Long arm mounting

[Eck]

So I'm at the point of mounting the brackets for the homemade long arms we made during the tech day last year. I have the 4* C bushings in and completely tightened down. My issue now is that the brackets do not line up on the frame. I can get both driver and passenger sides to get to about half way (1.5") lined up to the frame. My thought would be to mount at that location and gusset reinforce the bracket to the frame.

Any ideas or thoughts from those of you that have mounted your long arms? Did you have it lined up outside the frame at all? If so, how did you reinforce it and did you have any interference issues doing so?

Both driver and passenger side:

[Digger]

Honestly there is enough give in the C-bushings, I would loosen them up a few turns, weld your brackets on under the frame and then re-tighten the C-bushings.

Are your long arms bent or straight?

[Eck]

Honestly there is enough give in the C-bushings, I would loosen them up a few turns, weld your brackets on under the frame and then re-tighten the C-bushings.

Are your long arms bent or straight?

They are bent a little.

[Digger]

I looked again and saw you have MetalCloak joints. You'll probably want to un-bend the arms to get the brackets inboard a little. You don't want them hanging outboard of the frame, it will add articulation stiffness to the front axle.

[Eck]

I looked again and saw you have MetalCloak joints. You'll probably want to un-bend the arms to get the brackets inboard a little. You don't want them hanging outboard of the frame, it will add articulation stiffness to the front axle.

The bend actually bends in towards the frame. If the bend wasn't there, I think it would be further outside.

[Jesus_man]

1.5" of movement at the end of the arm isn't all that much stress on your C-bushings. I'd push them in and weld them on.

[ZOSO]

1.5" of movement at the end of the arm isn't all that much stress on your C-bushings. I'd push them in and weld them on.

Not the stress on the c bushings. It s the side loading on the metal cloak joints. They wont last long with a heavy side load on them. Best bet is to un bend them a touch.

[Jesus_man]

Depends on the force required to get them where they need to be. If it can be done by hand, then I wouldn't worry and force them into place.

But Eck says they may need a little more bend to get them to align with the frame.

Eck - can you post a more complete picture of the entire arm setup?

[Gunnibronco]

But Eck says they may need a little more bend to get them to align with the frame.

That is confusing to me. I have not seen these arms in person, but I'm wondering if they need swapped left to right.

Pics please.

[Kinder]

Pardon the crude drawing, in BSD sitting in traffic. Top down view, "unbending" the arms a bit will bring the ends to the frame and only slightly mess with the angle of the brackets that attach to the frame.

ImageUploadedByTapatalk1457447545.115778.jpg

[Eck]

Kirk's picture explains it well. The straighter the arm, the more angled the bracket would need to be to get the metal cloak joint straight.

Here are a couple of pics that will hopefully help a little.

[Digger]

I looked again and saw you have MetalCloak joints. You'll probably want to un-bend the arms to get the brackets inboard a little. You don't want them hanging outboard of the frame, it will add articulation stiffness to the front axle.

The bend actually bends in towards the frame. If the bend wasn't there, I think it would be further outside.

Kirk's drawing sums it up well. I still think there is too much bend in the arms.

[Eck]

So I was trying to do a little research on this as it had been a while since we made the long arms and came across this: viewtopic.php?f=6&t=7118&hilit=lars+bars&start=90

Starting about halfway down-- forgot that mine were the only bent arms and the conversation continued that it would make alignment and mounting much more complex. LUCKY ME!!

Question 1: What would it take to bend them back straight and is anyone able to help me do that or know someplace I can take them to bend them straight?
Question 2: If the arms were bent straight, wouldn't the geometry of the mount not line up parallel to the frame? Isn't that the goal? It seems that with the metal cloak joints it needs to have a straight shot at the C channels?

Does anyone remember the angle of the bend that was put in it? The LARS BARS builds say 9* on theirs-- was there more or less on my set?

[Justin]

It was about 7 degrees. They sucked to bend, and would suck equally badly to un-bend. I'd run the metalcloaks till they die, then swap them out for a heim or something else that isn't as finicky. Most Broncos don't get driven enough for it to really matter much what joint you're running. I'd buy the joints off you if you wind up deciding to not run them.

[Eck]

Here is a picture of Lars' arms mounted on his frame:

[Digger]

S
Question 2: If the arms were bent straight, wouldn't the geometry of the mount not line up parallel to the frame? Isn't that the goal? It seems that with the metal cloak joints it needs to have a straight shot at the C channels?

With any bushing, including Metal Cloak joints, the goal is to have the bracket square to the bushing. This usually results in the brackets at some angle to the frame.

It's okay to have a bend in your arms, but yours need slightly less bend to bring the mounting brackets under the frame. The arm's position is going to be dictated by the axle since the C-wedges are mounted a specific distance apart, at a specific angle. I drew a quick photo showing the original arm geometry (in green) with an extended arm geometry laid on top of it (in red).

Arm geometry.jpg

The extended arm has to follow the same path as the original coming off the front axle because the axle dictates its position, but if the arm is to be mounted further back on the frame, it needs a bend to correct the arm's path and make it line up under the frame. Now on my old truck, I kept the arms straight (shown in orange), so as the mount point moved further back, it also had to move further inboard. This geometry reduces roll stiffness and improves flex, but forces you to get more creative when fabricating the mounts since you can't just weld them straight to the frame.

[Jesus_man]

With some creative fabricating, you could adapt what you have to mount to your frame easy enough. I think I'd try to fab a U shaped piece that would fit tight to the frame out of 3/16" and extends nearly to the top of the frame, weld your bracket to it, then gussets from the bracket up the U-shape with 3/16". The U-shape needs to extend in front and behind the bracket enough to get a good weld in there (1/2"?) and then perhaps some circle cut in the vertical sides for plug welds. Perhaps that would be overkill, but it wouldn't fail!

[Gunnibronco]

I was thinking about mounting my radius arms to the side of the frame for clearance, but as Digger said, it would make the suspension more stiff/less flexible than if the arms are mounted under or on the inside the frame.

I looked at brackets like these. I think this is what JD is describing:

http://www.barnes4wd.com/Ultra-100-Uppe ... p_345.html

http://www.barnes4wd.com/Adjustable-Inn ... _p_65.html

http://www.ruffstuffspecialties.com/cat ... MLB10.html

[Jesus_man]

Chad, - not quite. Here's a section view of what I was thinking for the passenger side. It's crude - sorry!

Looking at a side view, if your link bracket is 6" long, you'll want this U-shape to be 7" long and perhaps have some holes in the side for plug welding.

Clear as mud?

[ZOSO]

Mike I put a bend in mine also. But not as much as we did on yours. If Mine don't line up exactly right then I'll do what J.D. drew up. I don't want to weaken the tube more than we already have by unbending the tube.

[Eck]

Mike I put a bend in mine also. But not as much as we did on yours. If Mine don't line up exactly right then I'll do what J.D. drew up. I don't want to weaken the tube more than we already have by unbending the tube.

I assume you haven't tried to install yet? I'd be interested in maybe mocking yours up on my axle to see where they line up... Let me know if you're interested...

[Gunnibronco]

Chad, - not quite. Here's a section view of what I was thinking for the passenger side. It's crude - sorry!

Looking at a side view, if your link bracket is 6" long, you'll want this U-shape to be 7" long and perhaps have some holes in the side for plug welding.

Clear as mud?

Makes sense to me, somewhat a compromise between what I linked and the standard mounting point.

I like it.

[ZOSO]

Mike I put a bend in mine also. But not as much as we did on yours. If Mine don't line up exactly right then I'll do what J.D. drew up. I don't want to weaken the tube more than we already have by unbending the tube.

I assume you haven't tried to install yet? I'd be interested in maybe mocking yours up on my axle to see where they line up... Let me know if you're interested...

They are not installed yet. but will be soon so if you want to mock them up you can come get em. I plan to install them in the next few weeks.

[Eck]

Chad, - not quite. Here's a section view of what I was thinking for the passenger side. It's crude - sorry!

Looking at a side view, if your link bracket is 6" long, you'll want this U-shape to be 7" long and perhaps have some holes in the side for plug welding.

Clear as mud?

Yah that makes sense. The inside of my drivers side frame rail may be VERY hard to extend a U brace very far. It is a tight fit between the D20 and my fuel and brake lines.

Question- does the U brace your referring to add that much more strength than welding the long arm brackets directly to the frame and welding gussets directly to the bracket and frame?

[Gunnibronco]

I would think adding 3/16 or 1/4 to the bottom & outside of the frame, then welding the bracket & gussets to the reinforcement would work. Your frame is only 1/8" now, so adding 3/16" or 1/4" is adding a significant amount of extra strength. Also consider our frames are fully boxed from the factory. Many trucks only have C shaped frames where the radius arms attach (78/79 Broncos for one), so we are ahead of the curve, in that respect.

[Jesus_man]

That design spreads the load across the frame better, so it would add significant strength. Even if the bracket were to align on the frame perfectly, I still would have been temped to run something similar.

Chad is correct in that the EB frame is quite strong as a hole. But if you're only welding to one side of the frame, it's only to 1/8" material.

If you decide on the U-shape design, just extend the vertical sides up just past the weld seam. That is the strongest part of the frame to weld to. I would go to the top weld seam on the outsides of the frame tho. So now it becomes a J-shape? LOL!

[Eck]

So I was able to get a little more accomplished in getting the long arms lined up today. I think that it is a little less dramatic than I originally thought. I will make a U shape bracket out of 3/16" plate which will actually widen the frame to the outside by 3/16". This only leaves about an inch the long arm bracket will extend to the outside of the frame. I also removed the D20 today and moved my fuel lines to go above the frame rail so that I can get a legitimate bracket welded to the frame. Pictures to follow.

I do not have CAD or anything fancy, so I threw this together to demonstrate what my intentions are. The long arm bracket is angled by 1/8" front to back and I don't think very much undue stress will be put on the metal cloak joint.

Let me know if you see anything I should change...

[Eck]

[Gunnibronco]

I think you have a good plan. You could make the 3/16" plate for the bottom of the frame hang outboard past the frame to match the link bracket.

[Gunnibronco]

Or add a section of C channel or rectangular box to the outside of the frame, to make it a bit wider where you need it.