I thought I'd start a discussion on body roll. Sitting on coil-overs makes me feel as though I'm sitting on top of a slinky. I really like the articulation and the ride. I really dislike sidehills even moreso than before and I hated them then. The problem is the body roll. Yeah ok I'm a whiner and eventually I'll get used to it. But there has to be some creative or not so creative ways to help eliminate it.

Some things that have been tossed around are products like Curries Anti-Rock Bar or similar anti-sway bars. They do reduce the overall articulation and is a easy/cheap fix.

What about forced articulation?

What about limiting straps on winches that can be tightened on the high side to bring the roll back down?

I'm not looking for control around corners as I don't drive as fast anymore. ;) I don't want some mega buck never been done before solution either.

Anyone have any thoughts?

sounds like a sway bar with quick disconnects is your best option. since you don't want to mess with your spring rate or shocks.

What about dialing in some more pre-load, or additional damping? A stiffer shock, should allow for similar low speed crawling yet, will reduce the speed at which the inside rebounds and the outside compresses. I don't remember on your coilovers, but I suppose that can only be done by sending them back to the mfg? I have heard good things about increasing the damping on Sway-a-way Coilovers.

Are you looking for a full-time solution or something just to use when you are sidehilling. I think it would be interesting to have s selective balncer (like you said- forced articulation) to cpress the up-hill side while side hilling but not have any effect unless engaged.

What about a front drivers/rear pass sway bar set up? would help on side hills but would allow artulication.

Never seen it, just a thought (always thought using hydrolics to do this would be cool!)

I'm used to the body roll in my XJ now.

I like the way it levels out on them banked freeway onand off ramps :D

On the trail I don't notice it at all.

supplemental airbags with individual controls?

I know I know,,, leave to a rover guy.....

j

Hey Mike - I may have a sway bar for ya. Come on over and we'll see what we can dig up.

Originally posted by rokryder
Hey Mike - I may have a sway bar for ya. Come on over and we'll see what we can dig up.

Fawk the sway bar. Find you some fat ass friends (Hey I know where you can find some even!) and set em loss in the back with some beer. Then you can just yell out, "EVERYONE ON THE DRIVERS SIDE NOW" :D:D:D Yeah kick ass. I'll even gain some weigh to be included in that one!! :D:D:D :flipoff2: :laughing:

You going tonight Mike??

Very common problem with coilovers. Most people run really stiff spring rates to combat it, but this isn't the best way. IMHO, the best solution is to run a somewhat soft swaybar, it shouldn't limit articulation that much but it will increase overall vehicle performance tenfold.

I'd imagine when you run it up the ram the rear suspension flexes more than the front and I'd say put a softbar like 3/4, 7/8" or 1" in the rear and I bet your problems will go away.

CJ

hey michael, why don't you use a ratchet strap where one would normally put a limiting strap. just two up front and thats all. you can crank it down as tight as you want for 10 feet, then just unlock it and let it go. thats all you want this for anyways, ten feet of trail. why spend big bucks to kill the flex you built into the beast. i think one big problem though is those front links and that torque flex. if you could cancel that out with different upper control arms maybe, that would help alot.

maybe lower the thing about 6 inches while your at it.:flipoff2:

Originally posted by GloNDark
Fawk the sway bar. Find you some fat ass friends (Hey I know where you can find some even!) and set em loss in the back with some beer. Then you can just yell out, "EVERYONE ON THE DRIVERS SIDE NOW" :D:D:D :laughing:


:laughing: Kinda like this blast from the past... :D

I hung up this photo at work, it got nicknamed:
"The Buba Sling" :D :D

your body roll is a function of your suspension geometry. You need to get your roll center higher. Stiffer springs will help but you will loose articulation.

That pic is scary with that guy slinged in like that... :eek: :eek: :eek:

What the hell were you guys thinking???? I am for sure going to put that in the redneck death wish filed on the pc.

[Edit]: whats even more scary is that those pics are being taken at a comp it looks like. What the fawk were the organisers thinking. We dont have many comps out east, is that a regular think to do. :laughing:

Yeah the closer your roll center is to your center of gravity the less body roll you will get.

Originally posted by 2manyJPs
Yeah the closer your roll center is to your center of gravity the less body roll you will get. Ok, I'm having a hard time visualizing this. How does raising the vehicle help the body roll?

At 15*(suspension) the body rolls over to near max. The truck isn't rolling over because I haven't broken the COG over the wheels. At 20-25* (suspension) the body is at full tilt. The truck is still quite stable but, I won't know when the COG has been breached as I won't know when tires are coming off the ground since I'm already sitting on the door handles.

Maybe I'm just not understanding the terminology.

Lowering is an option and an avenue to pursue but unfortunatley would mean $$replacing$$ all the coilovers and going to 12-14" in front instead of 16" and 8-10" in back as opposed to 12". Anyone planning a coil over project that wants to trade?

I'll be at the meeting tonight.

I'll see what you've got B, maybe that will help a lot.

sidehills are something I have become uncomfortable on since I lifted my EB another 2" (5.5")and went to 36" sx's (from 33's). I assumed it was just me and I needed to get used to it. But last time out my buddy and I were parked on the same slope with identical spring combo's and mine leaned more than his just sitting there. I don't know how to combat that besides wider axles for more stability. It's not a width problem though it was just a quick fix until I figure it out. I can go into more detail if someone thinks they might be able to help, but I didn't want to barge you post. Thanks guys, Jake

Originally posted by Malltero
What the hell were you guys thinking???? I am for sure going to put that in the redneck death wish filed on the pc.


:eek: Be carefull what you say.... You might get struck down by the POR police.... :D

Someone want to help him out with who that is... ;)

This is my understanding of it. The roll axis is the axis that the body rolls around. It is determined by the roll center of the front and rear axles.

For example if you have a three link suspension when looking from a top view. The bottom two bars are parallel to the frame and the upper bar is a V-shape with the point of the V at the center of the axle. With this type of set up on the front and on the rear the roll centers on both would be at the point of the V.

The closer that you get the roll axis to the CG, the less of a moment the CG has to roll the body. On lifted vehicals it is sometimes hard to do but, it can be done by playing with suspension geometery.

Hey mike, how about some water balast tanks down by the frame rails. Super low on the CG, you could pump it from one side to the other VIA an RV water pump or something like that.

Cheap, easy enough, however never been tried. MUUUHAHA :evil:

Damn, look at me, beer drinking ideas, and no beer?? WHOO HOOO!!

Originally posted by GloNDark


Fawk the sway bar. Find you some fat ass friends (Hey I know where you can find some even!) and set em loss in the back with some beer. Then you can just yell out, "EVERYONE ON THE DRIVERS SIDE NOW" :D:D:D Yeah kick ass. I'll even gain some weigh to be included in that one!! :D:D:D :flipoff2: :laughing:

You going tonight Mike??

ROFL, hey GLO, this is a sound plan, with that beer esky, ill even put on some kilos and try anf join in!! :rasta:

redneck death wish?
yeah, GET IT!!
would take some balls

Oh well so be it... the guy still has a death wish IMHO. Now I really trust my driving, I know the limits my pos has, but I still wouldnt trust myself to have some on tethered in like that.

Maybe two straps you can grab, but like that he has no chance in getting off if it rolls. :rolleyes: :flipoff2:

here is your hairbrained never been seen (at least by me) solution
install a swaybar set-up that has electromagnetic disconects such as the ones used to hold open doors. I found some at this website (http://www.rofu.com/magnetdh.html) that are 12 volt but they only hold 50 pounds maybe you could find some stronger ones

i don't think this thread is working, as no one has a decent idea yet except for lowering it and making the coilovers stiffer. you can still use the same coilovers with higher top mounts for them. essentially dropping the amigo lower onto the suspension. i like that idea the most. take those coilovers right through the hood. its not like the thing isn't a trailer queen anyways now. and it will be alot cheaper than accidently rolling the thing.

through the hood...I like that idea for some reason :D :D :D

Originally posted by Belly Dragger
Ok, I'm having a hard time visualizing this. How does raising the vehicle help the body roll?

At 15*(suspension) the body rolls over to near max. The truck isn't rolling over because I haven't broken the COG over the wheels. At 20-25* (suspension) the body is at full tilt. The truck is still quite stable but, I won't know when the COG has been breached as I won't know when tires are coming off the ground since I'm already sitting on the door handles.

Maybe I'm just not understanding the terminology.

Lowering is an option and an avenue to pursue but unfortunatley would mean $$replacing$$ all the coilovers and going to 12-14" in front instead of 16" and 8-10" in back as opposed to 12". Anyone planning a coil over project that wants to trade?

I'll be at the meeting tonight.

I'll see what you've got B, maybe that will help a lot.

Do you have any pics?? I'm having a hard time imagining "At 15*(suspension) the body rolls over to near max"...

Originally posted by aaronlosey
i don't think this thread is working, as no one has a decent idea yet except for lowering it and making the coilovers stiffer. you can still use the same coilovers with higher top mounts for them. essentially dropping the amigo lower onto the suspension. i like that idea the most. take those coilovers right through the hood. its not like the thing isn't a trailer queen anyways now. and it will be alot cheaper than accidently rolling the thing.


Plus it would look cool with big old springs through the Hood:flipoff2:

Roll Centre is the answer.
now go learn what it means.
no swaybar, or stiffer springs, or off the wall imaginary band aid devices require.

what about cheapie air shocks from pep boys?? install one at each corner then plumb them to 2 switches right/left, air in the downhill side works great and when the air is out they are not even there, specially if you drain the fluid this is assuming you have OBA of some sort.

Originally posted by aaronlosey
i don't think this thread is working, as no one has a decent idea yet except for lowering it and making the coilovers stiffer. you can still use the same coilovers with higher top mounts for them. essentially dropping the amigo lower onto the suspension. i like that idea the most. take those coilovers right through the hood. its not like the thing isn't a trailer queen anyways now. and it will be alot cheaper than accidently rolling the thing.

What is wrong with CJ's suggestion of adding a soft rear swaybar?

Actually, a HIGHER roll center will produce less body roll theoretically. The reason being is that the further the roll center is from the center of gravity, the less leverage there is to make the body roll.

I can say from experience that on these 4 wheel drive vehicles we are working on, the roll center approach isn't going to yield the results your looking for. About the highest roll center you can get is from a 3-link with an upper wishbone, mounted high above the diff. The roll center is the point at which wishbone attaches and this point is generally higher than most conventional designs(trackbar, triangulated 4link, etc)

Here is another solution...make use of your adjusting nuts on the swayaway shock bodies. Place them anywhere from 1" to 3" above the rubber piece inbetween the two coils at ride height. This will mean on compression the upper spring will only be used for the first few inches of compression to give you that caddillac ride but on turns you will mainly beusing the lower spring which is usually a stiffer rate. As soon as that rubber piece hits those adjusting jam nuts only the lower spring is used. The upper spring will then be used to give a comfortable ride and as a tender spring to keep pressure on the lower spring during full extension of the shock so the coils dont fall out.

I hope that makes sense.

Although, to get it to handle like a properly setup vehicle should, your probably going to need to add a swaybar. It seems people aren't keen on this idea and I don't know why, they work incredible.

CJ

Originally posted by Malltero
That pic is scary with that guy slinged in like that... :eek: :eek: :eek:

What the hell were you guys thinking???? I am for sure going to put that in the redneck death wish filed on the pc.

[Edit]: whats even more scary is that those pics are being taken at a comp it looks like. What the fawk were the organisers thinking. We dont have many comps out east, is that a regular think to do. :laughing:

All he has to do is let go and jump off:rolleyes:
Is that Roggy's rig? I haven't seen the sheetmetal that straight before:eek: :D

I'm having the same dilemma since going to coil overs on the front of my Explorer. I know I need more rebound damping. We ordered the shims from Bilstein about a month ago, but one shim from the stack is on back order. I'm hoping the additional damping will keep the shock from pulling out so quickly and keep things more in line while crawling.

I did what one of the guys said and set my jam nuts up so I come on the main springs pretty quickly. that has helped a bit.

The coil overs have really changed the trucks handling characteristics, the body leans much easier over the suspension. In fact while pushing my truck to see how it did off camber I put it on it's side. On the other hand it takes high speed runs like a champ soaking up the bumps like crazy. The additional flex is also great. The truck stays level over much more difficult terrain. It's just that off camber stuff that is nasty.

We just got back from Moab and the pucker factor was incredible on a few of the runs. We did real well though and kept the rubber side down.

One thing I did to help another problem was add a center axle strap to keep the body from lifting too high over the axle while climbing. The strap still allows full articulation, but helps considerably with the lifting.



http://www.explorerforum.com/moab02_day2/P5012459.jpg

http://www.explorerforum.com/layover/P4042038.jpg

Originally posted by CJ Lagos


Although, to get it to handle like a properly setup vehicle should, your probably going to need to add a swaybar. It seems people aren't keen on this idea and I don't know why, they work incredible.

CJ

Because if you design your suspension properly, a swaybar will do nothing but hamper you. In other words, if you have a proper link bar configuration, and choose good spring rates, you will only lose from having a swaybar. If you want proof, just look at most of the rigs competing. Schaffer has won two RRCA events in a row (the only one ever to do that) with a CalROCS win in the middle of them, and you don't see his rig running swaybars.

Speaking of Schaffer, the rig was built in his shop, so why don't you ask him? You can ask all these internet "pros" till you're blue in the face, but you probably won't get too many helpful suggestions. Sitting here at my house I can't watch your rig to see what it does and how it acts. I can't see how the links are setup, I can't see what kind of angles the shocks are at, and can't feel how the spring rates seem work for your rig. I can't tell what kind of clearance issues you have with the possibility of lowering the rig either. Mike and Bob know what they are doing a hell of alot more than most the people on this board, so I would think their opinion would be a little more helpful.

Then again, maybe I'm just full of shit. Who knows....... :rolleyes: :rolleyes:

If you really want to know....
One word is all that needs to be said

Coilovers

Many of us quietly sit back and watch as over and over again people put these things on rock crawlers. You do realize they were build for race trucks. Designed to launch a truck way up in the air, allow the tires & axles to drop WAY DOWN to soak up the impact energy. These same trucks run stiff stabilizers to correct the natural instability of this spring system in the turns.

Consider an example rock crawler. Total weight of 4500 lbs. Axles ( 1 tons FR ) ~800 lbs, tires and wheels (say 38-39") weigh ~500 lbs for a total unsprung of 1300 lbs. That's about 30% of the total weight of the vehicle. That mass is also centered about 18" above ground level. The rest of the weight (motor/driveline/frame/body .. etc) will have a CG upwards of 36 to 40" above the ground (and nearly over the TOP of the tires). All tied together, the low heavy unsprung weight adds a HUGE amount of stability to the vehicle. However, if you let this weight drop away with nothing to restrain it, you do not recover any of this stability until you hit the ends of the coilovers or limit straps. At that point it may be too late!

Think of the unsprung weight as a boats keil. If you put the keel on a hinge, then put straps to limit how far it can pivot, imagine what it would be like to ride in this boat. Just flopping from one extreme to the other. I bet it's not far off how it feels to ride in some of these trucks! Now attach a spring to the boat and the keel. As the body of the boat rolls, it stretches the spring. The boat gradually stabilizes. If the spring is sized right, you will get a little extra roll, but nothing unstable or unsettling.

There is a way to make these things work, and work well for rock crawling. If the spring was captured, they could be very effective. Attach the spring to the coilover ends, so the spring has to stretch with the drop. You'll get rid of a lot of the extreme flop and it's tendency to hang tires under stuff. :)

Now that's my $.02 worth...

Originally posted by Malltero
That pic is scary with that guy slinged in like that... :eek: :eek: :eek:

What the hell were you guys thinking???? I am for sure going to put that in the redneck death wish filed on the pc.

[Edit]: whats even more scary is that those pics are being taken at a comp it looks like. What the fawk were the organisers thinking. We dont have many comps out east, is that a regular think to do. :laughing: Um ya, that would be Lance hanging off of Roggy's rig and I'm sure that maneuver was executed with total control too :p

Originally posted by KeithF
Um ya, that would be Lance hanging off of Roggy's rig and I'm sure that maneuver was executed with total control too :p

BINGO!

The file was dated 9/2000, So I'd guess it was taken early 2000. Early in the rock crawlin' competition days.... :)

Originally posted by NECKSTER



Then again, maybe I'm just full of shit. Who knows....... :rolleyes: :rolleyes:

Well we all knew that :flipoff2: :flipoff2: :flipoff2:

j/k man.. ive seen you guys work...and well it works:p

You guys going to compete in Cal rocs in september???

Well I've been playing with my coil-overs for a year now. I've come to the conclusion that:

1. A high roll axis is the way to go.
2. You want the track width of the shocks as far apart as possible.
3. I do not like the uncontrolled drop that coil-overs offer. The only way I see to fix this is to add a sway-bar.

#2 is a critical point you all forgot to mention, by moving the coil-overs as far apart as possible you will gain large amounts of stability which will allow you to keep the softer springs and actually use all of the 16" of travel.

Originally posted by okcrawler

There is a way to make these things work, and work well for rock crawling. If the spring was captured, they could be very effective. Attach the spring to the coilover ends, so the spring has to stretch with the drop. You'll get rid of a lot of the extreme flop and it's tendency to hang tires under stuff. :)



Thats an excellent idea..... anyone tried this??

This is a rather interesting problem since it is difficult to correct. Since body roll and articulation are essentially the same movement anything that reduces body roll will reduce articulation, unless it involves the suspension geometry. So if you increase the spring rate or add a sway bar you will reduce the amount of articulation. If you raise the roll center so that it is closer to the CG you will decrease the amount of body roll, but you will increase the load transfer between the tires and reduce the ability of the vehicle to not slide down the hill. The best way to eliminate most of these problems is to lower the CG which is a difficult task for most off road vehicles. Lowering the CG is also the only way to drastically increase the angle the you can take without rolling. So to answer the original question that you posted as to what to do, you could do lots of stuff, but my suggestions is to actually find out how far you and tip the thing before it rolls over and then learn to drive it knowing that limitation. I know that this isn't the most helpful advise, but maybe it will help

All I have to say is talk to the desert racing guys who use these shocks for a living and see what they say about the use of swaybars...they'll say it is pretty much required.

You can control weight transfer to a point with suspension design but you can't eliminate the problem we are talking about.

When you goto an all heim jointed suspension there is absolutely no roll resistance which is at the heart of why people get so much body roll. These shocks are the best there is to do what a shock does, they aren't designed to control body roll the way everyone wants them to.

I've noticed the competition guys are more and more putting swaybars on the rigs. All the Baja teams use them, we're just kinda slow catching on. Once people realize how big a benefit swaybars are, they'll be like second nature with a coilover install.

The biggest problem is most people who put coilovers on try to combat body roll with different things like stiff spring rates which is not a good way to do it. Swaybars are designed to control body roll, and they go A LONG way to improve vehicle performance without hindering articulation. It's one of those things, the people who hate them and say they don't work have never used them.

CJ

Originally posted by okcrawler
:laughing: Kinda like this blast from the past... :D


OMFG Is that what that thing looked like new?!?!?! WOW....It used to be purddy:D I dig that rig! It's like the Juck Yard Dawg (NOT REFERING TO THE FABWORK OR PARTS WHAT SO EVER!!!) It just looks and sound like One Mean Dawg!!! :D

Originally posted by Suprdlux
Since body roll and articulation are essentially the same movement anything that reduces body roll will reduce articulation, unless it involves the suspension geometry. So if you increase the spring rate or add a sway bar you will reduce the amount of articulation. If you raise the roll center so that it is closer to the CG you will decrease the amount of body roll, but you will increase the load transfer between the tires and reduce the ability of the vehicle to not slide down the hill. The best way to eliminate most of these problems is to lower the CG which is a difficult task for most off road vehicles.

body roll and articulation are NOT the same thing. articulation is cuase by a change in force on the tire. If your suspension is set up perfectly (roll center at cg) it will still flex. However when you go around a corner fast you will have no body roll. Body roll is a function of horizontal forces while flex is a function of verticle forces.

Adding stiffer springs does help counteract body roll however you are only putting a bandaide on the situation. You really need to get the roll center closer to your cg.


As far as coil overs not being good and having uncontolled droop. That is a good thing for a properly designed rock crawler and a bad thing for a shity design.

SOLUTION TO ALL OF YOUR PROBLEMS:

GET YOUR ROLL CENTER CLOSER TO YOUR CG. you can't expect some ghetto peice of shit to perform like an engineered champ. so get on with the engineering already.

Originally posted by okcrawler
If you really want to know....
One word is all that needs to be said

Coilovers

Many of us quietly sit back and watch as over and over again people put these things on rock crawlers. You do realize they were build for race trucks. Designed to launch a truck way up in the air, allow the tires & axles to drop WAY DOWN to soak up the impact energy. These same trucks run stiff stabilizers to correct the natural instability of this spring system in the turns.

Consider an example rock crawler. Total weight of 4500 lbs. Axles ( 1 tons FR ) ~800 lbs, tires and wheels (say 38-39") weigh ~500 lbs for a total unsprung of 1300 lbs. That's about 30% of the total weight of the vehicle. That mass is also centered about 18" above ground level. The rest of the weight (motor/driveline/frame/body .. etc) will have a CG upwards of 36 to 40" above the ground (and nearly over the TOP of the tires). All tied together, the low heavy unsprung weight adds a HUGE amount of stability to the vehicle. However, if you let this weight drop away with nothing to restrain it, you do not recover any of this stability until you hit the ends of the coilovers or limit straps. At that point it may be too late!

Think of the unsprung weight as a boats keil. If you put the keel on a hinge, then put straps to limit how far it can pivot, imagine what it would be like to ride in this boat. Just flopping from one extreme to the other. I bet it's not far off how it feels to ride in some of these trucks! Now attach a spring to the boat and the keel. As the body of the boat rolls, it stretches the spring. The boat gradually stabilizes. If the spring is sized right, you will get a little extra roll, but nothing unstable or unsettling.

There is a way to make these things work, and work well for rock crawling. If the spring was captured, they could be very effective. Attach the spring to the coilover ends, so the spring has to stretch with the drop. You'll get rid of a lot of the extreme flop and it's tendency to hang tires under stuff. :)

Now that's my $.02 worth...


...thus my idea I posted a while back about somebody producing some limited stretch limiting straps. However if someone wants a link to prod their ideas on captive coils, somebody posted a link of someone that makes an add-on kit for making standard coils into captive coils - wouldn't work on coilovers though they way they'd built it. I thought I'd save the link but can't find it now. I'm sure someone up here has it though.

body roll and articulation are NOT the same thing. articulation is cuase by a change in force on the tire. If your suspension is set up perfectly (roll center at cg) it will still flex. However when you go around a corner fast you will have no body roll. Body roll is a function of horizontal forces while flex is a function of verticle forces.

I didn't say that articulation and body roll are the same thing I said they were the same motion, which they are. Both involve a rotation of the axle with respect to the frame, so a sway bar or stiffer springs will control body roll by increasing the roll resistance of the suspension. At the same time these fixes decrease the articulation of the suspension.

If you raise the roll center so that it is closer to the CG you do decrease body roll and it does not effect the roll resistance of the suspension it does nothing to improve the angle that the vehicle can take before rollover since this is determined by CG height and track width.

Originally posted by Beartrack

...thus my idea I posted a while back about somebody producing some limited stretch limiting straps. .

This is a great idea, fall protection uses this concept. It consists of strap which stretches sewn to a strap which doesn't. When the person falls, the first strap stretches until it reaches the limit of the second strap which doesn't stretch. Kind of a fixed distance bungee cord. This stops the person from hitting the ground, but doesn't tear them intwo when the strap catches.

This would help keep the vehicle centered, but if rates were design properly, that heavy SX, wheel, and axle would still put enough force on to stretch the strap and get maximum droop.

Originally posted by ramv


This is a great idea, fall protection uses this concept. It consists of strap which stretches sewn to a strap which doesn't. When the person falls, the first strap stretches until it reaches the limit of the second strap which doesn't stretch. Kind of a fixed distance bungee cord. This stops the person from hitting the ground, but doesn't tear them intwo when the strap catches.

This would help keep the vehicle centered, but if rates were design properly, that heavy SX, wheel, and axle would still put enough force on to stretch the strap and get maximum droop.

Exactly the implementation I was thinking; that way you don't have to add additional mounting points for a second strap. I think the idea has both trail and marketing potential but I don' t have the time/$/expertise to follow up on it personally.

Originally posted by Suprdlux


If you raise the roll center so that it is closer to the CG you do decrease body roll and it does not effect the roll resistance of the suspension it does nothing to improve the angle that the vehicle can take before rollover since this is determined by CG height and track width.

ACTUALLY IT DOES. because now you have a force and a moment pulling the truck over where as before you merely had a force. Because now you have the same force plus the distance it acts at. Here is an example

Ex
weight =4000lb

roll center=cg

the force on the roll center = 4000lb

roll center not= to cg

force on the roll center = 4000lb + 4000*distance from roll center to cg

say that distance is .25ft you now have an additional 1000lb*ft pulling you over.

I have seen some go cart suspension(mini-baja) that used a trailing arm and a realy stiff bungee cord for the spring. It takes like 4-5 guys to get the thing to move an inch. SO, some degree of "bungee cord" could be used for your idea Beartrack...maybe. I plan on using the antirock in the rear of my linked suspension when i get around to it.
greg

If you want to mess with your existing setup before doing major mods, you may wat to try bumping up the rebound dampening a bunch. That should help slow the roll rotation some and reduce that pucker factor somewhat. You may also need to reduce some of the spring preload to reduce the amount of stored energy in the spring. If any of this makes a real positive difference, you may want to rethink your spring rates.

ACTUALLY IT DOES. because now you have a force and a moment pulling the truck over where as before you merely had a force. Because now you have the same force plus the distance it acts at. Here is an example

Your example makes no sense to me. Gravity is the force that pulls the vehicle over and it act through the CG not the roll center. The roll center is the coupling of the unspring mass to the spring mass and it is the axis through which the sprung mass rolls. Since the weight of the vehicle doesn't change when you move the roll center up or down the force of gravity doesn't change so there is no force magnification. As you move the roll center down from the CG you do create an internal moment, but internal moments have no effect on external forces acting on the vehicle. So in your example where the roll center is slightly below the CG and you calculate an increase of 10,000ft*lb that moment has no effect on the vehicle weight which is what is pulling the vehicle over.

Originally posted by Suprdlux


Your example makes no sense to me. Gravity is the force that pulls the vehicle over and it act through the CG not the roll center. The roll center is the coupling of the unspring mass to the spring mass and it is the axis through which the sprung mass rolls. Since the weight of the vehicle doesn't change when you move the roll center up or down the force of gravity doesn't change so there is no force magnification. As you move the roll center down from the CG you do create an internal moment, but internal moments have no effect on external forces acting on the vehicle. So in your example where the roll center is slightly below the CG and you calculate an increase of 10,000ft*lb that moment has no effect on the vehicle weight which is what is pulling the vehicle over.

Your right however that internal moment is causing the body to roll more and if I am thinking about it correctly (i believe i am) it causes an external moment too. If i could draw a picture that would help but let me try to explain it in words.

when the body rolls the cg moves around the roll axis. With no roll on a 45 degree side hill the moment pulling you over is the w*1/2 track width. with cg not at roll axis the equation is w*(1/2 track width + (distance from cg to roll axis)*sin 45). I could explain better with a picture.

more words:

the cg has now rolled around the roll axis so the force pulling it over now acts at a larger distance; ie larger moment. Right?

when the body rolls the cg moves around the roll axis. With no roll on a 45 degree side hill the moment pulling you over is the w*1/2 track width. with cg not at roll axis the equation is w*(1/2 track width + (distance from cg to roll axis)*sin 45). I could explain better with a picture.

I don't know where you are getting your numbers from. I drew it all out on paper and the over turning force on a slope is the weight of the vehicle times the sine of the angle of the slope. The overturning moment is the overturning force times the height of the CG. I ran through some calculations to see how much the overturning force would change as you dropped the roll center. My imaginary vehicle parameters are.

Weight 3000lbs
CG height 36"
Track 60"

If the roll center is at the CG then this vehicle will begin to roll over on a slope of 39.8 degrees.

If the roll center is 12" below the CG and the vehicle is running springs with a rate of 600 lbs/in located 8" inside of the wheel the body will roll about 6 degrees and the vehicle will roll on a slope of about 40.3 (Sorry I had a miss calc. in the original post) degrees

I can see the point in the roll center to c/g realtionship argument, except you seem to have forgotten what that would do to the pitch angle as far as the i/c of the rear driving axle causing very excessive anti squat. a good example is the scorpion. The first one suffered from wicked handling under acceleration due to the extremely high/rearward instant center. A second counteracting air bag had to be added to patch it.

TRD, you are absolutely correct. SuperDelux, i want some of the crack you are smokin cause it must be good. Getting the roll center closer to the COG is GOOD. This has already been explained several times, so i will instead use an analogy. Think about a Formula 1 car. The roll axis and COG are in the same plane, the COG may even be lower than the roll axis. A formula 1 car could easily sidehill 70 degrees, and if you move past that number, it would simply slide down the surface, it could never roll over. Even at an 89* incline, it would just slide down the slope, NOT roll over.

TRD i understand your argument, and i think you are correct. Maybe this analogy will help others see it too.

Think about a Formula 1 car. The roll axis and COG are in the same plane, the COG may even be lower than the roll axis. A formula 1 car could easily sidehill 70 degrees, and if you move past that number, it would simply slide down the surface, it could never roll over. Even at an 89* incline, it would just slide down the slope, NOT roll over.

Okay so I am thinking of the formula cars that I have helped design and build and I am sitting in line for the tilt test at the competition while the car in front of me is tilted to 56.7 degrees. Looking at the car the CG is probably 4 inches off the ground and the roll center is somewhere around 4 inches off the ground also. So they tilt the car and low and behold the sucker picks up the upper two tires. It would have fallen off the tilt table if there wasn't a safety rope attached. How did this happen, it happened because the track width was way to narrow. So I don't understand the analogy. I realize that alot of stuff has already "been explained" on this board, but alot of the stuff that I read on hear with respect to suspension design is incorrect. That is why I continually post here. I am trying to correct some of the misconceptions so that better rigs can be built. I realize that I am a newbie on this board, but I have taken a number of vehicle dynamics classes and I have built a number of racing vehicles so I am not smoking crack.

Thought Id throw an opion in here cause it sounds like a good discussion.

As an example- if you had a rig that has the cog at the same height as the roll centre, really soft springs and can handle a side angle of 45deg before the top tyres cone off the ground. It would do this at this point with no body roll cause the cog and roll centre are the same.

No lets say you lowered the roll centre. So what happens? As the rig is side hilled the body will lean over on the axles. Now what point does the body lean about? It leans about the roll centre (not the cog) so that as the body leans the cog will move to the down hill side of the roll centre. So now the cog is further to the downhill side on the tyre track width and will cause the vehicle to roll at a less of a side slope.

As an extreme example imagine if you had a very hing cog, say 20feet, and really soft springs. If the roll centre is also at 20feet the vehicle will ba stable on level ground ans sit there. If the roll centre was at 2 feet instead, a slight push on the body will cause the body to lean over and it will keep leaning (soft springs) untill the cog is outside of the track and the vehicle will fall over on level ground.

Sam

Thanks sam, that is the best analogy I have heard yet.

But again, how would one get the roll axis that close to the c/g
( Usually just above the crankshaft centerline on an average 4x4)
and maintain resonable anti squat/anti dive in the pitch axis?

EDIT: I hope I don't come across as trying to act like I know what am talking about. I am trying to design the link system for my own buggy and have been perplexed by what seems to be an impossible task. Getting a good I/C for rear axle torque and reasonablre roll center when your c/g is chest high. It was alot easier when the car was 3" off of the floor. :D

another great discussion on P4x4.
this is why i sift through the BS.

another great discussion on P4x4.
no shit. damn i have to love my leaf springs....thus my idea I posted a while back about somebody producing some limited stretch limiting straps. ough, its called a coil. why aren't these things attached at both ends? oh well, continue the struggle while we drink beer and laugh at everyone trying to make a comp rig work "the best" on the trail.:laughing: i love this stuff.

I'm glad I could start a subject that is stimulating. I'm also learning alot.

First off, I love my coilovers in every situation, except the sidehill. If I ran super soft, to the point of being useless leaf springs, I think the same situation would occur.

Ok here is some pic's I took in the side yard. It's the best sidehill I have at home. It's really mild but you can see that the body is already leaning more than the slope itself. The truck is still very stable as it sits. It is however leaning at 35* in the cab. If I fire it up and begin to move the torque will roll the body till the limit strap max's out. If I push it, as in climbing a small ledge, at that point it will actually pull on the limit strap and begin to lift the drivers front tire. I still don't think it would go over but it is very disconcerting.

Note: The truck weighs 4960 unloaded with the spare in the back. If I use a hilift and lift via the frame the jack has very little effort required to raise untill I begin to actually lift the suspension. I would estimate that the above frame weight is easily 1/3 of the entire vehicle weight.

http://www.mjw.com/amigo/images/bodylean-03x.jpg

http://www.mjw.com/amigo/images/bodylean-04x.jpg

I've looked into the option of lowering the vehicle and my examination indicates that I would have to take the lowering out of up-travel and I only have maybe 4 inches of that as it sits. I considered pushing the coils through the hood as well as up into the back. I only see this as a benefit to locate the bottom's out of the shocks higher up and forcing me to get bumpstops which would'nt really help lowering the vehicle, unless I wanted to sacrafice up-travel. I think I'll just have to get used to the body lean. ;)

Belly Dragger,

Looking at your pics, I think I would first start looking at the rear coilovers. I think that the angle they are mounted at is contributing to the concern. I would look at changing the upper mount so it is further out and not angled so much. By having such an extreme angle on them the effective rate of the spring is decreased. Now you may have gotten coils to compensate for that, but the way they are place there is a lot of weight on the outside of the upper mount pulling it down. Kinda like a lever arm working against the coilover, move the mount out and the weight will have less leverage on the coilover.

Hope this makes sense.

good idea. as for worthlessly soft srings, i just use longer springs with a higher rate.;)

I'm building a rig that is similar to Dragger's ride. I'm not as concerned about the body roll as I am about the coils(not coilovers) unloading on steep climbs. In addition to a centered limiting strap on the axles, I have been working on an electric ratcheting strap on all four corners. With a toggle switch(actually my former power mirror switch!) I should be able to crank down and release each corner. I really have no idea as to how this will make the rig react on climbs, but can't be any worse than leaping off of a cliff backwards :) .
Any thoughts on this?

Originally posted by twistedmetal
I have been working on an electric ratcheting strap on all four corners. With a toggle switch(actually my former power mirror switch!) I should be able to crank down and release each corner. I'd be very intersted in seeing what design you have going on this. Yes it will help you from popping over as coils tendancy is to unload. ;) I know a lot just use the winch to crank down the front for vertical climbs but something like what you are talking about would work for any corner. Hmm.

Originally posted by KeithF
Um ya, that would be Lance hanging off of Roggy's rig and I'm sure that maneuver was executed with total control too :p

Well then Lance has to have the biggest balls known to man. Look at the picture again, he cant just drop off... the sling goes around his back. There would be no jumping off in a roll quick enough ... and then no more Lance :( . Just cause he is the one in the picture doesnt make it some dangerous.

Still stand by my comment that being teathered in like that is some redneck shiet. :flipoff2: :flipoff2:

Cruiserrg is right. i think the angle of the rear coil-overs is the main prob. It appears that they are at about a 30-40 deg. angle at rest. That is a serious prob. You would need to be running 500/500 springs to get any sort of stability back there. Move the upper mounts out towards the tire about 3 inches on each side. I think that will help your situation drastically.

Good Luck!

leafs front, coils in the rear. been preaching it forever but once again nobody listens to camo :flipoff2:

How come it looks like you have about 700 psi in those swampers? Just wondering. Everytime I open POR I think you're running Cepeks F/C's. Also, The name Tin Benders? Shouldn't that be changed to Tube:skull: Benders?:flipoff2: :flipoff2:
Just razzin' ya'!

Originally posted by twistedmetal
How come it looks like you have about 700 psi in those swampers? Just wondering.

because you are looking at the uphill tire with no weight on it. duh :flipoff2: i run them at around 5 psi most of the time

http://community.webshots.com/photo/31970705/32045350UyTZLaOMix

Just getting back to the swaybar idea... What if you were to use some small stiff shocks for the swaybar links? That would give you the siffness you need to control sway but also allow free movement of the axle for articulation. Many swaybar links that I have seen have an eye approximately the size of the eye on a shock so it couldn't be that hard to try it.

why not just put in a stiffer spring? or at least a sway bar like the currie anti rock ?

Yup, after reading everyone input, I'm still of the opinion that the sway-bar is the way to go. It seems to be the only good way to control the droop. Wether the rig leans or not on a sidehill, the droop needs to be restrained somehow.

captured spring would make it act like a 1/4 'lip ad not allow free falling
I think the bungee cord idea is totally lame

Originally posted by Ant
Yup, after reading everyone input, I'm still of the opinion that the sway-bar is the way to go. It seems to be the only good way to control the droop. Wether the rig leans or not on a sidehill, the droop needs to be restrained somehow.

Yes - the sway bar is to go to restrain the drop. You shouldnt have to end up with any less travel but what should happen is that instead of the coilover extending and always pushing the axle away untill the shock limits the travel and finally lets the axle pull on the body to stablise it. With the sway bar you should set it up so that as the axle moves away, the spring pushes and the sway bar will pull on the axle allowing the axle weight to stablise the body. Ideally (IMO) the sway bar should limit the travel at the same time as the shock does so that you get the exact same travel except that as the wheel extends you go from the spring pushing on the axle with a smooth transition to the axle pulling on the body. You will end up with very similar amounts of travel and a much more stable rig.

To me running coilovers without sway bars is the same as running normal coils that drop out of the spring buckets or the same as running buggy leaves or revolver shackles. All you get is lots of uncontrolled droop which makes the rig very unstable.

Also another thing with coilovers is that besause of the stacked spring rates which allows the two stage spring rate (when the top spring bottoms) what happens is on a side hill you end up with the down hill spring going to a high spring rate and not compressing and the up hill spring extending at a really soft rate and what this does is raises the centre of gravity of the rig and makes everything much worse. The sway bar will also correct this somewhat.

Sam

Oh yea this all just my opinion and I dont run coilovers its just what I think happens - take it for what its worth.

Originally posted by camo
leafs front, coils in the rear. been preaching it forever but once again nobody listens to camo :flipoff2:

SOA front 1/4 rear been a happening thing for a while now :D Coilovers kinda fall into the same category ;)

How about a crossed swaybar? That would go from Right Rear to Left Front and another the other way? This would keep body roll down and articulation up.

How about the same thing with hyd. rams filled with air (or hell fill it with oil = no body roll...just don't jump it)? Attach the Right Rear to Right Front with a air line and another on the other side?



Think about a Formula 1 car. The roll axis and COG are in the same plane, the COG may even be lower than the roll axis. A formula 1 car could easily sidehill 70 degrees, and if you move past that number, it would simply slide down the surface, it could never roll over. Even at an 89* incline, it would just slide down the slope, NOT roll over.

F1 cars have a very low roll center to reduce jacking effects and also because the front view IC must be close to the ground to keep the track width from changing with suspension travel. They don't roll because their spring rates are about the same as the tires spring rates.

The reason for sway bars with coil overs is the lack of tension offered before streaching to the bottom of the liimiting strap. Frame mounted coils and leaf spring can pull at the bottom of their useful stroke adding stability with useful articulation.

If you can get the COG below the roll axis, it will cause instability problems the same as if it were above. The body might try to straighten out, but that will only be at the expense of the cog moving down hill. COG and roll axis should target the same height.

If you want to use forced articulation, push the COG up HIGH where you can push it around to your advantage.

look closley and you will see the sway bar arm. the sway bar it self is built exactaly like a torsion bar because in fact it is a torsion bar.

note that this is craig stewarts trophy truck that has aprox 36 of wheel travel and goes 145 + mph. oh and by the way i have seen him sliding completly sidways at 70+ mph through 2 foot whoops and i didn't notice any body roll. :flipoff2:

Originally posted by ...
How about a crossed swaybar? That would go from Right Rear to Left Front and another the other way? This would keep body roll down and articulation up.

Actually, a crossed sway bar would work basically the same as a normal sway bar.

When you "ramp" (stuff) the right front up, you want the left rear to stuff too. A crossed sway bar would push down on the opposite tire and make it want to "droop."

What you need is something in the middle of that bar to make it do just the opposite... like an open differential.

Here's an idea sorta like that, that I and a couple of others have had for a while now, but have never seen tried (or even really discussed):

Have a driveshaft mounted directly to each axle housing, and instead of having a t-case between them, have an open differential w/ the case (carrier) mounted sideways to the frame so that it could not spin (drive shafts connected to side gears). An IFS diff might work pretty well for this since its already got flanges on each side.

This would completely eliminate body roll without reducing articulation.
As the front axle twists one way, the rear axle twists (and is actually *forced* to twist) the opposite way through the differential.
The axles can never turn the same direction as the frame at the same time, so there is no body roll.

The only problem with this is that if you hit a bump w/ say one front tire at some speed, then the body would be forced to roll half the amount that the axle pivoted (very quickly). The "very quickly" part is the problem. You would probably have to mount the diff in such a way as to let it turn to some extent but be limited by some spring setup, or use torsion bars as one or both of the "driveshafts" so that it would have some "give." The spring rate of the spring or torsion bar setup would basically allow a certain amount of body roll, but it could be adjusted and it wouldn't matter if it was fairly stiff.

Does that make sense to anyone? Thoughts? :confused:

ErikB, i understand what you are getting at. it sounds like a good idea in theory, but probably wouldn't work out too well in application. There are already so many things under our rigs, i think space limitations would be a killer. Also, wouldn't you have to somehow prevent the pinion from rotating in order to make it work?

Originally posted by ErikB


Actually, a crossed sway bar would work basically the same as a normal sway bar.

When you "ramp" (stuff) the right front up, you want the left rear to stuff too. A crossed sway bar would push down on the opposite tire and make it want to "droop."

What you need is something in the middle of that bar to make it do just the opposite... like an open differential.

Here's an idea sorta like that, that I and a couple of others have had for a while now, but have never seen tried (or even really discussed):

Have a driveshaft mounted directly to each axle housing, and instead of having a t-case between them, have an open differential w/ the case (carrier) mounted sideways to the frame so that it could not spin (drive shafts connected to side gears). An IFS diff might work pretty well for this since its already got flanges on each side.

This would completely eliminate body roll without reducing articulation.
As the front axle twists one way, the rear axle twists (and is actually *forced* to twist) the opposite way through the differential.
The axles can never turn the same direction as the frame at the same time, so there is no body roll.

The only problem with this is that if you hit a bump w/ say one front tire at some speed, then the body would be forced to roll half the amount that the axle pivoted (very quickly). The "very quickly" part is the problem. You would probably have to mount the diff in such a way as to let it turn to some extent but be limited by some spring setup, or use torsion bars as one or both of the "driveshafts" so that it would have some "give." The spring rate of the spring or torsion bar setup would basically allow a certain amount of body roll, but it could be adjusted and it wouldn't matter if it was fairly stiff.

Does that make sense to anyone? Thoughts? :confused:

Crossed anti roll bar does the exact same thing and is a lot simpler.

When the front LHS moves up the roll bar makes the rear RHS move up.

Sam

Originally posted by Beartrack
Why am I getting the impression that some folks replying are referring to torsion bars and not sway bars? How could a Currie Antirock NOT limit your articulation? I can see how a sway bar might not limit your travel as such, but it sure as heck is going to limit your articulation! How often do any of us use or even WANT say 16" of droop on both ends of the axle????? What we are looking for is articulation and maybe half or 2/3 that much droop from both ends of the axle at the most! As it's been stated, the whole axle dropping away just raises your CG as well as messing with your link bar geometry quite a bit. Now I could see where some type of torsion bar working on each end of the axles movement might have some merit, or some type of limiting strap though personally I think that a limiting strap would be more effective with some stretch as mentioned before to progressively add more resistance (with a second one to fully limit droop.) Either way though IMO you are superior to leaf springs if this unloading issue can be resolved if not just for the fact that with coils you can get 90 degree-plus entrance and exit angles. Try that with full eliptical leaf springs. And quarters on the front would be pretty abusive on the main leaf...

A sway bar doesent necessarity limit articulation. Done properly you should get the same articulation except as the wheel droops the axle will start pulling down on the frame to the extent that at the bottom of the max droop it is pulling down with the entire weight of the axle combo (exactly the same is if thee coils were totally captured and the coils limited the travel and not the shocks). This is where the stability comes from - the heavy axle pulling on the frame. Mega travel coilovers with no anti sway bars allows the axle to droop and the spring is always pushing the axle away from the frame throught its entire droop all the way to the bottom untill finally the shock stops the travel and pulls on the body.

Sam

Originally posted by elf_cruiser
ErikB, i understand what you are getting at. it sounds like a good idea in theory, but probably wouldn't work out too well in application. There are already so many things under our rigs, i think space limitations would be a killer. Also, wouldn't you have to somehow prevent the pinion from rotating in order to make it work?

Yeah, but if it worked well, we'd MAKE it fit somehow, right? :)
The drivelines and diff thing don't need to be centered or mounted in any particular way, so they could be mounted just about anywhere, I think...

Yes, you'd have to prevent the pinion rotation. That's what I meant by "carrier mounted to frame," but I guess I didn't 'splain it too well. :emb4:

You could use a carrier by itself mounted to the frame (no R&P gears needed), or use a full IFS housing or something and then prevent the pinion rotation somehow, or attatch the pinion to some spring setup to allow some body roll or whatever...


Originally posted by Strange Rover
Crossed anti roll bar does the exact same thing and is a lot simpler.

When the front LHS moves up the roll bar makes the rear RHS move up.

Sam

No it wouldn't. Think about it.

Or maybe I don't understand your "crossed" sway bar design. :confused:

Here's what I'm picturing:

|____| *standard sway bar, kind of a wide U shape, one side goes up, the other side goes up.

|____
.........| *crossed front to back, kind of like a lazy S shape, one side goes up, other side goes down (long section could be perp. or parallel w/ frame- wouldn't matter)

AHHH... I think I see.... Keep the U-shape but somehow run it diagonally front/back? That would REALLY be interesting to try to mount up...

Not that my driveshaft thing is easy, but the driveshafts have joints you could connect anywhere on either axle and they would flex up and down as the axles moved up and down too. All they have to do to function is turn as the axle articulates relative to the frame...

I dont have time to read thru the Bull Shit buuuuuuut, what about just putting a sway bar on it and tell everyone to go f-themselves. IT WORKS!!!
ericfilar@fatcity

Here's what I'm picturing:

|____| *standard sway bar, kind of a wide U shape, one side goes up, the other side goes up.

|____
.........| *crossed front to back, kind of like a lazy S shape, one side goes up, other side goes down (long section could be perp. or parallel w/ frame- wouldn't matter)

AHHH... I think I see.... Keep the U-shape but somehow run it diagonally front/back? That would REALLY be interesting to try to mount up...

I think your getting it now...I should have described it better.
What about doing a
|____
.........| type that was attached to the front and rear wheels on the same side? Same kind of effect as the |____| going diagonally but you don't have to go under/over the t-case

Or (really starting to stretch with this one) a leaf type spring (almost a beam to be strong enough when that long) that was pinned in the middle and the ends were attached to the front and rear wheels on each side?

I still like my hyd. ram idea the best...with OBA you could jack up the side that was low and keep the body level...but even if you left it be it would still roll less and maybe even flex more. Oh the fun you could have with some hyd. rams on your truck.

Damn...I'm full of ideas today (or full of $hit...you decide).

The sway bar is the way to go, but why go through all the effort of linking when leaf springs work just fine up front. I agree with Camo on this one. I ran leafs up front on my Flatty and 1/4 in back. The truck could drive up the side of the bowl in the sluice box without any shocks and not lean all that bad. The leafs really do help out a lot. As for flex, well most people know how the rig flexed. Lets just say it did fine.

Dimitri

Originally posted by Beartrack


First no, that isn't a torsion bar, that's a sway bar, every sway bar utilizes a torsion principle but that doesn't make it a true torsion bar. What I am talking about is of course the type used for example for the suspension like on an IFS Toy. Dial it in for reverse lift and it would cause progressively increased droop resistance.



Have you ever seen the one like the Currie Anti-Rock Sway-Bar? It IS a torsion bar with two arms splined on each end, Identical to your Toy IFS torsion bar.

so this body roll thing is a problem?

I can tip Ant's fj about 6" (at least) to the side I climb on.......

I have an idea for my rig for a "sway-bar" though.......

16" sway aways, and mild springs, sway bars front and rear

with an added feature.....


--Sherpa

Originally posted by SHERPA RIG
so this body roll thing is a problem?

I can tip Ant's fj about 6" (at least) to the side I climb on.......

I have an idea for my rig for a "sway-bar" though.......

16" sway aways, and mild springs, sway bars front and rear

with an added feature.....


--Sherpa

.......and what would that added feature be......? :D

Spill it.....

Originally posted by Beartrack


I am guessing it doesn't have decent true articulation as far as opposing tires in relation to the frame. Those rigs are obviously set up for lots of droop, fair amount of compression, but do they allow one tire under big compression with the opposing tire in droop?

your correct it is not set up for articulation like we have but it would easily still put a rear tire on a 4' rock and not lift the other three.

Originally posted by Ant
Spill it.....

hehehe, got ya thinking a bit? Or am I just bench-crawling
again?

--Sherpa

Bench Crawling as usual....... LOLOL

O.K. back to the topic, what effect, if any, does having very dissimilar front and rear roll centers have on body roll. It would seem that that would induce some resistance to body roll, or am I smokin crack?

Originally posted by Suprdlux


Weight 3000lbs
CG height 36"
Track 60"

If the roll center is at the CG then this vehicle will begin to roll over on a slope of 39.8 degrees.

If the roll center is 12" below the CG and the vehicle is running springs with a rate of 600 lbs/in located 8" inside of the wheel the body will roll about 6 degrees and the vehicle will roll on a slope of about 40.3 (Sorry I had a miss calc. in the original post) degrees

To me these numbers make sense, the reason is with the CG above Roll center when the body leans the CG becomes lower and the weight of the outside wheel and axle gain more leverage on the body as it gets closer to the inner wheel, or pivot point.

Ive seen some much wrong information here its making me sick. But there are a couple people in here that have good information. Its making me dizzy.

We must all look at this much simpler. Lets think back to our Physics class.
1. Draw your truck as a block on an incline
2. Isolate the obect and draw a free body diagram.. This is a diagram with arrows discribing the forces.
3. The forces must be broken up into there component forms F=ma Newtons 2nd law
4. For example the force in the x direction is F(x)=mg sin(theta) theta = angle and mg=wieght of truck. etc, etc.
5. Force in the y direction = mg cos (theta) with a coefficient of friction = ? depending on tires and trail conditions. etc, etc.
6. By simply drawing these forces it will help determine optimum cog and roll centers, when a truck will tip over, etc.


Actually if I could draw a picture it would be easy to explain. I dont feel like typing out more of an explaniation.

:smokin: :smokin: Hummmmm. How about mounting a gyro in the cab and then feeding the output to either hydrolic arms or airbags to level the vehicle. :rasta:

Originally posted by stemp
:smokin: :smokin: Hummmmm. How about mounting a gyro in the cab and then feeding the output to either hydrolic arms or airbags to level the vehicle. :rasta:

...or what I was thinking was the option of using a mercury switch assembly. Tough to get one now though - they stopped selling them at Radio Shack due to terrorism I was told when I checked into this for doing that. But it seems like you could make one easy enough; basically just a dish-shaped glass assembly, some mercury and electrodes located around the edges and a center electrode.

Originally posted by Beartrack


...or what I was thinking was the option of using a mercury switch assembly. Tough to get one now though - they stopped selling them at Radio Shack due to terrorism I was told when I checked into this for doing that. But it seems like you could make one easy enough; basically just a dish-shaped glass assembly, some mercury and electrodes located around the edges and a center electrode.


I thought about this exact setup a while back. Nice in theory, but I doubt it would work in practice. Three problems that I can think of...

1) The reaction time of the system would prolly be too slow and by the time the cylinders or air bags reacted to the input from the switch you´d either be over the obstacle or on your side...

2) If not set up perfectly, the system could go spazo and flip your truck on level ground with just a light push on the body. The push would be reacted to by raising the air bagas on the opposite side, which would then be reacted to by the other air bags, which would then be reacted to by the other air bags, which would then be reacted to by the other air bags... You get the idea.... It´d be funny as shite to see tho...:p

3) You´d likely need a fawkin´ computer and proportional valves to control it all...

Then again, maybe I´m all wrong...:flipoff2: :p

:beer:

Capture the coils to slow down and control the droop, fill the gas tank, and wheel the Mo-Fo? Buy a bunch of spare fenders and call it a summer!

Originally posted by billj



I thought about this exact setup a while back. Nice in theory, but I doubt it would work in practice. Three problems that I can think of...

1) The reaction time of the system would prolly be too slow and by the time the cylinders or air bags reacted to the input from the switch

<snip>

3) You´d likely need a fawkin´ computer and proportional valves to control it all...

Then again, maybe I´m all wrong...:flipoff2: :p

:beer:

Actually you can get air systems with reaction times so fast that you can flip the vehicle over on level ground. Some of the low-rider types have competitions now to do just that (go figure.) They are massive pumps, moderate resevoirs and massive dump valves. No rocket science to it really. The concern about the system going haywire though I think isn't really a concern, we are talking just the connection of 2 electrodes via mercury as the electrical conductor - pretty simple/fail proof. No need for any computer or anything like that. You just wouldn't want to use bags with a huge throw anyway, this is an assist, not a primary suspension and it doesn't necessarily need to even fully level the vehicle, just assist.

Personally though I think that the real trick might be 2 of these switch setups: one switch system extends whatever side is low; the second system sucks up the suspension on the high side via (on a coil over rig) some type of hydraulic vacuum. It would be an interesting setup for someone with lots of money and/or their own fairly sophisticated fab shop. I hear that Walker Evans on that skeleton S10 pickup had the King coil over shafts center-drilled and set up for hydraulic forced suspension, this idea isn't far from that it just takes that principle and extends it to an "auto" mode.

What I can't figure out though is with all the highly 4-wheel motivated computer geeks and math whiz's on this list why someone doesn't get off their duff and build an app that allows you to calculate such things as IC, RC and all of that, then takes those figures and determines incline angle/sidehill angles and determines when you'd roll over; hopefully it would allow you to compare how changing COG and IC and RC would impact those max incline and sidehill angles. You know that there has to be folks up here with the know-how and there certainly has to be a market for it to some degree - though shareware/freeware would be awesome of course.

Ok I've played around with the coils and spring settings a bit and I've seemed to have stabilized the body roll somewhat. I didn't buy new anythings just adjusted what I've got.

Some before pics...
http://www.mjw.com/amigo/images/bodylean-03x.jpg

http://www.mjw.com/amigo/images/bodylean-04x.jpg

The Amigo sits about 1" taller than in the "before" pics. I've adjusted the bottom spring lockout down 1-1/2" in back and 1" in front. This was partly because the rear end was getting into the bottom of the shock too easy. I then compressed the upper coil by 1-1/2" using the top coil stop. The ride is quite a bit more solid and the body doesn't seem to roll as easily as it did. Note in the after pics the body has rolled less but actually shifted more downhill without leaning as bad. One thing for certain is I'm not sitting on the bottom of the shock in back on the downhill side and that really seems to help.

And some after pics ...
http://www.mjw.com/amigo/phill-02-06/images/02-06-68.jpg

http://www.mjw.com/amigo/phill-02-06/images/02-06-71.jpg

Did you notice any adverse effects by doing that? less flex, or anything negative?

I don't remember after reading all of the thread if one of the mechanical solutions would be to apply atv winches (1 per side) run along the side to compress the uphill suspension when needed. Possibly 2 cables on the winch run along the frame to a point above the axle around a pulley to the axle itself. there are several ways to execute this but this was one thought. Atv winches are usually 50 bucks and should have enough pull to compress the suspension. You could run the cable inside the frame for durability and astetics.
Just a thought, Jake

Originally posted by FatCity
I dont have time to read thru the Bull Shit buuuuuuut, what about just putting a sway bar on it and tell everyone to go f-themselves. IT WORKS!!!
ericfilar@fatcity

Ha, I've tried to tell them too. Some people have to learn the hard way.

To make things easier on you guys...I can tell you where to get trick swaybars:

www.stockcarproducts.com

DO NOT ask them about 4wheel drive, they are a circle track company that makes their own stuff...they won't have a clue what we are talking about. They have swaybars ranging from .75" up to 1.5" or so. Generally 3/4" to 1" is what we are looking for. They stock all sizes in 37.5" long and can make custom lengths but it takes them close to two weeks. The swaybars slide into 1.75x.083(I think, wall thickness might be off)and you use their teflon bushings on either end. The splines on the bars are 1"-48 i think. They also sell the arms that are very nice too.

You just want the swaybar to add some resistance to the suspensions, not something real thick like a factory swaybar. This is why you don't lose articulation...it is just adding resistance.

CJ

Originally posted by FatCity
I dont have time to read thru the Bull Shit buuuuuuut, what about just putting a sway bar on it and tell everyone to go f-themselves. IT WORKS!!!
ericfilar@fatcity

becasue it doesn't fix the real problem of your roll center being too low and limits flex (they have sway bar disconnects for a reason).

Originally posted by TRD


becasue it doesn't fix the real problem of your roll center being too low and limits flex (they have sway bar disconnects for a reason).

You guys are killing me. When you build these long travel heim jointed suspensions you have a suspension with NO ROLL RESISTANCE in it. Stock suspensions have bushings that provide roll resistance which limit body roll. They made disconnects for thickass factory swaybars, come on...expand your mind a little.

We build these awesome suspensions that do one thing really well and one thing only. They hold the axle very securely in position throughout travel. There is no vaugeness anywhere, all the movement is transfered to the shock. So, now that we have a suspension built to make 100% use of really high quality shocks...

We spend $2000 on the coilovers, the best shocks out there. They are designed to dampen the suspension movements and the coils support the vertical loads, not the body roll. Once again, They are not designed to control body roll, they are built to dampen the movement. IMHO, it'd be silly to use bushings with these shocks because you want the shock to see every movement, you dont want vaugeness, you just dropped 2k on shocks, use them :P

So you've got a suspension that holds the axles in position, high quality shocks that dampens the ride so you feel like your in a caddy...at this point ADD A FRICKING SWAYBAR TO CONTROL BODY ROLL, that is what they are for. Use things what they are designed for. A light swaybar shouldn't limit articulation, we aren't talking thick factory ones...just something to give the suspension some resistance so the body doesn't go flopping around...I promise you'll like the results :P

I am speaking from experience. You can mess with the roll center in relation to center of gravity but when it comes down to it this isn't going to make the difference you're looking for. Swaybars make all the difference in the world and their benefits aren't just because they control body roll. I talk to people all the time who don't like coilovers...and the reason is because they are seeing unfinished suspension, finish your suspensions with a light swaybar to add some resistance to travel.

CJ

Ok, if one were to buy into this sway bar idea, which axle would be better to tie up, the front or the back?? Why??

Let´s assume the example of the Isuzu in this thread...

:beer: :beer:

Originally posted by billj
Ok, if one were to buy into this sway bar idea, which axle would be better to tie up, the front or the back?? Why??

Let´s assume the example of the Isuzu in this thread...

:beer: :beer:

Now we are getting somewhere! We really should start a thread on swaybars. On my old Jeep, almost all the weight was up front. Without swaybars the rear suspension would move around a whole lot before the front would even start to flex. So, I put a swaybar on the rear which made them work almost equally. On my new Jeep with rockwells I put swaybars on both ends.

A classic example is rear quarter-eliptical suspensions/front leaf springs. Take a look at just about ANY rig with this and you'll see exactly what I mean. The rear suspension is totally flexed out to the max and the front is parallel with the frame. IMHO, this isn't good at all, you want both suspensions to be working, not one doing all the work. The reason the quater elipticals do this is the rear has no roll resistance and the front has a good bit with the plain jane leaf springs. So, they should increase roll resistance in the rear so the front is able to work.

On the Amigo, it is hard to tell. It seems to me the weight is fairly well balanced with all that rear sheet metal. I personally would put one in the rear and make the front work a bit more.

So it really depends on your situation as to what you need.

CJ

Originally posted by CJ Lagos

A classic example is rear quarter-eliptical suspensions/front leaf springs. Take a look at just about ANY rig with this and you'll see exactly what I mean. The rear suspension is totally flexed out to the max and the front is parallel with the frame. IMHO, this isn't good at all, you want both suspensions to be working, not one doing all the work. The reason the quater elipticals do this is the rear has no roll resistance and the front has a good bit with the plain jane leaf springs. So, they should increase roll resistance in the rear so the front is able to work.
CJ

You are right there, but I have seen some 1/4 and SOA rigs, that did a lot of work to their 1/4 to make it work well.

No matter what spring, link suspension takes a lot of thought and work to make 'em work well, and not just "flex"

I agree 100% with what has been said about sway bars. Let me take it a bit further(in the other direction, though). I have been toying with an idea to further the use of a sway bar. If you absolutely MUST have a buttload of flex(which you don't), I have a suggestion. Cut your sway bar in half in the middle. Sleeve it with some round tubing attached to one half, but lets the other half rotate. Now attach some square tubing(2 pieces) to the sleeve so they touch each other, but still move separately. Now rig up a larger square tube that will slide over the two halves with the pull of a cable thus connecting the two halves making a sway bar. Kind of a center disconnect for a sway bar. Any good?

You want to control roll stiffness without impacting articulation?

Why not dampen the roll moment? Build a suspension system that slows down the acceleration of the CG through the roll axis (the feeling that the sway will be accelerated into a tip-over)?

Think about what this requires? Something has to oppose the roll (spring, shock, and linkage). Sounds easy, like you can Band-Aid a scab to make a poor system work (what it seems people are looking for)? The problem is not easy, and requires a system approach rather than a single fix.

You talk about staging the stacked constant rate springs, to balance the droop with the soft spring, and compression load with the stiff spring. It works, it does help, but the slinky droop springs are not a favorite with a tire in a hole, neither is the stiffer compression springs straddling a crack. Anyone consider variable rate springs (for one or both spring stages) or a progressive link system (somebody has to remember the old motorcycle linkages)?

The shock/spring location has not been mentioned much, why? Shocks angled in on top will allow the body to rotate without benefit of the shock dampening (what is required to slow the rollover feeling). This makes the lay-in shock position undesirable. Shock placement (with coilovers more than other systems) has a direct impact on the roll dampening (not much mentioned about shock geometry). You need to get the shock position to combat the roll acceleration (or make it part of the balanced system).

You already discuss the anti-sway bar as a method to oppose the roll, with the problem that it also restricts articulation. Each discussion, except for a few comments, limit the discussion to fixed links and short arms like a factory system. Why limit yourself to only fixed anti-sway bar links (somebody mentioned dampened links, why not)? You use long arms on the suspension, why not the anti-sway bar?

I like all the CG vs. roll axis height discussion (better than late night TV). The paved track racing suspension basics are good to learn, but placing the FBD models on a hill will provide better analysis (better than the moving the PC closer to the couch).

A high roll axis will minimize the suspension from compressing on side hills, because the vertical resistance to gravity is acting through a (virtual) fixed link (not the travel leverage of the suspension or shocks). The high roll axis systems demand excessively soft springs to articulate at full compression travel, they fight articulation near full compression, because the links are taking most of the compressive weight force and working the springs through poor leverage. The poor leverage and the soft springs amplify the sway instability. The great leverage you have when level at the static ride height is restricted quite a bit when leaned over. Someone mentioned you might consider a lower roll axis (and got hammered)? So why not add to the thought and throw in progressive spring rates to allow articulation without the stiff static ride, and with a better shock placement to resist roll movement, and a non-linear connection to resist sway?

I also think someone had mentioned the idea of treating the occupant cage as a suspended capsule, with the frame and axles as separate systems? This line of thinking will not help the stock body conversions, but it may help the custom tube frame builders. It gets the design view of making the axles articulate without consideration of the occupant easier to deal with.

The good about a high roll axis is the CG induced sway feels to be minimal, the bad is the feel before the suspension stalls (jacks) and the vehicle rollover "just happens" may be too fine a line for control. The problem you fear may be more the lack of warning (poor feedback) before a rollover, more than just a strange laid-over body position? The need for rollover approach feedback may be more important than ultimate articulation at slow speeds (considering the current trend to timed course events where impact on the suspension stops is more and more common)?

I think I'll go back to wheeling the rocking chair...(and play chicken with the rollover potential).

Happy Trails!

Originally posted by Ed A. Stevens


A high roll axis will minimize the suspension from compressing on side hills, because the vertical resistance to gravity is acting through a (virtual) fixed link (not the travel leverage of the suspension or shocks). The high roll axis systems demand excessively soft springs to articulate at full compression travel, they fight articulation near full compression, because the links are taking most of the compressive weight force and working the springs through poor leverage. The poor leverage and the soft springs amplify the sway instability. The great leverage you have when level at the static ride height is restricted quite a bit when leaned over.


I have never thought about this before. Is this the same as with a high roll axis for a given amount of axle articulation the springs have to compress and extend more than an equivalent system with a low roll axis???

Sam

PS good post! Got some great ideas happening here.

A high roll center is all fine and good, but actually placing the links at the angle required to get the roll center above the CG causes all kinds of other complications. like seriously screwing up the instant center in rear axle rotation, severe front axle caster change, and excessive axle steer during artuiculation. I hear alot of engineer waanabe types spewing alot of theory (I am not one, I is just a mekanik)but they seem to be limited in practical experience. It is one think to quote stuff out of a book, it is another to have built a rig with a 105" wheelbase and a 36" high CG.

Originally posted by zags
A high roll center is all fine and good, but actually placing the links at the angle required to get the roll center above the CG causes all kinds of other complications. like seriously screwing up the instant center in rear axle rotation, severe front axle caster change, and excessive axle steer during artuiculation. I hear alot of engineer waanabe types spewing alot of theory (I am not one, I is just a mekanik)but they seem to be limited in practical experience. It is one think to quote stuff out of a book, it is another to have built a rig with a 105" wheelbase and a 36" high CG.

I carnt see that roll centre has anything to do with instant centre of the rear axle. With rear steer I dont think that this is a problem with a crawler and long links goes a long way to reduce this anyway to accaptable levels. And you are right quoting stuff is one thing and building it is another. But if somebody just quotes me a whole heap of shiat out of a book then thats OK cause I can take the info for what its worth and see in my own mind how and if it has any relevance to me building a better rig.

I think Stevens post is a good one even if he has never seen a 4wd in his life because what he said brings new ideas and I think that this is a good thing.

And if its me thats an "engineer waanabe type" then im cool with that anyway :flipoff2:

Sam

i thought some pics were in order of what belly dragger was talking about. i took these while we were out in moab with him. sorry they are so late in getting here!!

http://www.thedesignarmada.com/galleries/moab%20page%202/images/116-1692_IMG.jpg

http://www.thedesignarmada.com/galleries/moab%20page%202/images/117-1725_IMG.jpg

FLEX

http://www.thedesignarmada.com/galleries/moab%20page%202/images/117-1726_IMG.jpg

that was some scary shit up on moab rim in that amigo! i remember getting out and someone asking me why i was so pale.

a high roll centre seems real easy to do, even a mekanik should be able to have the suspension links converge at the frame mount rather then below the axle.
all I see in the pics is that roll centre being way below the cg and amplifying the felt body roll.
other then the weight rolling towards the lee side a bit it will not change the roll over angle much.
just will feel scary.

roll resistance pretty much = bind for CJlago

How's my Roll Center vs CoG? :flipoff2:

Originally posted by aaronlosey
http://www.thedesignarmada.com/galleries/moab%20page%202/images/116-1692_IMG.jpg This picture reminds me of that "Keep on Truckin'" dude from the 70's. :D

You should have been with me last weekend Aaron. I need to carry spare shorts. :D Fawking hard stuff easy, easy stuff hard.

DR; looks ggod, so about 0 flex. Not knocking it, I was the one who has posted the is articulation overrated and is flex really necessary threads.

I am going to be doing swaybars. I talked with Currie and although they did talk with me, basically they said if it isn't a Jeep it's going to be totally custom so why pay Curries prices for something I'm going to severly alter. Once I have the swaybars installed I will post some sidehill shots and ramp pics in this thread so once and for all the swaybar=no flex argument can be settled.

Originally posted by Ant


Thats an excellent idea..... anyone tried this??

Ant, do you mean something like this?

http://www.safarigard.com/Droopkit.htm

However as this was designed for simple coils and not coil overs, I think this type of design would be difficult to implement, even modified quite a bit. Just thought it might add to the "idea pool".

How's my Roll Center vs CoG?



Funny, really really funny. Got me laughing. Kind of makes you think.

Bolt on leaf springs and you know what you're ganna get.

Bolt on coils/coil-overs and you better be ready to dial it in.

Doesn't mean I'll go back to leafs, only that coils don't just bolt on.

see ya,

tony k