without reincarnating the suspension GOD thread i need some 4 link front and rear design help

Camo if you were building yours again would you try to triangulate top and bottom links (XX) ? (similar to Desertoy's)
or are you happy with yours ? (IVI)

Desertoy's setup (XX) appears to have very little rear steer

i made a mock up this weekend both ways ( IVI and XX ) and either way i can make my links same length front and rear top and bottom (about 52") is this too long ???

(in the front this lines up with with the CV joint in the driveshaft.)
throughout travel there is less than 1/4" silp required in the driveshaft

(in the rear the frame mount for the links is 12" in front of the CV)
throughout travel there is 1 1/2" silp required in the rear driveshaft this is still alot less than even the factory setup (i could move the rear links back in line with the CV but them link lenghts would not be common front and rear

dazed and confused
(my Jeep looks funny with wooden axles)

Your going to have horrible bumpsteer unless you get your draglink perfectly flat, even then you still might have a little.

CJ

CJ... i was hoping that you would chime in... i tried to view your recent pics and your page wont come up ???

as far as the drag link goes i hav'nt got that far yet... just figuring out the 4 links... any tricks to help drag link straitness would be appreciated. (FWIW the pitman arm is in front of the pumpkin at full compression of the drivers side)

Brian

personally, i prefer deserttoy's method, (XX). I would also make the rear arms coneect to the frame at the same point as the driveshaft. This will keep the u-joints from binding if you ever bottom out the suspension, and have to throttle it(i.e. hi-speed jumping, or getting high-centered). making the arms shorter will also increase the sideways angle on both upper and lowers, and that should help keep the axle centered under the rig a little better.

just my opinion-

i agree on the shorter arms will be stronger.
i can make the rear axle arms shorter easily.

but the front.... if i line them up with the front CV the arms are 52" or so (not much angle) i can triangulate the front uppers sharper (shorter) but not the lowers i just dont like the pinion change with longer lower and shorter upper.

i just dont like the pinion change with longer lower and shorter upper.

yeah, i hear that. I am gonna run a 3 link and panhard in the front. two lowers as long as the driveshaft will be outside the frame, and one upper that is a little shorter will be directly under the frame on the pass. side. Then a panhard, and voila!

just another thought, hehehe.

elf, Ideally your upper link would be longer than the lowers, otherwise on extension the pinion would rotate downwards, which in turn worsens the u-joint angles. Otherwise connect the upper link back into the lower and you would wind up with a setup that would function like a wristed radius arm, and always keep the pinion pointed at the transfercase.

elf... i just dont like the the panhard rod because of the lateral movement of the axle from compression to droop. (on a typical lifted 6" TJ this can be as much a 6-7")

crazy... let me propose an even better idea that does work... mount all your arms such that the arms and driveshaft (CV) all start in the same horizontal plane. I did this (mockup) and the pinion always points at the CV (even at 80 degree droop of both axles (tires would touch on the lift) My only problem is the lenght of the front arms would be 52" i am not sure that they would be strong enough to support the Jeep laterally.

Originally posted by redruM
elf... i just dont like the the panhard rod because of the lateral movement of the axle from compression to droop. (on a typical lifted 6" TJ this can be as much a 6-7")

crazy... let me propose an even better idea that does work... mount all your arms such that the arms and driveshaft (CV) all start in the same horizontal plane. I did this (mockup) and the pinion always points at the CV (even at 80 degree droop of both axles (tires would touch on the lift) My only problem is the lenght of the front arms would be 52" i am not sure that they would be strong enough to support the Jeep laterally.

tou need the lateral movement in the front to eliminate bumpsteer, or are you going full hydraulic steering? Otherwise what happens is the drag link travels in an arc, but w/o a track bar the axle moves straight up and down. This difference in movement causes violent bumpsteer, and would make the truck almost undriveable on the street. I'm trying to figure out how you had things mocked up for your suspension, because equal length paralell links won't kep the pinion pointed at the CV joint throughout travel, they'll keep the pinion in the exact same orientation to a reference plane throughout travel (perfect for a non CV driveline). To rotate the pinion upwards under droop (like you need for a CV driveline) the upper links must be longer than the lowers...I've beed working with this, and modeling it in CAD, since I'm building a link setup for the back of my EB this summer...

Originally posted by elf_cruiser


yeah, i hear that. I am gonna run a 3 link and panhard in the front. two lowers as long as the driveshaft will be outside the frame, and one upper that is a little shorter will be directly under the frame on the pass. side. Then a panhard, and voila!

just another thought, hehehe.

I would expect that setup to bind up like a mofo. I would consider just going 3 link.

I am no expert here but the numbers I had been running pointed me toward 25"-30" arms for a stock wheelbase TJ.

[B]redrum [B]- I would highly recommend the opposing A-links or 4 independent links in the same shape(like Desertoys). It has worked really well on my truck so far and there is no rear steer at all which is quite nice. If you can run it up front, that would be even better. I will eventually, but for now, I have switched over a standard 4 link for now until I am finished wheeling for the season.

For reference on the link lengths, I run arms that are only 29"s long. I would recommend different length arms to keep the pinion pointed properly, but it hasn't really effected my setup much. Even with short arms, I have no rear steer.

If you want to see a very old writeup that hasn't been updated in a few years, then go here:
http://www.sierrarockcrawlers.com/tech/projects/willys/projectwillys.html

If you want to see it in motion, you will have to look at the stories section of the website.

-Sam

p.s. - don't run the bronco bushing or the S2-link design. They can work, but I had poor luck with them.

if you run a fore-aft steering link the same length as the suspension links it would eliminate bumpsteer pretty well. saw this on a jeep in the magazines at one point, either ran the steering box under his seat somehow or had a link back from it to a pivot and then forwards to his axle

http://www.sierrarockcrawlers.com/images2/w0048.jpg

Is something like this a trail only setup? How would this handle on the road?

CrazyHorse:otherwise on extension the pinion would rotate downwards, which in turn worsens the u-joint angles.

the arms won't be more than a few inches different in length, so i don't expect a whole lot of pinio rotation, and i don't have a CV shaft up front so I want the pinion to stay somewhat level.

Otherwise connect the upper link back into the lower

If i did this i would have to get a CV front, not a realy big deal, but i kinda want to keep it as hassle free as possible.

thanks for the input, have we covered anything redrum?? or are you still not sure??

Originally posted by mytzlflick
if you run a fore-aft steering link the same length as the suspension links it would eliminate bumpsteer pretty well. saw this on a jeep in the magazines at one point, either ran the steering box under his seat somehow or had a link back from it to a pivot and then forwards to his axle


I've been thinking about this, I was looking at my brother-in-law's Outlaw sprint car yesterday, they have fore-aft steering accomplished by mounting the steering wheel directly to a steering box with a longer shaft to the pitman arm. The pitman arm sits outside the body and has a 3' drag link with heim joints running to the knuckle, wouldn't bind at all, but it might turn your wheels when one side of the axle drooped. Wouldn't want a leaky box dripping hot fluid on your toes tho.

Originally posted by attachcurrie
http://www.sierrarockcrawlers.com/images2/w0048.jpg

Is something like this a trail only setup? How would this handle on the road?

attachcurrie - Not sure which part you are referring to about the setup of the rear suspension. If you are referring to the whole thing in the picture, yes it can work fine for the street. It locates the axle really well and doesn't have any weird movement to it to throw the truck around. So far, the only problem I have had on the street with the truck is the 4 link front which lets the axle walk forward and back as it articulates. Mix that with soft coils and I get leanover steer. Running full hydro steering also adds to it which creates for an interesting ride above 35mph. It's a trailer queen and my "run to the border" rig for when I need to pick up some burritos in style, so I rarely have it on the street anyway.

-Sam

Redrum,

If your building your suspension from scratch you can eliminate most of the problems of the stock suspension design. Not all trackbar suspensions have as many downsides to them as the stock setup lifted 6". You can actually achieve very similar handling and suspension geometry if you are willing to make some modifications to your jeep, which apparently you are.

A triangulated 4 link suspension moves straight up and down. A draglink running from the pitman arm to the steering knuckle when compressed straight up and down will steer to the driver's side on compression and to the passenger side on droop, holding the steering wheel centered. So if your driving your jeep at 65mph on a highway and there is a big dip in the road, your suspension might compress 4" let's say. The triangulated 4link will compress straight up 4". Now the draglink which is at an angle will will move the knuckle to the right, steering you right completely on it's own.

If you build a trackbar around the steering geometry...you can get them to move very very similar. So that on that compression of 4", the axle is moving over exactly the same amount that the draglink is trying to turn the wheel. So, in effect they cancel out and you continue straight, just like you thought you would.

You can certainly make your draglink operate at normal suspension travel so that the negative effects of the mis-matched setups aren't very noticible....but it isn't the most ideal thing in the world.

You also need to make the roll center the exact same height as your draglink attachment point on the steering arm so that when you turn the wheel sitting still, you don't create a lever arm which will rock the vehicle. Watch some trucks, if the person turns right the body will roll to the left....it ideally should stay still.

Some random thoughts for ya.

CJ

Brian, would it help you to just drive mine?

I have wheeled it in the rocks, works great, I have driven it on trails, it does fine and have even had it up to 70 on the highway and it tracks straight and true. The only issue I have had is jumping it. I was sprinting down a dirt road, hit a hump in the road that had a culvert in it at about 50mph and I did get bump steer. A real surprise to me as I had experienced no strange handling up to that point. It is actually much more driveable in all conditions than the leaf springs.

Let me know.

Ed

SAM-

I run the S2 link in the front of my cruiser but instead of the radius arm i used separate upper and lower trailing arms.
It works ok on the street.

When it flexes up it does flex sideways to some degree causing some steering problems.
I am going to change to two lower trailing arms and an upper a frame front and rear.

all right this is what i was hoping for...

CJ...
i completely understand what you were saying about the bumpsteer now. let me ask you a question... if your draglink was perfectly flat with a suspension that wants to travel straight up and down... bumpsteer would be kept to a minimum correct ?

Roll Center... i have been trying to figure this out in my configuration i think my roll center is parallel to my upper arms. i will post a sketch after i draw it and scan it.

i am not 100% oposed to a panhard rod but i still have yet to see one that "worked with the steering geometry" have you figured this out ?

Crazy...
Yes to Hydrolic Steering

Crazy, Sam...
As far as pinion angle (front) if i have all my arms the same lenght, starting on the frame in the same plane as the CV Joint on the front driveshaft conecting to the axle 8" apart up and down in a XX configuration... the pinion will always point at the center of the CV and if you get it perfect the driveshaft would not need any slip (as mine is mocked up now it only slips 1/4") i can drop the axle all the way to the 90 degrees under the truck and the pinion is still pointed at the CV

Taxi...
Sure driving would be cool... but i would rather have you come over and look at mine... if you ever get over Lewisville way call me i would like to show you my wooden axles/conduit before i start on the real ones. 972-824-8610

if your draglink was perfectly flat with a suspension that wants to travel straight up and down... bumpsteer would be kept to a minimum correct ?

Yeah, that is true. If you are planning on full hydro soon, then i say go for it, and if its too hard to drive, just don't go fast until you can get hydro steer.

On the panhard rod, it just needs to be the same length as the draglink, and at the same angle. The longer and flatter these can be, the less the axle will move side to side.

Good Luck!

sketch

not going full hydro just hydro assist

how do you keep the panhard and the drag link same? one in front of the other ???

ok, now with your pic I see what you're doing, I thought you were talking about equal length and paralell, which would act as I described earlier. With the links converging in the side view, you're right, it will keep the pinion pointed more at the CV joint. My upper and lower a frames will be paralell to each other, but the uppers will be about 3" longer. AS for keeping the drag link and panhard paralell, you can either have the drag link in front of the panhard bar, or you can try to have them more one over the other. The critical thing to have paralell is actually the arcs that the axle ends of them travel in, if you disconnected the drag link and trac bar from the axle, and traced the ark yhey travel in, I deally they would be in paralell arcs.

in the sketch above is there any need for a panhard ???

i need to put a draglink on my wooden axle (mockup) and see if it is affected

redrum - In the sketch, there is no need for the panhard. That is exacly what I run now and I have no movement in the axle.

Also, for the pinion movement problem, I only see it when I get vertical travel out of the suspension (jumping for example). I built 2 idential A-arms that oppose each other and the pinion actually comes up and hits the crossover in the top A-link under heavy compression. I built them years ago when I didn't know anything in attempt at an idea. I was looking for the ideal 100% 2 point rotation suspension to combat axle walk. I have since tested it of course and found that running 4 independent links will not be quite the same, but close enough to not even notice a difference. For the next revision front and rear, I will be switching to the 4 independent links in the same configuration to have trail spares, front and rear interchangeabilty, and shortening of the front links to increase the undercarriage approach angles. I like the 29 inch links that I have now.

-Sam

sam

do you drive yours on the street much... i love Sierra site and your S-2 link is where i started... the only reason i abandoned it was you said you couldnt make it work right... any further ideas ?

FWIW i am shooting for 105" WB and 50" arms F&R with 5" seperation should get me there

are the aerostar coils still holding you up or did you change them out because they were too soft ?

Redrum - I think that the weight of your TJ might be a little much for the Aerostars actually. I just built another Slinky rig for my buddy Randy and it was on a Suzuki that has been gutted. Still pretty soft, but actually pretty good. I personally like the Slinky as it is. Most think that it is too soft and it probably is, but it is so much fun to drive. It is probably too soft for most people who want the go ANYWHERE rig, but I am really happy for where I have been able to go so far which is pretty much everywhere so far :)

If you want super duper squishy ride, then these coils are for you, otherwise, stay away from them. Even super soft, I still can get around. Might roll sooner though ...... but oh well. ;)

-Sam

http://www.sierrarockcrawlers.com/images2/1064.jpg

CJ
is your site down been trying to check out your progress for 3 days now ???

Sam
do you have any problems with bumpsteer?

i think the aerostar springs will be way too light for mine... i saw a picture of your slinky sidehilling and the body looked ready to go over but the tires were still sticking...

two questions about the aerostars

do you have them retained top and bottom ?

if so how much do they stretch ?

redruM - I do have the coils retained top and bottom. I like to have the suspension all tied in. They stretch out pretty far since they are so soft. The only thing though is that I have actually yielded the springs throughout all my twists on trails and cycles of the suspension. Because they are so cheap to get (my buddy has been really cool in hooking me up with a 6 pack of em.) that I don't worry too much about wearing them out.

-Sam