Ok... so I gotta know. When an upper link "fails" ... what breaks? Is it the rod end?... the link capture?
link suspension opinions... (3 Viewers)
- Thread starter 1978fj40
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thanks for wording that better than i was able to
bellydoc, that all depends on the weakest part, i've usually seen the frame end mounts fail.
of the two i've seen, one was the link bolt that broke, turned out to be a chinese made "grade 8" from home depot or lowes....
he other time the link mount just ripped off the top of the axle, he didn't get enough penetration on the welds i think...
This seems to be pretty common with housings that have a cast center section. IMO it's really worth it to build your truss so that it can be welded as much as possible to the center section. If you aren't personally personally capable of welding to the cast, then having a shop do it is cheap insurance.
Most of the DIY type guys who are building stuff in their garages really don't have welders capable of burning into the axle tubes enough to withstand the leverage that a tall upper link mount creates.
I don't remeber exactly, but I think one was the bolt. The other time it was the rod end, but he had it extended out too far. I guess he was wishing his links were longer and it broke at the shank. Both were one of the lowers that I have seen break in person. I think your more likely to damage more if a lower goes vs an upper in a 4-link. I haven't hung my rig and tried to see how much it will move side to side. But when I'm putting it together, the axle will rotate much more with a missing lower vs an upper. Put some power into that pinion flange and it rotates with force. That is what will cause most damage, but you can not account for every situation.
I remeber you saying that you had 1"+ dia. shanks on your heims. Much bigger than the one I saw break, it was also most likely damaged before it broke. As long as your links are built to the length you want, not way to short, you'll be fine. Some adjustment is the point, you just don't want to push the limits there.
Dead on. the additional weld will help considerably with making up for "poor" sections of the weld. It also depends on what cast center section you are welding to. 14 bolts are notoriously difficult to weld to. I know of VERY few welds on 14 bolthousings that have held up (even professionally). People will probably bring up the trimmed and welded bottom plates that are so common on 14 bolts but that section may hit rocks, but it does not have 14,000 (or more) ft lbs trying to rip it off either. Dana axles are much nicer to weld to...
Also, if you can, weld to the axle tube, it will prevent the center section from spinning around the axle tubes them selves..
Bolt failures are not as common with good quality bolts (from what I have seen). Poorly designed suspensions that bind up, killing either bolts or heims are..
Carnage is kinda cool as long as you are not behind it
You are gonna hate me for this but..... This statement is wrong. The length of the axle upper link mount (distance from the axle centerline) has nothing to do with the forces that are put on the weld between the axle tube and the link mount itself. It does decrease the forces on the link itself, and on the frame side upper link mount.
The forces that tear the link mounts off of the axle are based on the axle itself (gross simplification but).
People compare the length of a tall upper link mount to a breaker bar. The longer it is, the greater force you have to turn the nut. It's the opposite. You are not trying to "Turn" the nut, you are trying to keep it from turning.
Think of it like a 1/4 hp electric motor. If you put a 1" T on the end grab a hold of it and turn the motor on, it will most likley rip out of your hand and spin. Now, replace the 1' T on the motor, grab the end of the handle and turn it on. Most likely, you will be able to hold the motor in place. The motor is still providing the force, but you are able to hold it easier because of the leverage.
In this example you are the link mount, and the electric motor is the axle.
Having too much shank showing on your rod ends is definitely a common problem. Alot of guys also skimp on them and just run stuff that is too small. I run 1" shank Johnny Joints on my uppers and 1.25" on the lowers(my rig weighs under 2500lbs.) My suspension sponsor is clayton offroad manufacturing. Clayton Walters who owns the company and is a mechanical engineer said that he wouldn't sell me 1" shank JJ's for my lowers even if I had wanted them, regardless of the weight of my rig.
Says the guy who had to redesign his upper link mounts how many times???
I wouldnt' say I hate you for it, but i disagree 100%. It is alot easier to snap a bolt off with a 3 foot breaker bar than a regular 3/8" ratchet...even though in a link setup the torque would be going from the bolt to the handle, it's still being passed through the bolt(weld). I'm no engineer so maybe I'm backwards but a longer moment arm is a longer moment arm in my book.
Says the guy who had to redesign his upper link mounts how many times???
I wouldnt' say I hate you for it, but i disagree 100%. It is alot easier to snap a bolt off with a 3 foot breaker bar than a regular 3/8" ratchet...even though in a link setup the torque would be going from the bolt to the handle, it's still being passed through the bolt(weld). I'm no engineer so maybe I'm backwards but a longer moment arm is a longer moment arm in my book.
There isn't many forces put through your rod ends/links, that wont be absorbed through the suspension. I'm not talking power from the engine as much as forces from impacts. Any time you hit something with your lower links, even right at the frame mount, almost all of the inertia is eaten by the suspension. Not all but most, the majority of the weight that would cause these forces are sprung, and dampened. Your suspension takes away all the momentum that would creat aditional intertia, and resulting extra forces.
I would say your sponsor is wanting you to run overkill parts. Thats a good thing! I understand from his point, he sponsors you to promote his biz. If your suspension breaks, in competition, with his ad's all over your rig, how would he look, bad! You can get away with less,
I would say your sponsor is wanting you to run overkill parts. Thats a good thing! I understand from his point, he sponsors you to promote his biz. If your suspension breaks, in competition, with his ad's all over your rig, how would he look, bad! You can get away with less,
Mace, you are not quite correct, not all forces seen by the mounts are rotational delivered from engine power. If you bounce the truck and come straight down on it perpendicular to the links the moment delivered by a tall mount is going to be significantly more. Forces will remain the same despite mount height.
get away with less, yeah...especially in a lightweight rig, but for longevity and reliability i wouldn't use less than a high strength 1.25" shank for lowers, and no less than 1" shank for uppers
Says the guy who had to redesign his upper link mounts how many times???
Actually, only once
and that was directly because I tried to weld to a 14 bolt It is not replaced by a BTF 14 bolt truss (god those things are beef)..Exactly, no matter what, the force remains the same on the weld no matter how long the lever arm is.
Now the link itself and the frame side link mount will see less
You actually have a good point. But that being said, are those forces greater than a 400 ft lb engine through a 4:1 tranny, 5:1 tcase and 5:1 gearset? considering you have to try pretty hard to come straight down on those links to bypass the shocks ( not to mention the tires). I'm sure it can be done. But the honestly, on that one I have not done the math..
Also, in that instance, was the person on the gas at the same time??
I'd bet that more failures like that were from people on the gas when they hit vs the compressional stresses on the upper links.
Uppers don't see much by way of compressional stresses, they are primarily extensional (there are always exceptions to the rule).
Woody runs high quality 3/4"x5/8" heims all the way around on his 40 with great success.
I run 1.25 on the axle end lowers, and 2" RE joints on the frame side with no issues.
I do prefer the "bashability" of the 1.25's on lower links over the 3/4" jobies. Too many rocks get hit.
upper link forces are pretty grey area in my head, I can see them being in tension, compression and even being neutral. The case I present would be worst case and have seen it happen several times when trying to climb a big vertical-ish slab then losing all traction
Seen it too, and I agree with you to a point. Most of the suspension explosions I have seen in that situation the dude was pretty much standing on the throttle at the same time. The violent hit and instant traction = :nuke:
any clue to which way the mounts tore off? Link in compression or tension?
Actually, the pinion was always pointed up, so tension in the end. But they were also standing on the throttle at the time. People tend to back off when s*** goes BANG!!!
Actualy, that would be awesome to see in slow motion
You are right tho, in that situation, I can see how the upper links would be in compression.
unless you put the lower links slightly above the axle centerline
I love suspension s***
Actualy, that would be awesome to see in slow motion
You are right tho, in that situation, I can see how the upper links would be in compression.
unless you put the lower links slightly above the axle centerline
I love suspension s***
im taking off the leaf springs on back my buggy and looking to do the Y style link set up wher u have just the lower arms and the top arms conect to the lower , with coil overs , i seen they got that on some of the newer jeeps any body here have that set up are seen it work ?
I think you're describing a version of the radius arm. There's a lot of technology involved in maxing the capability of radius arms. I've done some reading about them, but rather than regurgitate what I learned, I suggest you read about this yourself. There are some controversies about the value of radius arms versus conventional linked supsensions, so you may find you've just opened a can of worms.
yeaa figues best to stay old skool 4 link cant go wrong , just trying to see if any one done this are seen any thing but a jk run this i seen it in a catalong rubicon express sells a kit
Radius arms are old school.
Most likely, they will have some pretty serious quirks associated with them in a rear application with a reasonable amount of articulation.
Best to go 3 or 4 link.
Most likely, they will have some pretty serious quirks associated with them in a rear application with a reasonable amount of articulation.
Best to go 3 or 4 link.
