneck.



Welding the tabs and gussets on. Some triangular gussets are planned for the inboard sides of the tabs. Again, just doing the tabs pretty much took all day. The gussets were melted on a week later.
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[brokenujoint]

Thanks a bunch, Art! I did my very best, and was very careful. Not even OEM trannies are indexed perfectly. Time will tell if it's good enough but my intuition tells me that as long as I'm not dumping the clutch at 10K RPMs I'll be just fine. Maybe I should have Curtis take it for a spin? Anyway, so far so good. Hopefully by the time I put 20K on it, redneckin' will be an option, not a necessity.

Art didn't say 20,000 miles, he said 20.000... Thats only 20 miles.... You probably passed the redneck challenge already...

[inVERt'D]

Good catch! And here I was worried about that cheesy $5.00 clutch alignment tool I used.

[inVERt'D]

The ACME ARSS - Adjustable Redneck Suspension System

Back in May/ June 2011 was getting into the rear 4-link crossmember. By then I had spent a fair amount of time doing research, playing with 4-link calculators, and laying under my Jeep staring off into space. At one time, I had planned to tackle my suspension in a git'r done fashion. But things had changed. My life had changed. I had changed.

What you're about to see is going to be a little different. I did it to make me happy. Basically, no single suspension geometry configuration could satisfy what I wanted to do with my Jeep.

If you are a non-reader, please feel free to skip to the photos.

Most of us who tinker with vehicular suspensions don't really understand some of the important implications of our modifications. Thing is, changing things can have side-effects which may be unforeseen and undesirable. For example, a lot of hotrodders and tuners like to lower their cars for looks, and they think, for better cornering performance. The thing is, lowering a linked vehicle (including those with 4-links, A-arms, MacPherson suspensions, etc.) is likely to increase the amount of body roll, rather than stabilize it. This will happen if the suspension roll-center is lowered more than the vehicle's center of gravity. This is due to simple physics. There is an invisible lever-arm between the roll-center and the COG. Increasing its length increases its ability to throw the vehicle body around. This runs directly in another issue with 4-link suspensions: raising the vehicle will tend to increase the suspension bias towards roll-oversteer, while lowering it will tend to increase the bias towards roll-understeer. This is due to simple 3D geometry.

To be fair to us tinkerers, this field of inquiry is called suspension theory because not even suspension engineers can perfectly understand or predict how these dynamic systems work in the real world. Even with fancy mathematical models and expensive software to crunch them, they need real-world testing to prove and refine their designs. Whoever the true experts in long-travel, off-road suspension engineering may be, they don't seem to be publishing books on the subject. We're lucky to get some useful information in the online forums, and a lot of that has to be sifted through. The single most useful thing I have found has been Triage's 4-Link Calculator--thank you, Triage!

Some of my motivation:
1) I didn't feel confident I could design the ideal suspension geometry for my Jeep for any particular type of driving/ wheeling and nail it the first time.
2) I want to use my Jeep for practically every type of non-competitive driving imaginable (except rush-hour traffic and mud bogs).
3) There is no single ideal suspension geometry for every driver, let alone every type of driving and wheeling, or even every rock crawling situation. I want to be able to adjust my Jeep for different situations and even as I evolve as a driver.
4) I want to be able to change things about my Jeep--like ride-height, wheelbase, sprung and unsprung weight, axle widths, tire sizes, shocks, springs, etc.,--which may have undesirable side-effects if not compensated for.
5) I want to be able to experiment so that I can understand the practical effects of suspension geometry. I want to understand the real-world effects of the formulas and numbers in the books and 4-link calculators.

Conceptual mockup:


Drilling the holes.


Line of holes, 34 top, and 34 bottom. For each bracket, 8 of them have to line up at the same time. It works, but it's tight, which is what I want.



That's about as far as I got on that for about a year. This is just one design I came up with. I chose it because of the materials and tools I had available, and because some of my other ideas made it seem tame by comparison. As I expressed to someone who was inquiring about my rear 4-link some months back, I don't recommend my design to anyone. In fact, I would recommend they don't. I have sacrificed both ease of construction and low-maintainance to gain high-adjustability.

Anyway, moving forward...

Making the laminates for my brackets. They're sitting on some rusty old 1/2” stock I used along with the 1/2” x 3” strap I used for the axle LCA tabs.


The slider becomes the inner hinge. TIG welded the root with 200 Amps, then did probably 3 passes with 5/32” 7018 at 210 amps, DCEP.


The outer hinge was tack welded with MIG for some reason.


I don't think I used any TIG on the outers, just two or three passes of 7018 on each side. It was hot enough. I got a full-section weld through 1/2” plate. After a good weld, this junk would take 3-4 hours to cool.





Welded the brackets onto the outer hinges. Rect tubing can be handy for brackets, but the stresses that are built into it can make wonk out. I pushed it a little too far with the way I cut these up, and they warped. I straightened the bases then welded them.


This is how I straightened the rest. It bows out a little here to compensate for the metal's tendency to spring back. This was one of the last times I used a MIG welder to tack weld something before TIG welding.







Still had more to do before they'd work, but the rest was gravy. Well sorta.

EDIT: The outer hinge/ brackets are on the wrong sides in this photo. They have a built-in bias pointing them outboard.


More coming. Ran out of steam awhile ago.

[aw12345]

I like the idea, you just need to design an adjustable brace for your crossmember. Since that is the piece that will flex and break

[inVERt'D]

I like the idea, you just need to design an adjustable brace for your crossmember. Since that is the piece that will flex and break

Thank you, Art. Great minds think alike. I have designed adjustable bracing that I like, and plan to implement it before I try any hopping wheel-stands, but to this day I haven't. Part of what I have in mind for the bracing now promises to be a royal PITA to weld in-place, and I've been working on other things. One of these days I'd like to sleeve those holes as well.

Will post more up later today. After going to bed late and very tired, I was awoken a few hours later by a thunderstorm. Battened down the hatches and and stayed up for awhile. Time for more coffee.

Funny I just noticed the brackets are on the wrong sides in that last photo.

[aw12345]

Brace it it before you do some serious wheeling, Chuck broke his crossmember and it didn't have all the go fast holes, mine flexed before I braced it. That or try some different challenges figure out what works best and then weld the whole shebang. There is only so much triangulation you want to mess with. The bigger advantage is in anti squat and roll center/ over/ under steer. That's the stuff that makes a happy Jeep and Jeeper when you get it in the ball park

[inVERt'D]

Will do Art. I've looked at the material strength numbers enough to know that bracing will be needed, and I actually have some pretty serious bracing in mind. The most serious wheeling I've done so far has been climbing some little dirt berms and banks here on the property. Much of the floor is gone, so I had a good view, and have yet to detect any flexing from the mild stuff I've done. Mind you, some of this was also with my thin-walled fence post control arms held together with tack welds. I was a lot more worried about those, but they held up too.

As far as welding it all up, that's always an option, but I've come this far (and farther still), so I intend to keep it adjustable. I do have a configuration that I'm confident should work well all-around, but being able to fiddle with things without all the unmaking and remaking is why I've gone through all this trouble. Besides wanting to experiment and learn, the day may come where I want to throw some 31s (or even 30s) on the Jeep and drive it across the country. Anti-squat can be adjusted at any of the link brackets. Seems that Roll center height is best adjusted by the upper link brackets. Roll steer geometry is primarily adjusted by vehicle ride height versus the inboard/ outboard position of the LCA crossmember brackets.

I have not ruled out using some easily-removable welds to hold the hinges in place so all the stress isn't on the adjusters. In fact, I probably will do that from time to time.

[aw12345]

Lowering the rear control arms about an 1.5" at the frame side has done more for my Jeep as far as climbing ability and body roll than fudging with the upper control arm height on the frame side

[inVERt'D]

That's good to know. If possible, I'd like to keep the UCA mounts at the top positions to maximize my roll center height. I still don't have a rear sway bar, so all the more reason to minimize body roll in other ways. As far as the lowers go, I expect to get the best performance by using the lowest frame-side LCA position, and the highest axle-side LCA position. I never really expect to use the upper two frame-side LCA positions--they're just there as far as the control arms are concerned. However, I do plan on using the top position as part of the bracing we were talking about. On the other hand, I can flip the brackets upside-down and swap them left for right, which will give me a slightly lower bottom position, with slightly better ground clearance, but with less protection for the joint. I've actually a designed a weld-on slider for this purpose, but it's filed under low-priority.

[aw12345]

It'll be fun and interesting to experiment with all the positions. The pain is to get the axle square and centered to the frame
Funny things happen when it's not. The Pitbulls were very forgiving in this the 37" tires I rolled under there afterwards were not.
Made for an interesting trip to work, talk about the @ss end off the Jeep having a mind of it's own.

[inVERt'D]

Yeah that whole alignment thing--details, details!

[aw12345]

You'se gonna get adjusteritus before it all said and done feller

[inVERt'D]

You'se gonna get adjusteritus before it all said and done feller

Yeah, but right now I've got picturosis.