How's my numbers?

[arse_sidewards]

So not to derail the H3 thread anymore....

As you raise the axle side mount you start to make it a lever arm that pushes laterally on the track bar whenever the axle articulates. The taller that mount is the longer the lever and more push you get side to side. You will feel the body being pushed around. It is a similar feel, but different to having a lot of angle on the track bar itself. It reacts to different terrain than the track bar angle issue, but creates a similar feel.

So it sounds to me like if you need a high roll center more than you need it to feel good in the whoops that's the way to go.

What are the desert guys who run parallel 4-links running for separation between axle centerline and track bar mount and how much angle are they running?

I know historically some of those guys have run stupid low roll centers but I'm not sure what the current state of things is.

 

[06h3]

So not to derail the H3 thread anymore....


So it sounds to me like if you need a high roll center more than you need it to feel good in the whoops that's the way to go.

What are the desert guys who run parallel 4-links running for separation between axle centerline and track bar mount and how much angle are they running?

I know historically some of those guys have run stupid low roll centers but I'm not sure what the current state of things is.

Looking at 3 links with track bars in desert trucks I have seen them use super long frame side mounts, and axle side mounts in line with axle centerline. Then the opposite for Jesse Haines type cars. Both are extreme examples and probably most need to end up somewhere in between

 

[Ghetto Fab.]

So not to derail the H3 thread anymore....


So it sounds to me like if you need a high roll center more than you need it to feel good in the whoops that's the way to go.

What are the desert guys who run parallel 4-links running for separation between axle centerline and track bar mount and how much angle are they running?

I know historically some of those guys have run stupid low roll centers but I'm not sure what the current state of things is.

I don't know that I've seen anyone in the desert run a parallel 4 link or any trackbars. Its all triangulated or IFS of some kind.

Unless you want to get unreasonably extreme I don't think roll center height makes much difference. There are bigger gains to be had elsewhere. I think the high track bar heights on a lot of the early comp crawlers was a result of people thinking it made a big difference. Its hard to change after the fact and those guys wouldn't notice any of the downsides anyways. I think if you built the same exact car both ways, I doubt you'd notice much difference. Sure it might lean a tad bit more, but it isn't going to change the angle at which the vehicle rolls over, and you'd still push it that hard in a comp anyways. I don't keep up with everything, but I don't know that I've seen any newer comp based cars or any crawlers that are using those tall track bar heights anymore. Of course rock crawling is a very odd use case in the automotive world.

 

[Treefrog]

Yes, but not as much as a lot of people think. Generally the perfomance benefits that come from the stability of lower belly heights outweigh the drawbacks of a low belly. Most modern buggies with 42/43" tires are being built with sub-20" belly heights, which is lower than my Bronco II on 37" tires. Obviously, it is hard to stay very low with big tires on a full-bodied rig.

I thought it was still somewhat expected terrain based.

And if done improperly can exacerbate it. Kind of like the old advice about putting the upper 3rd link on the passenger side instead of the driverside on a front axle, but that also depend on the upper link angle.

The reason it is a big if.

True, but in a pure crawler application, you want all the roll center height you can get,

I think we will have to agree to disagree. I would be wary of jacking forces. Though 06h3 is probably correct in thinking of roll center as a percent of COG, at least for predicting perceived stability.

Sure it might lean a tad bit more, but it isn't going to change the angle at which the vehicle rolls over, and you'd still push it that hard in a comp anyways.

I agree with you on most people probably would not notice an 5% or 10% change. But a rig that leans more will roll sooner. Leaning shifts the COG toward the downhill side. It is the reason I put a disclaimer saying prediction only on the roll over values.

 

[06h3]

Where do you think the other gains are to be had? Ghetto Fab.

In the end is the issue more of my roll center height or just the angle that I am at ride height and have to deal with the axle swing? I can have a high or low roll center with the same angle so is the issue the roll center or more the angle?

 

['84 Bronco II]

I thought it was still somewhat expected terrain based.

The reason it is a big if.

I think we will have to agree to disagree. I would be wary of jacking forces. Though 06h3 is probably correct in thinking of roll center as a percent of COG, at least for predicting perceived stability.

I agree with you on most people probably would not notice an 5% or 10% change. But a rig that leans more will roll sooner. Leaning shifts the COG toward the downhill side. It is the reason I put a disclaimer saying prediction only on the roll over values.

Belly height is dependent on terrain, but the days of 2-3' belly heights being competitive are long gone for anything other than maybe mud.

My buggy which has a proven suspension design will be right around 95% anti roll front and rear according to the calculator.

Look at these pictures of 3-link cars since it is easy to estimate roll center height on a 3-link:

Scrapper looks like it has a rear roll center around 30" (39" tires, 17" wheels) and looks to be right in line with the sprung COG, so ~100% anti roll.

Pokey looks to also be around 30" (40" tire, 17" wheel). I is worth noting Jesse also raced Pokey at KOH and did fairly well considering the car was originally built to be a comp crawler. He did say it was pretty brutal riding though

Prickle is a little hard to tell in this picture since it is flexed out, but the axle end is well above the top of the wheel (40" tire, 17" wheel)

Current JHF Production Moon Buggy that has a roll center 32-33" (42" tire, 20" wheel) which is probably above 100% antiroll. Also notice how the upper link is centered like I mentioned earlier as well.

It would be interesting to see the numbers for the latest crop of 4-link cars. Tigger is the first car Jesse has run a 4-link front on since before Pokey. He said he is building something new to replace Tigger now, so it will be interesting to see what he does.

Obviously 06H3 isn't building a comp rig, but I don't think shooting for an anti roll of 60-80% is unreasonable for his build, especially if he wants to run without a swaybar. His build is definitely a lot more crawler than desert runner.

 

[Ghetto Fab.]

Where do you think the other gains are to be had? Ghetto Fab.

In the end is the issue more of my roll center height or just the angle that I am at ride height and have to deal with the axle swing? I can have a high or low roll center with the same angle so is the issue the roll center or more the angle?

Angle more than height. Your not going to be able to effect much change on a full bodied rig with height anyways. Get it to roll understeer so its stable to drive at speed and isn't all over the place, then tune out body roll with shocks and swaybars. Keep in mind this is just my preference from experience I've had.

 

[Renowest]

Hello,

I posted this on Race-Dezert and was advised this forum would be better for my questions. Here is a breif synopsis of what I am dealing with and what i would like to accomplish. I recently purchased a Class 8 race truck, it is three linked in the rear and A-arm in the front. It has the four link mounts and that is what I would like to convert it to. Currently the truck has zero squat on take-off and wants to try and lift the inside front tire any time it is turned and feels like it wants to roll the truck at higher speed. All I can think of is how the Gordon Stadium trucks behave.

After putting the numbers in the old calculator it looks like I have an extremly high Anti-squat for a desert race rig. My plan is to drop the front of the trailing arms down 4-5" to acheve a better link to bar parrallel and lower the anti-squat. Hopefully this will also eliminate the truck trying to drive the inside front up as well. I tried the new calculator, its more information than I understand. One issue I see is when lower the front of the link in the old calculator the plots go off the front of the chart it looks like.

Any help is greatly appriciated.

 

[Treefrog]

Hello,

I posted this on Race-Dezert and was advised this forum would be better for my questions. Here is a breif synopsis of what I am dealing with and what i would like to accomplish. I recently purchased a Class 8 race truck, it is three linked in the rear and A-arm in the front. It has the four link mounts and that is what I would like to convert it to. Currently the truck has zero squat on take-off and wants to try and lift the inside front tire any time it is turned and feels like it wants to roll the truck at higher speed. All I can think of is how the Gordon Stadium trucks behave.

After putting the numbers in the old calculator it looks like I have an extremly high Anti-squat for a desert race rig. My plan is to drop the front of the trailing arms down 4-5" to acheve a better link to bar parrallel and lower the anti-squat. Hopefully this will also eliminate the truck trying to drive the inside front up as well. I tried the new calculator, its more information than I understand. One issue I see is when lower the front of the link in the old calculator the plots go off the front of the chart it looks like.

Any help is greatly appriciated.

So for some reason the old calculator is not putting out the correct values for where things meet in space. I don't know why. This affects antis and roll stuff. Because that 98% and 28 inch roll center are wrong.

What do you mean by three linked? Three links and a panhard or triangulated with a wishbone upper?

Dropping the frame lowers that much puts them at risk of hitting the ground. How much travel do you have front and rear?

Do you have anti-roll bars front and/or rear?

I highly recommend using the new calc version it is the same information, just laid out different. You will need to change the drive bias to rwd. You can model the fronts antis by putting the frame mounts in with the travel set to 0.

 

[Renowest]

So for some reason the old calculator is not putting out the correct values for where things meet in space. I don't know why. This affects antis and roll stuff. Because that 98% and 28 inch roll center are wrong.

What do you mean by three linked? Three links and a panhard or triangulated with a wishbone upper?

Dropping the frame lowers that much puts them at risk of hitting the ground. How much travel do you have front and rear?

Do you have anti-roll bars front and/or rear?

I highly recommend using the new calc version it is the same information, just laid out different. You will need to change the drive bias to rwd. You can model the fronts antis by putting the frame mounts in with the travel set to 0.

Sorry I should have specified, it currently has a Wishbone upper link and am going to four link. Rear has an anti roll bar. Front ravel is right at 24" and rear is at 30". I will try and work through the new calculator some more. Thank you

 

[69 Landcruiser]

Hello, first time posting ,hardcore rock crawling California
5.7 vortec t400 5.0 atlas, fj40 front 30 spline rcv, dana 60 rear 35 spline chromo 4.56 gears ( shortened) full buggy build .112" wheel base
King 2.0 14" front 16" rears .. guessing on weight and axle weights for now . my placement seems like many buggys that work well.

goals=
1. no hopping
2. no body roll
3. climb ledges like a goat........
kinda set on axle mount locations/ and lower frame position

seems like upper frame side location is the key ?
trying to get it right from the beginning ( no adjustment in upper frame links) cut and re weld

i like the old calculator lot less numbers ,,,, this one just confuses me..... : (

thanks in advance
looking for proven experience not off the wall opinions... no offence....to anyone....

 

[chaplinfj60]

not sure where you upper frame mounts are but they can be put on out side the frame rail. i think yours maybe inside the frame rail just by the numbers. i have mine way out side and have i think 46 inches between and feel like i am pretty stable on side hills and such. but thats just my 2 cents.

 

[69 Landcruiser]

not sure where you upper frame mounts are but they can be put on out side the frame rail. i think yours maybe inside the frame rail just by the numbers. i have mine way out side and have i think 46 inches between and feel like i am pretty stable on side hills and such. but thats just my 2 cents.

i appreciate the comment , but doesn't explain what that would change (numbers wise / or what numbers are off?)
starting with 36"L frame rails 34" w.... numbers posted are , if i came off the frame- tube to motor mount/ bumper

but yes if needed i could mount on tube from frame to rock bar also

 

[69 Landcruiser]

i appreciate the comment , but doesn't explain what that would change (numbers wise / or what numbers are off?)
starting with 36"L frame rails 34" w.... numbers posted are , if i came off the frame- tube to motor mount/ bumper

but yes if needed i could mount on tube from frame to rock bar also

 

[chaplinfj60]

not mine but here is an idea of what i am saying

and this is his thread. way good read.

 

[chaplinfj60]

Dirt Squirrel 3.0 - The 2nd Mortgage

I figured i would start a build thread on the new buggy, mainly to ask questions to those with more experience, and to document parts, dimensions, thought process, etc. for the build. I just sold version 2.0 which was also a tube buggy, but built around a 79-83 first gen toyota Cab. It had 2x3...

irate4x4.com

 

[chaplinfj60]

i cant explain it why it works but wider is better, at least in my mind. and uppers out side the inner frame you gain room for exhaust and drive shafts. dont rush it.
i think i spend two weeks mind fucking myself the first time i did it. i just could not wrap my head around how to get it wider at the upper frame until i was told to go outside the frame rail. light went off. now this may not work every single time but it was just good for me

 

[69 Landcruiser]

not mine but here is an idea of what i am saying

and this is his thread. way good read.

ty , i think the difference is full width vs mine...and if it helps the numbers and still clears the tire,,, it is a possibility
ill look at his build when time allows ty

 

[Treefrog]

Hello, first time posting ,hardcore rock crawling California
5.7 vortec t400 5.0 atlas, fj40 front 30 spline rcv, dana 60 rear 35 spline chromo 4.56 gears ( shortened) full buggy build .112" wheel base
King 2.0 14" front 16" rears .. guessing on weight and axle weights for now . my placement seems like many buggys that work well.

Is rear steer in the picture?

goals=
1. no hopping

I'll address that one below.

2. no body roll

You will have some. Your choice if you counter it with geometry or an anti-roll bar. The torque roll portion can be avoided. Only way to completely avoid torque roll is independent suspension. 3 link setups can do it at a certain ride height. 4 links as well, technically. But lots of math and weirdness to do that.

3. climb ledges like a goat........
kinda set on axle mount locations/ and lower frame position

X,Y, and Z? Or can Y be adjusted some?

seems like upper frame side location is the key ?
trying to get it right from the beginning ( no adjustment in upper frame links) cut and re weld

i like the old calculator lot less numbers ,,,, this one just confuses me..... : (

It should be the same info. As an FYI, highlight travel is the red x that moves along the plots. It's meant for looking at values along the curve travel point. You can set it to

thanks in advance
looking for proven experience not off the wall opinions... no offence....to anyone....

As far as the numbers go, looks pretty good. The front is getting a little close to the 40 degree limit for angle between links. I wouldn't be shocked if you get a little hop. The antis front and rear could cross the 100% line on steeper sections.

 

[69 Landcruiser]

Is rear steer in the picture?

I'll address that one below.

You will have some. Your choice if you counter it with geometry or an anti-roll bar. The torque roll portion can be avoided. Only way to completely avoid torque roll is independent suspension. 3 link setups can do it at a certain ride height. 4 links as well, technically. But lots of math and weirdness to do that.

X,Y, and Z? Or can Y be adjusted some?

It should be the same info. As an FYI, highlight travel is the red x that moves along the plots. It's meant for looking at values along the curve travel point. You can set it to

As far as the numbers go, looks pretty good. The front is getting a little close to the 40 degree limit for angle between links. I wouldn't be shocked if you get a little hop. The antis front and rear could cross the 100% line on steeper sections.

rear steer not in immediate future..... sway bar possible / but want geometry close as possible first ( front and rear suck down in the plan)

x,y,z

rear lower axle possibly wider (will have axle back this week hopefully )
rear upper axle +\- 2"

rear lower frame can go wider
rear upper can go wider

front upper axle can go narrower a few 2"?
front lower axle not much play (tires)
front upper frame can go wider
front lower not much play ( driveline)

hard for me to under stand what the numbers affect (bare with me )
point me in direction and ill change and repost ...

ty

 

[69 Landcruiser]

Also uppers frame side f/r can put wherever... can shorten to help anti but trying keep driveline decent

 

[Treefrog]

rear steer not in immediate future..... sway bar possible / but want geometry close as possible first ( front and rear suck down in the plan)

x,y,z

rear lower axle possibly wider (will have axle back this week hopefully )
rear upper axle +\- 2"

rear lower frame can go wider
rear upper can go wider

front upper axle can go narrower a few 2"?
front lower axle not much play (tires)
front upper frame can go wider
front lower not much play ( driveline)

hard for me to under stand what the numbers affect (bare with me )
point me in direction and ill change and repost ...

ty

My initial guess is to move the rear upper frame up or forward slightly to move the IC farther forward to help keep anti's in check. Up front, upper frame back or up for the same reason, with preference for up.

 

[69 Landcruiser]

My initial guess is to move the rear upper frame up or forward slightly to move the IC farther forward to help keep anti's in check. Up front, upper frame back or up for the same reason, with preference for up.

well fn brain hurts..... lifted the uppers frame side / didn't lower anti much.....( trying keep level or down..like most i see.)

this posted is with upper shorter / seems to level anti out,,,,, pinion seems fine but it seems most buggy's have longer uppers now a days/

appreciate the feed back.... opinion on this vs the first 1 i posted......

if original is better for what i want to do with it let me know.... ill get the rear in and dbl check my measuments again....

building from scratch so......things can move a lil


really appreciate everyone's time.....

ty

 

[Treefrog]

well fn brain hurts..... lifted the uppers frame side / didn't lower anti much.....( trying keep level or down..like most i see.)

this posted is with upper shorter / seems to level anti out,,,,, pinion seems fine but it seems most buggy's have longer uppers now a days/

appreciate the feed back.... opinion on this vs the first 1 i posted......

if original is better for what i want to do with it let me know.... ill get the rear in and dbl check my measuments again....

building from scratch so......things can move a lil


really appreciate everyone's time.....

ty

Looks like it should be slightly better than the first one posted.

I should clarify my earlier post. The ride values were in a good range. The adjustments and small shifts were to tune the full extension. Ideally you don't want the anti's to cross the % bias, it is where hop tends to occur. In the updated one, that line is only crossed at full front extension. A slight tweak to get it under 60% will help prevent hop. However, 60.4% is close enough that you should be fine.

Since it seems that you are building a crawler that won't see much high speed, I've been somewhat ignoring the roll axis slopes. A quick glance shows that all 3 are near zero, so it shouldn't be too much of a handful. The info you should be looking at when considering body roll is circled below. The shorter the distance from the CG to roll axis, the less it will roll.

 

[69 Landcruiser]

Looks like it should be slightly better than the first one posted.

I should clarify my earlier post. The ride values were in a good range. The adjustments and small shifts were to tune the full extension. Ideally you don't want the anti's to cross the % bias, it is where hop tends to occur. In the updated one, that line is only crossed at full front extension. A slight tweak to get it under 60% will help prevent hop. However, 60.4% is close enough that you should be fine.

Since it seems that you are building a crawler that won't see much high speed, I've been somewhat ignoring the roll axis slopes. A quick glance shows that all 3 are near zero, so it shouldn't be too much of a handful. The info you should be looking at when considering body roll is circled below. The shorter the distance from the CG to roll axis, the less it will roll.

Awesome that is the info and direction I needed, I felt close ....just needed some confidence...

I appreciate the response....
When I get my parts.... I'll post one more time ..... before burning them in...

Ty

 

[67StingrayJ]

I downloaded the 6.10v of the 4BarLink calculator. When I open it, my work disables the macros. Could that be why I'm getting all these #NAME? cells everywhere?

 

[Treefrog]

I downloaded the 6.10v of the 4BarLink calculator. When I open it, my work disables the macros. Could that be why I'm getting all these #NAME? cells everywhere?

Yes.

 

[cwwlcx]

First time posting here, looking for 2nd set of eyes on my numbers. Working on a front 5-link conversion for my radius arm Ram 2500. Goal is a do it all rig: towing, hauling, road trips/overlanding, serious wheeling (mostly rock crawling in Colorado/Moab/Sand Hollow, not much high speed, other than washboard dirt roads). I think my numbers are pretty good, but I've been told I need more anti-dive, not sure if that's old thinking or not. The frame side mounts use the existing radius arm bracket for the lower, and an existing frame hole for the upper, so I'd prefer not to move them. I don't have a lot of room to raise the axle-side upper, unless I move the shocks, or go to coilovers. I can lower the lower axle mount, but I'd rather keep the links as flat as I can. Do I need to increase link separation at the axle (currently 7.5")? Any other major concerns? Thanks for the help, this tool is amazing.

Note: CG Height, Brake Bias, Unsprung Mass are guesstimates

 

[Treefrog]

First time posting here, looking for 2nd set of eyes on my numbers. Working on a front 5-link conversion for my radius arm Ram 2500. Goal is a do it all rig: towing, hauling, road trips/overlanding, serious wheeling (mostly rock crawling in Colorado/Moab/Sand Hollow, not much high speed, other than washboard dirt roads). I think my numbers are pretty good, but I've been told I need more anti-dive, not sure if that's old thinking or not. The frame side mounts use the existing radius arm bracket for the lower, and an existing frame hole for the upper, so I'd prefer not to move them. I don't have a lot of room to raise the axle-side upper, unless I move the shocks, or go to coilovers. I can lower the lower axle mount, but I'd rather keep the links as flat as I can. Do I need to increase link separation at the axle (currently 7.5")? Any other major concerns? Thanks for the help, this tool is amazing.

Note: CG Height, Brake Bias, Unsprung Mass are guesstimates

Low anti dive in the front helps keep the vehicle from loading the suspension during braking. This keeps the suspension more free. So when you get on the brakes when in rough terrain, it is not as rough of a ride. Flip side, the vehicle pitches more. I think your anti dive is fine.

With the size of the rig, you need more spacing. And some heavy duty bracketry.

For a do it all rig, I would recommend having understeer in the front. I would recommend moving the lower axles up so that they are flat or drop as they go to the rear.

Try to have the panhard the same length and angle as the steering link.

 

[cwwlcx]

Low anti dive in the front helps keep the vehicle from loading the suspension during braking. This keeps the suspension more free. So when you get on the brakes when in rough terrain, it is not as rough of a ride. Flip side, the vehicle pitches more. I think your anti dive is fine.

With the size of the rig, you need more spacing. And some heavy duty bracketry.

For a do it all rig, I would recommend having understeer in the front. I would recommend moving the lower axles up so that they are flat or drop as they go to the rear.

Try to have the panhard the same length and angle as the steering link.

Thanks! I can raise the lowers, but that further reduces the link spacing, unless you meant lateral spacing?. Of note: the radius arm mounts are only 6.5" apart, I would think a radius arm would put more stress on the mounts than a 4-link, but maybe I'm missing something. Yes, I'm making sure the panhard and drag link match...is the drag link in the tool somewhere that I missed?