I need a suspension analysis, CAD drawings included

[wrecked]

So I'm throwing out my Ford arm's and building up a 3-link. I need some analysis though. I don't really know what I'm doing as far as preventing anti-squat and all that.

So heres what I came up with...
*orange= coils
*red= axle/tierod mount
*blue= cross member(already in place on the jeep)
*grey= frame and links

-The upper link will be mounted to the lower link. I wanted to get some help quick and I figured that you guys are smart enough to figure out that it would be attached.

-Everything should be to scale, except tubing diameters.

-The red block on the left between the coil and the upper link is where my tie rod mounts currently. I put the upper link so that my tie rod wont hit when at full compression or ride hieght, I shouldn't have to worry about it hitting at droop due to the tie rod moving up and out of the way.

-The link length is 44.8 inches. Seems like that may be a little bit long, but I'm going to use the cross member(1/4" thick, braces the frame) that I already have on my heep and it fits that length perfect, plus I want alot of articulation as I 90% if my offroad time on rocks.

-I'm on fullwidths and the link placement in the design is based around that. I also curved the links to mimit the chance of the links hitting the frame during up travel and allow for my to turn a 37" tire to full lock.

Things that I'm looking for are:

1) Is the design is good.
2) What side do I need the upper link on to prevent the axle rotating. I think that I recall that it matters as the drive shaft turns one direction and if your link is on the wrong side it tries to lift that side or something of the sort.
3) Any predictions as to road manners.

Something along those lines.

For the joints

At the frame should I run...

Option A
Uniball

Option B
Spherical Flex Joint

Option C
Jimmy Joint

Option D
The typical rod end

For mounting all 3 links to the axle I will be using bushings. Mainly because using a flexible joint at both ends I believe wiall allow too much play in the axle and it really not nessacary.

Please all that can, chime in with your two cents. I've got to get this project done and driving again in a month and as many problem that can be elimintated as possible before hand would be awesome.

Thanks in advance and sorry for misspellings and bad grammer, its late.

-Kevin

 

[sixshooter]

I am just finishing my fabbed front suspension. I used one upper link from the lower arm to keep the pinion angle from changing. If you can wait about 2 weeks, and possibly remind me, I will let you know how mine worked. I only have an upper arm on the passenger side...no reason in particular, just want to see how only one works. I used a johnny joint for my chassis mount, for the simple fact of vobration. I had a heim end that I was going to use, but I think it will transfer too much noise and vibes for me, especially since I will be driving it on the street.

 

[wrecked]

I am just finishing my fabbed front suspension. I used one upper link from the lower arm to keep the pinion angle from changing. If you can wait about 2 weeks, and possibly remind me, I will let you know how mine worked. I only have an upper arm on the passenger side...no reason in particular, just want to see how only one works. I used a johnny joint for my chassis mount, for the simple fact of vobration. I had a heim end that I was going to use, but I think it will transfer too much noise and vibes for me, especially since I will be driving it on the street.

Ok, that helps me a bit as mine will be getting me to the local college and then to work everyday(10 miles max round trip..small town).

Do you have your link length figured out yet? I'm guessing that your building it with DOM tubing. What thickness? My links i'm sure will be sliding on rocks.

Thanks for the help. Please keep it coming.
-Kevin

 

[gearwhine]

I would advise against bent lower link if you can. I doubt you're tires will be able to stuff enough for one of the links to start point upward, therefore meaning they don't need to be bent for clearance. About tire clerance, try it out, mount a tire, and turn it by hand, take some measurements, and see where you can place straight links. If you can't, then go for bent links, but brace them accordingly.

It is still just a radius arm suspension. TONS of people have them, and you will get the same road manners. The upper arm placement doesn't matter in this case, middle far left, crossed to the opposite side, etc. All that does is prevent the axle from completely rotating. If the upper was attached to the frame, then the placement would matter.

For the bushings at the axle end...you will be getting more play with them than with rod end type joints. With the single upper arm, you are relieving the bind making bushing not needed anymore, so go with a more solid connection. Also, mount the upper arm on a bridge/truss at least connected to the diff.

_nicko_

 

[wrecked]

I would advise against bent lower link if you can. I doubt you're tires will be able to stuff enough for one of the links to start point upward, therefore meaning they don't need to be bent for clearance. About tire clerance, try it out, mount a tire, and turn it by hand, take some measurements, and see where you can place straight links. If you can't, then go for bent links, but brace them accordingly.

With the single upper arm, you are relieving the bind making bushing not needed anymore, so go with a more solid connection. Also, mount the upper arm on a bridge/truss at least connected to the diff.

_nicko_

My current suspension uses the Ford radius arms which do sit slightly outside on the frame end but the positioning on the axle end will be the same. I already have to limit my turning with steer-stops on the knuckles and thats with only a 35" tire. I will be running a 2" narrower tire, but it will be taller and on a wheel with more backspacing to bring everything in closer. I've measured what I could to get it to full lock, but I havent gotten my tires yet or the wheels so I'm not totally positive.

As for the truss... Do I really need a truss coming from the diff? that would be one very long truss. I was thinking I would just add gussets between the already existing panhard mount and the upper link/torque link mount and then again another gusset from the other side of the torque link mount to the axle tube. The torque link mount of course will not be left as 2 plates but rather as a boxed in portion.

Let me know if you still think that this is incorrect.

Thanks.
-Kevin

 

[XJoachim]

Do not bend the lower links. :lecture:

I'm running this setup for over a year now and i know it's downsides. For the joints i used the RE superflex joints on both ends because they are easily maintainable and easy to repair.

The lower link on the passenger side just broke in 2 halves a few weeks ago. It was a lower arm 2" dia. with .120 wall and it just broke.

I'm building new ones right now from 2" dia .4 wall DOM so this will not happen again.

Truss the upper axle mount and use heims for the upper link, they provide less play than any other bushing/joint and that's a good thing for the upper so you don't see shock loads.

The lowers will clear the frame easily, i doubt you will see any clearance issues.

 

[sixshooter]

I am not using a radius arm set up, so my arm lengths wont help you out.

 

[JeepFreak21]

I don't have time to read this thread very thoroughly, but the first thing I'd do is raise the axle side upper mount. There is a lot of torque on that one arm.
Billy

 

[wrecked]

Do not bend the lower links. :lecture:

I'm running this setup for over a year now and i know it's downsides. For the joints i used the RE superflex joints on both ends because they are easily maintainable and easy to repair.

The lower link on the passenger side just broke in 2 halves a few weeks ago. It was a lower arm 2" dia. with .120 wall and it just broke.

I'm building new ones right now from 2" dia .4 wall DOM so this will not happen again.

Truss the upper axle mount and use heims for the upper link, they provide less play than any other bushing/joint and that's a good thing for the upper so you don't see shock loads.

The lowers will clear the frame easily, i doubt you will see any clearance issues.

I wonder if that has anything to do with the welding being right there as the reason it broke. I know with biking alot of bikes with gussetts around the headtubes broke due to the guesset actually weakening the frame. Maybe not though.

As far as the links go, I'm working on redoing with straight links. Hopefully I can pull it off and still get a good turning radius.

If I were to move the axle side link mounts alittle furth inward, would that make the ride less stable or give weird ride characteristics.

Thanks for the help.
-Kevin