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How To Fabricate a Hinged & Pinned Radius Arm

 
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johnl
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PostPosted: Mon Sep 20, 2004 11:52 am    Post subject: How To Fabricate a Hinged & Pinned Radius Arm Reply with quote

How To Fabricate a Hinged & Pinned Radius Arm (Rev E):
by Quinn Dusenberry

1) Remove stock shock brackets.
2) Sandblast entire arm
3) Cut the inner (filler) and outer (hinge) plates from 1/2" thick mild
steel
-1/2" nearly perfectly fills the inner I beam cross section
-the inner piece is the width of the bottom of the I beam *before* it
transitions up the wall
-it follows the expanding width of the I beam as it goes along
-it is 1.75" wide for 1.50", then transitions to 1.125" at the far end
and is 10.25" long
-the outer piece follows the outside profile of the radius arm and is
2.022" wide at the narrow end and transitions to 2.5" wide 8.40" away. It is
10.00" long.
4) Weld in one inner piece completely, butting it up against the transition
radius at the back of the "C" portion of the radius arm
5) Weld in both the inner filler pieces completely filling the I beam
section, then grind flush with the filler plate
-weld in short sections alternateing between sides to keep warpage down
6) Tack weld both outer pieces onto the arm
-the outer piece starts 0.100" behind the leading edge of the inner
piece
7) Drill and ream 4 holes to 7/8"
-first hole is 1.50" from leading edge of outer plate
-second hole is 4.50" from leading edge of outer plate
-third hole is 6.80" from leading edge of outer plate
-fourth hole is 8.80" from leading edge of outer plate
Cool Remove both outer pieces noting their original position (ie which side
they were on, orientation, etc)
9) Cut arm in half at 5.75" from leading edge of inner plate
-both the hinge bolt and pin bolt need to be on the same side of the arm
after cutting in half
-cut should be halfway between 2nd and 3rd holes
10) Fabricate "hidden" pins with 7/8" bar stock
-they should be about 0.050" or so below flush on each side
-they will go though the 2 inner plates, the radius arm *and* the outer
plates
-these provide an extra measure of safety in the event that the welds holding the outer plates to the main arm fail
-they also are needed to ensure that the arm maintains the exact same length and relationship between the 2 sections of the arm after it is cut apart
11) Install hinge and pin bolts through the arm
-ensure that you reinstalled them the same way as how they came off
after match reaming the holes
12) Weld in "hidden" pins and grind off flush
13) Weld the outer plates to the aft portion of the arm only
-should put a generous bevel in the weld zone to allow for more
penetration
14) Remove hinge bolt and pin bolt and open the cut plane joint up enough to
allow free rotation of the joint
15) Fabricate new lower shock mounts and weld in the location that allows
equal up and down travel of the forward section of the arm. It should be
close to the same position as stock on the outer plates
16) Sandblast and paint

Using this procedure will ensure that all the holes are *perfectly* lined up
and the arm remains the exact same length as stock. I used reamed holes to
ensure more uniform contact (no line contact) of the bolts in the holes. I
also recommend using Grade 5 fasteners since they are less brittle.

Sample images




[/img]
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BigMac
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Location: East Texas

PostPosted: Tue May 24, 2005 9:00 am    Post subject: Reply with quote

At the risk of sounding totally ignorant, what is the goal of this conversion and what are the benefits of it? Would it not allow intense axle wrap?
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Chuck66
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PostPosted: Fri Jul 07, 2006 6:27 am    Post subject: Reply with quote

I looked at doing that as well but decided that all of the drawbacks were not worth the effort. I did find a great solution thow. I cut the end of the radius arm off were it attaches to the frame and hinged it there. I ramped it forwards and backwards and I can stuff the 36" super swampers as well as my 38" swampers , I am well over 1,000 on the RTI using a 30 degree ramp. It runs down the road at 75 mph with no problem and improves the total performance of the vehicle both on and off road. I have pics if you would like. I have also done the following mods; hydraboost brakes, on board air, on board welder, 351W, etc.... I will post them for all with pics as soon as I get it all captured.
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Mherriford
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PostPosted: Fri Jul 07, 2006 6:28 pm    Post subject: Reply with quote

lets see those pics!!!
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Chuck66
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PostPosted: Sun Jul 09, 2006 6:35 pm    Post subject: Reply with quote

I will if you can tell me how to post them on this site.
Thanks

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Chuck66
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PostPosted: Sun Jul 09, 2006 6:55 pm    Post subject: Reply with quote

OK
I put them in my gallery so you can see them until I figure out how to get them in here.
I just took some pics of ramping tonight with the 38's and man is the back tire stuffed. I only have it at 30" because it always rolls back some before I can get out to take the pics and measure. I should mark the ramp some day soon.
As soon as I figure this pic posting thing out I will post some cool shots.

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Chuck66
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PostPosted: Tue Jul 11, 2006 11:44 am    Post subject: I posted the pics Reply with quote

All right go to the following site and you can see the hinges and how they work off road and on a ramp ( it always rolls back a little on the ramp so I am not quite 32")
http://profile.myspace.com/index.cfm?fuseaction=user.viewprofile&friendid=92303918
My daughter showed me how to do this< I will add more later and if you have questions about the welder or air let me know.

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Chuck66
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PostPosted: Thu Jul 13, 2006 9:10 am    Post subject: Reply with quote

My bad the RTI score is over 1000 on a 20degree calculation I will try it again on the 30 degree ramp to see how close I come to the 1040 I got on the 20. I can tell that the front coils need to be changed to get more movement on the front axle, but not to bad for stock length arms. The rock I am on in Uwharrie is about 42" high if that helps.
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freebee_bII
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PostPosted: Tue Sep 19, 2006 10:07 am    Post subject: Reply with quote

Couldn't you just take large heim joints and mount them to the frame and get the same effect for flex or am i missing something in the design. I love the design but it looks to me like you could do the same exact thing with heim's, fedup nevermind the heim joist would allow it to go side to side causing axle wrap right. Thats why you make a joint like you did. now here is my other question could you hinge both in this style as long as you have limiters in place "only for offroad of course", or would it make it too unstable I'm building my BII becasue for one it was free and number two because it's small. I live in utah so I'm building it to be a moab rock crawler. I'm hoping to get the maximum flex and stability out of this rig. it's gonna be a trailered rig always. Any advise from you guys would be helpful thanks.
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Chuck66
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PostPosted: Thu Sep 21, 2006 6:01 pm    Post subject: Joints on both radius arms Reply with quote

With the joint at the frame end of the radius arm it will twist and flex on and off road. By keeping it all the way up at the bushing and keeping the bolt tite it will allow you to drive it with both sides hinged with no problem on the road as I said I run down the road 65mph++ and it handles better than stock, especially when you hit railroad tracks.
Are you going to run a solid axle set up od the independant suspension? The BroncoII radius arms are shorter and a little differant but this should work the same. If you are going to trailer it you mite want to put longer arms on and really free up the travel.

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freebee_bII
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PostPosted: Thu Sep 21, 2006 10:50 pm    Post subject: Reply with quote

I'm gonna run the same radius arms as you are I've got a d44 off of an 78 bronco fs. but the only thing that sucks is the mounts are casted to the axle so I can't adjust my angles much on my pinion. that's so crazy that your axle doesn't flop around that way because everyone claims if you do it close to the axle on both sides it causes axle wrap.
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PostPosted: Thu Sep 28, 2006 10:19 pm    Post subject: Reply with quote

hey chuck how tall is your suspension lift it looks like you didn't have to lengthen the radius arms at all but I'm going with 5.5 cage in the front and not sure how long my arms need to be to aviod rocks and any other thing that might snag on the trails
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PostPosted: Mon Nov 20, 2006 5:26 pm    Post subject: How tall? Reply with quote

I'm only running 3.5" lift duff springs, I thought about lengthening the arms but decided to do this first. I really like the way it works so This part is done.
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bkennedy
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PostPosted: Sat Mar 22, 2008 7:52 pm    Post subject: Reply with quote

I know this is an old thread, but I want to wrist my radius arms on my solid axle Explorer. This is the best write up I have found on hinging the arms. Where did you get the pin bolts?
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Chuck66
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PostPosted: Sat Mar 22, 2008 9:25 pm    Post subject: wristed arms Reply with quote

I used number 8 grade 3/4" bolts from Fastenall.
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bkennedy
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PostPosted: Wed Mar 26, 2008 8:53 am    Post subject: Re: wristed arms Reply with quote

Chuck66 wrote:
I used number 8 grade 3/4" bolts from Fastenall.


So, you just used two bolts, instead of a bolt and a pin bolt?
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