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wanting to relocate lower control arm brackets

I am fairly new to fabrication and was just wondering what gusset means ..
On the other hand the friend I have helping me with the project..
is an experienced fabricator and I want to be able to pass along to him any help thtat you all give me..
I really couldnt do it with out my friend cause Im not going to try all this without his help and tools.. ie . plasma cutter , stick welder , mig welder ., lots of spare metal and a 20 ton shop press ..its nice to have friends.. oh by the way he is doing all this for free. :)
 
AugFrontD44Update08sm.jpg
 
Let me ask you guys something. If you raise the LCA bracket should not the UCA bracket be moved up the same amount? I guess if you are using the long type it would not matter but I don't like the binding issue with those plus 24" of wheel travel at each wheel out of a stock type susp. is fine for me. Just asking though?
 
simonsxj said:
Let me ask you guys something. If you raise the LCA bracket should not the UCA bracket be moved up the same amount? I guess if you are using the long type it would not matter but I don't like the binding issue with those plus 24" of wheel travel at each wheel out of a stock type susp. is fine for me. Just asking though?
Click to expand...

I thought this through pretty thoroughly before I did this, and I ended up with what I thought out (mostly). I noticed that as I lifted, the upper control arms (UCA) didn't need as much adjustment as the lowers. They are shorter. The angle that the UCA was sitting at with my 6"ish lift was significantly more 'flat' than the lower control arms (LCA). So I started out trying to improve the LCA angle.

When Brent (long ago) and I were talking through his long arm setup, that's pretty much what he was after and he achieved, but I wanted to try something a little different.

My LCA and UCA are within 3/8" of an inch in length and thereby 'droop' within a very similar radius. I like it a lot more than the stock design with the exception that I would lower the mounting point on the axle mount (where you place the bolt for the LCA axle end) to slightly below the axle centerline. That would combat some of my experienced brake dive.
 
I would also think that by raising the UCA mounts equal to the amount the LCA mounts were reaised would help combat brake dive. It may not be as much as if the LCA mount remained below the axle, but I would think it would help some. With more lift there is enough clearance to raise the UCA mounts without worrying about interference.
 
Just remember by changing one arm and not the other you are moving the instant center of the front suspension - by moving it (LCA @ the axle) up you are actually decreasing the amount of anti dive - if you move both arms up you will have similar to stock but the axle may eat bushings more often due to increased leverage...

Matt
 
VegasAnthony said:
I am fairly new to fabrication and was just wondering what gusset means ..
On the other hand the friend I have helping me with the project..
is an experienced fabricator and I want to be able to pass along to him any help thtat you all give me..
I really couldnt do it with out my friend cause Im not going to try all this without his help and tools.. ie . plasma cutter , stick welder , mig welder ., lots of spare metal and a 20 ton shop press ..its nice to have friends.. oh by the way he is doing all this for free. :)
Click to expand...

Anthony, contrary to a few respected comments, I think you are fine with two tabs as a mount for the control arms. They should be 3/16" or 1/4", I use 3/16, should be wide enough to handle the load, and should be properly welded. Many rigs are fabbed up with tabs like that for control arm mounts. If you're a green welder, I'd add a little more beef, but if the welds are strong the tabs will hold, and I'd weld on both sides.

I like using 3x3 boxed tubing, 3/16 wall, to fab up all of my mounts. The 2 5/8" ID is what all the factory mounts are, and what the normal johnny joints are, and it's pretty easy to form mounts out of the square tubing. I always cut out one or two sides, depending on what I'm making. Here's a link to pics of stuff that I've done:

http://www.fototime.com/inv/9C8535B28D6A9A8
 
well gentelmen I did do it and it came out very well the brackets are 1/4" thick and bullet proof..
the problem of brake dive is very evident..
now I guess I will have to change the placement of the upper control arms.. if this doesnt fix the brake dive I will just get another Dana 30 and just beef up the lower control arm mounts so the wont be an issue if the are banged up..
thanks for all the help and advice..
 
Hey there Anthony, haven't seen ya since Training Day with socalxj. You probably wouldn't recognize my rig these days.

On your topic, what you may be experiencing is a lack of torque control on your axle. This could be potentially "really bad" and if the arms loose all control the axle will twist & destroy most everything on the front end.

Can we see some pics? I'd like to know exactly what we're discussing before making too many assumptions.

Jeep positioned the LCA in pretty much the ideal location relative to the axle center. Raising it is going to cause a lack of torque control at some point in the axle's travel (probably on the uptravel side), this is even evident in the stock axle but only at a point where it drops so far that the LCA becomes almost vertical and the axle is able to flop forward & back.

You're best bet is to locate the LCAs ahead & above the axle. Of course this will only work if you're at about 7-8" lift, but you'll maintain torque control throughout all but the extreme bottom of droop (like stock).

Good luck, and dont get crazy trying to make your LCAs work directly behind the axle center, I learned my lesson & had to cut & remake all my mounts a few months back. After hacking on your front suspension you should remove the coils & fully cycle it and make sure that you wont have a problem before driving it and potentially dying.
 
I planned to take pics for anyone ever instrested in this mod..

sorry Im so slow...

actually it drives great execpt for the the brake dive.. better than the stock mount......
stiffer shocks wil help the brake dirve for sure...
I will be in moab if anyone is intrested in checking my work
 
Irregardless of what the common perception if "torque control" and how it relates to link placement, you can place the links off the back side of the axle or even in line with the axle center and above the tube.

The amount of leverage the links have on the axle varies according to placement; however this does not mean with the correct joint (preferably a high quality heim) that you cannot make a safe system (yes OEM rubber bushings will shred as they are implemented for a specific setup where the amount of loading should not excede an accepted figure and are as cheap as possible to do the job)

Just look at most competition rigs out there currently; about 90% of them run the links entirely above the axle center - they rigs are abused heavily and you do not see axles unhinged and flopping out of rigs with failed links or brackets - build it smart with an appropiate amount of material in the link, joint, and bracket and you will have no problems...

Geometry issues like anti-dive/anti-squat are a function of the link relation to the wheelbase and the COG location (and the other links on the axle) - those issues need to be addressed when building the rig and possible altered if undesirable behavior presents itself later (excessive front suspension dive, ect....)

Matt
 
Matt said:
Irregardless of what the common perception if "torque control" and how it relates to link placement, you can place the links off the back side of the axle or even in line with the axle center and above the tube.......
Click to expand...

When your control arm (upper or lower) becomes inline with both the body & axle mount it isn't doing anything to control torque on the axle. It's that simple.
 
vintagespeed said:
When your control arm (upper or lower) becomes inline with both the body & axle mount it isn't doing anything to control torque on the axle. It's that simple.
Click to expand...

Clarify this for me because I think you and I are making assumptions that need to be cleared up...

I believe you are talking about a short arm system at a high lift level with steep operating angles (8+" of lift) as the system droops you can loose rotational control when the arms approach a near vertical postion... A short arm system is good for a stock XJ without excessive amounts of travel or lift you cannot expect that system to remain factory and retain control over the axle at 15"+ of droop...

I am talking about a system that is designed with proper link angles in mind - this means going to a drop bracket or a long arm 4 link or radius arm system at 8+" of lift

You are telling me that in my set up I have no rotational control - I have an upper link that is ~6" above the axle centerline and two lowers that are directly behind the axle... If I disconnect any one of these points the axle can be slid all over by hand - why does this not happen on the road or the trail!

new_lowers2.jpg


Same for my traction bar in the back (ladder style) - the lower mount is on the same horizontal plane as the axle center and the upper is above and behind the axle - if it has not rotational control ho wis it that I can shatter a 5/8" bore heim joint with the throttle pedal....

Finally on my current rig I am building the lowers are above the axle itself - it has been proven over and over again it is the amount of seperation, distance and height from the frame mounting points that determine the amount of leverage the links have on the axle...

front1.JPG
 
Anthony is running a standard short arm XJ suspension (as far as I know) and in this case there is a definite point in the suspension travel that if the lowers are mounted directly behind the tube they will not be controlling torque at all. At a point in up travel where the lower axle mount is raised to the same height as the body mount the axle will rotate forward without anything to keep it from doing so (other than the TB). The same would happen on extreme droop where the upper control arm mount lines up with the upper body mount, at this point the axle will flop backwards without any control. The second case is most likely not going to happen, cause that's alot of droop for a short arm. But it is very likely to happen on up travel.

On my 3 link + TB, I had originally mounted my LCAs behind the axle this way and beyond full droop it would not control the axle at all. The point is that this loss of torque control on the axle is progressive as the axle cycles to a point that it looses ALL control of the rotation of the axle tube. This worried me to a point that I cut all my mounts off & relocated the lowers to a point below the axle centerline to avoid over-stressing them.
 
Cool - just wanted to make sure we were both on the same page - longer arm (25 - 30") is the way to go!

On that MB the links are 43" long and the uppers actually run to a higher mounting point on the axle than their original location on the frame...

On your 3 link is it a triangulated 3 link or more of a wristed radius arm style w/ panhard... Got any pics?

Matt
 
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