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also .. lower links above axle centerline.. some love it .. some hate it..
i think for getting it it makes it easier to keep your link flat and still get it up high.
all i can see is good from that .. yet some people are very against it..
i would think everyone racing koh would have them like that.
yes you have to build your upper links up higher to get vertical separation . but isnt having your upper links higher a good thing?
I agree with this idea but will be one of the KOH racers not running this..
You have to build the car around that idea.

I noticed a big difference in the front's ability to soak up hits when I dropped the ride height 1in. I think it is because the links are actually pointing up and recess back during the up travel.

Mounting the lower links above center line could give me this at the 1in taller height I want.

In crawling I really cared about the rear link geometry for shooting waterfall climbs, There was no answer for the best setup, all different numbers work by different drivers on different climbs..

but now for going fast getting the front to soak up hits is hard. The rear link geometry seams alot less critical for the go fast.

Body roll is one of the other hard to manage issues with going fast. My next rig I will build around front and rear sway bars. Just doing the rear was great for trails but for go fast I want more body control.
 

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This thread died for awhile but it did continue on in others. As drivers have been building new rigs, there has been great discussion around their choices and compromises. I think this thread, and KOH stimulated some more of the open "talk."

Going fast, "Getin it" has made everyone up their game in all details. Driver/Co-driver safety, steering response, shock/spring tune, suspension design, axle weight and design, tire size, communication, pit work, etc..... The morphosis from crawl'in to race'n.

And then there is the DRIVER; their endurance, and their experience with get'n it and actually being able to read the terrain, lines, and when to use either pedal.

Maybe a list?????

A healthy Budget $$$$$$
A RIG/JUNK that is built to SKID! ROLL! Retain parts. Promote visability, and protect! With speed come consequences. $$$
BIG Power that is dependable mechanically, electrically, cool, and not starved of fuel, oil, air, or $$$.
A drive train that can take the shock abuse of the desert and rock crawling, and run from 1 to 120 mph+. $$$
Tires and wheels that can handle a big hit/washout/bouldered terrain. The trend is taller, stickier, tougher, and hopefully lighter. Bead Locks and inner liners of some kind. $$$
Axle systems that can take abuse from shock, rock/tree/terrain hits, articulation, and promote ground clearance and low weight. $$$
Suspension, Suspension, Suspension
Articulating rear suspension near 20" with minimal articulating rear and roll steer, and provisions for a sway bar. Link triangulation, anti squat, kick, and pinion angle are words understood and engineered into the build. IRS may be another soon if belly height and $$$ become less important than preventing rear steer and independent articulation in the "nuisance" rocks. $$$
Front IFS suspension get's it as the race'in moves to desert/2-track speed instead of crawl'in. Steering precision at speed, driver comfort, and independent articulation over the nuisance rocks has led to this development. Watch for more work here. Improved design solid axle, triangulated link builds still win when the wheelin turns tough. $$$
Newer coil-over shock and bypass technology and undrstanding continue to make rigs faster in the rough, and extend some older designs. Tuners are in high demand, and even a perfect suspension needs these guys! Possibly someone to consult BEFORE you build. $$$
An understanding family endeavor, with lots of friendly and hard working build and pit people... LOVE...COMMITMENT
Good friends, fellow racers, sponsors, promoters, and spectators to help and cheer you on!


One hell of a lot of people have contributed to get'in to the above!

What did I miss? I'm sure I missed A LOT!
I'm just a guy looking to build my own someday. Get'in it when I want to.
 

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Joined
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5,599 Posts
This thread died for awhile but it did continue on in others. As drivers have been building new rigs, there has been great discussion around their choices and compromises. I think this thread, and KOH stimulated some more of the open "talk."

Going fast, "Getin it" has made everyone up their game in all details. Driver/Co-driver safety, steering response, shock/spring tune, suspension design, axle weight and design, tire size, communication, pit work, etc..... The morphosis from crawl'in to race'n.

And then there is the DRIVER; their endurance, and their experience with get'n it and actually being able to read the terrain, lines, and when to use either pedal.

Maybe a list?????

A healthy Budget $$$$$$
A RIG/JUNK that is built to SKID! ROLL! Retain parts. Promote visability, and protect! With speed come consequences. $$$
BIG Power that is dependable mechanically, electrically, cool, and not starved of fuel, oil, air, or $$$.
A drive train that can take the shock abuse of the desert and rock crawling, and run from 1 to 120 mph+. $$$
Tires and wheels that can handle a big hit/washout/bouldered terrain. The trend is taller, stickier, tougher, and hopefully lighter. Bead Locks and inner liners of some kind. $$$
Axle systems that can take abuse from shock, rock/tree/terrain hits, articulation, and promote ground clearance and low weight. $$$
Suspension, Suspension, Suspension
Articulating rear suspension near 20" with minimal articulating rear and roll steer, and provisions for a sway bar. Link triangulation, anti squat, kick, and pinion angle are words understood and engineered into the build. IRS may be another soon if belly height and $$$ become less important than preventing rear steer and independent articulation in the "nuisance" rocks. $$$
Front IFS suspension get's it as the race'in moves to desert/2-track speed instead of crawl'in. Steering precision at speed, driver comfort, and independent articulation over the nuisance rocks has led to this development. Watch for more work here. Improved design solid axle, triangulated link builds still win when the wheelin turns tough. $$$
Newer coil-over shock and bypass technology and undrstanding continue to make rigs faster in the rough, and extend some older designs. Tuners are in high demand, and even a perfect suspension needs these guys! Possibly someone to consult BEFORE you build. $$$
An understanding family endeavor, with lots of friendly and hard working build and pit people... LOVE...COMMITMENT
Good friends, fellow racers, sponsors, promoters, and spectators to help and cheer you on!


One hell of a lot of people have contributed to get'in to the above!

What did I miss? I'm sure I missed A LOT!
I'm just a guy looking to build my own someday. Get'in it when I want to.
You missed seat time.
Which is more then driver experience, it is like burn in testing for everything on the rig. Any one little change or maintenance not raced is risky.

But its a catch of 22, burn in testing is destructive, the more you race the more aged everything on the rig becomes. Priority 1 is a well maintained experienced combination, that will win endurance over more $$$ and blips of speed.
 

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Seat Time=Driver's Experience

:shaking: Buncha rookies in this thread anyway:shaking:

:flipoff2:
 

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Rookies are making it tougher on the experienced.
Rookies are getting experienced quicker.
The list of potential winners is increasing every year.
:rolleyes:

Agreed that new builds are problematic. Stretching technology.

In motorcycle racing, I give a top rider about 90%+ of the win.

In KOH racing. I give the top teams: Driver about 55%, the rig 25%, support 20%.

:smokin:
 

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This thread should be linked with the spring tech thread from Zukizzy. Reading both made my head hurt for a week, but on my buddys current rig tfab 100 proof we made changes based on both and have come leaps and bounds.
 

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Shannon Campbell went to a 4 link on the rear of his new rig .. there must be something to it :)
You get to see a lot of rear suspensions when you start at the back of the pack, or are lapping them... I'll bet there was some homework there also, as many don't work...
 

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His trailing arms are 41 inches flat and triangulated only a few degrees if any at all..

His uppers are mounted wide on the axle .. It seems like that helps with body roll.

Also at the race last weekend I noticed on the landings guys with flat/ inverted lower links (I'm assuming very low anti squat ) landed a lot smoother!
 

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His trailing arms are 41 inches flat and triangulated only a few degrees if any at all..

His uppers are mounted wide on the axle .. It seems like that helps with body roll.
Not from what I recall, body roll is a function of the distance between roll centers and CG. Closer to the CG your roll center is the less body roll from the chassis.

Also at the race last weekend I noticed on the landings guys with flat/ inverted lower links (I'm assuming very low anti squat ) landed a lot smoother!
I don't think the AS has much to do with the landing, I would guess the it's a combination of the vehicle setup and the arc the arms travel in.



As for mention of the numbers for various setup, it's important to realize that there are no magic set of number for a setup. The point of calcualting the numbers is so you can start to establish trends. Bad part is this require lots of work and many multiple setups to get dialed into to a area that works well for the vehicle or to get the setup to trend in a favorable direction.

So the standard range of number suggested here are really a conglomeration of many various vehicle and some good guestimation.
 

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I don't think the AS has much to do with the landing, I would guess the it's a combination of the vehicle setup and the arc the arms travel in.
The lower anti squat will transfer more of the force into the shocks, instead of through the links into the chassis. This could potentially make a difference in the behavior of the landing, but I would guess that it has more to do with the fact that putting the force into the shocks makes them easier to tune.
 

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Not from what I recall, body roll is a function of the distance between roll centers and CG. Closer to the CG your roll center is the less body roll from the chassis.

there is more than one way to skin a cat.. you are correct with the Cg and roll center but you can also build roll resistance into a suspension..

mock up a 4 link with pencils, Popsicle sticks ect. then cycle it and change the triangulation lots of triangulation on both ends makes it really easy for the chassis and axle to pivit( that could be good or bad)

on the land rover discovery1's the rear lower links/trailing arms have a bolt coming strait out of the link going into a bushing.. adding lots of roll resistance



I don't think the AS has much to do with the landing, I would guess the it's a combination of the vehicle setup and the arc the arms travel in.
from what i've noticed most low anti squat setups.. have flatter longer links.. resulting in a more gradual arc..


As for mention of the numbers for various setup, it's important to realize that there are no magic set of number for a setup. The point of calcualting the numbers is so you can start to establish trends. Bad part is this require lots of work and many multiple setups to get dialed into to a area that works well for the vehicle or to get the setup to trend in a favorable direction.

So the standard range of number suggested here are really a conglomeration of many various vehicle and some good guestimation.

i know every rig is different but 18 inch lower links on a 20* angle up to the chassis from the axle doesn't work good on any rig..

so i'd think #'s that are awesome on 1 rig should be decent on just about anything..
i do realize some rigs cant fit the same geometry as others like most rigs dont have room to have a really ugly tower on there rear axle like this..


but ugly tower allows for mounting lower links high on axle(keeping them flat) but still gives offers 8 to 13 inches of vertical seperation or something like that
 

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Link don't add roll resistance unless you have some kind of binding on your joints. The only thing that can add resistance is a spring or some kind. A bushing would be a spring although I don't really know what kind of rate it would add to the overall system. I would tend to think it would be small but you would have to do some work to determine the exact effect. Roll resistance or Roll Moment is a function of RC height and spring separation on each end of the vehicle.


As for the number that's not exact right. Are the CG the same, link lengths, link placements, wheel travel, spring rates, etc? usually no. Can we be stupid and throw out scenarios that obviously will give problems? Yeah but what's the point it doesn't prove anything. Can we get some basic assumption from one test rig? Sure but the only way to really evolve and confirm the assumptions is to do more testing with a baseline vehicle. As you change one function you start either moving closer or further from your desired effect. I guess if all your concerned with is copying AS values then that would work but won't tell you what the trends for the rest of the system. AS is one characteristic and probably not really all that important, imho.
 

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Link don't add roll resistance unless you have some kind of binding on your joints. The only thing that can add resistance is a spring or some kind. A bushing would be a spring although I don't really know what kind of rate it would add to the overall system. I would tend to think it would be small but you would have to do some work to determine the exact effect. Roll resistance or Roll Moment is a function of RC height and spring separation on each end of the vehicle.


As for the number that's not exact right. Are the CG the same, link lengths, link placements, wheel travel, spring rates, etc? usually no. Can we be stupid and throw out scenarios that obviously will give problems? Yeah but what's the point it doesn't prove anything. Can we get some basic assumption from one test rig? Sure but the only way to really evolve and confirm the assumptions is to do more testing with a baseline vehicle. As you change one function you start either moving closer or further from your desired effect. I guess if all your concerned with is copying AS values then that would work but won't tell you what the trends for the rest of the system. AS is one characteristic and probably not really all that important, imho.
so your saying horizontal separation of links has nothing to do with the stability.. if thats the case i'd think everyones lowers would me mounted right next to each other chassis side and uppers right next to each other on the axle side..
 

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I have a new design project going. I have read this thread a few times now and seed some more info.

This vehicle is going to be an all around thing. Front mounted engine, 12" travel shocks, 6up/6down, 40" tires, etc. Front suspension is a 3-link + panhard as illustrated in the following screen captures....

Static ride height.



I tried to attain some rearward 'wheel recession' from ride height. Nice flat control arms helped that. This chassis sits pretty dang low overall for 40s with about 18-19" at ride height. Front axle roll axis is tuned for slight understeer. Anti-Dive was tuned to be fairly neutral at close to 50% ( I had to start somewhere?). That should be able to be tuned with a few additional frame side upper mounting points.....going up or down is pretty possible.

This chassis will be running a conventional steering box, so I am stuck with a panhard I think. I can't really see any way to raise the roll center without going WAY into a negative roll axis. The roll center is only about 13" away from the spring CoG ( which is a pretty big guess at this point with the CAD models )

Now for the fun stuff.......what the heck happens when things start moving around??!?!??!

Here is the suspension at full bump. I didn't go through the headache of keeping the link length constant just yet. I just dropped everything to full bump. I hope the calculator, in the 3-link version, can automate this. With the arms being approx 30" long I didn't see the need to get that precise yet.



So....

-The roll axis goes WAY negative....just about 10 degrees. So as the suspension compresses it is going to ??????. My guess would be that it is going to understeer much more. The axle is going to almost anti-steer right? At full bump and trying to corner it is going to take a lot more steering input right?

-anti-dive goes NEGATIVE? Basically this means that at static height approx 50% of the CoG brake transfer force is going into the springs/shocks. As it approaches full bump the spring/shock is going to see more and more of the transfer force due to braking. When it goes negative the suspension is basically going to see a small multiplication of that weight transfer braking force to the front suspension?

-I need someone to explain anti-lift to me more? And how having a negative number at full compression will affect things? My understanding is that the suspension might fight itself slightly when getting on the power at full bump....like adding rebound damping?

-Roll center. At static there is 12" between it and the roll center. At full bump this decreases to approx 10". The roll center basically drops below the axle tube I think? The panhard is envisioned to do this...it is forward mounted similar to the older Tri-County Gear design. This is basically a packaging consideration. The frame end of the track bar shouldn't be lower than the pumkin at full bump. Having a normal steering box is a total headache.

I guess most of my questions revolve around static and full bump....

Here is the suspension at full droop.....



-The roll axis slope goes positive to just over 6 degrees. I am worried that this will make the chassis a little twitchy when the tires are first contacting the ground? Roll oversteer I guess is the term?

-The roll center goes up, but the separation between the CoG and the roll center also goes to 14" approx from 12" at static height.

-Anti-Dive goes up to 93%. I am wondering how this will effect the suspension if I where to have to brake right as the vehicle is coming back onto the ground? Basically, I worry that the suspension might get a little 'stuck' at this point?

I am working on the rear suspension now, but wanted to get the questions flowing.....

Thanks for any help.
 
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