i just built my first 4 link and i'm getting a lot of rear steer. how can i fix this. there are pics of my rig on a seperate post called "buggy leaf my coils?" . or am i getting worried over nothing. it's a off-road only rig. probably never see 20 mph anyway.

thanks guys

what have you decided not to jump it now. i am pretty sure you will get it over 20 mph, but i am sure it will be in good fun. the best way to get rid of rear steer is longer locating links. the more flex you have, the more the axle is going to twist around. so the longer the links the less they steer. not a true answer but it is what i have noticed in the mock ups we have done. just my 2 cents mike

I just tested out my rear suspension this weekend and it has almst no rear steer at all. You dan't have to triangulate both upper and lower like I did to get rid of rear steer. If you just triangulate the lower and put the uppers straight it will help also.
<IMG width=432 height=323 SRC="http://www.pirate4x4.com/ubb/uploads/Pa9270016.jpg">
<IMG width=432 height=296 SRC="http://www.pirate4x4.com/ubb/uploads/frostober1a.jpg">

I remember thinking that your links looked real short in your pics. Did you use tractor links??

Has anybody thought about trying to make the links so that the body does not move so far of center when it articulates? Or beter yet, make it move the other way so the wieght will be on the up hill side.

you mean having the roll axis plane and cg plane almost ontop of each other...yes i have thought about it as I am sure others have to. However, the problem I have encountered is space constraints. You can only move the rear roll axis up so much unless the rearend of the rig is just choped off.... <IMG SRC="smilies/fj.gif" border="0">

Originally posted by desertoy:
<STRONG>I just tested out my rear suspension this weekend and it has almst no rear steer at all. You dan't have to triangulate both upper and lower like I did to get rid of rear steer. If you just triangulate the lower and put the uppers straight it will help also.
<IMG width=432 height=323 SRC="http://www.pirate4x4.com/ubb/uploads/Pa9270016.jpg">
<IMG width=432 height=296 SRC="http://www.pirate4x4.com/ubb/uploads/frostober1a.jpg"></STRONG>

Do you have any close up pics of your suspension links?

that is the closest one I have for now. What exactly do you want to see?

Originally posted by Convertiyota:
<STRONG>I remember thinking that your links looked real short in your pics. Did you use tractor links??</STRONG>

yes, theyare tractorlinks. and about 30" long on all 4. my idea was carry one spare. but i'm also a semi novice builder so it ws also easier for me to do. but will the rear steer cause any real problems anyway. and as far as jumpin goes, i'll be goin straight anyways....i hope. but if i lengthen the bottom arms, it will help right ??????

do you run into any problems triangulating both upper and lower links?

Originally posted by BeaconBasher:
<STRONG>do you run into any problems triangulating both upper and lower links?</STRONG>
Not so far <IMG SRC="smilies/biggrin.gif" border="0">

I don't see how rear steer can cause to much problems. i say drive it and see how you like it if it bothers you fix it. I like desert toys rear end looks simple and effective

From what I have read, the two ways to eliminate roll steer are 1)have the longest links you can fit, 2)make sure your roll axis is horizontal. Since you allready have yours done either option is a lot of work. I say just wheel it. If you don't like it you can allways change it latter.

Kev

P.s. Pig Pen- I told ya so!

Originally posted by Pig Pen:
<STRONG>You can only move the rear roll axis up so much unless the rearend of the rig is just choped off.... <IMG SRC="smilies/fj.gif" border="0"></STRONG>


How do you mean? Please explain, and how it helps to havethe rear chopped off?

And what's your opinion on both sets of links being triangulated, especially for flex, stability, and road use. My coilover set up will be on the rear of a 90's style x-cab tubed out cab back. It will be my DD for a while.

what is the way I can find out my CG?
And desertoy How long are your links and at what angle is the uppers triangulated at (if you don't mind)

[ 10-16-2001: Message edited by: ToyFamily ]

[ 10-16-2001: Message edited by: ToyFamily ]

just a dumbass question from me since i would like to 4 link mine, It seems like it would be necessary for the uppers and lowers to be the same length, am I right or stupid?

Originally posted by ToyFamily:
<STRONG>
How do you mean? Please explain, and how it helps to havethe rear chopped off?

And what's your opinion on both sets of links being triangulated, especially for flex, stability, and road use. My coilover set up will be on the rear of a 90's style x-cab tubed out cab back. It will be my DD for a while.

what is the way I can find out my CG?
And desertoy How long are your links and at what angle is the uppers triangulated at (if you don't mind)

[ 10-16-2001: Message edited by: ToyFamily ]

[ 10-16-2001: Message edited by: ToyFamily ]</STRONG>
THANKS FER THE INPUT GUYS. I'LL DRIVE IT AND SEE WHAT I THINK.

I can't remember off hand how long my rear arms are( I think between 40 and 50"). What I did was make the rear of the arms in line with the axle centerline and make the front of the arms in line with the center of the deiveline u-joint. That way I don't have to worry about the driveline changing lengths too much as the suspension works.
I kept the same wheelbase also, 105".

Originally posted by ToyFamily:
[QB]
How do you mean? Please explain, and how it helps to havethe rear chopped off?

And what's your opinion on both sets of links being triangulated, especially for flex, stability, and road use. My coilover set up will be on the rear of a 90's style x-cab tubed out cab back. It will be my DD for a while.

what is the way I can find out my CG?
And desertoy How long are your links and at what angle is the uppers triangulated at (if you don't mind)
QB]

What I mean is that the rear half of the frame would have to yacked in order to mount the links high enough so that the roll axis would be in the same plane as the cg roll center.
As for triagulation, its hard to explain with out pictures but link, lenths, angles, & place all dictate how how the suspension will react. I remember awhile back Gordon put up some good pics of how to determine roll axis. Its a picture from the millikin book.

Originally posted by rokcrawla:
<STRONG>just a dumbass question from me since i would like to 4 link mine, It seems like it would be necessary for the uppers and lowers to be the same length, am I right or stupid?</STRONG>

Not neccessarlily(spell check anyone??) You should keep in mind that driving on the road you suspension doesn't really move that much, so in my opinion that is something to take into consideration. Off road, say your suspension flexs out while you are crawlin, how fast are you driving????? Fast enough to feel a driveline vibe if you pinion angle chages slightly, highly unlikely.

Pig Pen is right about needing to hack the rear off a vehicle with a link suspension. You can run one a stock vehicle, but the body and frame constrains how much benefit you get out of it. There is so much potential in a link suspension and the rear frame and body need to be designed around it in order to take full benfit of all your work. If you rub your tires on the frame or fenders now with leaf springs, there only going to rub even harder after you go 1/4 or coils.
Does anyone know if it is good to have a high or low roll axis height when rockcrawling? Does it matter at such a slow almost static speed?
Kev

Yes Kev...........as to wether it is good to have a low or high roll axis on a crawler.....would you like to roll your vechicle while driving to the supermarket??? not me.......the closer the roll axis of the suspension to the plane at which the cg is the more stability there is.

[ 10-17-2001: Message edited by: Pig Pen ]

...What about switching the links? I really like how Desertoy has his set up, and was thinking that'd be the best way to go...

But if you were to put the "point" of the triangle at the bottom of the axle instead of the top, that should change the pivot point of the axle to one where the body won't move quite so far off of the center of the axle... And also, it should flex better, leverage-wise, I would think...

But I may be totally wrong. <IMG SRC="smilies/biggrin.gif" border="0">

Does anyone see anything wrong with this concept, I have been kicking it around for about a year.

<IMG width=489 height=526 SRC="http://www.pirate4x4.com/ubb/uploads/linksktch.jpg">

Originally posted by ToyFamily:
<STRONG>Does anyone see anything wrong with this concept, I have been kicking it around for about a year.
</STRONG>

Ok. I'm bored. And probably wrong. But here. <IMG SRC="smilies/biggrin.gif" border="0">

I think it's a great idea. I do think that you need to either lengthen the upper arms or shorten the lower arms a little so that the line running between the upper and lower axle mounts remain parallel with itself when you compare any two points of vertical only travel. As it sits now, I think it will create some squat upon acceleration.

It looks like there won't be much reer-steer...

Also, the bends might create an increased possibility of breakage.

Well one problem I see is the 90 degree bend in the lower links. A straight tube is much stronger in tension and compression than a tube with bends. Having said that you could engineer your tube size to acount for those forces.
Dave-are you so sure? <IMG SRC="smilies/fj.gif" border="0"> I have been readin up a little this weekend. It seems that you don't want to go to high with the roll center either. It seems that roll axis height controls mostly how stable a vehicle "feels", and not the vehicles ability to resist rolling over. With a low roll axis the cg can exert a larger torque on the body giving it more sway in turns. But, with a high cg the forces on the tire contact patch creat a large verticle lifting force causing weight jacking. In essence it will cause the inside tire to lift without the body swaying as much. The question is, if you were designing a rock crawler, and not a sports car, which way would you go, high or low?
Of course I could be all wrong too.

Kev

Oh and one more thing, I would definately try to triangulate the lower links. It seems that with triangulated upper and lower links it is easier to get little rear steer with some anti-squat. With parrallel links it becomes more of a challenge. Correct me if I am wrong, there seems to be a balancing act between rear steer and anti-squat.

Kev

Originally posted by Ghetto Fab.:
<STRONG>Well one problem I see is the 90 degree bend in the lower links. A straight tube is much stronger in tension and compression than a tube with bends. Having said that you could engineer your tube size to acount for those forces.
Dave-are you so sure? <IMG SRC="smilies/fj.gif" border="0"> I have been readin up a little this weekend. It seems that you don't want to go to high with the roll center either. It seems that roll axis height controls mostly how stable a vehicle "feels", and not the vehicles ability to resist rolling over. With a low roll axis the cg can exert a larger torque on the body giving it more sway in turns. But, with a high cg the forces on the tire contact patch creat a large verticle lifting force causing weight jacking. In essence it will cause the inside tire to lift without the body swaying as much. The question is, if you were designing a rock crawler, and not a sports car, which way would you go, high or low?
Of course I could be all wrong too.

Kev</STRONG>


Yes Kev that a boy........the point I was trying to make was that having the sus. roll axis closer to the cg would be better than having it far away. Theoritcally if the cg and roll axis were in the same plane the vechice would have no body roll going around a corner (fast) and would indeed lift a tire causing some "jacking"...
<IMG SRC="smilies/smokin.gif" border="0">

[QUOTE]Originally posted by ToyFamily:
[QB]Does anyone see anything wrong with this concept, I have been kicking it around for about a year.

Looks ok but i am with ghetto on this one.........no bends on the lower dude.....oh by the way I think I met you one time on the con. You asked to borrow some gear fluid, some thin about how you flat towed the 4runner up there and puked all the fluid out of the front diff vent????

you must be talking about my dad (we're under the same "tag") but what I was thinking is to not nessesarily make the bends at 90 but less drastic and have an upper tube with plating in between, making a fin like link, somewhat like the Raptor.

So the links (upper & lower) want to be moving closer as they head to the front of the truck, or be parrallel......? (for the rear susp)

Originally posted by ToyFamily:
<STRONG>you must be talking about my dad (we're under the same "tag") but what I was thinking is to not nessesarily make the bends at 90 but less drastic and have an upper tube with plating in between, making a fin like link, somewhat like the Raptor.

So the links (upper & lower) want to be moving closer as they head to the front of the truck, or be parrallel......? (for the rear susp)</STRONG>

ok yea it must have been you dad, nice guy by the way. Anyways, triangulate the uppers toward the center of the diff. Try and triagulate the lowers towards the t-case. Now imagine a top view of this set up. Make two points , one where the uppers converge and one where the lowers converge. Now if the lowers had hardly trigulated at all don't make that second point. Now in the side view mark the point where the uppers converge at and the lowers. connect the dots(lalala). The angle of that plance in the side view is the roll axis of the suspension. If the Lowers are barly triaglulated the draw the roll axis parallel to the lower links in the side view from the point where the uppers converge.

This is hard to say in words but thats my best shot , a picture is worth a thousand words in this situtation.

Dave

One more thing instead of the bend why not just mount the lowers on top of the housing.

to be different, and gain clearance? Just to tinker. Way back I was told that the lowers had to be mounted belowthe centerline of the housing, so I came up with that, and hadn't seen anyone else try it so I thought it would either fail miserably or be a new fad.

that's what I got???
<IMG width=439 height=369 SRC="http://www.pirate4x4.com/ubb/uploads/sketch.jpg">

now is there any way to describe CG?

[ 10-18-2001: Message edited by: ToyFamily ]

Originally posted by ToyFamily:
<STRONG>to be different, and gain clearance? Just to tinker. Way back I was told that the lowers had to be mounted belowthe centerline of the housing, so I came up with that, and hadn't seen anyone else try it so I thought it would either fail miserably or be a new fad.</STRONG>

not true about the lowers needing to be below the centerline, look at the pics of lances cruiser. that thing is sick, and hes got all the links on top, only problem i could see is more leverage/stress on the weld holding the bracket to the housing, but apparently it can work with good welds

Originally posted by ToyFamily:
<STRONG>that's what I got???
<IMG width=439 height=369 SRC="http://www.pirate4x4.com/ubb/uploads/sketch.jpg">

now is there any way to describe CG?

[ 10-18-2001: Message edited by: ToyFamily ]</STRONG>

Peliminary drawing looks ok. However, the lowers don't need to be that triangulated I say this because you might have interfearance issues with the frame on that yota. Suggestions: Mount lowers on top of housing and put the uppers up higher (taller truss or however you plan to make it.

Is there any way we can archive this thread so that people can refer to it in the future? I'd think that it would be a great resource for anyone looking to build their own link suspension. After looking at those pictures and reading what was said I think I'm going to change my design to incorporate some of those ideas. One question though, if the lowers dont need to be triangulated as much, what would be the ideal amount of triangulation (<--- is that even a word? <IMG SRC="smilies/biggrin.gif" border="0"> )

Originally posted by ToyFamily:
<STRONG>Does anyone see anything wrong with this concept, I have been kicking it around for about a year.

<IMG width=489 height=526 SRC="http://www.pirate4x4.com/ubb/uploads/linksktch.jpg"></STRONG>

That design is goign to tilt your pinion WAY down as it droops.

J. J.

Originally posted by Pig Pen:
<STRONG>ok yea it must have been you dad, nice guy by the way. Anyways, triangulate the uppers toward the center of the diff. Try and triagulate the lowers towards the t-case. Now imagine a top view of this set up. Make two points , one where the uppers converge and one where the lowers converge. Now if the lowers had hardly trigulated at all don't make that second point. Now in the side view mark the point where the uppers converge at and the lowers. connect the dots(lalala). The angle of that plance in the side view is the roll axis of the suspension. If the Lowers are barly triaglulated the draw the roll axis parallel to the lower links in the side view from the point where the uppers converge.

This is hard to say in words but thats my best shot , a picture is worth a thousand words in this situtation.

Dave</STRONG>

The following is all referenced from a side view of the links....

When looking at that drawing from the side, what correlation is there between the converging angles of the upper and lower links? In other words, say the mounting points on the axel for the upper and lower links are 10 vertical inches apart from each other, should the mounting points be the same distance apart where they're connected to the frame? It seems to me that they should be converging, but how/what does that change by moving them (upper and lower links) from being parallel to each other to a converging angle at the frame by the x-fer case and how do you determine what angle would be ideal? Does that make sense?

Are there any problems with fabbing up a front suspension setup like the rear of deserttoy's rig?

http://www.pirate4x4.com/ubb/uploads/Pa9270016.jpg

I want to do this type of setup front and rear so my suspension is balanced but I don't know if all the stresses related to steering and braking on the front axle will cause problems. Can anyone tell me if this type of setup is a good choice for a front application?

It will work fine just use good stuff and make sure you have clearance around the driveshaft when articulating and the tires at full turn. My center links miss my crankshaft pulley by about 1/2" at full compression, and they miss my starter by about the same at max articulation
(R wh. up/ L wh. dn) : )

Originally posted by dirtrod:
<STRONG>It will work fine just use good stuff and make sure you have clearance around the driveshaft when articulating and the tires at full turn</STRONG>

What tubing size are you using? I want to go with 2" .500 wall DOM with 1" or 1.25" heims. I think this will be plenty strong in a straight link configuration (i.e. no bends). I will be running a 1 ton D44 front and a 1.25 ton D60 rear out of a military truck with 39.5" boggers so that is alot of weight to consider. I'd much rather overbuild the hell out of it than have something bend or break on the road or on the trail but I cant really go up too far in tubing size because I have a limited amount of space to work with under there. Oh yeah its for a '95 YJ if that helps at all

Great Discussion!!!!

Here are my thoughts for what they are worth.

To set up the rear suspension to drive up hill or to hook up properly when you throttle it you dont want any anti squat. If you have anti squat the rear will try to walk underneath the rig when you hit the gas. Two things give you anti squat. Firstly having the links at too much of an angle going down from the chassis to the diff as what happens when you lift a standard truck up to much. What happens here is when the rear pushes forward it will push up at an angle on the rig and lift it and the rear will start to walk underneath and make the angle worse and so on. Long links fix this and horizontal links also fix it. This is why you should mount all the links on top of the axle to keep the links as horizontal as possible while still giving you the lift you need. Generally the higher you lift the frame off the axle the harder it is to get rid of the anti squat. The second cause is when looking from the side of the frame if the upper and lower links are not parallel and converge to a point (or converge at all). What this does (if they converge to a point) is lift the rear of the rig from the torque reaction of the diff. When you gas it the rear diff trys to rotate backwards and if the links go to a point it will lift the rig at that point and unload the rear and start to walk etc.. If the links are parallel then the rotation of the rear is controlled by the diff pushing and pulling on the frame through the parallel links and does not produce any lift (or anti squat effect)

So I believe the best setup is to have the links parallel and as horizontal as possible (when looking from the side). This means if the rig is lifted they should all go on top of the diff (just like Lances cruiser, from what I here it climbs umbelievable) and be parallel.

These are just my thoughts and I have never built a four link but I am going to real soon!!

<IMG SRC="smilies/biggrin.gif" border="0">

I have got some ideas on the roll centre bit as well but have got to go so if what I have said here is total BS then flame me and Ill shut up other wise Ill post the rest of it soon.

Originally posted by BabyWrangle:
<STRONG>What tubing size are you using? I want to go with 2" .500 wall DOM with 1" or 1.25" heims. I think this will be plenty strong in a straight link configuration (i.e. no bends). I will be running a 1 ton D44 front and a 1.25 ton D60 rear out of a military truck with 39.5" boggers so that is alot of weight to consider. I'd much rather overbuild the hell out of it than have something bend or break on the road or on the trail but I cant really go up too far in tubing size because I have a limited amount of space to work with under there. Oh yeah its for a '95 YJ if that helps at all</STRONG>

For the uppers I'm useing 4130 1" x .120
with a 1 3/8 x .095 sleeve over it with rosette welds every 6" oc, the lowers are the same with a piece of 2" sch40 pipe sleeve over that to keep the outer tube from getting kinked on rocks. I'm useing 5/8 x 3/4 40,000lb rod ends and I've beat it harder than I've ever seen anyone beat one of these things, without breakage... so far.

I'm no fuggn engineer, so this is all jmho...
2" x 1/4 or 5/16 would be enough for the lower links, 1 1/2 x 1/4 would be plenty for the uppers. Those 1" rod ends would be nice, but, I bet they cost $60-70 ea. . Make the brackets strong 1/4" or thicker and keep the machine as low and light as possible.
Those 39.5 boggers will eat that D44 every time they get a hold of something, maybe you could try a 8" wheel and 15lbs of air. I was busting a ft44 with 38 x 11.5 boggers on a 7" wheel, on a regular basis, in a 4000 lb cj... 44s are wimpy with big tires.

well cody i belive you have got your moneys worth. there is plenty of info to get you started. but i would still wheel it first and see if you have any problems. by the way guys great thread. mike

You guys remeber the God Of Suspension thread a few months back???? The tread was soooooo prime...pure comedy and lots of good info.

Originally posted by dirtrod:
[QBThose 39.5 boggers will eat that D44 every time they get a hold of something[/QB]

Still not 100% sure about what axle I'm going with. I might just have to pony up the extra bucks for a D60 front so I never have to worry about anything happening to the front. Also, the reason I'm going to go with such a big heim joint is because it will be a helluva lot stronger than what I need, which is good for peace of mind. I'd much rather spend the money up front for something I KNOW will never break because this rig is my daily driver and will be for the next few years until I get out of college(4 and a half more years...damn masters degree). Plus I don't want to have to worry about something coming apart at highway speeds. Better safe than sorry.

On another note, you said you were using tubing that you sleeved with another piece of tubing. What is your reasoning for doing this? Does it make it stronger than a tube of the same size overall? Like if the two sleeved pieces end up being the same I.D. and O.D. as a single piece of tube, which one is stronger?

i got a line on some auroras (1 1/4), want some???

A d60 won't hold up to massive stupid abuse with those 39.5s either, but it will take alot more than a 44.
Like I said I'm not a engineer, but I did the sleeve thing to keep the bar intact if I creased it on a rock. I started with just 1x.120 upper bars with out the sleeve, but I bent one beating the jeep against a rock, so I sleeved the uppers, then I dented one of the sleeved lowers, so I put a big ugly piece of plumbing pipe over the lowers. No problems yet. : )

Originally posted by Pig Pen:
<STRONG>i got a line on some auroras (1 1/4), want some???</STRONG>

This profect wont get started until mid december so I will let you know then. Thanks for the offer <IMG SRC="smilies/biggrin.gif" border="0">

Originally posted by dirtrod:
<STRONG>A d60 won't hold up to massive stupid abuse with those 39.5s either, but it will take alot more than a 44.</STRONG>

Well I'm not one to give my rig massive amounts of stupid abuse but it will see its fair share of use.... It's my daily driver so I can't have huge things breaking on me all the time <IMG SRC="smilies/tongue.gif" border="0">

Ok, got it...just remember one thing about a Triangulated 3 or 4 link front (as opposed to a panhard), if a hiem joint or bracket, or a control arm/bar/link/rod or whatever you want to call them lets go, the whole machine is gonna fall off to one side and you won't have any control at all, so if it's a daily driver, be careful and don't skimp on shit.

Originally posted by dirtrod:
<STRONG>Ok, got it...just remember one thing about a Triangulated 3 or 4 link front (as opposed to a panhard), if a hiem joint or bracket, or a control arm/bar/link/rod or whatever you want to call them lets go, the whole machine is gonna fall off to one side and you won't have any control at all, so if it's a daily driver, be careful and don't skimp on shit.</STRONG>

One though I had about that was to keep my JKS adjustable trackbar that I'm running now. It's got heims at both ends and is fully adjustable for length. I could just keep that on there with the 4 link and undo it for wheeling. That way I get the best of both worlds...good handling and safety on the street and good flex from the front offroad. The only thing is it might not be long enough with all that lift....guess I will have to see about that when I get everything fabbed up and if its not long enough I can build a bracket to raise it up off the axle. Sound like a good idea?

I don't know if you want to follow this Pig Pen guy's advice. He almost rolled his junk on its maiden voyage through campus tonight. I thought I was going to die! <IMG SRC="smilies/eek.gif" border="0">

About link convergence from the side. I see your point about the axle creating a torque around the convergence point. But, that point would need to be so close to the housing to really matter. If you run a regular driveshaft then parrallel links are ok, but for a cv rear shaft they need to converge somewhere so as to keep the pinion pointed at the t-case throughout its range of motion. Besides under acceleration, uphill or otherwise, I would think you would have so much weight transfer that it would easily cancel out any lifting forces. I aggree that longer links are better though.

By the way, my lower links are 1 5/8ths .25 wall dom with 1 1/4 heims at the end. From the info I have that my old roommate left me, at there 40" long length they will hold roughly 7 times the weight of my jeep. Of course its only a cj5 and I am no engineer.

Anyhow see ya,
Kev

hahaha.......that was fukin awsome!!! Just hooked up the brakes and took it for a spin (no Shocks yet). Took a corner with a bump on it at abour 25 and just got on it hard. The front drivers side tire pulled 3 feet in the air. I almost pissed my self.

Originally posted by Pig Pen:
<STRONG>hahaha.......that was fukin awsome!!! Just hooked up the brakes and took it for a spin (no Shocks yet). Took a corner with a bump on it at abour 25 and just got on it hard. The front drivers side tire pulled 3 feet in the air. I almost pissed my self.</STRONG>

damn, do it again and get pics! <IMG SRC="smilies/eyemouth.gif" border="0">

Originally posted by rokcrawla:
<STRONG>damn, do it again and get pics! <IMG SRC="smilies/eyemouth.gif" border="0"></STRONG>

Thats the first thing I thought of after checkin my drawers...After I get use to this and feel the limits i might try and get a pic. However, when the shocks go on I dont think it will be nearly as bad.

Originally posted by Ghetto Fab.:
<STRONG>
If you run a regular driveshaft then parrallel links are ok, but for a cv rear shaft they need to converge somewhere so as to keep the pinion pointed at the t-case throughout its range of motion.

Kev</STRONG>

Why wouldn't you want the pinion to be pointed at the x-fer case throughout its range of motion with a normal driveshaft too? So by running parallel links it doesn't keep the same pinion angle but converging links do? So how do you determine the ideal convergence angle of the upper and lower links (when looking at them from the side)

Originally posted by Pig Pen:
<STRONG>Not neccessarlily(spell check anyone??) You should keep in mind that driving on the road you suspension doesn't really move that much, so in my opinion that is something to take into consideration. Off road, say your suspension flexs out while you are crawlin, how fast are you driving????? Fast enough to feel a driveline vibe if you pinion angle chages slightly, highly unlikely.</STRONG>


see above

Originally posted by BabyWrangle:
<STRONG>One though I had about that was to keep my JKS adjustable trackbar that I'm running now. It's got heims at both ends and is fully adjustable for length. I could just keep that on there with the 4 link and undo it for wheeling. That way I get the best of both worlds...good handling and safety on the street and good flex from the front offroad. The only thing is it might not be long enough with all that lift....guess I will have to see about that when I get everything fabbed up and if its not long enough I can build a bracket to raise it up off the axle. Sound like a good idea?</STRONG>

You really can't run a panhard/trackbar with triangulated links... the links won't let the chassis move from side to side at all, and the panhard won't let the chassis move up and down without going side to side. :0

Originally posted by dirtrod:
<STRONG> You really can't run a panhard/trackbar with triangulated links... the links won't let the chassis move from side to side at all, and the panhard won't let the chassis move up and down without going side to side. :0</STRONG>

Yeah I got to thinking about that today during one of my boring classes and I figured that out. Oh well <IMG SRC="smilies/tongue.gif" border="0">

Hey guys this is an example of the benefits of the bent link and how I was talking about making it like a fin for strength.
<IMG width=494 height=348 SRC="http://www.pirate4x4.com/ubb/uploads/linkpic.jpg">

Got the anti squat thing down, but I still want to know how to make the thing lean (or shift) up hill when it is twisted so you keep the cg withen the triangle.

Originally posted by 2highToy:
<STRONG>Why wouldn't you want the pinion to be pointed at the x-fer case throughout its range of motion with a normal driveshaft too? So by running parallel links it doesn't keep the same pinion angle but converging links do? So how do you determine the ideal convergence angle of the upper and lower links (when looking at them from the side)</STRONG>

Anyone ??? <IMG SRC="smilies/confused.gif" border="0">

<IMG SRC="smilies/beer.gif" border="0"> <IMG SRC="smilies/beer.gif" border="0"> <IMG SRC="smilies/beer.gif" border="0">

Originally posted by 2highToy:
<STRONG>Anyone ??? <IMG SRC="smilies/confused.gif" border="0">

<IMG SRC="smilies/beer.gif" border="0"> <IMG SRC="smilies/beer.gif" border="0"> <IMG SRC="smilies/beer.gif" border="0"></STRONG>

i all ready answered this, sort of. Read above dude.

Originally posted by ToyFamily:
<STRONG>Hey guys this is an example of the benefits of the bent link and how I was talking about making it like a fin for strength.
<IMG width=494 height=348 SRC="http://www.pirate4x4.com/ubb/uploads/linkpic.jpg"></STRONG>

Benefits???? Ok dude, mount the link on top of the axle housing and get a flatter roll axis and less anti squat and the same amount of clearance. A straight tube is always stronger than a bent one. GET IT

Originally posted by 2highToy:
<STRONG>Why wouldn't you want the pinion to be pointed at the x-fer case throughout its range of motion with a normal driveshaft too? So by running parallel links it doesn't keep the same pinion angle but converging links do? So how do you determine the ideal convergence angle of the upper and lower links (when looking at them from the side)</STRONG>

You can use a compass, a tape measure and a piece of paper to figure it out. ; )
I like the pinion to rotate so I don't get alot of angle in the U-joint at full travel. That little difference in strength and clearance can be the difference between a machine that can hammer thru some nasty spots and a machine that spits out parts while hammering.

[ 10-19-2001: Message edited by: dirtrod ]

Originally posted by 2highToy:
<STRONG>Anyone ??? <IMG SRC="smilies/confused.gif" border="0">

<IMG SRC="smilies/beer.gif" border="0"> <IMG SRC="smilies/beer.gif" border="0"> <IMG SRC="smilies/beer.gif" border="0"></STRONG>

With a regular drive shaft the pinion angle hs to be the same (or close to) the flange on the t-case. The reason you can point the cv is cause your suppost to have it pointed straight at the t-case (or within a few degrees)

Originally posted by dirtrod:
<STRONG> I like the pinion to rotate so I don't get alot of angle in the U-joint at full travel. </STRONG>

If your axle housing rotates that much through it's range of travel then under articulation it is going to be trying to twist. It seems like your links could be fighting each other enough to limit articulation.

I like the pinion to rotate so I don't get alot of angle in the U-joint at full travel. That little difference in strength and clearance can be the difference between a machine that can hammerle thru some nasty spots and a machine that spits out parts while hammering.
EXCELLENT post, Dirtrod. Seems like a lot of folks sweat the angle/oiling issues, and the pinion/driveline angle, but don't consider the relative strength of the u-joint at various degrees of bend. Yeah, I know, keeping all of these things in mind at onece is tough, but the best designers do.

Randii

Originally posted by ToyFamily:
<STRONG>Does anyone see anything wrong with this concept, I have been kicking it around for about a year.

<IMG width=489 height=526 SRC="http://www.pirate4x4.com/ubb/uploads/linksktch.jpg"></STRONG>


Toyfamily, you theif! You plagerizing-rip-off artist! You know you stole that idea
(picture) right outta my brain! arg..

Actually, my idea is sooooooo rip-off close
to your pic, (and I got my idea from the
currie long-arm front link; but they do theirs below the axle-yuck)

I've had the (yours) same exact idea in my
head for about 2 years now... I even bought
some 1.75 x .375wall dom tube for the links.
I'm using 1.250 aircraft-heims for it. I too
had thought the mounts should-be below axle
centerline, but after seeing lots of others
done in all fashions, I think staying above
will be fine. and the 90' bend thing, it
doesn't have to be 90', mine will probably be
around 45'. it's funny to see someone
else's sketches, and they look exactly like
your own..... And just for reference.
Sam's "slinky" from Sierrarockcrawlers.com
rig is built just like deserttoys rig (as for
the rear links)... pretty much zero rear steer. now the spring-issue could use a look
at maybe..

--Sherpa

OK guys - heres just a few numbers to thow at the effects of converging arms (when looking from the side) giving unwanted anti squat.

Lets say you throttle it a bit to punch up a hill with a modest 100ftlb in a modest 50 to 1 overall reduction this get a torque in the rear axle of 100x50 = 5000ftlb which has to be constrained by the rear links.

Now say your links converge and are 4ft long, to resist the torque the arms will lift at the chassis at the convergent point. This lift will be 5000 divide by 4 = 1250lb which will be lifting up 4 ft in front of the rear springs on the chassis and unloading the rear springs by the same 1250lb. This means that instead of the rear axle supporting all its weight above the axle 1250lb of it is supported 4ft in front of it which takes weight off the front axle and loads more on the back.

say there was 2500lb on the rear suspension and 1500lb on the front before you throttled it with the rear lifting up 1250lb at the 4ft mark this will (now say the wheelbase is 8ft long) unload the front suspension by 625lb and throw this extra weight on the rear so now you have 875lb on the front and 3125lb on the rear. Now this is BAD you want the weight on the front axle to drive up hill not the rear and the anti squat is doing the exact opposite.

This calc was done at modest torque and gearing and will get much much worse with more right boot.

The other thing this does is the 1250lb not going through the rear springs will unload the rear springs (say each spring is 300lb/in times 2 is 600lb/in) now 1250divide by 600 = 2 inches (this is ignoring the weight transfer effect from above cause my brane hurts) thus lifting the rear by 2 inches which increases your effective rear lift thus the rear angle of the arms giving you more anti squat by the arms pushing up on more of an angle which will lift the rear more and transfering more weight to the rear tyres etc etc . Which is again BAD.

The above calc is very rough but im sure that the numbers are about right.

Believe me if you want to get it awn and throttle it up hills you have got to get the power to the ground and anti squat is the killer. Get some videos of blokes with mega lift and buckets of anti squat throttle it and watch that back axle walk and the rig go no where.

Sam

More numbers!!

The effect of the angle of the links (when looking from the side) isnt as great as the effect of converging arms on anti squat.

Say the same 100ftlb at 50:1 gives 5000ftlb at the axle. If we have 36in tyres this gives a tyre radius of 1.5ft. So that the forward push on the links from the tyres will be 5000 / 1.5 = 3333lb.

If the same 4ft links are at an angle coming down from the chassis to the axle with a 1ft drop then the lift on the chassis will be about in the ratio of 4 to 1 so that with every 4lb pushing you will get 1lb lifting at the chassis mount point.

So with 3333lb pushing you will get 833lb lifting at the chassis. And if you mounted all the links on top of the axle to get the arms as horizontal as possible I doubt that you will have 1ft drop from the chassis mount point to the axle mount point. So that the 4 : 1 ratio should be much less. So that the 833lb should also be much less in reality.

This compares with the 1250lb lift caused by the convergent arms which if you do have converging arms to get the pinion always facing the transfer you will always get and there is no other way around it.

Sam

Originally posted by Strange Rover:
<STRONG>More numbers!!

The effect of the angle of the links (when looking from the side) isnt as great as the effect of converging arms on anti squat.

Say the same 100ftlb at 50:1 gives 5000ftlb at the axle. If we have 36in tyres this gives a tyre radius of 1.5ft. So that the forward push on the links from the tyres will be 5000 / 1.5 = 3333lb.

If the same 4ft links are at an angle coming down from the chassis to the axle with a 1ft drop then the lift on the chassis will be about in the ratio of 4 to 1 so that with every 4lb pushing you will get 1lb lifting at the chassis mount point.

So with 3333lb pushing you will get 833lb lifting at the chassis. And if you mounted all the links on top of the axle to get the arms as horizontal as possible I doubt that you will have 1ft drop from the chassis mount point to the axle mount point. So that the 4 : 1 ratio should be much less. So that the 833lb should also be much less in reality.

This compares with the 1250lb lift caused by the convergent arms which if you do have converging arms to get the pinion always facing the transfer you will always get and there is no other way around it.

Sam</STRONG>

THANK YOU SAM!!! I am building a rear 4 link/60 setup right now and this type of good technical post is waht I need! I do want a little bit of clarification. What you are saying is that for the purposes of four wheeling the upper and lower links should be roughly parallel, and that anti-squat is bad for four wheeling, right? My upper and lower links will be sloped down from the frame to the axle, but I can make them parallel if that would be best. If you need info on my rig to help I am running the stock 4.0 engine, the AX-15 tranny, and the stock np231 (for now), the rear (and front) will both be 60s, the rear control arms will all be roughly 45 inches long. My crawl ratio is a pathetic 60 to one. Thanks.

I threw a few numbers around just to demonstrate what anti squat actually does. When you gas it and have anti squat in the rear the effect is the same as if you moved the rear axle forward on the rig and had a big honkin rear overhang. Anti squat takes weight off the front and loads it on the rear because part of the weight the rear springs support is actually supported where the links attach to the chassis ie forward of the rear axle.

It dosent really mater what the numbers and ration and lengths you end up with but you should understand what anti squat is, what causes it, and how to minimise it because it is the difference between building a four link that can flex and one that can flex and hook up and get the power to the ground when you gas it.

To minimise the anti squat the upper and lower links should be parallel. The biggest cause of antisquat is using links that converge to one point on the chassis (when looking from the side)

The other cause is the links coming down from the chassis to the axle on an angle although this dosent cause as bad an effect as converging links. If the links came down at an angle of 45 deg this would be really bad but if they dropped by say 6 to 10 inches over a 45 inch long arm then this would be good.

If the arms were totally horizontal and parallel then you would have no anti squat and the rig would squat on the rear springs when you gassed it (cause there is no lift from the links to help). This may not be such a good thing either cause as the rig squats on the rear springs you will again get a weight shift to the rear so some anti squat could be a good thing.

Generally to build the links and fit everything into your rig you will have the arms coming down at a bit of an angle from the chassis to the axle and you probable will have them converging a little bit as well so I feel that just fitting everything in gets enough anti squat and you should just try to minimise it.

Sam

Originally posted by Strange Rover:
<STRONG>I threw a few numbers around just to demonstrate what anti squat actually does. When you gas it and have anti squat in the rear the effect is the same as if you moved the rear axle forward on the rig and had a big honkin rear overhang. Anti squat takes weight off the front and loads it on the rear because part of the weight the rear springs support is actually supported where the links attach to the chassis ie forward of the rear axle.

It dosent really mater what the numbers and ration and lengths you end up with but you should understand what anti squat is, what causes it, and how to minimise it because it is the difference between building a four link that can flex and one that can flex and hook up and get the power to the ground when you gas it.

To minimise the anti squat the upper and lower links should be parallel. The biggest cause of antisquat is using links that converge to one point on the chassis (when looking from the side)

The other cause is the links coming down from the chassis to the axle on an angle although this dosent cause as bad an effect as converging links. If the links came down at an angle of 45 deg this would be really bad but if they dropped by say 6 to 10 inches over a 45 inch long arm then this would be good.

If the arms were totally horizontal and parallel then you would have no anti squat and the rig would squat on the rear springs when you gassed it (cause there is no lift from the links to help). This may not be such a good thing either cause as the rig squats on the rear springs you will again get a weight shift to the rear so some anti squat could be a good thing.

Generally to build the links and fit everything into your rig you will have the arms coming down at a bit of an angle from the chassis to the axle and you probable will have them converging a little bit as well so I feel that just fitting everything in gets enough anti squat and you should just try to minimise it.

Sam</STRONG>

Thank you. Finally, a great old style hard-core POR tech post...

yea ggod post Sam , I think people have asked the question of set up many times but the response is always "depends on the variables" never the basic "what you need to do" then add into account your variables.

I worked on setting up my housing last night and if I keep the fire burning like I have I will have my link set up done by the end of the week. I don't think I will be running the links to the back of the housing like I wanted because of intereference. I want to have the links out wide and the coilovers as wide as poss for a stable rig I have the 16" travel shocks so I got "'s to spare. I will post pics.

[ 10-23-2001: Message edited by: ToyFamily ]

This is all very interesting discussion, and I am learning. But are there any good references out there for a home fabricator like myself to better understand the concepts?

Thanks,
Phil

Originally posted by 1TONTJ
This is all very interesting discussion, and I am learning. But are there any good references out there for a home fabricator like myself to better understand the concepts?

Thanks,
Phil

READ THE SUSPENSION GOD THREAD, AND BUY THE MILKIN BOOK CALLED GROUND VEHICLE DYNAMICS.

Sams calculations are good from what I can tell, but they consider a rig who is unbalanced to the rear. If you are unbalanced towards the front like most rigs the effects will be oposite of what he says, this is do to the anti squat will be acting behind the center of the vehicles mass intead of infront of it. All this means is that his assumptions like all of ours dont take into all the variables and consiquances of this very complex system. with your calculations you woulld have the entire rig being lifted from the antisquat whcih I Havent seen from a 4x4 setup before.