Custom Radius Arms

t120r · Nov 10, 2011

Hey guys, I need to build extended radius arms for my Full Width SASed '90 Ranger. Once I get them made, a second set will be fabricated for my '66 Bronco. Call the Ranger a test run.

I want them adjustable and with the 3 Heims per side, there will be no side tension on the C-Bushings. Here's a quick sketch I drew:

The Top link will be the support, while the bottom will be used for adjusting caster (Tiny bit) and eliminating axle wrap. Is there anything I'm not seeing or accounting for?

Also, what length should I shoot for? I am using stock '79 Bronco arms now, should I go longer or is this fine?

stupidboy · Nov 10, 2011

Looks like a good ider to me.

Action · Nov 10, 2011

Long arms

Myself-I would put the long arm on the bottom!
Jack

shamu · Nov 10, 2011

Great idea.

DirtDonk · Nov 10, 2011

Agree with Action. Don't know from geometry-wise, but there would be less to hang up and bang up.
And still adjustable.

The lower overall angle might be a benefit, but on a trail rig I think you can deal with the trade-off.
Not an engineer though, so wait for others to chime in.

Paul

ken75ranger · Nov 11, 2011

Action said:
Myself-I would put the long arm on the bottom!
Jack

Absolutely correct. The lower link sees most of the force when driving. The upper link only keeps the axle from turning and it sees a good amount of force when using the brakes.

The way you have it drawn the lower link will be trying to bend the upper link most of the time. The guys that make radius arms that are welded together can do the long link on top since it's a welded assembly.

Ideally you want the lower link full length and the upper link as long as you can make it to put the braking force away from the middle of the lower link.

HGM · Nov 11, 2011

As a "Holiday Inn Express Engineer", I'm going to go the other way. I think the long link needs to be on top. In order to get the benifit of the longer arm, the idea is to keep the arc it follows relatively flat.. By putting the long link on the bottom, you're at rest possition is in a steeper arc.. Idealy for ride quality, you want the axle to travel in a vertical manner as much as possible.. So, my suggestion, based on the strength comments, would be to make the lower link longer. Get it closer to the frame pivot of the upper..

t120r · Nov 11, 2011

Thanks for all the comments/ideas. I posted this on Pirate4x4 as well. Between these 2 sites I have my plans hammered out. I will redraw the picture to scale with all the corrections. I will then repost it.

I wish they made narrower johnny joints to fit. I know they aren't cheap, but I love them and they are rebuildable.

fablife · Nov 12, 2011

I built mine similar to yours a while back.

they articulate great, but using the original mounting locations makes them short and will affect pinion angle when dropped out.
I used poly bushing on all the joints and never had a problem
I built mine without castor adjustment, and was never a problem until I moved up in suspension...go figure that...
and of course, when I was the stainless nut..they were built from 1" sch 160 ss pipe. never had a problem until...being winched out and got lodged on a rock the size of a VW. needless to say, they didnt support the weight of the rig and got slightly bent.
my input would be,
make the shorter link as long as poss.
use poly bushings
adjustment is not necessary, but handy
JD

t120r · Nov 12, 2011

Thanks for the picture. It's very similar to what I want to do. I'm gonna use DOM steel threaded on the inside for the rodends... Possibly poly joints if I can get one with a stud on it. I am even thinking of johnny joints as they make a thinner one which would be nice. That way I can replace the tubing if I bend it up.
I also have to extend them 12 inches. At least that's the concensus on pirate4x4. They'll fit my frame perfect then and have great articulation. I'm gonna post pics of before and after.

fablife · Nov 13, 2011

I might add, the upper bar bent right at the joint where the lower connected to it...as mentioned in earlier posts.
I think speedway has the ends, but probably not the size you need. I see more fab in your future!! JD

t120r · Nov 13, 2011

I see a lot of fab in my future as well. I dunno about you guys, but I have made so many parts a second and third time to improve on them. I can hope to do this once, but odds are I'll break/bend something and have to redo it. But that's the fun right?

fungus · Nov 13, 2011

After you settle on a design & price parts, checkout the Rubicon Express radius arms they make for heaps. One of the Norcal guys works for them & runs a pair on his EB. Flexes real nice! Might be worth looking at once you figure in parts & your own labor to build a set from scratch. VERY similar in design to what you're thinking.

burntfish · Nov 14, 2011

Check these out . http://www.battlementfab.com/Radius-Arm-Kit_p_8.html

t120r · Nov 18, 2011

I can build a set for about $200. I`ve got all the equipment and a spare set of radius arms. I just have to pick up some DOM steel and some rod ends. I even have 2 Johnny Joints sitting on my shelf that I can use to mount to the frame. So it won`t be too expensive. Plus, I love to build things.

Custom Radius Arms

t120r

Sr. Member

stupidboy

My wifes porn star.

Action

Sr. Member

shamu

Lucky as the day is long.

DirtDonk

Bronco Guru

ken75ranger

Bronco Guru

HGM

Sr. Member

t120r

Sr. Member

fablife

Full Member

t120r

Sr. Member

fablife

Full Member

t120r

Sr. Member

fungus

Bronco Guru

burntfish

Sr. Member

t120r

Sr. Member

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