Long Arms breaking Front UCAs

[Timzjatl]

Alright here's my setup-


Custom Long Arms, Front setup like Clayton's/RE with a Long lower arm and short uppers coming off of there to control Axle Wrap/pinion angle. I have heard that this setup wants to twist the axle tubes under flex, and an easy model would be using your index and middle fingers on both hands to model the arms... now articulate the "axle" and see what I mean. Originally I figured that the rubber bushings at the axle end of the uppers (heims at the arm end) would be enough to allow misalignment during flex... apparently I am mistaken
This weekend Both Pearce and I (both running my setup) broke our drivers side upper control arms on the front. The trail we were running was a lot of large V ditches, lots of flexing... I broke the Heim (3/4" economy steel heim) and he broke the welds that hold the upper arm to the U shaped bracket that mounts to the arm tube.
Now here's my question-
has anyone with another long arm setup had this happen... our simple finger model proves that the front definitely tries to twist the axle under articulation. I know that Claytons/RE have roughly the same setup. I don't want to beef these arms up more, because I'd rather break them than twist the axle tubes or break the axle end mounts off. I know that Rockcrawler runs the same setup in the front, except for only one arm, but the jeep is not as "Solid" feeling with only one upper. I suppose I could make a "disconnect" front arm, or just take one out for wheeling, but I'd rather do something that fixes the problem... thanks for any insight-
Tim

[Chris L]

Tim, any pics?

[Timzjatl]

Will post some later tonight...
basically I'm trashing the UCA on the drivers side, anywhich way I can

[brent]

tim, when I first did my long arms, I tore the passinger side bracket off the axle, so I beefed it up a lot, and this last trip I took, I tore the drivers side off the axle, after doing that, I ran sledge hammer with only one, I did weld the drivers side back on and took the arm allong incase something happened to the pass side, but I had no problems, and since then, I came home, moved the lower arm mounts up directly behind the axle tube, and beefed up the passinger side axle mount. this is what it looks like now.

[brent]

another

[brent]

drivers side

[Timzjatl]

Brent-
That is really sweet, looks beefy as hell... I guess the theory is that the closer the upper and lower arms are to each other, the less twist on the axle housing, bushings etc... (when they completely converge its much like a Ford Radius arm) Aren't you worried about twisting your axle tubes now? Basically you've still got the same problem of the twisting motion, albeit less than before, but still there.... And now your mounts aren't going anywhere... Whats gonna give? you gotta pray its the arms... Appreciate the input, I still wonder how the RE, Claytons, and others are getting away with using stock mounts etc... Now maybe I should just find a D44 out of a bronco, and adapt the radius arms to mount to my mounts....
Tim

[brent]

tim, there is only one upper arm, its the one on the passinger side,

[Timzjatl]

Ahhh... sweet. I shoulda cought that, but didn't... i thought of that, but problem is my jeep feels less stable with just one arm. Guess the disconect arm is sounding better and better. Of course putting my front swaybar back in might make it feel more stable as well... I'll drive Pearce's and see, he has a front swaybar in.... Thanks again-
Tim

[cbassett]

Hmm, I don't seem to be having that problem Tim.
http://home.off-road.com/~bassettsbe...1/04210075.JPG



Search for Borton's posts last year on the pirate4x4.com General forum, as his first rev ripped front uppers. Although his 1st rev's problems were due to welded joint (joint a flexible joint) where the uppers met the lowers, you may find some insight on those threads. It could be that one/more of the joints you're using are not allowing enough flex, something has to give. Without seeing where the rips occured, it's possible that your design is sound but the welds were inferior.

[cbassett]

Oh yeah, pic 69 is NOT my arm! It's another rig in my group.

[chadjans]

Is this the very reason Blaine used J-arms with his setup? Seems though that the factory mounting location would reduce axle wrap and mounting the arms directly behind the tube with cause more axle wrap. Although I am not a physics major j-arms would be the best in controling axle wrap. Tim this is a difficult problem you have been presented with. MMM

Chad

[Timzjatl]

One of this weekends failures likely could be due to an inferior weld... although the bracket that broke got pretty tweaked, the arm peeled off, bending 1/4" plate... The other one, I ripped the Heim at where the upper arm comes to the lower arm to shreds, fractured the part that wraps around the ball and straitened it out. If you look in my long arms album at http://community.webshots.com/user/timzj you can see how the uppers meet the lowers, with a heim. In theory this joint shouldn't even move, right? If this Joint moves, then the relation between the UCA mounts and the LCA mounts on the axle has changed = BAD... Anyways I'll take pictures of the failed parts tonight and post them...
Thanks
Tim

[brent]

Originally posted by cbassett


Search for Borton's posts last year on the pirate4x4.com General forum, as his first rev ripped front uppers. Although his 1st rev's problems were due to welded joint (joint a flexible joint) where the uppers met the lowers, you may find some insight on those threads. It could be that one/more of the joints you're using are not allowing enough flex, something has to give. Without seeing where the rips occured, it's possible that your design is sound but the welds were inferior.

well first off, if I could find that pic of the torn off passinger side, I'd post it, but when I tore it off the axle, It was just after I did the long arms, and where I now have a Heim joint (where the uppers meet the lowers) it was welded, now I don't think it would make any diffrence if this was welded or not, that bracket was going to come off the axle, it was braced in the wrong axis, and I just eliminated a lot of other stresses limiting flex with the long arms, and this is where the "give" was happening when the housing was being used like a tortion bar, since I tore that one off, I braced it better and added the heim joints, this did a couple of things, it allowed for a little give in the arms, they could twist a little and they would also twist the lower arms allowing for a little more give, all was fine till I ran in pheonix, when I had stressed the tube that goes over my front pumpkin enough that it finally tore allong the outside of the upper controll arm mount and its gussetts, this got me thinking why do i need two arms???? Rock crawler's long arms only have one upper link, Richard Gaunthier has had good luck with his one upper arm, so I ran in JV with only one upper, then came home and changed things yet again, I put the lower arms directly behind the axle tube, these will now take most if not all the pounding force backwards, the upper arm is there to keep the pinion / caster / axle wrap in check. only time will tell if it is going to hold up, but it won't be breaking due to the axle being used as a tortion bar while flexing.

with the ford radius arms the bushings take the twist stress., and I thought about putting one radius arm on one side, running no upper arms, and one of the lowers I now have on the other side :idea:

[Pearce]

brent,
Any thought to using the single upper on the drivers side vs the passenger side? I ask since one is a welded bracket and the other cast in the pumpkin. Or did you not realy have any reason for one or the other?
Its funny, I actually chose not to wheel the rest of the day like that, and I belive Tim's was also broke for some time, and it worked just fine.

[brent]

Originally posted by Pearce
brent,
one is a welded bracket and the other cast in the pumpkin

the stock 30 is long gone, both mine are welded on the 44

[Timzjatl]

Thanks again Brent. Do you notice any difference in High Speed stability with only three arms? Mine seemed much more stable with four, possibly because the front axle is acting like a torsion bar. Of course I am not currently running a swaybar, so maybe if I re-install that it'll get better. I am thinking my current plan of action will be to beef up the factory passenger side UCA mount and carry a spare arm to attach to the passenger side just incase.... That and re-install the front swaybar(for stability). Long term plans may include a D44 from a bronco and use the radius arms. we'll see what finances and what I can come up with will provide.

[cbassett]

Hey Brent, didn't know you were on here else would've just hollered at ya to speak up.

Tim,
Look forward to seeing the pics. Is it possible the heims you used did not allow enough degrees of rotation, and they were too small to withstand the pressue of the flex they were subjected too?

This joint should twist, actually. I'll butcher this explanation but, when the axle droops/flexes, the axle end of the arms are not on the same plane as the frame end. This is where the joints and bushing come into play; aside from isolation, they provide the difference between those two planes and allow for flex. In this respect, I looooooove running radius arms: Simple, nothing to them. I extended my arms to get better flex. I haven't had a problem with the breakover angle yet. By the end of the summer I'll know if I want to go back to std length arms and just wrist one. For now, the front is giving adequate flex and I'm getting a bit of control from the radius arms too (I'm not running sway bars front or rear).
The rear flex is just sic. I need to triangulate my shock mounts and extend the coil retainers to take advantage of it. Got a souvenir from the last trip, courtesy of crappy Currie welds; ripped the shock bracket right off.

[Pearce]

couple of pics from the run:

[Pearce]

.

[Timzjatl]

Chris-
I suppose its possible that the heims i used don't have enough travel, but i doubt it. Mine that broke looks more like it was pulled apart in tension, rather than twisted apart, or sheared sideways... there will definitely be pics posted tonight, I am going to get into fixing this tonight. Once I have it setup to use just one arm I'll beef that heim up to a 3/4" Chromoly high strenght one, instead of el-cheapo I used before. This D30 front end isn't the final vision, just a step along the way...
Tim
Pearce's Pics show some of the ditches, there were bigger, flexier ones were later in the day after I got tired of taking v-ditch pics, but i think the all day flexing is what made the arms break saturday, I have certainly beaten this thing harder at Tellico, but Tellico isn't full flex left- then right -then left.... I'll get some pics of the broken stuff and maybe if I get to it some pics of the solution....
Looks like rain too, so I think I'll hafta clean out the front half of the garage...

[Timzjatl]

Ok got some pics and a few things done today....
Here's my broken Heim-
Here's pearce's broken arm
I decided to run just one upper on the passenger side, so I gussetted the UCA mount on that side... sorry its kinda hard to see... I also replaced the cheap steel heim with a chromoly one
Hope the pics work, webshots has been a bitch lately
Tim

[dwells]

I haven't done this yet.

That said, aren't you guys trading the UCA axle mount as a fuse for an unknown? Isn't the basic problem that you've introduced another link (fixed-joint control arms) and it's forcing axle rotation against the other links?

While picturing the passenger-side links, imagine drooping the driver side through its arc. Need more rubber or fewer links, no?

Until now the UCA has been the odd man out. I'd hate to see the failure move down to the UCA ->LCA mount.

What if you moved the tbar & lca mounts inboard of the spring and combined two to eliminate rotational conflict?

Just priming for the summer project.

-Dave

[Timzjatl]

Dave-
Agreed, you'll move the failure somewhere else with the beefed UCA mounts and four links, but my plan is to run only three (at least for wheeling) and have the upper be on the passenger side. In theory with three links you dont experience any bind at all, or at least a minicule amount compared to the four link setup. I DONT want to break the cast in mount on the top of then diff, so I'll use the otehr side, but beefed up for that one mount... then if something were to happen to the other upper I can put in my other upper on that side and continue on. I will however run four links on road, because the stability difference between four links and three is quite substantial. Just disco the drivers side link and hit the trail!
Tim

[dwells]

Tim,

I'm new at this but what about the tbar? With two lowers, one upper, and the tbar, drooping the driver-side has to generate huge torque on those mounts. Without eliminating a link or combining their axle locations I can't see how it would work.

Am I imagining it?

-Dave

[Timzjatl]

I see what you're saying, and I'm not sure how to conscider the Tbar. I am building this based on what I have seen others do, as well as what other companies are producing and adapting that along with a few of my own ideas... I tried the claytons type setup, with bad results, although Clayton does use rubber for the UCA-LCA junction I think... if not rubber a small Johnny Joint. It seems others are getting away with a single upper, as well as Rockkrawler. I think that the ideal setup is a radius arm like Cbassett, but this requires a new front axle among other things. I'll have to ponder the Tbar for a bit....
TIm

[brent]

using radius arms dosen't require a diffrent axle, just strip your housing, weld on the little <> c bushing widgets, and clamp them on.

BTW, I drove mine to work this morning, doing 70 down the freeway, it is as tight now as it was before with all 4 arms. I've got a 2" JJ at the axle, and a 3/4 heim where the upper meets the lower. the lower arms have 2.5" JJ's on all ends.

[Pearce]

Tim, you have to use the attach file thingy.

[Pearce]

>

[Timzjatl]

I did and those were working earlier... don't now.... WEbshots is flaky as hell lately
Tim