REAR 1/4 Elliptical suspensions for XJ's

[C-ROK]

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 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 :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!!!

I also really like my front limiting strap.

See rok, we do need to get together.......on some real rocks. 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 arty: 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.

 

[XJEEPER]

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.
I just want to see him climb out of UHelldo without a winch

 

[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).

(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? 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]

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 arty: 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]

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????