how's this rear 4-link design look?

[3/4tonYJ]

1st off, sorry for the bad pictures.
I've copied others designs i think i'm capable of building and changed alittle to fit my plan, searched and read.

any critiques welcome, flame away if desired...........

lowers are 40" long
uppers are 34" long, 30" as viewed from side
both lower ends and rear upper ends use "johnny joint" style ends.
upper front uses standard sleeved poly bushings.
@ 7" seperation at front
@ 10" seperation at front
using springs with a compressed length of 15"
and own 38" TSL's about 37" actual height

i know it been posted about alot, thanks for any help...........
http://www.pirate4x4.com/forum/attachment.php?attachmentid=186138&stc=1
http://www.pirate4x4.com/forum/attachment.php?attachmentid=186139&stc=1
threw in one of my "rock ring"
http://www.pirate4x4.com/forum/attachment.php?attachmentid=186137&stc=1

[BrettM]

don't oreint your upper's frame side bushings like that unless you're doing a 3 link. with a 4 link you want the bolt going through that bushing to be perpindicular to the link in all planes.

[rioshilo]

Ditto that, you'll want mounts that angle out from the frame. Like the one seen here standing upright on the edge of the table...

http://members.cox.net/carlinenicole/four%20link%20039.jpg

[3/4tonYJ]

don't oreint your upper's frame side bushings like that

thanks, that design was made to make mounting simpler, but i don't want simpler if it's not a good idea,

"rioshilo" thanks for the picture, i like your design. i was also am planning a mount that had multiple location choices for the uppers.

my reason for choosing a "Poly" bushing is because i've read about designs that use all rod ends are alittle too rigid...... i can't imagine the upper/forward ends requiring much range of motion,(just up/down pivoting on the bolt axis) think a fixed rubber or poly end would be a better choice than "johnny joints" all around?

[DownNDirty]

I believe that you can get all the flex you want with ploy or rubber bushings on both the lower and upper frame ends. Why did you do a little triangulation of the lowers? It seems like there isn't enough there to justify the added fabrication effort. Also shouldn't you move the lower axle tabs down just a little so that they are below the centerline of the axle. This will help keep the axle from trying to wrap around on you. The forces with it parrallel are pretty nasty. Thanks for another 4 link post though. It is always nice to see into others heads when it comes to suspension.

[JohnC]

Fights rear steer.

[Devil Dog]

lookin good gregg... and ya.. keep the bolts perpindicular with the arms they go thru... will take a lot of stress off of them... but you cant do anything from italy silly squid.... ive hacked my jeep in half... putting in quarter elliptical.. have the springs in... just need to fab the 4 link when i return next year...
keep in touch..

[3/4tonYJ]

lookin good gregg... but you cant do anything from italy silly squid.... keep in touch..

lol patrick, i hear that, but my plan is to buy, make or get made everything i can think of for a 4-link rear and 3-link front. so when i get back, i can go to work.
working on my 2wd Yota is fun, but not that fun.

"downndirty" the slight trianglation of the lowers i figure will help "some" with left/right movement of the axle, with a small about of extra work....(they will actually be angled alittle more than pictured, it dependings on tire/wheel clearance, "full width dana 70 with hummer wheels")
so rotating the lower aft mounts down, will add more leverage to fight axle wrap..........do you think 1" will make a lot of different? i guess it will also add more link seperation, which is good?

[DownNDirty]

Well I am still crunching numbers and trying to figure out my 4 link setup. One reason I am happy to see another thread. With the link parrallel to the moment of force it doesn't help with axle wrap. Only the top link is really working to keep the axle from rotating since it is the large lever. Dropping the lower link below the center of the axle (place where the rotating force is) both the upper and lower link fight the wrap and also seperates the links more. Placing it equal only helps with ground clearence, but not by much since the pumkin still sits down so low. Just put a slight angle on the lower links and then they will be sliders as well as link mounts. I wasn't sure if the small triangulation would be worth the work on the lowers. I was thinking about double triangulation, and keep hitting binding issues. I am trying to run full width axles on a willys so I can really pull those lower links out if I need to.

[Infernal Jeep]

Really usefull thread!...I'm doing the same on a YJ with full width 1 tons.

[3/4tonYJ]

since the thread is still alive,
i'm now thinking about using factory Jeep lower control arm bushings on the foward end of the upper links. my experience is they can take alot of abuse (and are cheap to replace) but mainly i think it will keep it from having that rigid/harsh "i used all metal RodEnds" feel....(any comments welcome)
and get the bushing sleeves from rocklogic4x4.com
http://www.pirate4x4.com/forum/attachment.php?attachmentid=186437&stc=1

and for info, i'm using these "joints" that i purchased from suicidedoors.com
the thread is 1 1/8" and everything is nicely TIG welded.

http://www.pirate4x4.com/forum/attachment.php?attachmentid=186438&stc=1

[Bart CJ5]

and for info, i'm using these "joints" that i purchased from suicidedoors.com
the thread is 1 1/8" and everything is nicely TIG welded.

http://www.pirate4x4.com/forum/attachment.php?attachmentid=186438&stc=1

Cheese and rice, what are you building a Duece and a Half? 1 1/8th big enough?

[3/4tonYJ]

Cheese and rice, what are you building a Duece and a Half? 1 1/8th big enough?

you can tap 1" I.D. tubing to 1 1/8" thread.............so ya don't need any "threaded tube adapters" to weld in............ :D

[tobster]

when i was doing a 4 link on my yj we cut the rear end of the frame right before it starts to do the little half circle and built a tube frame in it place. it lets you have a shorter ride height but get the same flex out of it and it also makes your frame alot stronger. i know it doesnt realy have anything to do with a 4 link but just given you the idea

[MattPascoe]

With the link parrallel to the moment of force it doesn't help with axle wrap. Only the top link is really working to keep the axle from rotating since it is the large lever. Dropping the lower link below the center of the axle (place where the rotating force is) both the upper and lower link fight the wrap and also seperates the links more.
I don't agree with this. Your "lever" is dictated by the horizontal seperation, the 10" that he mentions. It does not matter if the 10" lever is all above the axle cl or split 5" above and 5" below. I ran my lower links similar to how he has them drawn, slightly above the axle cl to keep them outta the rocks.

i'm now thinking about using factory Jeep lower control arm bushings on the foward end of the upper links. my experience is they can take alot of abuse (and are cheap to replace) but mainly i think it will keep it from having that rigid/harsh "i used all metal RodEnds" feel....(any comments welcome)
I was concerned about this as well, but finally decided to use heims at all link ends. I have experienced no rigid/harsh feedback from the suspension. It's actually amazingly smooth compared to leafs.

3/4tonYJ, I like you link design (it was what I mentally started with) but I am pretty sure you will have a positive roll axis. What does that mean in terms of ride/handling? Beats me, but I know ideally you want a flat roll axis or slightly negative (sloping to the front)

[bigblackblur]

Im also going to be doing this except on a CJ7 starting in december, good to see some ideas getting out there. Have you thought of bending your lowers once you know your design is sound in order to get some more clearance under them? I think I want to do that but I cant think of how I would keep them off the frame upon uptravel... Anyone who can explain where to place the axle ends of the lowers in order to do that it would be appreciated.

3/4tonYJ have you run all your numbers through the 4 link calc? I think it would help you gain a better understanding for your design if you havent done that already. I've kinda been toying with it for a month or so and it really helps you understand what happens when you make changes to your link placement.

[1972CJ5+1]

Ditto on the upper link mounts at the frame. Here is a pic of mine. Very similar to what you are looking at, but with the angles you need. Mine are heims though.http://www.pirate4x4.com/forum/showthread.php?t=281886
Here is a link to my 4link build.

[ryankopecki]

I don't agree with this. Your "lever" is dictated by the horizontal seperation, the 10" that he mentions. It does not matter if the 10" lever is all above the axle cl or split 5" above and 5" below. I ran my lower links similar to how he has them drawn, slightly above the axle cl to keep them outta the rocks.


Still not right. The force is applied at the ground. So, if you have 10" of seperation, I draw picture.

http://img.photobucket.com/albums/v160/ryankopecki/misc/LEVER.jpg

I which does the blue lower link have more force on it?

Here I put the lower 5" above or below the tube to show the difference. But if you have 10" of seperation and the lower is 1" above the tube, it's really not gonna make enough difference to worry about than if the lower was 1" below the tube. You can put the lowers on top of the tube as long as you use strong enough joints.

[P&T Jeeps]

yup, keep the lowers where you have them. it wont make enough difference on the wrap and you'll greatly appreciate the ground clearance. you might get a few ideas from my TJ 4-link thread: http://www.pirate4x4.com/forum/showthread.php?t=274444

[MattPascoe]

ryankopecki , Thanks for taking the time to draw that out. Makes perfect sence when you look at it like that...

[crackerboyLV]

You are correct to a degree, but the moment is around the axle centerline not the ground. The force in the upper link is 15" from center while the lower link is 5" from center. The lower link will see 3 times the force of the upper link. The diagram on the left is stronger because the force on the links is equal. Before this starts a flame war, yes I know I have neglected the horizontal and vertical components of the equation as well as moments of inertia, anti squat, etc. I'm just trying to keep somebody from getting hurt. If you use that design for ground clearance (which is a good thing) make sure the links and brackets can take the extra stress. Be Safe:)

[XJ618]

I dono 4 links yet, but the rock ring is tight.