CK5 - The Full-Size GM Off Road Community

Has any one ran a rear 1/4 elliptical set up on the K5 or Full size truck? Any one have any pix of this too? Thanks
Cory

Its been done, let me look around. Even jeeps need big spring packs with 1/4 eliptical.

1/4 eliptical thread (http://coloradok5.com/forums/showflat.php?Cat=0&Board=garage&Number=871892&Foru m=,,,,&Words=1%2F4%20elip&Searchpage=2&Limit=25&Ma in=871892&Search=true&where=sub&Name=&daterange=1& newerval=1&newertype=y&olderval=&oldertype=&bodypr ev=#Post871892)
I was gonna direct you to a thread on Bluetorch Fabworks Forum but I looked and realized you came here from there /forums/images/graemlins/smile.gif

Here's the only pic I have of a quarter elip setup. They used to be somewhat popular in desert trucks, but from my impression people started going away from them cause they were hard to tune and added weight, which wouldn't be too important in your setup.

http://coloradok5.com/photos/data/9094/1799quarter1.jpg

http://tanner4wheel.com/fab/image/todd1.jpg

I know its not the best picture, but its from Tanner 4 wheel drive

wow imagine the springs it would take to 1/4 elip the rear of my suburban.... /forums/images/graemlins/eek.gif /forums/images/graemlins/eek.gif

http://coloradok5.com/photos/data/500/3081Buggy_wheelie-med.jpg
I've had the pleasure of playing around w/ my 1/4 ellip setup on my Buggy. I think it could be used sucessfully w/ a full size light weight crawler, but I'm not sure I'd want it on a 6000 lb full size truck.


Much like the image below illustrates - for a heavy truck, the spring pack can become so heavy that it approaches the "not worth it" zone.
http://coloradok5.com/photos/data/9094/1799quarter1.jpg

But I will go on to say that most guys (including myself) who are using the system take advantage of a trick to prevent the humongous spring pack. That is to have a bumpstop on top of the spring about mid-span across the leaf. This effectively creates a "dual rate" spring as compression of the suspension has a much stiffer spring rate than extension. You can see the passenger side rear spring in the top photo doing just that.... It's possible that I'll be replacing springs on a regular basis, but oh well. /forums/images/graemlins/dunno.gif

I think coil overs are cooler /forums/images/graemlins/waytogo.gif, prolly easier to tune, but significantly more $$ /forums/images/graemlins/frown.gif....

Marv

here's one of the guys we wheel with. its an old fj buggy with 2.5's and rear elipticals...works awesome for him.

rear shot (http://www.texasoffroad.net/galleries/ohv/album08/P1010008?full=1)

This is another subject that I keep coming back to. LEaving the front leaf sprung and going quarter in the rear.

Just cant decide between quarter and 63 inch springs.

/forums/images/graemlins/dunno.gif

on a stock body K5? What about the spring neccessity aren't you picking up on? 1/4 eliptical on a K5 is certainly doable but by no means the cheapest or best option IMO. Coils would be better and probably cheaper.

One year at SEMA a old Walker Evans Class 8 truck was on display. Had National Spring 1/4's on the rear. 27 leaves, I counted them. About 10" thick at the spring bolt. They had them set up such that the spring bolt was centered on a spring perch. The perch was welded to a tube and was free to rotate around an inner tube. Then that was a monster weight jack screw just forward of each tail light that the spring's rotation stopped against. That would allow them to dial in the rear ride height. Instead of a shackle they had a pair of vertical plates welded on the housing with a roller bolted btwn them.

mine is running 1-tons and 44s.

http://community.webshots.com/photo/93552719/93552868JivPSo

josh

Looks like you get a lot of rear axle steer with that set up

i don't mind a few inches of rear steer for over 4' of travel at the wheel....would you?

josh

Josh454: that is a sweet ride, I think its something unique and different that looks like it can perform. When i first posted up on this subject people on here showed me your k5 and i was in aww. Sweet ride.

D and C extreme in Colorado Springs makea 1/4 elliptical kit for Scouts. Looks fairly well engineered. Check them out here:

http://www.dandcextreme.com/product.asp?pkID=78 . Nice 4 link kits too.

I saw that, those kits are pretty awesome. Those spring packs are way think too.. I like the idea though maybe think about it for the K5 but 2500.00 is a little much for me right now..

Hey josh454 how did you deal with frame flex? My K5 busted a cage weld this weekend flexing so much!

if your going to go to the trouble of doing a link suspension you might as well run coils. I'm running jeep wrangelr rubicon front coils in the back and it's just right! you can buy them for $50.00 each at the dealership. I can make you some sick axle brackets and ship em out to ya if that's why you don't want to run coils.

frame is reinforced for pretty much the entire length of the truck due to all the suspension changes i made in the front end and the elliptical setup in the rear. i have had no problems with any welds breaking or even signs of that starting to happen.

josh454: would you recommend boxing it for a link suspension in the back? Can you box just the rear section, or do you need to box the entire thing if you are going to box it?

Balterbuilt: Do you have any pics of your linked rear end flexed out?

the decision might come down to more of a time commitment than anything else. perfect world you would box as much as you can if you were starting from scratch. i would try to box the main suspension points to the frame over as long of a stretch as you can do in a reasonable amount of time. i am sure you would rather be out wheeling than taking your drivetrain out to box the whole frame.

Yeah that is definetly true... I am actually now thinking of just going with 64" springs instead... save time AND money.

i haven't got to finsih mine, still waiting for a damn super flex joint tool to comei nthe mail..getting pissed!

here's how it stands right now...

it turned into a double triangulated 4-link somehow...haha. I didn't box the frame just built some beefy crossmembers off my stock crosmembers. check out the pics. ONly the upper link are on right now. and i still have to brace the suspension mounting points....


http://i76.photobucket.com/albums/j23/bbgirltink/truck%20stuff/uppersframeend.jpg
http://i76.photobucket.com/albums/j23/bbgirltink/truck%20stuff/uppersaxleend.jpg
http://i76.photobucket.com/albums/j23/bbgirltink/truck%20stuff/x-member2.jpg
http://i76.photobucket.com/albums/j23/bbgirltink/truck%20stuff/x-memb.jpg
http://i76.photobucket.com/albums/j23/bbgirltink/truck%20stuff/bridgeontable2.jpg
http://i76.photobucket.com/albums/j23/bbgirltink/truck%20stuff/bridgegusset.jpg
http://i76.photobucket.com/albums/j23/bbgirltink/truck%20stuff/brdigeonaxle2.jpg
http://i76.photobucket.com/albums/j23/bbgirltink/truck%20stuff/rearview.jpg

sorry it took so long to reply but this post never showed up in my UserCP for some reason.

1/4 EP is fundamentally different than running coils even on the exact same link setup. It allows a drooped tire to keep a lot of traction where a coil doesn't.

Mikey,

Please explain the basis for this. Understand that I'm not arguing... I just wanna understand what you mean.

Reason is.... I don't agree w/ you. Doesn't mean you're not right. But I've run 1/4 el. springs on both ends of my FunBuggy and now on the rear end of the Marvzda. I see no "fundamental" difference in them when compared to coil springs. There are only 2 advantages I've observed:

1) Leaf springs (1/4 el. included) seem to have more "rubbing" friction and so they have some "internal damping". You can see this when you "bounce" on a suspension w/ no shocks. The coil spring setup seems to be "free-er" than the leaf spring setup.

2) 1/4 el. springs are not light, but they keep the weight low. Usually they are mounted much lower than say coilovers - coil springs too - but coil springs don't weigh much, so it's really a non-issue.

Anyway, you are probably the 2nd person I've heard say something like this.... and I just want you to clarify.

Marv

Sorry, we got into a huge debate on one of my local boards and lost a friend or two. I really didn't wanna get into it again so I didn't elaborate. Oh well, let the games begin.

Pros:

When the suspension is drooped to the max, a coil will be attempting to pull the axle back up, and the drooped tire has nearly 0 ground pressure. Take a linked coil sprung rig out and cross it up real good, then walk over to a drooped tire and pick that side of the axle up, it's pretty easy. With 1/4 EP, it allows the axle to droop freely until it hits the limit strap. This means that a drooped tire will be able to put roughly 1/2 the total unsprung weight of that end of the truck into the tire and that translates into traction. 1/4 EP offers unihibited droop until you hit the strap. Also, with 1/4 EP the compressed side is trying to force the axle downward at a 90 degree angle to the body at all times. Coils...not so much. Now, coilovers and air shocks act much the same way as 1/4 EP would, but lots of people have leaf springs they can use, not many have an extra set of c/o's or airs just laying around.

You can achieve uninhibited droop with coils that aren't captured, as well as air shocks and c/o's but that's a whole nother topic...basically the coin of fancy stuff is prohibitive and I've seen more than one person lose or mess up uncaptured coils in the short time that I've been wheeling. Airs are a bitch to tune and the N2 setup is $200-$300, which brings the bill close to $800. C/O's are just in a different pricing league.

Cons:

1/4 EP offers almost uninhibited droop. This is a double edged sword. Good for traction, bad if you don't set up the links right. 3 limit straps are almost a must just because of the nature of the suspension. If you're going up something ridiculously steep and your links aren't set up correctly, (and you have no straps) there is a chance of your axle walking clear out from under your rig. I plan on 3 straps plus a winch to suck it down for steep descents. Another con is that they're not easily tuneable. You can buy coils in different spring rates...if you really wanna do that with leaf springs you're stuck finding out the spring rates of lift springs, paying through the nose for them, and having to CUT them and then test them to find out how they really act.

Disclaimer: I'm an engineering student, and although I have been present to witness events that back up all of my previous statements, a large bit of this is based in theory.

1/4 EP offers almost uninhibited droop.
Here you must be assuming that the "box" that houses the springs is hinged so that it can drop away from the frame.

Both (all 3?) setups I've done have the box fixed to the frame or are part of the frame. In that case, the spring can be extended to the point where it is actually exerting an upward force on the axle - just like a coil spring fixed on both ends. Maybe that's why I was thinking from a different perspective... Here's an example

http://i79.photobucket.com/albums/j129/marv_springer/Martinez3_06-080.jpg

Marv

Sorry, forgot to make that distinction. I wrote the paragraph with a box with a hinge on the end in mind. By the time you get to wicked levels of wheel travel, you're putting a ton of stress on the main leaf. A buddy of mine broke three springs in a weekend that way and then went to a hinged setup.

Mikey,
IF I'm understanding what you've typed correctly, and that is a big IF, then you are comparing a droop limited coil spring to a droop unrestricted 1/4 elip. Setting aside the difference in actual springs that isn't a good comparison.

With the way that coil-overs are made they can not exert any upward force as the only capture of the springs is compressive (stop collars, tender springs, etc.). Given the way that 'remote' coils (i.e. non coil-overs) tend to be captured they can exert an upward force if neither spring end is allowed to float and if the system is forcably extended far enough.

With 1/4's elips and no hinge or hinged but motion range limited, they too can exert this upward force if rigidly attached to the axle.

The way I see it is a spring is a spring is a spring. How you attach it makes the difference. Some springs work better for certain attaching methods than others. Unless you're building only with what's laying around, which set of pro's/con's you want determines which type of spring to use.

Alright, this is a LONG post. Before you read, assume when referring to 1/4 EP I'm talking about springs that are attached to the axle via a heim joint. Also, a lot of the bad properties are true for both captured and uncaptured coils.

To cut it off at the pass...we did a redneck test of different setups. We took Bill's YJ (1/4 EP 4-link rear, leaf front), Matt's Willy's (4 link remote coils front and rear) and Joe's CJ (leaves all around) and crossed them up. Joe's CJ was the control. When flexed out, you could walk up to the drooped tire (which was still in contact with the ground) and pick it up with one hand. To be fair between Matt and Bill we used a chain to make a limit strap on Bill's YJ that replicated the length of the one on the Willy's. The Willy's didn't run out of travel and the tire was still planted, however I picked the drooped side up with two hands. Bill was last and two cementheads couldn't budge his drooped tire with all of their might.

Yes, I'm compared captured coils to "hinged" 1/4 EP springs. This is because that overall, I believe a captured coil setup works better than an uncaptured one, and a "hinged" 1/4 EP setup works better than a fixed one.

In the interest of saving myself time. I'm just gonna paste a couple of my posts from the original board.

SNIP

Also, if I understand this correctly, which I believe I do...bill is saying that the springs are always applying force perpendicular to the frame because the frame side of the spring is held captive (clamped) and the axle end is allowed to pivot on a heim.

This means that if you're looking at a frame from the rear, you can draw a line between the two rails (like a crossmember) and then draw a line perpendicular to line #1 and that's the direction that the springs are actually pushing. So basically when your coils are trying to bind (if they're captured) and wasting valuable force trying to push the axle different ways, the 1/4 elliptical setup is trying to plant your tires firmly into the ground, and nowhere else.

If I'm analyzing this correctly, the only way you could replicate this is to use an air shock or coilover and mount it completely vertically, which would not only interfere with a tire when it was stuffed but would also use up a lot of travel in the shock/spring assembly as opposed to mount them tipped in ( / \ ) like a lot of people do.

SNIP

Alright, I've been nice, but I just put in a 12 hour day getting my junk one step closer to being wheelable and I don't care who I piss off anymore.

A spring is not a spring...if it were, how can a 1/4 elliptical be any more or less efficient than a coil sprung rig with the same link setup? Take an engine hoist and flex your suspension out, then take a floor jack and see if it moves vertically while flexed. If it doesn't, well...you have bigger problems. Take a TJ coil and sqeeze 1/2 of it, wants to shoot out to the side doesn't it?

Axle diving under truck more with 1/4 EP than all the other suspensions theory is bull****. You're never putting any tension on an airshock or coilover until it bottoms out. It's in the link setup. When one tire is two feet below where it normally is and you put it to the boards, the axle is gonna want to move forward under the truck, no matter the spring. If you don't like it, change your links. Guys run limit straps there to protect thousands of dollars in suspension pieces and center straps to keep joints from binding and exploding. 1/4 EP should have limit straps because there's no natural stopping point for droop until the end of shock travel. (sounds kinda like all those fancy airs and c/o's huh?)

Sure, I'd take a pair of coilovers any day, but unless somebody's gonna hand 'em over in return for a pair of Chevy 52's, they're out. You guys trash **** because it's not the latest, high tech, expensive stuff. I ran a fullsize on 40" boggers that weighed close to 6000 pounds, and it was damned impressive in the rocks for as heavy, large, and mud oriented as it was. Once I got beadlocks and got those boggers to wrap around rocks instead of bounce off of them it woulda beaten a lot of rigs that were better set up for Gilbert.

Sorry guys, but this is just too much bull****. The design works, and if everyone's getting their panties in a knot because somebody used half of a leaf spring instead of a TJ coil, get over it. My truck is going to be a mixture of Cadillac, GMC, B.O.P., Chevy, Ford, and Dodge when all is said and done. The important part is I'm gonna have a blast wheeling it. At this point I'm considering having a bigass bowtie cut to slap on the front just to make sure everyone knows it's not a Jeep in any way, shape, or form. But then again if you guys are right I suppose I should throw away my 500 cuz that's from the 70's, my york will have to go too, leaf springs, oh yeah, frame is late 80's, that's out, guess I might as well build a moon buggy with an LS2 and one of those newfangled balljoint 60's.

SNIP (I drove a member's YJ on 40's with 1/4 EP in the rear, posting my results brought on another fight among the forum members)

The thing is wicked stable. Period. Should some limiting straps probably be installed just for insurance...yep...did I run through tabletop twice without having ever used a manual transmission off road...that too.

My rear suspension will be 1/4 EP, no question about it. I was at the center of the kill radius and the only thing that got hurt was my pride when the shifter caught one of the twin sticks and I jammed it into 4th instead of 1st.

SNIP (This is Bill, the owner of the YJ, driving down the "buggy entrance" to a trail in Gilbert, to prove that it doesn't just unload randomly. The steeper than it looks rule applies. Also, I drove up and down that hill twice, the second time on the way down I stomped the brakes and it didn't get crazy like everyone predicted.)

http://www.chevihemi.com/temp/quarterelip.MPG

First let me state that I don't give a damn what it is that you wheel or what badge it carries. Hell, I'm contemplating a partly Sami tub'd, quasi tube chassised, yota axled, 100" WB thing powered by a 1955cc Air cooled VW backed by a yota trans & a Marlin doubler. WTF badge do I put on that? :D

I'm interested in your thots on what you've learned and tested. If I'm confrontational sounding, it's unintended. If I'm contradictary it's b/c what you've come up with disagrees what what I've come up with and I want to know why, b/c then maybe we'll both learn something. It is a long post and it'll take me a day or two to digest it.
I'll get back to it then.

I apologize if the posts sound offensive. There is a group of stuck up dickhead wheelers that makes up about 1/2 of the other board. Coilovers, buggies, and mogs...that sort of high $$ stuff. Jeep purists 'till they die but it's all Chevy stuff under the body or panels. When somebody comes up with a cheap idea it's immediately dismissed as inferior and the originator of the idea is generally ridiculed.

A bunch of us finally got pissed and basically told them to go to hell. The anger is in no way directed towards you or anyone else on this board. It turned into a giant us vs. them fight and got out of hand.

Take the ideas for what they're worth, post up what you think about them, and ignore the rest. The only reason I didn't cut those parts out is because I'm lazy.

It didn't sound offensive to me, but it did sound like you'd been thru the ringer over this & I wanted you to know where I was coming from.

I've been in enough net arguments (some I provoked on purpose, think dickheads like timmay) to not need any more. :D

At first read I'm thinking that the test btwn springs was unfairly compromised. Not by any deliberate intention, but by the way things are.
Three different rigs, unless they all came off the same chassis jig, are going to have significantly different amounts of droop, ride heights, and different linkage pivot points. By chaining the one rig it was artificially forced to have some residual pre-load on the spring. Might have favored it, might have favored the others.

The ease with which you can pick up a drooped tire is a measure of the remaining spring force on that tire. How it gets there is inconsequential. If you tell me you want X lbs. force on the tire at 14" of droop from ride height, I can give you that with any spring type.

What's needed is to know the effective Wheel Rate of each spring combo. Small changes in mounting points can have a large effect on the Motion Ratio, which directly affects the wheel rate even if the spring rates are all the same.
A spring is a spring, they all point a force in some particular direction. Simplicate them, draw a Free Body Diagram of them. Really doesn't matter what the orientation of the mountings point is, they will exert their greatest force inline with their mounting points. Depending on what arbitrary coord set you assign to the FDB they may have both Horizontal & verticle components, but that doesn't change their basic nature.

So what I'm saying here is that the spring rate, the Motion Ratio, limit strap length (if present), and the pre-load on the spring all effect how much force is left in the spring at full droop. The type of spring has some peripheral effects (tendency to bow, internal friction, etc.), but it doesn't change the resultant force left in the spring at full droop.

So where does that leave the arguement btwn 1/4's vs. C/O's vs. coil springs?
Nowhere.
Each type will do the job and properly set-up give you the characteristics that you're looking for, but those need to be designed in and not just attributed to the type of spring. It comes down to price, unsprung weight (if that matters to the application), & ease of packaging. To me the biggest downside to anything other than a C/O is the lack of knowing what the spring rate is, but that wouldn't stop me from using the others.

So after pouring over every SAE reference book I could find and reading your reply...I think I'm gonna do my own little experiment. When my buggy is done except for the rear springs I'm gonna build in coil mounts and 1/4 elliptical mounts. Run 1/4 EP one day and coils the next and see what happens. Do tests on both for travel, force, etc.

No it's still not scientific, but unless you wanna dive REAL deep into vehicle dynamics, we're all kind of up a crick.

BTW, are you a mechanical engineer by any chance?

Mostly an ME, my diploma reads "Prototype Engineer" which is a combo of ME and Manufacturing. I'm extrememly light on thermo & heavy on actually using manufacturing tools.

your proposal sounds reasonable. I think it's more about designing & building in the traits you want. One type of spring may make certain traits easier to get than other types. Each is going to have it's pro's & cons and until you've decided what exactly it you want you can't decide which type to use.

Conversely, if you are set on one particular type (for what ever reason) then you need to design to miniimize it's weaknesses in the direction you think you want to go.