Dan Wheeler's Radius Arm Build Thread

[SC74]

It just seams like a lot of work to modify the stock arms for a small gain vs doing a custom arm like these and getting a lot more flex??

I think the performance gain will be much better than "small." I've built arms just like these and the wheel travel gain is great in my opinion.

 

[rtreads]

I think the performance gain will be much better than "small." I've built arms just like these and the wheel travel gain is great in my opinion.

I didn't intend to down play his build. I think it is great! My brother and I are planning on doing something to combat his stock radius arms. But I was just thinking that with an arm like in the pic, you would eliminate resistance in flex all together (well, at least thru the range or motion that a bronco will require).

I was just throwing that option out there in case anyone had done it and had some info/results to offer up.

ryan

 

[Tito]

I have a question...

If you are going to go thru the trouble building an extended arm with the main goal more flex, why use the C busing at all? I have the duff long arms and think a set-up like rjlougee's would work MUCH better. And you wouldn't mess with damm C bushings to change your castor. I know the cost would be more as a result of the arm ends. It just seams like a lot of work to modify the stock arms for a small gain vs doing a custom arm like these and getting a lot more flex??

Oh, and as I mentioned this is not my bronco. It is rjlougee's. And I know the coil overs will add a lot too, but I am speaking of just the arms... since that is what the discussion is.

thanks

I would think this would make it super simple to get it dialed in for caster as well as allowing good flex.

 

[DanWheeler]

I would think this would make it super simple to get it dialed in for caster as well as allowing good flex.

Good point. I would consider going this route when I go full width if I could be sure the handling characteristics weren't unpredictable and I had a truss to strengthen the axle tubes on both sides of the center diff to keep them from spinning.

here's a thread on pirate that discusses wristed arm faults but now re-reading it a few months later I dont see much mention of handling problems so I'm not sure where I read that. The faults they point out in this thread dont really apply to the design in the picture above.

http://www.pirate4x4.com/forum/showthread.php?t=372561

As far as what I expect out of my arms, my expectations are low however I'm HOPING to be surprised since many people have done the same basic design and claim great results. I still believe the C-bushings are the culprit for lack of flex but if people are getting good results just by extending the arms then I have to assume its the extra leverage that overcomes the stiffness of the C-bushings. Take Bronco69er for example, he uses the stock rubber frame mount donut bushings in his design and gets great flex (he angles them down a bit before welding to the frame)

 

[lars]

Interesting thread. Dan, I think you'll be just fine. Just be sure to get a nice weld at the fishmouth at the front of the DOM tube, where it contacts the rear of the radius arm stub. You'll want to get all the rust off the radius arm. CLEAN metal. Make several passes.

As it turns out, I notched out the web of the stock arm also, just not as far as you did. I get paid to do structural steel stuff in a high-g environment, so I tend to worry a lot about stress paths. I wanted the top and bottom flanges of the stock arm tied together with the web for several inches back from the C, despite the presence of the extra metal of the DOM tube. But I notched out the back part of the web to reduce the sudden change in cross-sectional area at the aft end of the radius arm flanges, to avoid a stress riser at that location.

What's more, as beefy as the DOM tube appears to be, the stock arm is actually stiffer in bending about a horizontal axis (think coming down on a rock with the radius arm) until about 15 inches back from the C bushings. That said, I've come down on a rock with mine now a couple of times and only managed to scratch the POR-15 I used to paint the arms.

You guys all figured out my thinking on where to locate the bend. The forward part of my arms exactly follows the inward angle of the stock arms. That's not something I dreamed up; someone who made a set of arms much like this, but with straight tubes, pointed out that if he was doing it over he'd add the bend, because of how hard he had to pull sideways on his extended arms in order to line them up with the frame mounts. Lots of sideways preload in the C bushings, avoided with the bend.

Lots of people including Coby Hughey did experiments with various joints at the back end of stock radius arms years ago. They all claimed that the frame bushing had almost no effect on flex. But longer arms give more leverage on the real culprit, the C bushings. A wristed arm adds a pivot, effectively accomplishing the same thing.

My arms are extended 6 inches from stock. Everything's a compromise. I was trying to keep good street handling manners, since my Bronco really is my daily driver. I'm happy with how mine turned out, and I was pleasantly surprised when I ramped my Bronco. I have no trouble getting full stroke out of my 12" Fox shocks.

 

[lars]

caster adjustment

I added no caster with my arms. In fact I carefully measured several stock arms. There is no caster "built in" to them, so I made a weld fixture that held the front face of my arms perpendicular to the tubes. All things being equal, a 6 inch extension theoretically adds about 1 degree of positive caster (more like 0.9 degrees, but what's a tenth or so between friends?).

It's a bit of work, but I cut the inner C's off my D44 and rotated them back 10 degrees, then welded them back on. Then I went back to 2 degree C bushings. With this setup I have almost 6 degrees of positive caster and the differential pinion shaft is about 1 degree low from pointing straight at the CV joint on the transfer case. That has made for a comfortable return-to-center feel in the steering wheel, no front driveshaft vibes and no driveshaft binding with the front axle at full droop (the latter was a problem for me before I did this mod).

For the record, there's nothing wrong with using a MIG to weld the C's back on. That's how the C's were welded on in the first place in the Dana factory.

 

[DanWheeler]

I added no caster with my arms. In fact I carefully measured several stock arms. There is no caster "built in" to them, so I made a weld fixture that held the front face of my arms perpendicular to the tubes. All things being equal, a 6 inch extension theoretically adds about 1 degree of positive caster (more like 0.9 degrees, but what's a tenth or so between friends?).

thanks for the info, Lars. If I had the right cutting tools I would have kept more of the web near the C bushings as you mentioned and slotted the tube 2-3". Sounds like a lame excuse but I didn't have anything that could cut the web between the flanges without cutting the flanges so I cut it up closer to the C bushing where my cut-off wheel would fit to make a cut perpendicular to my cuts along the flanges.

When you went back to 2 degree bushings did you use rubber? if so, did you see any improvement in flex?

You mentioned you made a weld fixture to make sure the arms were perfectly perpendicular to the front face of the arms. Do you think I should be concerned about this? I know slight differences in even the stock arm configuration can cause the dreaded "bronco lean"

 

[cheesenip73]

Stick to your idea of the C being a MAJOR limiting factor Dan. I was curious about your broom handle idea and while sitting at my desk, I pulled out a paperclip and bent it up to be a square C channel. The 4 points, 2 frame mounts being the ends of the paperclip and the 2 bends being the attachment points to the axle. At rest it sits in a plane, When trying to cycle it the plane severly distorts. With weight and leverage you can get it to cycle, but it doesn't want to.

 

[lars]

thanks for the info, Lars. If I had the right cutting tools I would have kept more of the web near the C bushings as you mentioned and slotted the tube 2-3". Sounds like a lame excuse but I didn't have anything that could cut the web between the flanges without cutting the flanges so I cut it up closer to the C bushing where my cut-off wheel would fit to make a cut perpendicular to my cuts along the flanges.

When you went back to 2 degree bushings did you use rubber? if so, did you see any improvement in flex?

You mentioned you made a weld fixture to make sure the arms were perfectly perpendicular to the front face of the arms. Do you think I should be concerned about this? I know slight differences in even the stock arm configuration can cause the dreaded "bronco lean"

I tend to make fixtures for that sort of thing. It was pretty straightforward and avoids that sinking feeling that you get when you realize that the right and left are different. A lot less time to make a fixture than to try to rectify a problem later. I've attached a crappy picture of my fixture. I may have a better one on my computer at home.

I'm using urethane C bushings. As others have said, they are flex limiters, but I have plenty as far as I'm concerned. I still get enough anti-sway as a result (despite the extra leverage of the longer arms) that the street manners are reasonable. But then it's totally subjective, so I won't describe my results as "best" or anything remotely close.

As for cutting out those webs, what I did was almost shameful: oxyacetylene cutting torch, followed by a lot of grinding

 

[needabronco]

I do all of my radius arm cutting and grinding on the same 4.5" angle grinder, takes 3 cutting disks and 2 grinding disks...

 

[DanWheeler]

I tend to make fixtures for that sort of thing. It was pretty straightforward and avoids that sinking feeling that you get when you realize that the right and left are different. A lot less time to make a fixture than to try to rectify a problem later. I've attached a crappy picture of my fixture. I may have a better one on my computer at home.

holy cow, that is some serious attention to detail. Do you think I'll be OK putting one end of square up to the threaded/flat end of the radius arm and measuring the distance from the other end of the square to the tube in 2 different locations along the tube?

 

[needabronco]

The jig also helps keep everything from warping from all of the heat you need to put into those arms to weld them. I do mine in 3 passes to build up the weld area and to fill the gap between the DOM and the stock piece.

My jig is identical to Lars' design. Thanks again Lars...

 

[lars]

holy cow, that is some serious attention to detail. Do you think I'll be OK putting one end of square up to the threaded/flat end of the radius arm and measuring the distance from the other end of the square to the tube in 2 different locations along the tube?

Find a big piece of C channel, wider than the width of the front face of the radius arm, and a bit longer than that face. Locate/measure drill a hole pattern in the flat of the C channel so you can bolt the radius arm to it with the stock 9/16" bolts (use washers/spacers as needed since the bolts will be way too long). Find a piece of flat steel plate or bar. Carefully weld the C to it so it sticks up perpendicular to the flat.

Now you can clamp the flat plate to a table, and you'll have a vertical flat surface to which you can bolt the radius arm stub. Pretty much what you can see in the pic of my jig. Bolt the radius arm stub to it, and slide the tube into place. Now, with the tube held horizontal, measure the vertical distance from the table surface to the bottom of the tube. Carefully. Next, make a couple of spacers out of some square tube or similar, of that length. You can now use clamps to hold the tube to the spacers, and get everything into alignment. Just a thought. As needabronco mentioned, I also liked having a fixture because I could clamp the snot out of the assembly while I welded, to minimize the tendency of stuff to move around.

And yep, I guess I tend to get carried away with details. A learned behavior, as I've spent the last 6 years off & on working on the project shown in the attached pic (looks a bit more complete now).

 

[Bronchole]

Dan,

Don't let these guys convience you that you are wrong about where the "flex" is happening, YOU ARE RIGHT!

The joints at the ends of the arm can (but generally don't) limit the ammount the front suspension can drop, but are a relitivly insignificant part of what allows the front suspension to articulate.

The primary source of articulation comes from the C bushings deforming under the force that the arms apply thru them as the arms do their best impression of a sway bar for the front suspension. Going to Poly C-bushings actuall limit articulation in this situation, but usually are necessary to correct for lifting the rig.

By extending the radius arms you are increasing the leverage the arms have to apply force to the C bushings, this is where you gain the flex (articulation) in the front suspension.

Personally I am intending running mildly (8"+/-) extended arms thru rubber C- bushings and roatating the knuckels to correct the steering goemetry. I shill haven't decided weather or not to use stock rad arm bushings in slightly rotated mounts (so they are closer to neutral on my 5.5" lift) or just run some other type of joint on the end. I like the mounts you are using!

By the way, I like your name!

Happy Trails,

Dan

 

[DanWheeler]

Got some garage time in tonight and got the first pass done on the arms. I thought real hard about making a weld rig and then decided against it. I eyeball stuff - thats how I roll. If they came out perfect then I wouldn't have any motivation to go full width with a 3-link.

Hopefully I'll get the second pass done tomorrow night. I just got bored with welding these things and ran out of steam. Then all I have to do is weld on the threaded inserts and weld the mounts to the frame. I'm not looking forward to the mounts since I'll have to drop the exhaust and figure out how not to melt all my wires and fuel line runing along the frame.

 

[DanWheeler]

James Duff sells these C-bushings spacers for people who have gone Dana 60 and welded the wedges on a larger diameter axle tube.

I was wondering if I could make some spacers to give the C-bushings a little extra room to flex/move. Bad idea? My poly c-bushings are so tight I could barely crank down the bolts. I know leaving a little space between the radius arms and the cups would help with articulation but would it be dangerous?

 

[Dan74Bronc]

Lookin' good. Two more passes and you're done. Good job.

 

[bmc69]

On long arms, there is no significant flex difference between a heim, johnny joint, or stock stud mount at the frame.

Bingo. You are correct.... A couple personal observations that anyone can repeat:

1. IF you think that the bushings on the frame end have any effect on flex at all, jack the front of the truck up with nothing attached to the front axle EXCEPT for the radius arms. Betcha can't get the axle housing to lift off the ground with any jack in yr garage...;D Oh..and don't forget to unbolt the front brake line when you do this test. Ask me how I know that,,%)

2. With the front end removed and radius arms still attached. Block one radius arm off the floor near its frame end so its sitting horizontal. Stand on the frame end of the other radius arm. Measure the deflection. What?..no deflection?. Go get several buddies and all of you stand on the unsupported radius arm...still nuthin... Moral of the story: Those C-bushings are one powerfully inflexible joint. Makes perfect sense though..one little error in bolt-tightening sequence when installing them and the entire truck leans permanently like its got a flat tire.

Back to the regularly scheduled program...;D

 

[DanWheeler]

Lookin' good. Two more passes and you're done. Good job.

2 more passes? really? I was gonna do one more over the top granted I only know what I know about welding and thats not much. Do i want to go right over the top with both additional passes or off to one side for the 2nd pass and off to the other side for the 3rd final? any particular wire speed or setting for 2nd and 3rd pass? (1st was highest setting at low wire speed)

thanks
dan

 

[Dan74Bronc]

It's really up to you weather 2 more passes or not.

If you choose to do one more then I would flatten the first pass a little with a grinder and then weld it moving slowly, half as fast as your first pass, making sure your puddle developes completely side to side.

Two passes would be my choice. First off to one side about 1/2 to 2/3 covering the first weld , then the last on the other side.

Just looking at your pics, maybe one pass on top of the first where the tube is close to the beam, if you can fill the groove flush with one pass. It's hard to tell how deep the groove is in the pics. Then two passes near the end cap where the beams spread apart, since you already have a thick weld there.

Wire speed varies with machine and welding position. Your welds look fine. Keep doin' what you're doin'.