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Unread 12-29-2011, 03:50 PM   #31
Cresso
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Originally Posted by fratis View Post
the arms pictured are radius arms.
Agreed.

Quote:
like climbit stated, there is NO triagulation incorporated. they arent designed for it or to need it.
The radius arms shown do have triangulation. It's the horizontal separation between the main lower link and that abbreviated upper link (which doesn't truly deserve the "link" name, but that's what people will recognize). From what I can see in the photo, I'm guessing there's about 8-12" of horizontal separation there. Because of that separation, the axle will naturally want to remain perpendicular to each respective radius arm. The result: a centered axle. well, more or less. As stated, the slop in the bushings will allow the axle to move a few degrees away from perpendicular to the radius arm, which the driver will notice as lateral axle movement.

Quote:
without a panhard the axle assembly will move laterally a lot.
Agreed. That's what I said as well. "A lot" is a loose term, though. As a complete off-the-cuff guess, I'm guessing the above system will move laterally somewhere in the 6"-18" range. That's a LOT. However, it's not total freedom of movement as you suggest.

Quote:
unless i have misunderstood your point, this statement leads me to believe you have never incorporated rod ends into a one-off suspension. the slop in the bolt wouldnt allow lateral movement the whole multi-directional function of the rod end would. rod ends would allow even more lateral movement then a standard bushing would allow. once again these are radius arms and are specifically designed to be used with a panhard.
Yep, you misunderstood. It's not the misalignment capability of the rod end that provides the lateral movement in this case. It's the minimal amount of slop between the OD of the bolt and the ID of the rod end.

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Unread 12-29-2011, 05:20 PM   #32
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You, on the other hand, need to keep the face palms to yourself...Otherwise, I'm sure I would not be the only one laughing when that smart assed attitude of yours shows you what a real face palm is. Is this not a forum where people can come in, ask questions, or lend an opinion without worry of bull**** answers like this? Take your **** back over to the PBB if you're going to be replying to people in this manner. I've even never gotten flamed in that forum.
Easy there big guy... I was just trying to get the point across from all the previous posts. My flamethrower isnt engaged...

BACK TO TECH...

There's no difference between that radius arm setup and say an early bronco style except they're using heims instead of those big C bushings at the axle. There's less bind with the heims but it still ends up binding under extreme travel which you prob wont see being a mud rig. The geometry is still the same its 2 links, parallel with the frame without any triangulation in relation to the frame to keep it centered. So you'd need a panhard to keep the frontend where it should be.

If your going to be building a front linked suspension with a stock frame I'd run a true 3 link w/panhard. The geometry will be better than a radius arm and it isnt much extra effort to get it accomplisshed. It's also easy to package around the engine/frame. Look into the POLY performance mounts or ARTEC has some new trick brackets that make linking anything relatively easy. I basically used bootlegged poly style mounts for my 3link/4link yj. A friend and I ran the numbers threw the calculators and adjusted some angles and placement to better suit my axle/wheelbase. Then he ran them trew the torchmate and we slapped it together. It' ll do 80 down the highway with one hand on the wheel and has a ton of bind free usable travel with no wheelhop.
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Unread 12-29-2011, 05:49 PM   #33
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i meant the radius arms themselves are not triangulated with respect to the frame and axle assembly. they are not designed to located the axle assembly laterally. 18" would be "total freedom" enough with respect to front axle lateral movement on the road.
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Unread 12-30-2011, 12:45 AM   #34
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Originally Posted by Cresso View Post
Triangulation of just the links works fine. The problem here is the amount of triangulation vs. the amount of slop in the system. In the example pictured above with the orange links, there's very little triangulation. Judging by what I can see in the picture, there are rubber or poly bushings at at least 2 mount positions, possibly all 6. Bushings add slop unless the movement is constrained somehow. In this particular example, the slop of the bushings plus the limited triangulation will allow the axle to move laterally by quite a bit. Since it is triangulated, the axle will eventually stop, but it'll definitely have a few inches of lateral movement. I can't imagine that'd be good for any usage, especially mud racing at high speeds.

One way to improve the location of the axle would be to eliminate all the bushings for heims. Even then, lack of triangulation makes any slack whatsoever translate into a lot of axle movement, so even the inherent slop of the bolt riding in the heim might be enough to let the axle swing side to side a bit.

In a nutshell: more triangulation or add a trackbar.
wrong. completely and utterly wrong. it does not matter what kind of joint you use. you must have triangulation between the frame and the axle. IE the links need to create a triangle; ideally with the upper links being the sides of the triangle and the "bottom of the triangle would be an imaginary line drawn between the frame side upper control arm mounts. (with triangulated lowers the axle would be the "bottom" of the triangle)

the inherent slop or lack thereof has nothing to do with this equation. if there is any slop in suspension joints you will have very bad things.

oh and if you had rod ends at all sides with no triangulation, the axle would move laterally easier..

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Originally Posted by fratis View Post
this is why i thought this "hardcore" section was a bad idea...



' Swearing, flaming, posting demeaning comments to pound your own chest, slamming, bickering, acting like a child with an attitude and post padding will not be tolerated. ' -joe dillard
wait until we get a moderator and some more participation. then threads like this won't happen.

there was no more flaming in here than the average thread... in fact the OP is the one who got his panties in a massive wad when somebody used a forum approved emoticon because he refused to listen to anything anyone has said.


Quote:
to comply with the rules;
op you are asking about info on building a custom coil suspension for your jeep that i feel does qualify for the "advanced tech" section. if you knew exactly what you wanted or had all the answers you wouldnt need to ask those who have done what you are seeking. make sure that those you listen to have in fact build one-off link and coil suspensions rather then simply bolted on a tj kit. i have a feeling that this is not the case. look into polyperformance 3 link brackets. its a nice place to start. its not a kit but they will get you started in the right direction. link length, location and configuration all still need to be worked out per vehicle and axle assembly as well as link attachment style. in your application, with little need of massive articulation the panhard is a very viable option and shouldnt be shunned too quickly. i think the only thing that a panhard could be a detriment is mub build-up. a triangulated four link would avoid this a bit, however, they are quite tricky to accomplish on the front end without major reworking of major components. this is multiplied for a daily driver.

personally i think those who have not actually built a link and coil setup from scratch should sit this one out.
so wait, because someone hasn't actually fabricated a suspension means they can not understand the physics of one? thats garbage. sure when you move into the actual fabrication of the system and where/how to mount links you might have a case for listening to people who have done it successfully. but when we are still arguing basic geometry it doesn't matter how many suspensions you have or have not built. math is math.

Quote:
I am perfectly capable of distinguishing between radius arm and "properly triangulated" suspension...are you capable of distinguishing between traditional radius arm and other spin offs?
clearly you are not. and if by traditional you mean the "ford stuff"

<snip>

Last edited by Joe Dillard; 01-01-2012 at 10:53 PM.. Reason: clean-up
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Unread 12-30-2011, 01:18 AM   #35
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Originally Posted by Climbit View Post
so wait, because someone hasn't actually fabricated a suspension means they can not understand the physics of one? thats garbage. sure when you move into the actual fabrication of the system and where/how to mount links you might have a case for listening to people who have done it successfully. but when we are still arguing basic geometry it doesn't matter how many suspensions you have or have not built. math is math.
you make a valid argument as to the basic nature of the concepts being thrown around in this thread, however, i still feel that you can know all the theory and math you like but until you get under there and deal with why the link calc #s are impossible to achieve or deal with time or money constraints that guide a build or any number of real world stumbling blocks then its all moot. i see far too many internet experts trying to school others when in fact they have no practical hands-on experience with said topic. it is rampant on the internet and even jeepforum. i have a relatively tame post count and this is because i make an effort to not post on topics i have not had hands on experience with regardless of what i have read or garnered from others..
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Unread 12-30-2011, 01:39 AM   #36
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Originally Posted by fratis View Post
you make a valid argument as to the basic nature of the concepts being thrown around in this thread, however, i still feel that you can know all the theory and math you like but until you get under there and deal with why the link calc #s are impossible to achieve or deal with time or money constraints that guide a build or any number of real world stumbling blocks then its all moot. i see far too many internet experts trying to school others when in fact they have no practical hands-on experience with said topic. it is rampant on the internet and even jeepforum. i have a relatively tame post count and this is because i make an effort to not post on topics i have not had hands on experience with regardless of what i have read or garnered from others..
I agree with you somewhat, however the topic of this thread is very basic suspension geometry.

I won't tell anyone how to build their suspension, or what length links to use, or what angles to run everything at, or where to mount link brackets.. becuase I have not fabricated my own suspension, I have not needed to yet.

but I will tell you that if you don't have enough triangulation your axle is going to move all over the place unless you use a panhard.
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Unread 12-30-2011, 02:33 AM   #37
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wrong. completely and utterly wrong. it does not matter what kind of joint you use. you must have triangulation between the frame and the axle. IE the links need to create a triangle; ideally with the upper links being the sides of the triangle and the "bottom of the triangle would be an imaginary line drawn between the frame side upper control arm mounts. (with triangulated lowers the axle would be the "bottom" of the triangle)
There are two triangles there. If we were looking down from directly above, you'd see them. In fact, the system only needs one triangle to resist lateral movement. The second triangle makes it resist even more. Still, though, not enough triangulation. If the axle mount points for the upper "links" were closer to the center of the axle, it'd work a lot better and probably wouldn't need a trackbar. That causes lots of packaging issues on a front end, though. Similarly, you could mount the intersection of the upper "link" and the lower link closer to the frame, but it absolutely does not have to go to the frame. There are suspension behavior reasons to go to the frame (to achieve frame-side horizontal and/or vertical separation), but lateral location is not one of those reasons.

The location of the triangle doesn't matter, either. Think of it as a big square with joints at each corner. Put a fifth line joining any two adjacent lines of the square at any point. It doesn't matter where along the outside lines the inner line goes. Once that line is there, even if it's also attached by joints, that square can no longer shift in any way (non-square quadrilateral). The inside line would have to change length for that to happen. I'll include a picture here to help illustrate this. Squares 1, 2 and 3 have roughly similar triangulation. Square 4 has terrible triangulation. Square 5 has excellent triangulation. Note that it doesn't matter where that red line is. Rotate the square any way you want and it'll do the same thing. Also note that the red line in square 5 is still attached to the outside line segments, not going to the corners themselves. If it were going to the corners, it would no longer constrain anything. In all five cases, if the length of that red line doesn't change and the point at which it intersects with the outer black lines doesn't change, all five examples can only exist as squares, even if every vertex can be any angle (i.e. a flexible joint).



As for the type of joint, it absolutely does matter. Radius arms have inherent articulation bind. I'll assume we all know about that. Stop me if you don't, although it's really not necessary for this particular discussion. The punchline is that manufacturers intentionally design some slop into the attachment points to relieve some of this bind. They typically achieve this by using large, soft bushings that will give quite a bit, which is what the system pictured earlier appears to be using. It's not much slop, but it doesn't need to be. It's probably about the same or a tad bit more than the slop in a bone stock Jeep. However, this slop defeats some of the triangulation we were just talking about. The red inside line we used to hold our quadrilateral at right angles depends on the fact that the red line does not change length. The soft joints effectively allow the length of that line to change a little bit. This is where the amount of triangulation determines whether that slop translates into an imperceptible amount of lateral axle movement or a lot. The closer the two ends of the line are to the common vertex between the two adjacent outside edges, the less the inside line length changes for a given amount of angle change. Referring to the example squares above, if the red line in Square 4 is capable of changing in length even a small amount, joints in the corners will be freed up to move quite a bit. If the red line in Square 5 is changed the same amount, the angles in the corners will still hardly be able to move at all. And to draw this back to the radius arm suspension, any angle change means lateral axle movement.
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Unread 12-30-2011, 07:58 AM   #38
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Originally Posted by Cresso View Post
There are two triangles there. If we were looking down from directly above, you'd see them. In fact, the system only needs one triangle to resist lateral movement. The second triangle makes it resist even more. Still, though, not enough triangulation. If the axle mount points for the upper "links" were closer to the center of the axle, it'd work a lot better and probably wouldn't need a trackbar. That causes lots of packaging issues on a front end, though. Similarly, you could mount the intersection of the upper "link" and the lower link closer to the frame, but it absolutely does not have to go to the frame. There are suspension behavior reasons to go to the frame (to achieve frame-side horizontal and/or vertical separation), but lateral location is not one of those reasons.

The location of the triangle doesn't matter, either. Think of it as a big square with joints at each corner. Put a fifth line joining any two adjacent lines of the square at any point. It doesn't matter where along the outside lines the inner line goes. Once that line is there, even if it's also attached by joints, that square can no longer shift in any way (non-square quadrilateral). The inside line would have to change length for that to happen. I'll include a picture here to help illustrate this. Squares 1, 2 and 3 have roughly similar triangulation. Square 4 has terrible triangulation. Square 5 has excellent triangulation. Note that it doesn't matter where that red line is. Rotate the square any way you want and it'll do the same thing. Also note that the red line in square 5 is still attached to the outside line segments, not going to the corners themselves. If it were going to the corners, it would no longer constrain anything. In all five cases, if the length of that red line doesn't change and the point at which it intersects with the outer black lines doesn't change, all five examples can only exist as squares, even if every vertex can be any angle (i.e. a flexible joint).



As for the type of joint, it absolutely does matter. Radius arms have inherent articulation bind. I'll assume we all know about that. Stop me if you don't, although it's really not necessary for this particular discussion. The punchline is that manufacturers intentionally design some slop into the attachment points to relieve some of this bind. They typically achieve this by using large, soft bushings that will give quite a bit, which is what the system pictured earlier appears to be using. It's not much slop, but it doesn't need to be. It's probably about the same or a tad bit more than the slop in a bone stock Jeep. However, this slop defeats some of the triangulation we were just talking about. The red inside line we used to hold our quadrilateral at right angles depends on the fact that the red line does not change length. The soft joints effectively allow the length of that line to change a little bit. This is where the amount of triangulation determines whether that slop translates into an imperceptible amount of lateral axle movement or a lot. The closer the two ends of the line are to the common vertex between the two adjacent outside edges, the less the inside line length changes for a given amount of angle change. Referring to the example squares above, if the red line in Square 4 is capable of changing in length even a small amount, joints in the corners will be freed up to move quite a bit. If the red line in Square 5 is changed the same amount, the angles in the corners will still hardly be able to move at all. And to draw this back to the radius arm suspension, any angle change means lateral axle movement.
Props on a great post. This is exactly why I think radius arms have no place on an offroad vehicle. Slop + inherent binding = problems you'll just have to live with until you get smart.
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Unread 12-30-2011, 10:20 AM   #39
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Originally Posted by Cresso View Post
There are two triangles there. If we were looking down from directly above, you'd see them. In fact, the system only needs one triangle to resist lateral movement. The second triangle makes it resist even more. Still, though, not enough triangulation. If the axle mount points for the upper "links" were closer to the center of the axle, it'd work a lot better and probably wouldn't need a trackbar. That causes lots of packaging issues on a front end, though. Similarly, you could mount the intersection of the upper "link" and the lower link closer to the frame, but it absolutely does not have to go to the frame. There are suspension behavior reasons to go to the frame (to achieve frame-side horizontal and/or vertical separation), but lateral location is not one of those reasons.

The location of the triangle doesn't matter, either. Think of it as a big square with joints at each corner. Put a fifth line joining any two adjacent lines of the square at any point. It doesn't matter where along the outside lines the inner line goes. Once that line is there, even if it's also attached by joints, that square can no longer shift in any way (non-square quadrilateral). The inside line would have to change length for that to happen. I'll include a picture here to help illustrate this. Squares 1, 2 and 3 have roughly similar triangulation. Square 4 has terrible triangulation. Square 5 has excellent triangulation. Note that it doesn't matter where that red line is. Rotate the square any way you want and it'll do the same thing. Also note that the red line in square 5 is still attached to the outside line segments, not going to the corners themselves. If it were going to the corners, it would no longer constrain anything. In all five cases, if the length of that red line doesn't change and the point at which it intersects with the outer black lines doesn't change, all five examples can only exist as squares, even if every vertex can be any angle (i.e. a flexible joint).



As for the type of joint, it absolutely does matter. Radius arms have inherent articulation bind. I'll assume we all know about that. Stop me if you don't, although it's really not necessary for this particular discussion. The punchline is that manufacturers intentionally design some slop into the attachment points to relieve some of this bind. They typically achieve this by using large, soft bushings that will give quite a bit, which is what the system pictured earlier appears to be using. It's not much slop, but it doesn't need to be. It's probably about the same or a tad bit more than the slop in a bone stock Jeep. However, this slop defeats some of the triangulation we were just talking about. The red inside line we used to hold our quadrilateral at right angles depends on the fact that the red line does not change length. The soft joints effectively allow the length of that line to change a little bit. This is where the amount of triangulation determines whether that slop translates into an imperceptible amount of lateral axle movement or a lot. The closer the two ends of the line are to the common vertex between the two adjacent outside edges, the less the inside line length changes for a given amount of angle change. Referring to the example squares above, if the red line in Square 4 is capable of changing in length even a small amount, joints in the corners will be freed up to move quite a bit. If the red line in Square 5 is changed the same amount, the angles in the corners will still hardly be able to move at all. And to draw this back to the radius arm suspension, any angle change means lateral axle movement.
ok, you make a couple valid points.

however you are still wrong in thinking that all you need is triangulation of the uppers in a radius arm suspension.

even if the uppers were fully triangulated IE they ran from the center of the axle tube to the lower link right at the frame side joint (the most triangulation you could get) they would still do nothing to locate the axle laterally.

there has to be good triangulation between the frame and the axle.

what you are talking about would keep the axle located in relation to the lower links, but as long as you are only using one frame-side connection on each side of the axle there will be lateral movement unless you control it with the panhard.

without the triangulation of the lowers, or even the tiny amount of triangulation that the stock geometry offers there will be lateral movement of the axle regardless of the joints used.

yes, the slop in the bushings is what allows for that movement, but even if you ran a rod end or cartridge joint, the misalignment of those joints would also allow lateral movement.

and FYI that Rusty's offroad suspension kit uses Cartridge style joints at the axle and clevite bushings at the frame.

the only way you get a radius arm suspension like that to not allow lateral movement is to weld it to the frame and the axle so it can't move anywhere.
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Unread 12-30-2011, 10:29 AM   #40
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Quote:
Originally Posted by fratis View Post
i see far too many internet experts trying to school others when in fact they have no practical hands-on experience with said topic. it is rampant on the internet and even jeepforum. i have a relatively tame post count and this is because i make an effort to not post on topics i have not had hands on experience with regardless of what i have read or garnered from others..
I have a tame count as well for these same reasons. Threads like this and ones on pirate will assist me though in formulating my future suspension plans.
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Unread 12-30-2011, 10:35 AM   #41
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Wow, this went a long way from where it was left yesterday...well, for the most part.

Thanks very much to Cresso and fratis for understanding my point.

On the other hand, I guess I wasn't clear enough in explaining, or breaking my theory down Barney style for simple ****s like Climbit...yes, I understand that there has to be triangulation between the axle and frame, i.e. horizontal spread of the links from the frame end to the axle. That picture I posted with the orange links was simply an example. Not once did I say "I'm going to build my suspension just like this!" Frankly, I didn't even notice that the picture given had no lateral separation of the links at the axle end. Once again -- it was purely an EXAMPLE.

My apologies to ssyj94 for getting a little bent out of shape over his post. I don't usually have my wits fully about me when I'm on here first thing in the morning...I work from 3 p.m. to 3 a.m. every day, so sometimes I'm a little cranky.

<snip>
Let me try and be completely clear with what my original theory was -- I understand that radius arms need a panhard bar to prohibit lateral movement. The orange links in the picture are radius arms...I understand that. I know I called them y-links. They are, in fact, y-links though, am I wrong? Are y-links not the same basic principal as radius arms? Yes, they are. But what's the difference? The upper short link...aah, there it is, that's what makes them stand out from standard radius arms... The orange arms have the same BASIC design that I had in mind, minus the horizontal spread at the axle, and a larger "triangle" in the upper short links, if you could call them that. Along with the shorter uppers, they would have more horizontal separation between them and the lowers. If I could work a Paint program that well, I'd draw you a picture. Or if I had access to SolidWorks...at any rate, I hope this description was clear enough to get my point across. I think at least Cresso and fratis understand what I was getting at.

And by the way, no, I was not completely ignoring anyone that was telling me this simply wouldn't work. I was trying to get a clear answer as to why it wouldn't work. But then again, I wasn't clear enough with my description of what I had in mind.

Last edited by Joe Dillard; 01-01-2012 at 10:55 PM.. Reason: clean-up
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Unread 12-30-2011, 01:12 PM   #42
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ok, you make a couple valid points.

however you are still wrong in thinking that all you need is triangulation of the uppers in a radius arm suspension.
This might be a lost cause, but I'll try a few more Paint doodles. If you're still not a believer, we can agree to disagree. No harm done.

The triangulation can be between any adjacent lines in the square, as we discussed above. The reason for this is that a triangle with fixed length sides has fixed angles. We can even calculate those angles using the length of the links and the cosine rule. In the picture below, drawing 1 has this relationship. If you want, you can think of the black line as our lower link, the blue line as the axle and the red line as our upper "link". Assuming that all three lines stay the same length, simple geometry states that the angles also have to stay the same.

Drawings 2 and 3 illustrate the impossibility of changing the angles of the triangle while maintaining the same line length. Make the angle larger and the red line no longer reaches. Make the angle smaller and the red line is too long.

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Unread 12-30-2011, 01:48 PM   #43
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yes, I understand that there has to be triangulation between the axle and frame, i.e. horizontal spread of the links from the frame end to the axle.
Ya lost me there. Horizontal spread of the links from the frame end to the axle? That's the length of the link itself. A two foot radius arm has two feet of horizontal spread from the frame attachment point to the axle attachment point (assuming the radius arm is parallel to the ground). There doesn't actually have to be triangulation between the axle and the frame. The triangulation just has to exist anywhere in the square formed by the four attachment points of the main links.

Quote:
Frankly, I didn't even notice that the picture given had no lateral separation of the links at the axle end.
It does, though. If there were no lateral separation, the upper "links" would attach to the axle directly above the attachment points for the lower links. However, the axle attachment point for the upper "links" appears to be a good 8-12 inches inboard on the axle from the lower link axle attachment point. That's your triangle. One side is 8-12", the hypotenuse is the length of the top "link", and the third length is however long the lower link is from where it attaches to the axle to where it intersects the upper "link".

Quote:
Let me try and be completely clear with what my original theory was -- I understand that radius arms need a panhard bar to prohibit lateral movement.
Strictly speaking, radius arms don't need a panhard bar. They just need enough triangulation. That said, packaging sufficient triangulation can be very difficult in an off-road rig. There's driveshaft interference, oil pan interference, exhaust interference, and so on. Panhards are easier.

Quote:
The orange links in the picture are radius arms...I understand that. I know I called them y-links. They are, in fact, y-links though, am I wrong? Are y-links not the same basic principal as radius arms? Yes, they are.
Semantics. "Radius arm" is an industry term, not a geometry term. Same with "y-links". Marketing departments are coming up with those names, not engineers. The problem is that the name does almost nothing to describe the system. There's no need to spend any time describing what the name means, because it means different things to different people. The Ford radius arm is not the same as the Land Rover radius arm, which is not the same as the Rusty's radius arm, which is not the same as the T&T radius arm, et cetera ad nauseum. Instead of trying to define a y-link or a radius arm, just define the specific application you're talking about. It's still going to be difficult using just text, as shown on the first page of this thread by the necessity of using pictures to indicate which kind of y-link you were referring to. The best way to do it is to draw it out. Second best, assuming you're trapped with just MS Paint like me, is to use very specific terms to describe what you're envisioning, such as describing the number of links, the length of the links, the horizontal and vertical separation respective to others links at each attachment point, and so on. This is difficult and you won't know all the numbers exactly at this point of the process. That's why the best answer you can get at this point is: "It depends".

I'm not trying to give you a hard time here. I'm merely pointing out that the terminology we use causes confusion by its ambiguity. This confusion will make threads like this escalate unnecessarily. I'm picturing one kind of radius arm in my mind, you're picturing another, Climbit is picturing a third. That doesn't necessarily mean one person is right and two are wong. We just need to get on the same page. That begins with defining the suspension by a lot more than just the manufacturer's name for it.

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The orange arms have the same BASIC design that I had in mind, minus the horizontal spread at the axle, and a larger "triangle" in the upper short links, if you could call them that.
The horizontal spread creates the triangle. Without that horizontal spread, the triangle does not exist.
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Unread 12-30-2011, 02:22 PM   #44
Cresso
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Quote:
Originally Posted by Imped View Post
Props on a great post. This is exactly why I think radius arms have no place on an offroad vehicle. Slop + inherent binding = problems you'll just have to live with until you get smart.
Meh. Radius arms get a bad rep because of poor implementation and generic naming conventions. They definitely have some undesirable characteristics, but, in the grand scheme of things, those undesirable characteristics aren't that bad and they do have a couple advantages.

The main problem is that people consider radius arms to be a completely different setup than a four-link. The two are actually extraordinarily similar. In fact, from a design perspective, you can think of a radius arm suspension as a four-link with zero frame separation between the upper and lower links. If you were using one of the available link calculators, that's exactly how you'd enter a radius arm suspension: the horizontal and vertical separation between the two links on each side is zero. Once we start thinking about it in those terms, we can see how similar the two systems are. Consider a four-link where you mount the frame attachment point for the upper link one inch above the frame side attachment point for the lower link. When you plug it into a link calculator, vertical separation will be 1 and horizontal separation will be zero. The characteristics of that particular suspension, assuming everything else is the same, will behave nearly indentical to radius arms. Imperceptibly different. You'll have almost the same terrible anti-squat numbers as a radius arm, thus you'll have almost the same jacking characteristic that makes radius arms so maligned for climbing stuff. This four-link suspension will even have the same axle-side bind of a radius arm, because we didn't change anything at the axle side. That bind is not exclusive to radius arms, nor do all radius arms suffer from it. It's just that people often think of the classic implementation of radius arms by Ford and Land Rover when someone says "radius arms", and both of those examples have terrible bind. That's because the upper axle attachment points of those two types of radius arms are too far apart. The closer those attachment points get, the less bind there is. Put 'em right next to each other and you'd have a radius arm setup that's nearly identical to the extremely popular triangulated 4-link.

We could expand on this for pages and pages, but I don't want to get too far away from the original poster's topic, so I'm skipping a lot of great info for now. In a nutshell, radius arms aren't so different from other suspension styles and, therefore, should not be condemned universally. We'd need to analyze the specifications of each individual implementation of radius arms to determine whether or not it's a decent design.
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Unread 12-31-2011, 12:56 AM   #45
Climbit
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Quote:
Originally Posted by Scooter402 View Post
On the other hand, I guess I wasn't clear enough in explaining, or breaking my theory down Barney style for simple ****s like Climbit
wait.. what? becuase you did not understand what you were asking for, nor did you listen to what people were saying it is somehow my fault?

...
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yes, I understand that there has to be triangulation between the axle and frame
good.
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i.e. horizontal spread of the links from the frame end to the axle. That picture I posted with the orange links was simply an example. Not once did I say "I'm going to build my suspension just like this!" Frankly, I didn't even notice that the picture given had no lateral separation of the links at the axle end. Once again -- it was purely an EXAMPLE.
ok so you said you didn't need a panhard for a radius arm system, then when several people told you that you would, instead of listening you then posted a picture of a radius arm system that uses a panhard to prove us wrong. so naturally anyone would assume you were going to design your suspension like the example you posted, and try not running a panhard, which would be a very bad idea.

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My apologies to ssyj94 for getting a little bent out of shape over his post. I don't usually have my wits fully about me when I'm on here first thing in the morning...I work from 3 p.m. to 3 a.m. every day, so sometimes I'm a little cranky.
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To save everyone else the entertainment of an "internet arguement" I'll simply ask to just stop posting unless you have something constructive to add to the discussion.
I, along with others, was trying to help you by informing you that your example radius arm system would need a panhard... but you ignored that because you were too busy being offended.

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You have been nothing but argumentative with everyone because you apparently know everything about anything. My apologies, I did not realize I was in the presence of the Jeep God. I am not interested (nor would anyone else be for that matter) in someone making a poor attempt to flex their internet muscles as if to say "I've got bigger balls than you." Over an internet forum? Really?
I've been arguing the physics of a suspension in a thread about suspension...how dare me.

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Let me try and be completely clear with what my original theory was -- I understand that radius arms need a panhard bar to prohibit lateral movement. The orange links in the picture are radius arms...I understand that.
then why all the arguing

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I know I called them y-links. They are, in fact, y-links though, am I wrong? Are y-links not the same basic principal as radius arms?
Yes, they are. in most cases.

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But what's the difference? The upper short link...aah, there it is, that's what makes them stand out from standard radius arms... The orange arms have the same BASIC design that I had in mind, minus the horizontal spread at the axle, and a larger "triangle" in the upper short links, if you could call them that.
by horizontal spread do you mean the lack of triangulation, IE the links are almost parallel? because if you do, then I think I understand you.

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Along with the shorter uppers, they would have more horizontal separation between them and the lowers. If I could work a Paint program that well, I'd draw you a picture. Or if I had access to SolidWorks...at any rate, I hope this description was clear enough to get my point across. I think at least Cresso and fratis understand what I was getting at.
now that you actually said what you were thinking of doing I can understand what you are thinking. I honestly don't know that what you are describing would work. but at the very least you would need a panhard to control the axle for the steering links. and that would induce some bind, how much or where depends on your link geometry and length. unless you went full Hydro, that would solve that problem. but you still may end up with too much lateral movement.

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And by the way, no, I was not completely ignoring anyone that was telling me this simply wouldn't work. I was trying to get a clear answer as to why it wouldn't work. But then again, I wasn't clear enough with my description of what I had in mind.
alright... well to be perfectly clear, the rusty's kit you posted a picture of would not work without a panhard. any traditional radius arm suspension wont.

I will tell you that even with a panhard they are very popular amongst the go-fast jeep desert crowd. nearly every Jeepspeed style jeep I have seen uses radius arms in the front, it works well for those guys so it would probably work well for your. the sports are similar enough.

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Originally Posted by Cresso View Post
This might be a lost cause, but I'll try a few more Paint doodles. If you're still not a believer, we can agree to disagree. No harm done.
I believe that with the proper amount of triangulation you could keep the axle centered to the links. however there are other things to consider. once you start moving that axle up and down and articulating it, twisting it, etc you are going to get a lot of side-side movement, you will change the link relationships and then you are going to be very unhappy.

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The triangulation can be between any adjacent lines in the square, as we discussed above. The reason for this is that a triangle with fixed length sides has fixed angles. We can even calculate those angles using the length of the links and the cosine rule. In the picture below, drawing 1 has this relationship. If you want, you can think of the black line as our lower link, the blue line as the axle and the red line as our upper "link". Assuming that all three lines stay the same length, simple geometry states that the angles also have to stay the same.
right, but now swing those lines in an arc, add in some axle rotation and where are you.

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Drawings 2 and 3 illustrate the impossibility of changing the angles of the triangle while maintaining the same line length. Make the angle larger and the red line no longer reaches. Make the angle smaller and the red line is too long.
I'm not saying you would get a lot of lateral movement, but how much is acceptable? once you start rotation of the links and things start moving you are going to end up with some lateral movement. whether or not that is within acceptable boundaries depends on the specific link geometry.

OP
if you really want to run a radius arm suspension, run it with a panhard, and eliminate one of the upper links. then you will not get the bind inherent in the design. (think IRO) just use a bolt larger than 10mm and don't use that silly caster adjuster plate

Last edited by Joe Dillard; 01-01-2012 at 10:59 PM.. Reason: clean-up
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