REAR 1/4 Elliptical suspensions for XJ's

[Beezil]

Just getting some ideas.....been searchin my ass off on POR, and have seen lotsa ideas, and have gotten info on what everyone has been using for springs.....

I have a good idea for a height adjustable spring mount, that should help me get ride height dialed in, and I have a good idea on how i wanna run my links, which i will be adding to the 4-link thread for review.....I guess I'm just trying to clarify an XJ -specific strategy in terms of which donor springs to use, how long they should be and how to figure out a "shackle' or swivel mount solution.....

any thoughts would be helpful....

[Rev Den]

I think you may be a link short of a full chain.....but, I did find this:

http://www.jeepaholics.com/tech/quarterellip/

Hope it helps.

Rev

[Beezil]

yep, found that during the search.....thanks.

[C-ROK]

Hey Beez.

I run a detached quarter eliptic rear on mine.
For the spring pack you can use any 2 1/2" wide leaves, including the ones on there right now. You'll just have to stack until you get the spring rate you want. I'd estimate you'll need between 9 and 13 but that too can depend on the length. The longer you go, the more you'll need.
I use 9 or 10 leaves that came from CJs, Wranglers and my Cherokee.
I know people that are running as many as 15 leaves too.

My pack rides in a hinged arm. For the hinge point I used a poly spring bushing.

For height adjustment I have the airbag but I've seen people use a simple jack screw arrangement also.

Since mine is detached, the leaf spring rides on a bronze roller on the axle. Most of my friends here run attached and use a shackle and swivel combo at the axle. Both work fine.

[Beezil]

c-rok, I'd love to see pics if you are willing to share....

I was thinking on using my current springs laying around, but searching revealed that most folks seem to like 3" wide springs.....

folks are using all sorts of springs from 1/2 ton through 3/4 up to 1-ton, all sorts of different lengths, a common one seems to be ford f 250 leafs, the 57' ones IIRC.......how long are yours from eye to pin? did you fab up a swiveling mount right in front of the axle tube? how much height do you have from the spring eye to the centerline of the tube itself?

thanks

[C-ROK]

I can try to post some pics.... but I usually struggle with that.
I can e-mail you some.

Send me an e-mail at info@c-rok.com and I'll get some back to you. Along with some CAD drawings of the set-up. Don't have any CAD of the uniframe (since I saw you asking in the other post) but what I do have may be useful to you.

My pack is rearward mounted, not forward like most rock crawler set-ups. Rather than allow the pack to swivel, I actually fabed a pretty simple restraining system to hold the pack in place as the axle articluates and puts a twisting force on it. If you go the jack screww route, the jack screw mount should solve that part for you.

I wouldn't agree with "most people" here in AZ. I would say here of the dozen or two people that I know that are running (or have run) quarter elip, 90some% are using 2 1/2" wide Wrangler/CJ combo springs. If for no other reason than they're usually modifying a Wrangler or CJ and have those springs available.

I'll have to make measurements for the other questions.

[C-ROK]

Didn't forget about that.... but I didn't remember either.:doh:

There's actually a pretty good pic of the leaf pack arm and roller too.
http://www.4wdandsportutility.com/features/03024wd_crok/

Here's the pics:

http://community.webshots.com/scripts/editPhotos.fcgi?action=showMyPhoto&albumID=80159848&photoID=80159946&security=jiLSgb

http://community.webshots.com/scripts/editPhotos.fcgi?action=showMyPhoto&albumID=80159848&photoID=80160139&security=bnMwts

and thanks to Ted Z, da bozo C-ROK can post a pic :dunce:

Edit:
.....or maybe not. All I see is Red Xs.
The pains of being an idiot are sometimes nearly to great to bear :bawl:

here's the link to the webshots album:
http://community.webshots.com/scripts/editPhotos.fcgi?action=viewall&albumID=80159848

[vintagespeed]

I'm also going to be going with 1/4 elliptical maybe next year. I think these springs would be awesome, I dont know about the shackles but they look cool. :D

http://www.bluetorchfab.com/suspension.htm

[Beezil]

I think I am deciding to use my existing springs.....

now, I have some ideas on how to make frame brackets, so they are adjustable enough to tune on the fly. I'm thinking adjustable length vertical links, as well as variable angle spring brackets....

I can't decide if I should mount the spring brackets under the framerail, inboard, or outboard........

I can't decide how long my main spring should be, and if it matters where I position it in relation to the four link........

looks likea scale drawing or model is necessary.

[vintagespeed]

Well, since you're going to be using basically 1/2 of a spring pack you'll need to limit it's uptravel to give you a decent ride height. C-Rok uses airbags which is probably the best way to go and will allow you to mount the leafs really anywhere, but if you're not using bags then I'd mount them under the frame rail. You're going to need the support to build a uptravel limiting stop. As to where to mount the main leaf, it's pretty much gotta go on the bottom with the arch facing down, otherwise you'll have no droop.

[Goatman]

I think you'd loose ground clearance if you mounted the spring under the frame. Jimbo, you know me, I won't do anything that reduces ground clearance. The way our springs are mounted on the side of the frame is good, because we can slide on the frame until the tire can hit the rock or ledge, or at least the bottom of the spring pack. I just have one cocky thing to say to anyone who mounts their springs (or long arms) beneath the frame rail......follow me. :D

I was thinking about what could be the possible benefits of a rear 1/4 eliptic spring setup on an XJ. One could be tuning for a great ride, but I wouldn't want to loose weight carrying capacity. It would increase clearance behind the tire, no spring or shackle to hit, and that could be nice, although I've never seen anyone get hung up sliding off of their spring or shackle. I guess it could increase articulation, but who needs that, and it could very well add some undesirable rear steer depending on how well the rear links were set up.

Beez, for me, it would be easier to think about potential designs if the intended goal was clear. Are you working on plans for a new rig, or considering changes to your current one? What are you hoping to gain? I could see myself trying some form of rear 1/4 eliptic suspension down the road, but for now I'm trying to dial in my MJ leaves.

[4ward]

Beez, I think you should go with coils.

I'm planning on putting mine on the outside of the framerail. If I have enough clearance with the axle width I want, that's my ideal location.

Otherwise, I'll probably be cutting up the framerail in the back and disposing of it improperly. May be time to do some funky underneath tube work.

Richard, I don't think you have to lose the weight carrying cababilities. If you can tune a set of 1/2 elliptic leafs, you can do 1/4. My suspension will have an airbag assist, but my leafs will run in a permanently mounted frame box and a shackeled axle end.

I'm going to try my hand with a set of 1 ton springs and play with them. I think they'll give good tire dropping resistence (rebound) with very respectable articulation. My mixture will probably end up a mix of 1 & 3/4 ton though.

Sean

[Beezil]

One Coil,

how long do you think your main leaf will be from eye to shackle?

I'm seeing conflicting info on my searches.....

also, is there any strategy on placement of the spring pack frame mount? I figure a shackle of sorts at the axle end will take care of any "misalignment" between the links and springs.

goatkiddie,

I am trying to solve the problem of boredom. I'm also trying to design a rear suspension that allows for ample lift height that doesn't bully the rest of the rig into same attitude as the rear axle, and at the same time can sidehill like a champ, which is why I'd never go to coils.....I'm trying to get rid of my "stiff cricket" and Hagen will have to think of a different name in moab. Weight carrying ability is not a concern. I dont like to haul a bunch of crap in my rig.....as long as Hinkley has his welder nearby, that's all the support I need.....Actually, my whole problem is that the back of my rig is too light!!!

That's why I'm kinda in a debate over which springs to use.....OneSkippy wants to use 3/4 and 1 ton springs, and I'm ready to experiment with xj lift springs......

Some guys like to finish their projects.

Other guys are never satisfied with their end products and like to start anew

[C-ROK]

Originally posted by Goatman
I just have one cocky thing to say to anyone who mounts their springs (or long arms) beneath the frame rail......follow me. :D


Ummm, I have both my front long arms and my rear quarter eliptic pack mounted under the frame.

I'm pretty sure I could hang with just about anyone who desires to keep the paint on their vehicle.:angel:

The quarter elip is a good set-up..... and so are coils... and I'm pretty fond of my air bags. I wheel with a lot of guys that are simple SOA leaves and they do just fine too. I don't believe there is a ONE right answer.

Long arm suspension systems are very effective and can allow for great travel.
Quarter elips can allow for more travel than anything else out there and they could end up costing you about 1/10 of what long travel coil-overs would cost.

Articulation isn't everything for sure, but in general keeping your tires on the ground is better than not.

http://community.webshots.com/photo/80159848/80451446WCiXTX

[vintagespeed]

Yeah, you guys are right. I think Seq. has put a curse on me and turned me into a moron. I didn't mean to mount the leafs directly under the frame with a couple ubolts or something, but the 1/4 elliptical pack is going to be longer than 1/2 the stock length pack. Why not recess the leaf pack into the framerail? I like the Bluetorch leafs because they're built specifically as 1/4 elliptic springs and have lots of leafs, I couldn't bring myself to hack my Nationals anyway.

[Beezil]

vintage, you wierdo......I hope your next avatar isn;t a picture of my wife!

crok,

when i said "I wouldn't do coils" I meant coils, ya know, like coils from a tj or something......coil-OVERS is a whole different ballgame, which i would love to do someday on a buggy.....but not regular coils on an xj.......Not that I have seen many in order to formulate an educated opinion on the matter, but the ones I've seen have crazy body roll........

I think a tuneable 1/4 elip with 4-link is a better option than both coils and high-arch 1/2elip.....

[C-ROK]

Before I put a sway bar on my rear axle, I used to get some pretty silly body roll too. Quarter eliptic in and of itself is not a solution to body roll.

You can design to help reduce it by locating the leaf packs as far outboard as possible but I'm not sure you can reduce it enough to avoid a sway bar.

Just from my experience alone, the guys with long travel, high articulating suspensions that DON'T use a sway bar, all have some pretty big body roll.

BTW, I didn't notice any loss of articulation at all when I put my sway bar on. But it did do wonders for controlling body roll around corners on the street and help prevent the body from kinda 'flopping' over on off camber obstacles.

[vintagespeed]

Nope Beez, I dont have any pics of her that I could post here legally.........hehe jk jk jk.

C-Rok, what kind of rear swaybar are you running? Currie?

[C-ROK]

I actually run the stock Cherokee rear sway but modified to work off of my lower links. The standard Currie Anti-Rock is too short for my frame width.

The stock rear seems to work good. It's only about 3/4" dia and has a pretty low rate. The low rate coupled with mounting it on the link gives just enough resistance to control sway and roll but doesn't affect the articulation at all.

[Goatman]

beezhead,

I can dig the boredom thing, I just always have too much to do to get bored. I need to quit messing with all this XJ club baloney so I can really spend some time on my Jeep. :) I also have a stiffer ride since the cut down, so I'm trying the longer leaves. I'm not afraid of lift blocks, with a good traction bar, so I don't deal with high arch springs. Even with 8" of lift, my springs are pretty flat, bend backwards easily, and have tons of droop.

I'd still like to play with air bags somehow, and using them along with a 1/4 eliptic design could be a good way to go. As far as your project, I'd mount the leaves along side the frame rail, a little forward of the current front spring mount. It can't be too difficult to come up with a good mounting system. You may need a good bumpstop system. I don't know because I've never run them, but it looks to me that there would be less spring resistance on the 1/4's when nearing full compression than there would be on 1/2's. This could be more of an issue with our body/fender configuration than it would be on more of a buggy type rig.

crok, (I like that) ;)

You need to get out and wheel with us, we have a fun group of XJ wackos. I'm sure we'll be in JV in Nov sometime. We have a lot of fun ragging on each other, and I'm the resident naysayer of long arm suspensions. Your rear springs are behind the axle, so that doesn't limit much because you can slide right off of them. On your fronts, if the arms are mounted below the frame, I'm sure I could get a pic or two of you hung up on them.....I have them on everyone else. :D

Of course, the 38's help, and so would jacking the airbags all the way up to increase your breakover angle. Still, it's getting hung up that stops us most of the time, not a lack of traction. I sort of have a ground clearance fettish..... :) :)

[C-ROK]

Originally posted by Goatman
beezhead,
crok, (I like that) ;)

Cute Goatman. Cute.

I won't even touch the goat thing but I'm sure there are baaahd jokes available for that one.;)

I'm doing the NAXJA Moab thing in Oct and would love to do JV in Nov too. I'm really looking forward to meeting all of you guys.

I've honestly never been hung up on my front links. I slide on them a lot and they were built with that intention in mind.
You're not the first person to 'see' them and believe I'll hang on them though.

P.S.
It's pronounced "see-rock". You know, like as in: see rock, climb rock, pull Goatman up rock :eek: :cheers:

[Beezil]

goat...

longarms PLUS limiting strap ***IS*** awesome....

I tried a near-vertical ledge climb in attica not too long ago, basically just like dump bump, but more raggedy and crumbly.....one the limiting strap tightened up, it felt like some fat man jumped ont he front bumper.....

[Goatman]

Awhh....you know I just bag on the long arm guys because it became such a fad modification, and many guys made them without thinking through a proper design. With the mounts inside the frame rails, and real big tires, it's much better. I might even run them one day..........naw!!! :D

I also really like my front limiting strap.

See rok, we do need to get together.......on some real rocks. :rolleyes: Moab will be fun, it'll be good to meet you there. We can also talk about the next BOTW. :cheers:

Even though I've already gone another direction, the whole concept of 1/4 eliptics is very interesting. I've been tossing around in my mind the idea of a combo setup to be able to use some airbags. For years I've been looking at how to fit a set of long enough travel airbags to use with the leaf springs, to provide a little softer ride and provide some adjustability. Now, I'm thinking about a half arm, or even a couple of leaves in a 1/4 eliptic, that would run from the frame to the top of the leaf spring plate, and mount an air bag halfway down on that arm. That way, the bag wouldn't have to be so long, and the main leaf pack could use fewer leaves with some of the load being carried by the air bag. The thinner main pack would account for the added weight of the half arm or small 1/4 leaf pack. It could be mounted on the front of the rear shackle box, there's plenty of room for both a mounting point and the air bag, with a shackle/heim joint connection to the spring plate. I still have my old kicker shock mounts on the front of the shackle box, and they would work just fine.

I can see a number of benefits from something like this. Friction is the big enemy of leaf springs, and with fewer leaves in the pack there is less friction, and so less resistance to flexing. Under full droop, the air bag would push down on the spring causing more droop, plus there would still be some weight on the axle adding to the traction. Normally, there is little weight on that tire, just part of the weight of the tire/wheel/axle, when fully drooped. The adjustability would also be there, and since I sometimes run light and sometimes run totally loaded down (like for the Rubicon), that would be nice. Sounds complicated, but it actually would be very simple.

Hmmmm.......

[vintagespeed]

With airbags you've also got lots of options to control your rear articulation in certain situations. You can transfer the air between the bags for unhindered artic. or you can close the valve on one side to keep that bag from deflating or inflating, etc etc.

I used to bag street rides and they sure are fun to play with.

[4ward]

Goat, you're going to see an airbagged 1/4 ellip setup in Moab this year.

I've contemplated the cantilevered link type setup, but think that putting the bag on the leaf pack is a better way to go. My bags will go about 1/3 of the way down the pack. I plan on setting my packs so that if I lose pressure in the bags, I won't be riding all the way back to camp on my bumpstops.

Teardown starts this week :party: Think I'll have it done this time ;)

Sean

[C-ROK]

Air bag over quarter eliptic is exactly what I have too.

I really like the combo as I get the ride height and load carrying characteristics of the air bag and the drop afforded by the quarter eliptic.

http://www.4wdandsportutility.com/features/03024wd_crok05_zoom.jpg

[XJEEPER]

Originally posted by Beezil
you ARE an airbag.

Too much sun with the roof chopped off..........it's finally cooked Sean's noggin.........if he does pull of a good working design, he'll have plenty of hot air to keep the bags full.:D
I just want to see him climb out of UHelldo without a winch:eek:

[4ward]

C, you got a good poser shot of your junk fully flexed up? That's interesting to take the leaf pack from the back of the vehicle, but my main reason for going 1/4 is to hack the back off.

Sean

[C-ROK]

Here's a fairly notorious one (It's been colorized since it was actually white when the photo was taken but the suspension flex is genuine).
http://www.c-rok.com/coverpix2.jpg
(That pic is the lead shot on the website www.c-rok.com if the image attach didn't work)

Most all my CJ/YJ buddies bring the eliptic pack off the frame in front of the axle. It does effect how the vehicle rebounds and the overall effective spring rate. My eliptic set-up is more like what you would see on a trophy truck and more what I would call a "traditional arrangement". When people first started going quarter eliptic in the rock crawler scene some 6 or 7 years ago was the first time I ever saw the forward mounted spring pack.

The rearward mounted worked out for me and was the intended design from the begining. It does give me some overhang but still significantly less than with standard leafs.

[4ward]

I wanna see what your bags look like under droop. What bags are you running and how do you have them plumbed?

Sean

[C-ROK]

In the shot above the bag is fully stretch out, although it's kinda small to see.

The rear bags are Firestone double convolute. Don't recall the model number but they're about 8.5" dia and have a stroke range of about 6" (2.5"collapsed to 8.5" extended or something).

In droop the bag just basically extends out to full range. Since mine set-up is detached, there isn't any pulling force from the spring to the bag as you could get in an attached arrangement.

I plumbed the bags from a central solenoid manifold. Each solenoid valve is a dual solenoid. The solenoids are effectively 3-way (fill, closed, vent). The "fill" solenoid valve is plumbed to my central air system. The "vent" is plumbed to atmosphere.

I purposely went with a small Cv on the valves so that the fill/vent rate would be slow and easier to control on the trail. Each corner is independently controlled so I can force articulation to some degree.

[vintagespeed]

Those would be 2500 lb Firestone bags, single 3/8 NPT ported. Common street air bags, usually cost around $65-75 per bag. www.airride.com has a good deal on them. You can probably luck out & find used ones really cheap too, a few years back I bought a guys setup that he never installed for $100 for 4 bags.

[C-ROK]

That's close Jim. Mine are 1/4" NPT port (and they are available with 3/4" NPT also). I actually have a set of 3/4" NPT bags that I would be willing to sell. Exact same bags as I'm using just with a larger fill port.

My bags are rated higher than 2500lb too. I think around 4000lb. They are a little bigger diameter than the typical street bag or air-ride overloard assist bags.

Evidently though, I, uhhh, didn't get quite the deal that you did.

I got mine directly from Firestone. I downloaded the entire 95 page Engineering Design Guide and tried designs around several of the bags available before I settled on these for the rear.

[Matt S.]

Sean and Beez, have you guys narrowed down your choices on which 1.4 eliptic your going to run??

On C-roks rear overhang, it isnt BAD at all! quiet good compared to leafs as he said. But Is it worth to run the springs in the traditional front mount if your gas tank is still going to be under the a$$ end? And if your gas tank isnt going to be there, i am sure sean would cut off the back of the cherokee, but would beez be willing to hurt such beautiful work?:eek: IMO the reversed detached 1/4 eliptic is killer IF your keeping your back half together. It looks and keeps things clean and un crowded.

MATT

[Goatman]

Originally posted by OneTonXJ
Goat, you're going to see an airbagged 1/4 ellip setup in Moab this year.

I've contemplated the cantilevered link type setup, but think that putting the bag on the leaf pack is a better way to go. My bags will go about 1/3 of the way down the pack. I plan on setting my packs so that if I lose pressure in the bags, I won't be riding all the way back to camp on my bumpstops.

Teardown starts this week :party: Think I'll have it done this time ;)

Sean

I'm not ready to chuck the leaf springs and build a four link yet, so I'm looking for a way to use the air bags with the leaves. I'm not comfortable yet with a bag that will just set on the springs. There are issues with enough travel, and with how to connect the air bag to the leaf spring...I don't want to clamp the spring for the bottom mount. I'm thinking of the cantilevered set up because it can use a short bag, and with a short bag using half of the axle travel there can still be down force from the bag when fully drooped. I have everything I need other than the bags. I also need to rebuild my rear springs, so going to some type of air bag setup will determine how I rebuild the leaves. I need to get more air bag specs.

If I understand Greg's setup clearly, the axle is basically just hanging when fully drooped. What's the point of the 1/4 eliptics? From the pics I don't see how they flex or carry any weight, it seems everything is on the air spring. I think I'm missing something. Does it hurt the air spring to have the weight of the axle hanging from it, or do you have limiting straps?

[vintagespeed]

Air bags aren't meant to hold axle weight when fully extended, they will tear away from the mounting surfaces. If the bags are just providing support & load carrying ability, why do you need them for droop? Can't they be only secured on the top mounting surface and leave the bottom free to separate from the leaves?

[C-ROK]

Once the axle separates from the spring, it is just the unsprung weight holding the axle down. This is not at all unlike any set-up. In fact, with either coils or leaves there is actually a negative spring force pulling the axle UP from the static point at full droop (thus reducing downward tractive force). Check the arch of a static leaf spring (1/4 or 1/2, doesn't matter) laying on the floor versus one extended on a ramp (or trail). Same thing with a captive coil.
My wheel comes off the ground when the limit strap is tight and is 'holding' the axle up. In a captive spring arrangement (without limit straps) the wheel comes off the ground when the negative spring force matches the unsprung weight.

You don't get any downward spring force once you're beyond the static point.

The advantage of keeping tires on the ground is both traction and stability. There's a lot of weight between the axle and tires, having it down on the ground helps keep the CG lower and keep me upright.

With my set-up, when the air bag is inflated, I don't have a lot of up travel from the quarter eliptic. That's just due to the way the air bag levers against the spring arm. The air bag handles the compression and the air bag and quarter elip combined handle the droop. Hidden inside that spring arm is a bump stop that stops the quarter elip compression just before the roller contacts the arm.
From static ride height to the point where the axle separates from the leaf pack is about 15". Through all 15" of that there is downward spring (quarter and air) force on the axle. After the 15" it is unsprung weight only.

Compare the two above pics you can see how much travel there is from the quarter elip. If you look close you should be able to see the delta between the main leaf positions.

[Goatman]

Jim,

Exactly......a couple of friends tried them and would damage the bags because of extending them too far when drooped. I just haven't done enough research lately to see if a bag is made that has enough travel. I was wondering how Greg did it, and I missed that the axle drops free of the spring. I don't know about not attaching the air spring on the bottom, I would be concerned about it over extending itself (more research) and not coming back to the same spot when the axle comes up.....more checking. That new AirRock system has air springs that have to be long enough, but I'm only looking for a supplemental bag, not one that will carry the whole load.

Greg,

I get it now. For stability purposes, I prefer to have the weight of the axle and tire hanging from the vehicle, rather than dropping free. I can see the point of both views, but choose to not let the axle drop free. You have the axle dropping free, but are running a sway bar to add stability back in. It's pertty much a given that excess articulation decreases stability, not adds to it. When my front tire drops off a tall ledge, I want the weight of my tire and axle helping to hold my ass end down, not hanging there not attached. Just different ways of looking at it....... :)

My thought.....and it's only a thought at this point.....is to let the leaf spring locate the axle, and split the weight carrying job with an air spring to allow adjustability and a better ride. On your setup, it looks like the air spring carries all the weight, and the 1/4 eliptic only contributes to droop. I'd like to see it in action, to get a better idea of how it works. You've obviously put a lot of thought into it.

Moab, Moab..... :)

[C-ROK]

Originally posted by Goatman
On your setup, it looks like the air spring carries all the weight, and the 1/4 eliptic only contributes to droop.

For the most part "yes". The airbag handles the bulk of the load carrying and compression load but they both work together throughout the entire (contacting) suspension range.

When dropping down, the air bag also extends downward and rotates the spring arm further down and when compressing up, the quarter elip pack also provides compressive force.

In a sort of, kinda way, it's not that much unlike stacking two different rate coils on a coil over. It's still two springs stacked on top of each other.

[Matt S.]

So has anyone made any progress with there 4 links????

[woody]

You Earthlings are making me VERY angry.

I dunno if Mad Flex is the answer? How does it like Mad Throttle?

[Beezil]

woody....

mad flex is NOT THE PRIORITY!

my goal is to design a BALANCED suspension.....due to the chop-back, I have to take a different approach.....my current leaf springs just aren't a good match for my rig.

[Goatman]

I just picked up a set of older Chev 1/2 ton leaves......56" long with 8 leaves. I'm going to work with the 57" MJ main leaf and a combination of the Chevy leaves, with the full length plastic liners I've been using. I should be able to dial it in without using air bags, but I'm still going to move in that direction when I get a little more time. I found a strong bag that will move from 3" to 12", and can handle the suspension hanging on it, but I measured and that's still not quite enough travel if mounted on top of the spring plate. If mounted forward a ways, they would work, but the bag is just a touch too wide. Still looking.......

Beez, sell those stiff springs and play with a softer set of leaves before you go through the hassle of a link suspension........unless you're really that bored.

Have you tried actually going wheeling to reduce the boredom? :D

[Beezil]

yeah, wheeled not too long ago......

it was great! ripped a pair of doors off, broke 3 axle shaft assys, broke a tracbar mount, and de-laminated my entire framerail in the steeringbox area.....

now the jeep is on jackstands while I position the fullsize axles under them, and I am relocating imaginary links until I am comfortable they will work in the design.

I do not know how much time i will have, but the 1/4 E wants to be designed and bult before moab....

there' nothing like testing new mods on upper hell.

[Gil BullyKatz]

Ya know Beez....If ya do get tired of those springs and want to sell them....Lemme Know!
They're BOR's right?

Maybe if ya get really bored you could design a rolling setup using these and completely go out of this world!

http://mars.jpl.nasa.gov/mer/mission/spacecraft_edl_airbags.html

Gil Bullycatz

[Goatman]

Originally posted by Beezil

I do not know how much time i will have, but the 1/4 E wants to be designed and bult before moab....

there' nothing like testing new mods on upper hell.

We'll be there to either laugh or cry with you.......probably mostly laugh. :laugh: :D

Good luck with whatever you decide to do. We'll see what we each show up with.

[JnJ]

Bringing this one back.
First off, any updates on your designs/plans (not just beez, but any of ya)?
Second, I think in every 1/4 ellip setup I've seen flexed up there is a ton of rear steer. How big of a problem is this and can it be overcome?

[C-ROK]

Quarter elip has nothing to due with rear steer.
How the links are located, their length and the travel geometry of them is what dictates rear steer.
It is maybe more pronounced on quarter eliptic set-ups because of the typically greater travel, but the effect is a result of the linking and not the spring.

I have rear steer but it's because my lower links run parallel to the frame (or perpendicular to the axle). If the lower links are angled inward toward the vehicle centerline, rear steer is reduced. You can even do a lower wishbone set-up and completely eliminate rear steer.

You need to do some 3 view scale geometry (top, end and side) to illustrate, and calculate, the axle position throughout the articulated travel range. Rear steer can be avoided through design. Or, like me, you can live with it and 'try' to drive around it - so to speak.
:)

[Beezil]

c-rok, I'm having trouble visualizing why a lower wishbone would eliminate rear steer?

if the pivot point is in the middle (the wishbone) and your upper links operate on a radius short enough, rear steer will happen during a droop/stuff situation, at least that's how I am plotting it.

It seems to me that the only way to REDUCE rear steer in a 4 -link, even if one of the pairs is a wishbone, is to keep those links operating in a radius large enough, but still allows for the intended roll center and doesn't affect your designed anti squat.....

I'm stil learning, so i only have a half-understanding of this.....i think

[C-ROK]

I'm not sure I'll be able to adequately explain it in words.

Using a scale drawing, it becomes fairly easy to understand.

Imagine your upper links are either a typical 4 link set-up or wishbone.

For the lower links: imagine the axle end being located as far outboard as possible with the frame end angling in towards the center of the vehicle.

As one end of you axle articulates down, that side lower link travels in an arc moving that axle end forward right? Easy to understand. This is the action that generates rear steer.
But what is also happening is that same end of the axle is also traveling in an arc in the perpendicular plane and moving closer under the centerline on the vehicle. Imagine looking at an articulated axle from the direct rear view. The tire is moving UNDER the vehicle.
If you were to look now at a plan view of the link motion with the axle moving under the vehicle, you would see the link effectively pushing the axle backwards and thus negating the forward moving motion of the link dropping.

I might try to sketch this up and scan an image that would better illustrate.

A lower wishbone is fairly easy to understand. The axle pivots about the wishbone center. There is no action pulling the axle ends forward and genertaing rear steer.

[4ward]

B, I believe he is talking about a double triangulated setup :rolleyes:

And if he's not, well, it can still be done. You just have to have a little more room to make it all work. Lower wishbones need to come to a point at the frame end though to get them to work without losing massive clearance though.

My double triangulated 1/4 ellip rear will be on and operating by the end of next weekend. The truss that I need to build has me concerned about basic design principles that I'm in the process of researching.

[C-ROK]

"double triangulated"

Yes.

[CW]

Does anyone have a 1/4 elip with something other than airbags? I like the idea but I'm not so fond of the price of the airbags. I would like to see pics of coils or the jack bolts.

[4ward]

CW, it's actually kind of rare to run airbags with a 1/4 ellip setup. There are those of us out there that need all kinds of different gadgets to break on the trail though.

Mr. Chark, how drunk were you when you made that post. I too am fond of Hooters (in any form ;) ) You ever gonna take that beast of yours wheelin' again? Why don't ya pull your head out of that other place you call home and get out to Moab and play wit da' boyz.

[4ward]

Alright, here we go.

Assumed CoG is 82" in front of rear axle centerline and 38" up.
All links are 40".
9" of vertical seperation at the axle, 3.5" at the frame :eek:
101" wheelbase.
Antisquat calcs out to be 81%.
The lowers converge at the frame, uppers at the axle.
Links are yellow, frame is red, springs are blue, roll axis is purple.

I'm thinking of moving the upper frame mounts up 1" to get more AS and level the RA out completely. I'm definately open for suggestions as I have a decently remedial understanding of how suspensions work. I'm not sure how much axle steer I have, but there won't be much if I get that RA flat.

Once again, thanks to Dave for helping me get this pic up for you to see and critique.

http://www.ajsoffroadarmor.com/cgi-bin/upload/Suspension1.gif

[MaXJohnson]

Sean, at a glance, your anti-squat looks more like 120% than 81%. I think you reversed the operators when you divided the numbers. :)

What CG are you using; vehicle total or unsprung only? Everyone on POR has been basing AS calcs on total vehicle CG (sprung and unsprung) which is wrong. This will give you a % that is less than true AS. The heavier your axles and tires are, the more inaccurate this becomes.

If your drawing is based on total CG, then even 120% is low.

[4ward]

Max, I've done the calcs 5 different times so I think I get it right. Maybe I'm using the wrong formula, what do you use?

As far as the cog, I'm doing the pure guess of putting it at the back of the engine, top of the bellhousing. I don't have access to scales, nor could I even attempt to get it on the scales to do the calcs right now. I figure I'll get it as close as I can with the guessing and then I can find a set of scales sometime after Moab. There may be a set over at the Badlands that I can use when I go over there for testing next month though. I was going to go with the back of the crank, but I changed my mind and went with the top of the bellhousing. Pure guess is my junk is going to weigh appx. 3-3500 lbs. with 1200 lbs worth of axles and tires underneath.

Explain to me why you wouldn't use both please. The forces being applied aren't being applied to the axles, they are being applied to the body. My front springs aren't captured, so they won't pull the vehicle down. The only thing that will pull it down will be the limit straps once it hits max downtravel. Almost the same will apply with the rear since I'm running 1/4 ellip. I don't see it pulling down like a normal set off leafs. That seems to be the logical explanation to me, but I really don't know.


Who knows, I may tear the whole link setup off and redo after the test day. It wouldn't be the first time :D

Oh yeah, I reworked the link locations some, but haven't gotten the drawing up on the web yet. Should be up later tonight or tomorrow.

[MaXJohnson]

Sean,
I'm just eyeballing your drawing. For 100% anti-squat, the line extending from your tire contact patch through the IC will intersect with the front wheel centerline at the same height as the CG. Yours is about 20% above hence the 120% guess. I think the easiest thing to do is draw the 100% line first and then design your IC to land above or below the line depending on your design goals.

Eyeballing is also a pretty good method for locating the CG. There are methods and formulas floating around various websites to calculate the CG by weighing your Jeep on a level surface and then again with one end elevated. This is fine if you have some accurate scales and can elevate one end high enough. The problem is this gives you the CG of the entire vehicle. A while back, I posted a formula to calculate sprung CG based on the total CG, but it requires a a reasonable guess of the weight of your tires, wheels, axles, springs, shocks, suspension arms, drive shaft and steering linkage.

Use the eyeball method, but ignore the unsprung weight. Looking at a sideview picture of your Jeep when you first put in the cage, it appears that the sprung CG would be 6" or more above the top of the tires. If you had 35" tires on at the time, that would put your CG at around 41" or better. It's all a guess. Your 37" figure may be dead on.

http://home.everestkc.net/alynloya/Seans_CG.jpg

The real debate on this topic is; what is the optimum Anti-Squat? Why do I want more, why do I want less? How does driving up a 100% grade (45°) affect the calculations? The effects? I've yet to see some good answers to this.