Dan Wheeler's Radius Arm Build Thread

[DanWheeler]

ok, i may be a convert to the "bend near the frame" camp.

 

[carter2772]

I get it now. that makes perfect sense - bring the tube straight up to the frame where it would have been a straight shot for the stock arm then bend it straight back the rest of the way to the new frame mount which is further back.

Cage and Duff both have the bend down by the C bushing. Now I'm not sure if that was by design or because they dont want to bend 1/4" wall DOM.

with regards to your study wire example, yes the bend in the middle would be more likely to bend however if you put a bend at the end wouldn't the long section be more likely to bend? Either way, this DOM aint bending (we broke a bender die just trying to get 10 degrees)

also, regarding the c-bushings and flex - the C-bushings are absolutely responsible for a significant amount of flex. Imagine if one wheel was stuffed in the wheel well and the other was dropped down in a hole. There would be a difference in rotation of your radius arms which is handled by the C-bushings (albeit, not very easily and not very well) Either the c-bushings flex or the axle housing twists. (which we know its not supposed to unless you have the wristed axle housing)

Cage and duff both have a bend in the tubing itself, right before where their arms attach to the c bushing... But it also bends again to attach more square with the axle...

Also, IMO, i dont think there is any flex out of the c bushings. I have cage brackets that weld onto the axle, that does away with any bushing what so ever, on the axle.

 

[carter2772]

Here is the best picture i had of the duff arms. You can see the bend in the tubing right before where the arms turn into square stock, and then another bend in the square stock where they bolt to the c cups. There are 2 big bolts there.

 

[DanWheeler]

Here is the best picture i had of the duff arms. You can see the bend in the tubing right before where the arms turn into square stock, and then another bend in the square stock where they bolt to the c cups. There are 2 big bolts there.

look, i'm already bitter about not being able to afford the James Duff arms, did you have to go and throw that picture in my face?

ahhhh, bolt-on.

 

[carter2772]

I think your look good Dan.. And if they do end up bending from wheeling, I dont think they will, you can always fix them... Isn't that what all of us do? Build it, Break it, Fix it... Good luck!

 

[WyleCoyote]

From what I recall about the Duff arms - the bushings at the 2 bolts that attach the axle bracket to the arm are where you get the flex when you eliminate the C bushings. The Duff arms are designed to have both the C-bushings and the additional bushings to improve the bind at the axle.

 

[DanWheeler]

I met a guy that had removed the C-bushings and welded the Duff arms directly to his axle. He said he was going through those 2 bolt bushings every other time on the trail. I dont think those 2 bushings provide enough flex. I believe they are just suppose to supplement the C-bushings. it's a great design even if it makes for a sloppy ride in some cases.

 

[DanWheeler]

Got a little more done on the radius arms tonight but spent most of my time installing a 3G.

I decided on 10 inches of extension:

I put the tubing under the truck with the bend towards the front and towards the back and it does line up slightly better with the bend in the back so I went with that.

I finished slotting and fishmouthing the tube to fit into the radius arms. Everything seems to fit well so its ready to weld

 

[SC74]

The joint on the end of the arm does all of the flexing.

The bushing joint on stock arms (frame end) is one of the biggest limiting factors in the flex in my opinion. Even if you took a stock arm and replaced the end with a heim or johnny joint that is made to allow movement I think you would see much improvement.

 

[SC74]

I went with the 3" ballistic joints becuse they take a 3/4" bolt. Johnny Joints take a 9/16" bolt. I figured if 2 bolts are going to be holding my entire front-end in place then I would feel better if they were bigger than 9/16ths.

The bolt only keeps your axle from moving front to back. The coils are what holds the truck up, the trac-bar is what keeps the axle centered. They are basically the same things as a Reece hitch pin that we all rely on to tug trailers. I've never even measured a hitch pin but it's not even 1/2" is it?

When I built arms very similar I used the standard ballistic joints that accept a 9/16" bolt. Something I did do was make sure that none of the threads of the bolt were inside of the mount to create a weak place. I bought a longer bolt than needed and ran a die down it to where I needed the threads to end.

 

[DanWheeler]

When I built arms very similar I used the standard ballistic joints that accept a 9/16" bolt. Something I did do was make sure that none of the threads of the bolt were inside of the mount to create a weak place. I bought a longer bolt than needed and ran a die down it to where I needed the threads to end.

thats a good idea thanks for the tip. It is kinda funny to think how much force there must be on one small hitch pin. I guess double shear really makes it strong.

 

[DanWheeler]

The bushing joint on stock arms (frame end) is one of the biggest limiting factors in the flex in my opinion. Even if you took a stock arm and replaced the end with a heim or johnny joint that is made to allow movement I think you would see much improvement.

I gotta disagree there. IMO the C-bushings are the most limiting factor for flex. When I had my axle on the ground with the stock radius arms attached I couldn't lift one of the arms without the other arm lifting up the same amount to save my life. They are EXTREMELY stiff especially with poly C-bushings. The frame donuts however would easily allow 15 degrees of flex up or down if you just put a radius arm on the frame in the stock mount.

Consider the design of the C-bushings and how little bushing material there is between the wedges and the radius arm to allow for the rotation that occurs when one wheel is up and the other is down.

in fact, i'm a little worried all this effort i'm putting into these arms isn't going to net me much flex because I haven't addressed the REAL problem which is the C-bushings.

The reason the cage and duff arms work so well is because they have those 2 extra bushings in addition to the C-bushings.

 

[needabronco]

The C bushing locates the axle, when the suspension cycles I.E. one side drops and the other side is stuffed in the wheel well, the C bushing does have some 'give', but the real 'flex' is at the joint end. I believe your diagram is wrong. Think of it this way your axle shaft will stay in line with your axle and radius arms. This is why you seldom need a longer front drive shaft with most lifts. If your being a stickler for flex, you also need to consider the lack of 'flex' your stock track bar offers, those bushings take alot of abuse...

As an experiment of sorts, I installed a set of Lars' designed radius arms on a completely stock rig. The results are awesome, all I changed was the radius arms, I reused the shocks and the same C bushings. I do have better control of my suspension, and with out shocks (they are a major limiting factor) it out flexes the stock arms. I can now drive 70+ with one finger on the steering wheel, before it took 2 hands and you had to pay attention.

 

[Mark]

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

 

[DanWheeler]

i'm definitely open to the possibility that I'm wrong but I've spent a lot of time thinking about this and creating scale models with pens and legos and all kinds of stuff and I'm 99% sure in my mind that the C-bushings are required to flex to allow the axle to be high on one side and low on the other as long as the frame attachment points are at the same level (on the frame)

let me put it this way - why do wristed axle housings and wristed radius arms work so well? Because they allow different amounts of rotation of the axle housing relative to each radius arm.

 

[DanWheeler]

The C bushing locates the axle, when the suspension cycles I.E. one side drops and the other side is stuffed in the wheel well, the C bushing does have some 'give', but the real 'flex' is at the joint end. I believe your diagram is wrong. Think of it this way your axle shaft will stay in line with your axle and radius arms.

Pick up a broom and hold it in front of you horizontally with both hands gripping the broom handle about 2 feet apart. Now, try to lower the right side of the broom to waist level without bending your body or your wrist. You can't do it without bending your wrist.

oh, and dont let the broom handle rotate in either hand.

 

[Bronco73]

Pick up a broom and hold it in front of you horizontally with both hands gripping the broom handle about 2 feet apart. Now, try to lower the right side of the broom to waist level without bending your body or your wrist. You can't do it without bending your wrist.

oh, and dont let the broom handle rotate in either hand.

This example is not the same as the bronco. On the bronco the radius arm can and does rotate at the frame mount allowing one side of the axle to be lower or higher than the other. You would have to have rotation in your shoulder for it to be the same as the bronco set up in your given example.

 

[DanWheeler]

This example is not the same as the bronco. On the bronco the radius arm can and does rotate at the frame mount allowing one side of the axle to be lower or higher than the other. You would have to have rotation in your shoulder for it to be the same as the bronco set up in your given example.

Didn't really say you couldn't rotate your shoulder

(unless you interpreted your body as your shoulder which it technically is but... anyway)

so... your shoulders are your frame mounts. Your wrists are your C-bushings. Your arms are your radius arms. Elbows must stay straight. Broom handle must not rotate in either hand.

 

[rtreads]

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

 

[DanWheeler]

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

It's a good question. I thought a lot about a setup like that which is essentially a wristed arm.

I was concerned about the rotational forces put on a single radius arm as well as the axle tube and center differential section. It also requires a lot of modification to the axle including but not limited to removing the stock C-wedges, adding a link tower which would have been in the way of my track bar riser, new link brackets, spring mounts, shock mounts, etc.

Also, I read there were some strange handling characteristics related to wristed radius arms - can't remember exactly what they were though. Something about things going from normal to weird in an instant when your offroading.

The other reason is that I plan to upgrade to a Dana 60 in the front and didn't want to make a mess of my very nicely built Dana 44 so I can sell it later to someone who wants a nice stock D44 with wedges.

So this is kind of a temporary solution.