Four link and leaves?

I was thinking about different ladder bar setups today, and was wondering if running a triangulated four link would work. It would basically controll all movement and locate the axle, so the springs would be there only for the "spring".


This is what I was thinking.
I *may* switch to coils in the future, and this would make the transition faster also.
What do you guys think? Will it work?

Yep it works well. Actually a nice 1/4 eliptical work provide tons of articulation, but might not be so great driving 60 MPH. Some folks actuallty build too MUCH articulation into their designs, to the point that yes the tires might still have contact with the ground, but the weight distribution is so off-kilter you don' gain more in the way of traction. Law of diminishing returns and compromise are the tricks of good suspension design*

When I built my tracktion bar, I very much toyed with the idea of a four link. Plus is you go four link now, you can go to coils or coil-covers in the future.

SeanP

*caveat: all this is conjecture from a guy who's XJ has been out of the garage for a total of 14 hours in 11 months!

it will then be fighting the leaf springs.

the easiest way to make this work is to put a shackle on both ends of the leaf.

better would be 1/4 elipticals, coils, or coilovers.

mad maXJ said:

it will then be fighting the leaf springs.

the easiest way to make this work is to put a shackle on both ends of the leaf.

better would be 1/4 elipticals, coils, or coilovers.

Click to expand...

The front to back axle movement 'could' fight each other between the leaf location and the link arcs. But if it was all worked out ideal, maybe not. The double triangulation he has shown will dramatically reduce the normal drop steer affects of a 4 link. If the movement is harmonious with the axle movement associated with the changing arc of the leaf springs, it could all work out.......
and you would have completed all the necessary requisites for a masters degree in geometry by the time you got it working right as a double benefit.

4 link and leafs work great and are cheap, but just shackle both ends like recommended.
You get all the good benefits of a leaf spring, like compounding spring rate, good load carrying capability and the rotational and wrap control of a link. I personally think they're great systems.

Not near as sexy as coil overs but functionally, very, very effective.

if yer gonna go four link, and you want leaf springs too, then do a 1/4 elip.....

I have a design that's definitly dialed in.

Though I have not tried it myslef, what I have read is that in order to use a 4link with leaf springs you must use what is a called a birdcage. This allows the axle to rotate independent of the leaf springs, allowing only the 4 link to locate your differential. The dirt track racers use this setup.

XJguy

ellaborate.

we ignorant 4-wheelers dunno notin about no birdcage.

if we wheeled on dirt tracks, I'm guessing it wouold work.

well xjguy, you got me curious, so I went a' googling.....

do you know what a birdcage is?

I mean, if you are gonna suggest using one, I figured you'd have a full understanding......

throw out an uncommon term like that in these circles is asking for trouble, especially lately......

maybe I didn't do enough googling, but around here, they're just simply called "axle mounts"



CW....

link geometry is one of the most difficult concepts to understand and utilize effectively and practically in a 4wd application.

there are tons of books written on the subject, and only small portions of those texts are helpful when designing a jeep suspension. there are hundreds of link designs that can be viewed on jeeps on the various forums. It is unclear how many actually work. It is one thing to throw two pair of links to locate a rear axle, the challenge becomes making a hypothetical static model work under power and motion. I still only have a half-undersanding of it all, and I did exhaustive research for MONTHS....my jeep works pretty good, and I owe that to beginners luck, and copy-catting, more than I do calling upon my research.

I suggest you start searching on the many dozens of por threads.

"god of suspension" and "4-links for dummies" are two good posts, but be warned, within the good tech, is PLENTY of BS.

Well thats why I said I have not tried it but I do have several race car supplies catalogs that sell birdcage setups. The way I understand it, is that the setup is designed to alleviate binding. I have not researched it in depth because I do not plan on using it. Just tossing in my .02..No need to get the whole forum after me again. Thanks

XJguy

don't blame me for that....ever.

YOU get people after you.

I don't understand why you are trying so hard to involve yourself in topics you couldn't possibly have first-hand experience in. It smells a lot like corporate positioning to me.

its great that you have a little knowledge of non-jeep applications. Its very interesting to try to form analogies between racing concepts and jeeping concepts.....but we're a jeep foum, and people who post here are building jeeps, not circle track rigs. It'd be fine to try to blend in these concepts into offroad applications when they matter, but in MOST cases they don't. Floating birdcage bracketry does not. SOLID axle mounts are required. I know you are just trying to be helpful, but if you keep citing half-understandings of non-jeep applications rich, its simply not that useful. A better understanding of the goals to offroad suspension designs might help you draw more appropriate similarities to these discussions.

Just tossing ideas to look into. The more you know the better, Think outside the box, didnt you say that not too long ago?

Taken from a leaf spring technology website:

When the car is accelerating, the spring will be trying to wind up, causing axle tramp. The car looses traction. The usual way of reducing wind up is to fit a rebound leaf to the top of the spring pack. It needs to be quite thick, and because of it's poor location, the affect on spring stiffness is not consistent. Track rods stop axle tramp. But they may restrict movement of the axle in bump and rebound. As the axle moves from it's static position, the suspension will get progressively stiffer. This could cause oversteer, and poor traction on corner exit. The problem of suspension bind is overcome in by providing large flexible bushings. In racing, only the four link rear suspension with a "bird cage" (axle housing rotates with suspension movement) works properly - as in V8 Supercars. The Smithees single leaf rear spring will be stiff enough to avoid wind up, in most instances, without the use of track rods or rebound leaves.


XJguy

Beezil said:

if yer gonna go four link, and you want leaf springs too, then do a 1/4 elip.....

I have a design that's definitly dialed in.

Click to expand...

Touche' Beez. You have YOUR design dialed in. Many things could and will be different between the two vehicles I'm sure. Lift height, vehicle weight, allowable link mount locations etc.

As you know I run quarter elip but do NOT think it is a good design for the street without sway control. I think you can easily get away without sway control with a full semi-elipse leaf system.
Plus the quarter elip design is just a lot more involved for a first timer. I have done and seen several linked full leaf systems and they really are an effective albeit simple system. And one that is significantly easier for intial fabrication than a quarter system.

P.S.
Very good to finally meet you in Moab. If you midwest/east-er guys ever do want to make a out west and include a stop in AZ, I would love to tour you through some runs.

Just tossing ideas to look into. The more you know the better, Think outside the box, didnt you say that not too long ago?

Click to expand...

yeah, "outside the box" is a favorite buzz-phrase....

but that doesn't mean I waste a jeepers time talking about single leaf rear suspension designs used in EZ-GO carts cause I saw a picture of one in Golf Digest.

see the point?

Heh C-ROK

C-ROK...funny story... I was looking thru the latest issue of FWD&SU magazine and there I saw your pix. Pretty nice too! I was showing it to my secretary with the comment that I knew him from the last Moab trip. She says, "Isn't that the same Jeep that got rollover in the Hot Tub?" I have a 8x10 enlargement of your flip on my office wall. Made a great pix!
P.S. do REALLY like the two hats. Sent one to my son-in-law in Cali.

A 700hp race car is hardly a golf cart. I would think that anyone that gets info from here or anywhere would do some further investigation ,especially when faced with so little info as I initially offered. I did not say he had to do it that way, only that I read that is the way to go about it, suggesting he should look into it. (excuse my vagueness) Sorry in anyone feels I wasted their time; just disregard my comments.

BTW, I agree that with a quarter elipse the 4 link will work (again I did not use this setup, its what I have read, you may want to investigate this avenue further). They used that setup in race XJs campaigned a few years ago.

XJguy

I am shying away from the 1/4 elipt. because of my relative lack of knowledge of suspension design, and because this is my only vehicle. I am now at around 8" of lift, but it is untested because I am still working on dropping my stroker in. On one of my last of several 6" setups I got the axle wrap under controll by using more leafs and going to a one inch block, but the ride was stiff and I shattered one of the blocks. I now have mixed mj/xj springs with an mj/xj "scissor shackle" and a 1.5" block I made out of 1/2" plates welded together. With the extra horse power and higher lift I am pretty certain I will need some type of traction bar or 4 link. I like the idea of the 4-link and leaves because it "sounds" simple and will be a fairly easy build. If I do just put a shackle on both spring ends, do they need to be identical, or can I still run my "scissors" in the rear.
I did a lot of reading on PBB and I now have a better understanding of anti squat, IC, roll center....... From what I could tell, I have the right Idea with triangulating both the uppers and lowers, but I should make the uppers 75% the length of the lowers. Am I on the right track?

CW. said:

If I do just put a shackle on both spring ends, do they need to be identical, or can I still run my "scissors" in the rear.

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Don't know what "scissors" is. I think it's maybe like a Revolver or something?

I would assume you could still run it since the links will be doing all the axle locating, including lateral with the design you have. The front shackle length only needs to allow the axle to swing along the same arc as the links.

C-ROK said:

Don't know what "scissors" is. I think it's maybe like a Revolver or something?

Click to expand...

This isn't mine but very similar


What would you guys recomend using to build the links. I used DOM for my longarms, but that was a little spendy. Would 2" Sch. 80 be ok? Should I go with hiems or rubber bushings, or polly.?

then a four-link is not necessary.

the full-length leaf springs locate the axle.

to control wrap, you can add a traction bar.

I know it isn't "necessary", but niether are 36's and full width axles. I just want to build something a little unique that leaves the option of going to coils, or coil overs in the future. I would rather do this instead of a traction bar, but if I feel like I'm getting in over my head I'll just do a simple traction bar.