4-Link Analyzing Program: Request for Help

[JESSE_at_TLT]

There are a few guys on Priate4x4.com that have been developing a program to analyze 4-link suspension designs and they're requesting some help/feedback. I think this link has been cross-posted before, but I thought some of you guys might have some good/helpful information to contribute.

Click Here (http://www.pirate4x4.com/forum/showthread.php?t=204893)

[ntsqd]

Should be noted that the reason they're asking for input is that there is a new version out. They're not just on PoOR, they're also on cK5.com and OFN.

[JESSE_at_TLT]

That's why I posted it, but forgot to mention it. Have you played with it? Any thoughts?

[ntsqd]

Not the latest version. Downloaded it, but haven't had time to crack it open.
Here's the link: ExcelCAD 3.0 (http://home.earthlink.net/~triaged/Files/4BarLinkV2.1.zip )

[FABRICATOR]

Didn't we look at this before? As I recall...the squat was highly questionable.

[mattrick8888]

ok i have been playing with this program for fun and using the stock frame measurements from my truck it is hard to keep the antisquat % under 100, the roll axis in the negitive, and the instant center close to the front of the truck, all at the same time. getting 2 of the 3 is fairly easy. so does anyone have any input as to which of those variables is the most important to try and acheive? what happens when the roll axis in the positive? what happens when the instant center is way out in front of the truck? here are some numbers i got.

Geometry Summary:
Anti-Squat 31.393 %
Roll Axis Slope -0.0171 in/in (Roll Understeer)
Roll Center Height 27.233 in
Roll Axis Angle -0.978 degrees (Roll Understeer)
Instant Center X-Axis 529.765 in
Instant Center Z-Axis 38.412 in

this is mostly just me being curious more than anything.

[Josh_K]

As a side note to all this link stuff, Rob Park, "Tin Bender" on Pirate 4x4 now works in my race shop as my lead fab guy and we were discussing how some people try to make comparisons between crawlers and off road trucks today. He and I feel that they have about as much in common as a 1/2 pick up and a Kenworth.

If you are trying to use crawler parameters to build a race truck, you are going to be really misled.

Josh

[ntsqd]

Designs will be similar, design tools can be the same, design goals are different.

Somewhere in the middle are the street driven trucks.

Percent Anti-Squat makes no sense to me. Define 100% AS, then tell me what 50% means and what 150% means.

[Brian_99]

Percent Anti-Squat makes no sense to me. Define 100% AS, then tell me what 50% means and what 150% means.

According to what they've said, I believe 100% means you have 100% resistance to squat. Zero lift, Zero Squat. Over 100% means the suspension lifts and under 100% offers some resistance to squat. Basically a system with 75% resists squat more than one with 25%. Hopefully this makes sense.

Like Matt I've been playing with this a bit too, combined with Lower Links 101 I've been able to figure out a bit about geometry of link systems, etc. It's a cool little program to mess around with.

[GOAT1]

As a side note to all this link stuff, Rob Park, "Tin Bender" on Pirate 4x4 now works in my race shop as my lead fab guy and we were discussing how some people try to make comparisons between crawlers and off road trucks today. He and I feel that they have about as much in common as a 1/2 pick up and a Kenworth.

If you are trying to use crawler parameters to build a race truck, you are going to be really misled.

Josh

Rock Crawlers and off road race cars are totally different. This program doesnt give you any magical answers of how to build your link suspension, it is just a tool to analyse the characteristics the suspension will have (before you build it) and to compare different configurations. You can take your stand back, tilt your head and squint aproach to link suspension design, and define the caracteriscs of what works for you, so you can apply it to a different chassis configuration.

ntsq: 100% anti means that all the weight transfer is carried by the suspension links and none to the springs, so the suspension will not deflect when accelerating or braking. 0% anti means all the weight transfer is carried by the springs and the suspension will deflect proportion to the wheel rate. More than 100%, suspenion will lift, less than 100%, suspension will squat.

[FABRICATOR]

The “percent of anti-squat” calculations could work for a particular make and model of vehicle. However, changes to traction or dynamic weight bias will cause the calculation to be off. In other words, anti-squat is not completely determined by the rear suspension pivot points.

[silverstateracer]

The “percent of anti-squat” calculations could work for a particular make and model of vehicle. However, changes to traction or dynamic weight bias will cause the calculation to be off. In other words, anti-squat is not completely determined by the rear suspension pivot points.


Don't you figure for anti-squat at a given point of travel? I was under the impression that you have different percentages at different points throughout travel. I would like to learn more if this is incorrect.

[ntsqd]

Don't you figure for anti-squat at a given point of travel? I was under the impression that you have different percentages at different points throughout travel. I would like to learn more if this is incorrect.

Linkage geometry at any particular point in travel determines the Instant Center. The IC's relationship to a particular bent line on a diagram of the suspension determines the %AS. So if you could capture where the suspension is at a given point while in motion you could determine the AS for that moment. The external varibles that Fabricator pointed out would all be wrapped into this, including a dislocation of the bent line since it is dependent on the CG's location. The trouble is that you'd need some sort of D/A system looking at, say, damper shaft positions to accurately figure it out.

What I don't get is the translation of the IC's location into a percentage number.

[FABRICATOR]

Re: "Don't you figure for anti-squat at a given point of travel? I was under the impression that you have different percentages at different points throughout travel. I would like to learn more if this is incorrect."



BINGO!! That and other parameters. Everything about a pavement car centers around a predetermined ride height. Every effort is made to maintain and recover to that height. Dezert racing tosses that out the window. As I have said about a zillion times, ride height is determined by the terrain and the vehicle’s reaction to it and is constantly changing.

[mattrick8888]

ok i have been playing with this program for fun and using the stock frame measurements from my truck it is hard to keep the antisquat % under 100, the roll axis in the negitive, and the instant center close to the front of the truck, all at the same time. getting 2 of the 3 is fairly easy. so does anyone have any input as to which of those variables is the most important to try and acheive? what happens when the roll axis in the positive? what happens when the instant center is way out in front of the truck? here are some numbers i got.

Geometry Summary:
Anti-Squat 31.393 %
Roll Axis Slope -0.0171 in/in (Roll Understeer)
Roll Center Height 27.233 in
Roll Axis Angle -0.978 degrees (Roll Understeer)
Instant Center X-Axis 529.765 in
Instant Center Z-Axis 38.412 in

this is mostly just me being curious more than anything.

anyone have any opinions? i know this will vary from fabricator to fabricator.

[dadunc205x]

i didn't notice anywhere anything about change in pinion angle. it seems that could easily be figured into the program. It could give you #'s at bump and droop based off of your pinion angle at ride height. im not sure if the axle type would determine this as well.

driveshaft plunge would also be helpful, but i guess that would mean adding points for the d-shaft as well. i would think they could just have it as a 5th link that comes off of the diff. and have the x & z at both ends.

[mattrick8888]

driveshaft plunge would also be helpful, but i guess that would mean adding points for the d-shaft as well. i would think they could just have it as a 5th link that comes off of the diff. and have the x & z at both ends.

i was thinking the exact same thing.

[ntsqd]

Perhaps, for the sake of clarity, we ought to say "static ride height" as opposed to simply "ride height"? It does change with regard to the terrain.

[Rocker]

I second that idea about the driveshaft plunge on that program, would have helped me realize the problem I am having right now :)

[ntsqd]

It could be done. It would require yet another set of X,Y,Z, coords be input though.

I got less than 1/4" of plunge and less than 1/4* varience in UJ angle in the 3 UJ driveshaft using an iterative solve method in AutoCAD. So it can be done other ways. UJ angle was the customer's criteria, not mine.

[FABRICATOR]

Re: "ntsq: 100% anti means that all the weight transfer is carried by the suspension links and none to the springs, so the suspension will not deflect when accelerating or braking. 0% anti means all the weight transfer is carried by the springs and the suspension will deflect proportion to the wheel rate. More than 100%, suspenion will lift, less than 100%, suspension will squat."

All, none, all, lift? Hmmmm.....I think we are getting some pavement confusion in here again.

[Josh_K]

Well I guess I am bored sitting here reading all this on my lunch and I can’t help my self form pointing out one more thing about a good linked rear end setup,

Evan thou no one asked this question, I will expunge wisdom. Listen up!

A while back when this was a hot issue some people where trying to make the connection between pinion angel change thru the suspension cycle and traction. Some people have the idea that traction is an important factor to factor in. I remember some one even talking about how nitro dragsters design flex into a chassis to give the same result, and it is true it, it does.

My point is that for months I have been thinking of these poor miss guided people that haven’t realized a linked rear-end on an off-road race truck has nothing to do with a pavement application. If you are one of the people that think this way, picture a dirt bike. How does a bike get up a large gnarly hill climb? Wheel spin! A trophy truck, truggy, class 8 or 7 is the same way. If you put that average 250cc bike on a slight upslope, like a soft 15 deg. up sloping dune if would totally dig in. But, carry some speed and spin the rear wheel and you can go up a 45 deg. dune.

A race truck is the same way. If you want traction spin the wheels!

Over the last 6 months I have told the people on this board everything I know and I will shut-up and never speak of these topics again. I am going into seclusion.

Josh

[FABRICATOR]

Comparing wheel spin to traction is like comparing taxes to income...

[ntsqd]

An old dunes driver once told me that a machine's ability to make it up a dune is directly related to it's ability to pump it's weight in sand down the hill.

With spinning tires you're no long talking about traction, you're talking about maintaininng or even increasing some level of Inertia. At this point the tire becomes something very similar to a propellor. A propellor doesn't have traction on anything. The resistance a vehicle has in moving is less than the resistance the propellor encounters in trying to spin.

[FABRICATOR]

From P’4x4…
“Crap. . . I was going back over all of the travel calculations and noticed I forgot something. I kept the frame fixed and moved the rear axle. However I forgot to move the ground plane with the tire. Now for a strange question:

Should I move the front axle as well (4 wheel bump/droop)? That would change the CG (which now changes with axle movement) which would also change the AS value...

So should I only move the rear axle and keep the front axle and the frame fixed
OR
Move the ground plane, front, & rear axle up while keeping the frame at the same position?”

**********************
IMHO, speed is a big variable to the spread sheet, pavement knowledge, or any other attempt to standardize things. As speed increases so do the dynamics. Changes occur throughout the speed spectrum. There is a difference even between crawling and 4-wheeling. Then there are higher speeds such as cruising, pre-running, and racing.

As speeds increase, design priorities move away from the nuances of handling and toward essential vehicle stability. Roll centers are not nearly as important as roll velocities. Front and rear weight transfer can exceed 100% of vehicle weight even on smooth level ground, and even in dirt. Forces are referenced by vehicle attitude and relationship to the ground instead of ride height and tire slip. In other words, more like trajectory than driving. At speed, traction is a factor of nothing more than tires and how good the suspension works. Weight transfer, traction, and squat, are all one. Speed, especially off-road, affects every aspect of design and setup.

[DPpatrol]

Chuck,

How does weight transfer exceed 100% of the total vehicle weight?

jason

[ntsqd]

Inertia, not a long term effect.

[FABRICATOR]

This is not about inertia. A top off-road racing machine will power wheelie or come close to it. That means nearly 100% of vehicle weight on the rear wheels. Add some acceleration and it can go over 100%. Because of their ability to transfer weight, dirt bikes and some TT's can also exceed 100% of vehicle weight on the front while stopping.

The point is that more time is spent accelerating than decelerating or cruising. Extreme weight transfer and the corresponding changes to vehicle attitude can be present a majority of the time and should not be ignored.

[ntsqd]

Any non-static movement of weight about a vehicle can be defined as being the result of Inertia. You're talking about the dynamic loading of one or more tires. That's Inertia.

[FABRICATOR]

Inertia, not a long term effect.
Any non-static movement of weight about a vehicle can be defined as being the result of Inertia. You're talking about the dynamic loading of one or more tires. That's Inertia.


Thom, do you have any idea of what a wheelie is, where they come from, or even what it feels like? Here's a hint; it does not come from wheel spin.

[DPpatrol]

Unless you are talking about Inertial forces, you are not going to get more than 100% weight transfer. If you are in a wheelie, front tire in the air, all weight on the rear tire, then you accelerate, how can you transfer any more weight to the rear tire? Where would the weight come from? If the front tire is in the air it sure isn't coming from the front of the truck/car/dirt bike. Now if their is dive in the body associated with the acceleration, which there is, then there will be inertial forces at the tires to react the diving acceleration of the body/chassis. Once the chassis settles, the intertial loading at the tires is gone. This is why Thom said it is not a long term effect.

jason

[ChuckH]

My theory

The added weight/force ( over 100% ) would come from acceleration, like when a bike is doing a power wheelie with the front wheel 6 inches off the ground, with the bike not moving the amount of force that it would take to hold the front wheel 6 inches off the ground should approximate the force thats added above 100%, if a bike has a 60-40 weight ratio doing a power wheelie would make the rear wheel have 140% weight.

If a TT gets above 100% rear weight it would have to come from acceleration, of course thats not counting G forces from bumps.

[FABRICATOR]

This has somehow split into two directions. It was never said that weight transfer exceeded 100% for a sustained period, only that it does exceed 100% at times, and from forces other than bumps. The other is that substantial weight transfer, of 80-90% or more, can be present for hugely sustained amounts of time. This is what makes ride height, squat, and the formula, completely subjective.

[DPpatrol]

ChuckH,

If a bike is doing a power wheelie with the front end 6 inches in the air and not moving, where is the acceleration? Short answer there is none.

Also you have to ask your self what is holding the front end of the bike in the air. The bike is doing a wheelie with the front tire 6 inches off the ground because the sum of the torque reactions about the rear axle (sproket torque, wheel torque, and torque do to the weight of the front of the bike) all add up to zero or are in static equilibrium with the wheel 6 inches of the ground. If the sum of the torques does not equal zero, the bike will rotate about the rear axle. But the point of all this is, these torques do not increase the weight on the rear tire any more than the static weight of the bike regardless of their sum.

Don't believe me? Take bar, a tube, something kinda long but thats not cumbersome to rotate. Hold the end of the bar with the bar level. Now rotate the bar up wheelie style. Did the bar feel heavier when you did this? It won't.

If you rotate the bar fast enough, you may feel some inertial forces weighing down the bar. However you will only feel these for a split second as they only exist during the time the bar is being accelerated. Once the bar reaches a steady speed, which is quite quickly unless you are superman, these inertial forces go away. Hence like Thom said, not a long term effect. In fact I know of no vehicle dyanamics engineer who takes the inertial loads of the diving or wheelieing acceleration into account when calculating wheel loads. The load just does not exist long enough to make a difference from the vehicle dyanmicist's point of view. Now a stress analysis may care about these inertial loads, if they were large enough.

You are right that if a bike has a 60-40 weight distribution you add 60% of the weight to the rear tire to get the rear tire load during a wheelie. However you add 60% to 40% to give you 100%.

jason

[Josh_K]

To all of you...

BLAA,BLAAA,BLAAAA,BLAAAAA

I truly don’t think any of you even know it how these "forces" apply to a good working four link and if they are important issues to factor into a design.

I will make a bet. I bet the first truly good four-link design didn’t have any time wasted on it worrying about these issues.

IMHP,
Josh

[steveG]

LOL, I like it when Josh posts.

[ChuckH]

ChuckH,

If a bike is doing a power wheelie with the front end 6 inches in the air and not moving, where is the acceleration? Short answer there is none.

jason
er forward acceleration , like when your twisting the grip ;)

It takes acceleration ( from the rotation of the rear wheel) of the motorcycle to counter the weight of the front of the bike and hold it in the air, sure if you hold a power whellie at 6in there is no "rotation acceleration" ( that your stuck on)

Short answer there is acceleration:p

[matt_helton]

keepin it real.....

[ChuckH]

To all of you...

I will make a bet. I bet the first truly good four-link design didn’t have any time wasted on it worrying about these issues.

IMHP,
Josh
I bet your right, with 30 in of travel in the dirt there's not to much to worry about once your in the ballpark, shock tuning matters much more at that point

[FABRICATOR]

Is it really much different than a helicopter? Say a helicopter weighs 5,000 pounds and has 4,500 pounds of tension (hanging) on the rotor shaft while hovering. When the traction is changed by blade pitch (instead of weight transfer) and more torque is applied, there is now 5,500 pounds of tension on the rotor shaft as the craft rises. If it is powerful enough to accelerate, there could easily be 7,500 pounds of tension on the rotor shaft for sustained periods. Similar to before (but considering the craft must fly and blade speed is constant) thrust, blade pitch, and available torque, are inseparable.

It does matter because it radically changes the attitude of the vehicle for extended periods. Why do you think the disco pre-runners have the front end raised even when they are not moving? lol

[DPpatrol]

ChuckH,
When you said the bike was not moving, I assumed no acceleration. If there is acceleration present, it can cause an inertial force at the center of gravity which creates a torque about the rear axle. This torque wants to make the bike wheelie. I believe this is what you are saying?

The issue is the direction of the acceleration. When you twist the grip, you accelerate forward. The wheel loads are perpendicular to the forward acceleration. Acceleration only creates interial forces in the direction of the acceleration. Since the wheel load is 90 degrees to the forward acceleration, you get no more or less wheel load from acceleration than from weight transfer unless the direction of the acceleration is in the direction of the wheel load, i.e. vertical. If poppin wheelies put more load on the rear wheel than the weight of the vehicle, you'd see F1 cars wheeling down the straights.

This relates to the helicopter brought up. The hellocopter is different from a car/truck/dirtbike because when a hellocopter accelerates upward, the acceleration is in the direction of the prop shatf, so there is inertial loading in the prop shaft, or the load in the prop shaft accelerates the hellocopter up. This load is analogous to the frictional force between the tire and the ground. When a truck/dirt bike/car accelerates forward, the frictional force, like the prop shaft, must increase according to the inertia force associated with the vehicles acceleration.

jason

[ChuckH]

F1 cars use wings and shaping under the car to get down force that is far beyond the weight of the car, Cart and F1 get more down force at speed than the car weighs.

When i said not moving i was referring to weighing the front wheel holding it 6 inch's of the ground, that should be the amont of weight that acceleration is making ( when you do a power wheelie with the front wheel at the same height)

Example in this fine pic i made ;) that was a joke :)

Ok say the bike weighs 200lbs, and you used a counter weight to hold the front wheel off the ground ( that is how acceleration is working in this case ) so you would have the weight of the bike ( 200lbs) plus the weight of the counter weight ( about 80 lbs if its at the same distance from the rear axle as the front wheel) for a total force on the rear wheel of 280lbs.

Every Action has an Equal and Opposite Reaction, This is the third of Sir Issac Newton's laws.

[FABRICATOR]

ChuckH,
The issue is the direction of the acceleration. When you twist the grip, you accelerate forward. The wheel loads are perpendicular to the forward acceleration. Acceleration only creates interial forces in the direction of the acceleration. Since the wheel load is 90 degrees to the forward acceleration, you get no more or less wheel load from acceleration than from weight transfer unless the direction of the acceleration is in the direction of the wheel load, i.e. vertical. If poppin wheelies put more load on the rear wheel than the weight of the vehicle, you'd see F1 cars wheeling down the straights.

This relates to the helicopter brought up. The hellocopter is different from a car/truck/dirtbike because when a hellocopter accelerates upward, the acceleration is in the direction of the prop shatf, so there is inertial loading in the prop shaft, or the load in the prop shaft accelerates the hellocopter up. This load is analogous to the frictional force between the tire and the ground. When a truck/dirt bike/car accelerates forward, the frictional force, like the prop shaft, must increase according to the inertia force associated with the vehicles acceleration.

jason

IMHO, this is not quite accurate. Axle loads must also be considered. The axle loads do not stay perpendicular to the ground. Loads are only straight down or perpendicular while the load (vehicle) is coasting or not moving. You could not accelerate on a unicycle without tilting it's mass forward at the same time. If the axle in question is providing the acceleration or deceleration, the loading angle can deviate significantly from perpendicular. The only reason F1 cars do not wheelie is because they have little front to rear weight transfer in comparrison to an off-road race vehicle. They would simply spin the wheels if they were to try. They also skid the front tires while braking on a routine basis. The helicopter analogy was addressing only steady vertical pull on the prop shaft, not inertia. It should be valid as would be a ski boat or other similar things that are not bolted down. Well established proof of weight transfer and acceleration exceeding 100% of vehicle weight (1G) can be found in cornering acceleration. It is not uncommon for some pavement cars to achieve nearly 1.5 G’s while cornering. Traction in the dirt can often meet or exceed traction on pavement.

[DPpatrol]

Alright, I thought it was obvious F1 cars doing wheelies was a joke... I guess not.

ChuckH
Good application of Newtons 3rd law, however which one of his laws explains the weight hanging of the ass of the dirt bike? I suggest reviewing Newton's 1st law, a statics book, a dynamics book, a good vehicle dynamics, then reviewing my previous posts because you do not understand the mechanism holding a bike in a wheelie. I promise you the forces holding a dirt bike in a wheelie do not increase the wheel loads beyond 100% of vehicle weight.

Fabricator,
OK axle loads. If a car is moving forward we got 3 loads on an axle, vertical load from the weight, forward driving load trying to bend the axle backwards, and torque. You are right, the resulatant of these axle loads will not be perpendicular to the ground, however the vehicle weight component will always be perpendicular to the ground, and the driving load will always be parallel to the path of travel, aka the ground. The only axle load which contributes to wheel load is the vertical one from the vehicular weight, and last time I checked vehicular weight can not exeed 100% vehicular weight (except if there is vertical acceleration, then we get inertial forces aka D'Alembert forces).

About the unicycle, you lean forward to counter the torque caused by the inertial acceleration force which wants to flip you onto your back. Leaning forward does not increase wheel load. The acceleration does not increase wheel load.

For the heliocopter prop shaft, loads only increase if the hellocopter is accelerating vertically. If the hellicopter is moving up vertically with a steady pull, no acceleration and constant velocity, the load in the shaft is just the weight of the hellicopter. Don't believe me? Pick up a good heavy book. Now lift it up at a constant speed. Does it fell heavier?

Cars corner at 1.5g for two reasons. 1) Race tires are amazing pieces of rubber. It is not uncommon for them to have coefficient of friction of 1.5 on asphalt. That mean you put 100 lb vertical load on it, you get 150 lb of corning force, i.e. corning at 1.5g with only 1g vertical loads on the tire. 2) Race cars usually have aerodynamic dynamics downforce which increases the wheel/tire loads huge amounts. This translates into high g turning, braking, and acceleration. 1.5g turning has nothing weight transfer exceeding 100% of vehicle weight.

Traction in the dirt can often meet or exceed traction on pavement.

Are you joking? This makes me think you are just messing with me. If you are just trying to get a response from me and realize the ridiculousnous of what you are saying, then well played.

jason

[ChuckH]

About the unicycle, you lean forward to counter the torque caused by the inertial acceleration force which wants to flip you onto your back. Leaning forward does not increase wheel load. The acceleration does not increase wheel load.

jason

Leaning foward and accelerating does increass the wheel load, from the G force of acceleration, equal and opposite reaction, imagine if you had super strong legs ;) and do the 1/4 mile at 300 mph on a unicycle ( drag racers have 4-5 G's doing that ) just were would that equal and opposite force go ? ...yep straight into the wheel.

At this point i think we should agree to disagree :) plus this thread has been totally hijacked :rolleyes:

[DPpatrol]

The acceleration forces, if that is what we want to call them, are not in the verticle direction, they are in the horizontal direction so how can there be an equal and opposite reaction 90 degreees to the direction of the force, i.e. the direction of wheel loads? The equal and opposite reaction is from the friction force at the tire, equal in magnitude to the accel force, and in opposite direction (horizontal with 180 degree flip).

The one thing you are right about is we totally highjacked this thread. I don't even remember what the thread is about or how this conversation started. So I guess I better just shut up.

jason

[FABRICATOR]

No joke. The forces are not all 90 degrees and perpendicular form the axle up.
On the unicycle, leaning forward is not just to counteract torque. If the cycle was rocket powered or being towed, with either of those forces applied at the axle centerline, you would still have to lean forward while accelerating. That lean must be counteracted from somewhere. The force being used to hold you and the cycle at an angle is being counteracted and is being applied to the ground. More acceleration is more tilt and more force downward to the axle. Obviously there are differences between torque/balance and thrust/balance, but the results are similar. How much and where mass is placed also has an affect on downward force. The end :=)

[BA_DirtDriver]

Jason, think a little more about traction in dirt exceeding pavement. The post didn't say always it just said it can. Remember what is causing traction- contact patch. Now think about the various textures of off-road surface , not just a hard pack dirt road. I think that you might change your mind.

Remember everyone's opinion is worthless if you dismiss it or except it on face.


IMFSO


Bret

[Stephen]

The cool thing about dirt is that we're sometimes working IN the surface, not always ON the surface like asphalt. It's somewhat like watercraft or snowmobiles, especially in sand, silt or mud. I think that's where high cornering forces can happen, where a tire is actually dug into the surface and the sidewalls are supplying part of your cornering resistance.

Back to the subject.....
Antisquat can help add traction by increasing the load on the contact patch by taking the inertial loads from acceleration acting on the CG of the truck and forcing those inertial loads to the tire through the suspension linkage instead of squatting the suspension and rotating the CG around the rear axle. This is where you can actually jack up the back of the vehicle under acceleration. This is how antisquat works. It drives the body away from the axle.

The problem is that forcing the axle away from the vehicle stiffens the suspension and raises the ride height and the forces that make that happen depend on the traction surface which can change suddenly upsetting the process and making an unpredictable vehicle.

This matters in some situations, evidence would be suspensions with multiple mounting points on short course trucks, dirt track stock cars or even rock crawlers. These guys thing tuning this one aspect of the suspension is important enough to spend time fabbing parts to adjust and test this feature. In desert racing, other factors are apparently more important than max traction on acceleration or there would be more adjustment in the most successful vehicles. We need the ability to keep the tires planted on rough, variable surfaces without upsetting the chassis. Anti-squat numbers should be low.

How this applies to the program in question? Some people like to be able to analyze before they build and try, this is the basis of the engineering profession. The program is a tool for that. If you don't want to use it, don't.

A useful addition to this post (or any post about this program) would be some measurements or output results of a real vehicle or vehicles that have been raced enough to prove that they work.