nukegoat
Should have bought a Jeep
Weld a 30" long bracket to the axle right below the frame and connect it with a 1" long link. You think itll behave the same?
Edit: it actually will, though the bushings will be very unhappy
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another radius arm flip
- Thread starter bigdfzj80
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Edit: it actually will, though the bushings will be very unhappy
nukegoat
Should have bought a Jeep
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LINUS
Waiting for the Great Pumpkin
Yeah, that was my gut thought - but I'm out screwing off & only have my phone.
I've never gone as far as you in swapping in other axles or done full homebrew suspensions, just ran both sets of caster plates out there & by far the real centerline rotation ones act like stock over the ones that rotate on the rear bolt of the axle/arm mounts.
-I gotta google one of those suspension calculators when I get home, then I can back up my gut thoughts with real geometry - I've never played with one much.
-Interesting stuff to me, what suspension mockup site/app you using when you are using?
( @nukegoat )
- Thread starter
- #24
I agree i hate that ARB bumper it sticks out way too far. My next project im going to cut it and modify it and move it further back to improve my approach angle.I liked reason #4 on the original post. "Why not?" But a quicker and more effective rock crawling upgrade for me was to delete the ARBb bumper. That thing seemed like more of a rock magnet than my control arms were!
In a traditional link suspension setup it is really only the attachment points that matter. The link itself could have any shape you want. It is a little more tricky with a radius arm because it’s more a long pivot than a tradition link setup that requires upper and lower links. As long as the relationship of the center line of the axle and the frame side pivot don’t change the axle will have the same path of travel. You only change this if you change the length of the arm, or the location of the pivot on the frame side. Just my $0.02
nukegoat
Should have bought a Jeep
The classic 4 and 3 link calculator is great but you can just do the old school math approach too. If you pick up any books on race car suspension, a surprising amount of it applies to offroad. Some stuff is a bit counterintuitive, but most of it is trading compromises in one way for another. And some of it is just subjective
mudgudgeon
Resident galah
Linus! Stop sticking those damn crayons up your nose!
I dont follow your example exactly, but yeah, if you dont change the axle location or the pivot point (IC) the path of the axle wont change no matter how wacky you make the arm shape.
Here's some pictures of radius arms I have built in the past. I use the fact that the arm shape does not matter to my advantage, just like the OP intends to do. This gives me more floor clearance. A 1930s ford has this type of geometry front and rear. Also a 60-66 chevy truck uses rear radius arms.
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The way I see it, putting your arms parallel to the ground will help reduce twisting the axle about the z axis when flexing the suspension. Looking at the travel path of the arms from the side (circle) you'll be putting the starting position at the 90 degree point of the circle vs say 120 degrees. So, when 1 arm moves up and the other arm moves down, they follow the same path along the circle. (as long as they travel the same distance) If the arms started in the 120 degree position of the circle, the compressing side would push the axle away from the rear mount while the extending side would suck it towards the rear mount.
BlueCruiser84
SILVER Star
Edit* mostly bad information below.
The OP is raising the axle mount points by ~6" or so and leaving the frame mount as is. He is not changing the shape of the arms. Model it in the link calculator. Flatter arms (with respect to the ground) will typically have better handling chAracteristics than arms running at a steep angle betelween the frame and the axle. That's the premise behind drop brackets. That's also the reason that 80s with 5"+ of lift start to get squirrelly even with good caster numbers.
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Yeah, you can fix the caster by remounting the axle tube. Caster is not related to the path the axle follows or this discussion. What he's doing is not changing the IC. The mounting points on the axle are not pivots, simply bushing to allow flex. They do not factor into the angle of the arm. Look at those australian arms for the 80. They dont even mount in the same spot on the axle, left or right. You why? Because where it mounts on that end doesnt matter geometrically.
80 Series 2- 6 Superflex Radius Arms Landcruiser FJ80 FZJ80 [SUPR_SuperFlex] - $1,692.50 : Extreme Landcruiser, Upgrades for Extreme Offroad Performance
BlueCruiser84
SILVER Star
I understand that path of travel is the same and articulation will be similar because as you said the frame mount is just a pivot point. But I do not agree (whether correctly or incorrectly) that an 80 with (more or less) the factory suspension bits and a steeply angled radius arm will act the same as a flatter arm in terms of on-road driveability.
Are you saying that if you took an 80 at stock height and just lowered the axle mounting points of the radius arms 6" (giving the radius arm a steep angle) it would handle the same as a stock 80 on the highway?
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nukegoat
Should have bought a Jeep
You're still wrong, sorry. Instant center does remain the same, but there are so many other things that do change based on where the links around mounted on the axle.
Enjoy
Edit: except the calculator is assuming kinematic freedom between the lower mounting points, which isn't the case with a radius arm
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Doesn't work like that. Even though you have the same link dimentions described the program is assuming the axle end mounts pivot which is not how radius arms function. You need a radius arm or ladder bar calculator not a 3 or 4 link one.
Show us a picture of it modeled with the correct math behind it.
Show us a picture of it modeled with the correct math behind it.
nukegoat
Should have bought a Jeep
This is asinine. Polar geometry is polar geometry. Again, imagine a bracket with the link mount extended wayyyyy behind the axle. And now link that to the frame. You think it'll behave the same?
The burden of proof is on you to prove they're the same. But frankly I question your engineering if you don't see how they're different.
Edit: It will behave the same because the links are connected to each other, and Notch is a better fabricator in addition to being a better engineer than myself.
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Im looking at the three link calculator and it looks wrong because there is no third link. Although you have two mount points on the axle, the radius arm will travel in the same circle since the two axle mount points are rigid. Although there will be flex due to the bushing design. But that is just my obsevation. I like that calculator though, thats pretty cool. But i do see what you are saying avout how changing the attachment points on the axle affects all sorts of other crap. Oh well you guys need to figure it out so we can all benefit. Mean while, its beer 30 at my place!
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mudgudgeon
Resident galah
Nice work!
Orientation, and spacing of the bushes/brackets on the axle housing are going to have more impact on the way the suspension behaves, particularly when your chasing road manners, and off-road flex.
Have a look at superior engineering's superflex arms, they are all about changing flex behaviour by using different bush orientation
Well obvious gain is the axle housing will be back where it was originally at stock height vs where it was with angled arms. So wheelbase is brought back to factory settings. As far as handling goes I will sit back and watch the debate. Personally I would just go with lower suspension lift and either cut the fenders or install a body lift and get a better cog.
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It just seems like 4 years ago when we had the same debate
