Inelastic weight transfer

[JT A.]

I'm trying to stop thinking of roll centers from the kinematic perspective and start looking at them from the force based approach (looking at elastic vs inelastic weight transfer, jacking effects, etc). First I'd like to summarize my understanding so far, so please correct me if I am wrong on any of these concepts.

I am assuming that your total amount of inelastic weight transfer is determined by the roll axis and CG height. Basically drawing a line straight down from the CG, and finding the height where it intersects the roll axis. Say this height is 1.5", and your cg is 11", then 13.6% of your weight transfer is inelastic (1.5/11 = .136). The other 86.4% is elastic, transferred through the spring/ARB system, and the F/R distribution of the elastic weight transfer is determined by your LLTD or "magic number". Likewise, the inelastic weight transfer is distributed based on the roll center (or FAP) at the front and rear. If the front RC height is 1", and rear is 2", then 33% of the inelastic weight transfer happens at the front and 66% happens at the rear.

After reading an old thread about jacking forces, my understanding is that first of all, jacking forces are a transient effect and are separate from inelastic weight transfer (which remains present even after the car reaches some steady-state cornering force). They are calculated by finding the lateral force generated at each tire, drawing that force along the n-line (line from contact patch to IC of that wheel), then finding the vertical component of that vector. With IC's above ground, the outside tire creates an upward jacking force, the inside tire creates a downward jacking force, but since the outside tire is generating much more grip it "overpowers" the downward jacking from the inside resulting in a net upward jacking force.

So with that out of the way (and hopefully I haven't butchered those concepts too badly), I'll get on with the discussion. It seems to me, the most logical design approach in deciding force based RC heights is to evaluate these three parameters- total amount of elastic weight transfer, F/R distribution of elastic weight transfer, and jacking forces. If there is something else important that I am ignoring please let me know, but for these three parameters my thoughts are:

Total amount of inelastic weight transfer- The big deal about this is that it happens almost instantly, leading me to think that more inelastic WT would make the car quicker in response. However, when a tire sees an instant increase in load, it do not produce an instant increase in lateral grip. I have read it takes around 1/2 to 2/3 revolutions of the tire before it reacts to a change in load. So maybe large amounts of inelastic weight transfer are wasted because the tires cannot respond that fast. When trying to quantitatively optimize inelastic weight transfer, all I can come up with is "the more gradual the better", which means no inelastic WT, essentially putting roll centers on the ground. Anybody have first hand experience comparing roll center heights back to back and seeing if there is an increase in responsiveness? Is there a threshold of too responsive and difficult to drive?

Distribution of inelastic weight transfer- Logic says to make it the same as the distribution of your elastic weight transfer. Unless I'm missing something, I don't see any reason to make it different.

Jacking forces - From all I can tell, they are bad, but they are also pretty small for "normal" roll center heights, and figuring out some way to make them benefit you would take more time in analysis than it is worth. There is also the possibility of putting the force based roll centers below ground to result in anti-jacking forces, but brings me back to the question of responsiveness (would the car really be too sluggish, or is that idea just outdated kinematic RC theory that keeps getting printed without any reasoning or explanation?). This would again lean towards putting the roll centers on the ground.

Well for now I'll shut up and see what you all think. Thanks for any input you can provide

[JT A.]

I'm trying to stop thinking of roll centers from the kinematic perspective and start looking at them from the force based approach (looking at elastic vs inelastic weight transfer, jacking effects, etc). First I'd like to summarize my understanding so far, so please correct me if I am wrong on any of these concepts.

I am assuming that your total amount of inelastic weight transfer is determined by the roll axis and CG height. Basically drawing a line straight down from the CG, and finding the height where it intersects the roll axis. Say this height is 1.5", and your cg is 11", then 13.6% of your weight transfer is inelastic (1.5/11 = .136). The other 86.4% is elastic, transferred through the spring/ARB system, and the F/R distribution of the elastic weight transfer is determined by your LLTD or "magic number". Likewise, the inelastic weight transfer is distributed based on the roll center (or FAP) at the front and rear. If the front RC height is 1", and rear is 2", then 33% of the inelastic weight transfer happens at the front and 66% happens at the rear.

After reading an old thread about jacking forces, my understanding is that first of all, jacking forces are a transient effect and are separate from inelastic weight transfer (which remains present even after the car reaches some steady-state cornering force). They are calculated by finding the lateral force generated at each tire, drawing that force along the n-line (line from contact patch to IC of that wheel), then finding the vertical component of that vector. With IC's above ground, the outside tire creates an upward jacking force, the inside tire creates a downward jacking force, but since the outside tire is generating much more grip it "overpowers" the downward jacking from the inside resulting in a net upward jacking force.

So with that out of the way (and hopefully I haven't butchered those concepts too badly), I'll get on with the discussion. It seems to me, the most logical design approach in deciding force based RC heights is to evaluate these three parameters- total amount of elastic weight transfer, F/R distribution of elastic weight transfer, and jacking forces. If there is something else important that I am ignoring please let me know, but for these three parameters my thoughts are:

Total amount of inelastic weight transfer- The big deal about this is that it happens almost instantly, leading me to think that more inelastic WT would make the car quicker in response. However, when a tire sees an instant increase in load, it do not produce an instant increase in lateral grip. I have read it takes around 1/2 to 2/3 revolutions of the tire before it reacts to a change in load. So maybe large amounts of inelastic weight transfer are wasted because the tires cannot respond that fast. When trying to quantitatively optimize inelastic weight transfer, all I can come up with is "the more gradual the better", which means no inelastic WT, essentially putting roll centers on the ground. Anybody have first hand experience comparing roll center heights back to back and seeing if there is an increase in responsiveness? Is there a threshold of too responsive and difficult to drive?

Distribution of inelastic weight transfer- Logic says to make it the same as the distribution of your elastic weight transfer. Unless I'm missing something, I don't see any reason to make it different.

Jacking forces - From all I can tell, they are bad, but they are also pretty small for "normal" roll center heights, and figuring out some way to make them benefit you would take more time in analysis than it is worth. There is also the possibility of putting the force based roll centers below ground to result in anti-jacking forces, but brings me back to the question of responsiveness (would the car really be too sluggish, or is that idea just outdated kinematic RC theory that keeps getting printed without any reasoning or explanation?). This would again lean towards putting the roll centers on the ground.

Well for now I'll shut up and see what you all think. Thanks for any input you can provide

[J. Vinella]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JT A.:
I have read it takes around 1/2 to 2/3 revolutions of the tire before it reacts to a change in load. </div></BLOCKQUOTE>

Good, most people do not understand that.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">There is also the possibility of putting the force based roll centers below ground to result in anti-jacking forces, but brings me back to the question of responsiveness (would the car really be too sluggish, or is that idea just outdated kinematic RC theory that keeps getting printed without any reasoning or explanation?). </div></BLOCKQUOTE>

Kinematicly (new word), yes, but do the force vectors make sense?

[BillCobb]

Try to stick with the notion that force based roll mechanics is favored because the distortion in tire sidewalls, suspension and frame elements alters the geometric solution predictions. It becomes unified if the suspensions are side-to-side symmetric and frame/body is stiff with low compliance attachments and steering system. But, add the compliance and the asymmetry and it can't be ignored under high side loads. As they usually say: "stiff and long are Man's best attributes". The rest is just process...

[JT A.]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by J. Vinella:
Kinematicly (new word), yes, but do the force vectors make sense? </div></BLOCKQUOTE>

I just sketched out a hypothetical situation with IC's below ground and the force vectors did indicate downward jacking. Did I do something wrong, or is this the answer you were expecting?

Also thanks for your reply BillCobb, your point is one of the reasons we are abandoning the kinematic RC method of analyzing suspension. The other being the "invalid moment arm" created when kinematic RC's migrate away from the centerline of the vehicle. I believe valid moment arm from the FAP is important in selecting antiroll stiffness. Our previous solution was to spend hours tweaking geometry to keep kinematic the kinematic RC from migrating, but it seems like force-based rollcenters are a more practical and realistic way of understanding what is going on.

[cmeissen]

One thing to keep in mind is that the inelastic weight transfer, and consequently the jacking force, is a function of the tire lateral force, as well as the IC locations. The lateral force on the inside tires are much less, because it is unloaded, and thus the inelastic load transfer and jacking forces are less for that side of the vehicle.

Assymmetric tire forces create asymmetric weight transfer and asymmetric elastic/inelastic ratios.

[JT A.]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by cmeissen:
One thing to keep in mind is that the inelastic weight transfer, and consequently the jacking force, is a function of the tire lateral force, as well as the IC locations. The lateral force on the inside tires are much less, because it is unloaded, and thus the inelastic load transfer and jacking forces are less for that side of the vehicle.

Assymmetric tire forces create asymmetric weight transfer and asymmetric elastic/inelastic ratios. </div></BLOCKQUOTE>

I think I follow you in regards to asymmetric forces. I am calculating jacking using the lateral force of each tire, reacted to that tires IC, which seems to be the correct way according to what you are saying.

Where I lose you is when you seem to refer to each wheel having separate inelastic weight transfers. I think of weight transfer involving both wheels equally and simultaneously, ie one wheel loses 50 pounds, the other wheel gains 50 pounds.

[flavorPacket]

Ah, but the vehicle is not only an axle, JT A. If you use a force based convention, it's vital to look at the sprung mass as a rigid body that responds to forces in the same way that all rigid bodies do. Thus each force vector needs to be reacted into the rigid body. This will include both front and rear axles. To put it another way, caster isn't the only thing that puts weight on the rear tires...

[flavorPacket]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JT A.:
Distribution of inelastic weight transfer- Logic says to make it the same as the distribution of your elastic weight transfer. Unless I'm missing something, I don't see any reason to make it different. </div></BLOCKQUOTE>

The car needs to do 2 things to get around a corner: 1) rotate and 2) translate. Given the difference in speed of weight transfer between inelastic and elastic kinds, one can influence how fast each of these things occurs.The same rationale can be applied to having different low speed damping ratios.

[JT A.]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by flavorPacket:
Ah, but the vehicle is not only an axle, JT A. If you use a force based convention, it's vital to look at the sprung mass as a rigid body that responds to forces in the same way that all rigid bodies do. Thus each force vector needs to be reacted into the rigid body. This will include both front and rear axles. To put it another way, caster isn't the only thing that puts weight on the rear tires... </div></BLOCKQUOTE>

So to get the full picture of geometric weight transfer, I would need to draw the force vector from each tire patch to its IC, and break it into its horizontal and vertical components. Next, translate all of those force vector components to the CG of the sprung mass as forces and moments, Combine them all into a net force vector and moment at the CG, then solve for the vertical reaction forces at the contact patches like a statics problem. Correct?

The accuracy of these calculations obviously depends on how accurately you can approximate the lateral force of each tire. A tire model and some kind of iterative solver that also takes into account your elastic WT properties? Or is there a better/easier way?

I am particularly interested in being able to calculate the actual lift of the chassis due to jacking, because beside the obvious detrimental effects of raising the CG, we are a heavy aero-influenced car and the front wing is sensitive to height changes. When I translate all the force vectors to the CG and combine them into a net force and moment, is the jacking force simply the vertical component of that net vector?

[exFSAE]

1) Jacking forces and inelastic weight transfer are no different in my mind.

2) Net axle jacking (or anti-jacking) forces are not inherently bad. For that matter, bump-steer isn't bad either. Just another knob you can turn. There are times when such forces can be quite beneficial.

[flavorPacket]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JT A.:
So to get the full picture of geometric weight transfer, I would need to draw the force vector from each tire patch to its IC, and break it into its horizontal and vertical components. Next, translate all of those force vector components to the CG of the sprung mass as forces and moments, Combine them all into a net force vector and moment at the CG, then solve for the vertical reaction forces at the contact patches like a statics problem. Correct? </div></BLOCKQUOTE>

Don't forget the longitudinal component. The car drives in 3D.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JT A.:
The accuracy of these calculations obviously depends on how accurately you can approximate the lateral force of each tire. A tire model and some kind of iterative solver that also takes into account your elastic WT properties? Or is there a better/easier way?

I am particularly interested in being able to calculate the actual lift of the chassis due to jacking, because beside the obvious detrimental effects of raising the CG, we are a heavy aero-influenced car and the front wing is sensitive to height changes. When I translate all the force vectors to the CG and combine them into a net force and moment, is the jacking force simply the vertical component of that net vector? </div></BLOCKQUOTE>

Before you worry about implementing this kind of sim, ask yourself what you're really modeling: How much jacking force do you have? Is it really worth it to build this sort of thing to model 10lbs?

[Price]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by exFSAE:
1) Jacking forces and inelastic weight transfer are no different in my mind.
</div></BLOCKQUOTE>

This was always how I thought of jacking forces and inelastic weight transfer. However, I have only ever looked at kinematic analysis. I am not sure if they have a different effect when doing a forced based analysis.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JT A.:
jacking forces are a transient effect and are separate from inelastic weight transfer (which remains present even after the car reaches some steady-state cornering force)
</div></BLOCKQUOTE>

I am still fairly inexperienced with suspension, but I always thought that jacking/inelastic weight transfer were an instantly occurring result of the side load on the tire/car, and not a function of a change in the side load.

http://fsae.com/groupee_common/emoticons/icon_confused.gif

[exFSAE]

No different.

In any event, when you have some side load on the tires you have a jacking force on the left, and on the right. You can transpose these to be at one point under the CG, in which case you have a net force and net moment.

That net force is indeed only transient. It will make the sprung mass pop up or squat down (likely a trivial amount on a FSAE car to be honest), at which point you are left only with the moment - the instant load transfer that's been there all along.

[Buckingham]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Where I lose you is when you seem to refer to each wheel having separate inelastic weight transfers. I think of weight transfer involving both wheels equally and simultaneously, ie one wheel loses 50 pounds, the other wheel gains 50 pounds. </div></BLOCKQUOTE>

Jacking isn't actually side-to-side weight transfer. It is the transfer of vertical load between the suspension system (spring/bar/shock) and the kinematic system (a-arms, tie-rods, etc) due to lateral load acting on the kinematics.

Jacking doesn't change the vertical load at the contact patch. It is an internally resolved force that changes the amount of vertical load that the suspension system (springs,bars,shocks) thinks is at the contact patch.

Example: You have 200 lbs Fz at the contact patch. If you have 20 lbs of down jacking, Fz at the contact patch is still 200 lbs, but the suspension will compress to the same deflection that it would if there were 220 lbs Fz and 0 lbs jacking.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> That net force is indeed only transient. </div></BLOCKQUOTE> I believe the net force isn't transient, but internally resolved. Jacking can raise or lower the attitude of the vehicle in the steady state (agreed usually a trivial amount). Transient loads are possible as the sprung mass has to accelerate to the new attitude and decelerate as it reaches the new attitude, but the jacking load itself is a as steady state as the lateral load.

[cmeissen]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JT A.:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by cmeissen:
One thing to keep in mind is that the inelastic weight transfer, and consequently the jacking force, is a function of the tire lateral force, as well as the IC locations. The lateral force on the inside tires are much less, because it is unloaded, and thus the inelastic load transfer and jacking forces are less for that side of the vehicle.

Assymmetric tire forces create asymmetric weight transfer and asymmetric elastic/inelastic ratios. </div></BLOCKQUOTE>

I think I follow you in regards to asymmetric forces. I am calculating jacking using the lateral force of each tire, reacted to that tires IC, which seems to be the correct way according to what you are saying.

Where I lose you is when you seem to refer to each wheel having separate inelastic weight transfers. I think of weight transfer involving both wheels equally and simultaneously, ie one wheel loses 50 pounds, the other wheel gains 50 pounds. </div></BLOCKQUOTE>

First if we look at just an individual axle acting independent of the rear suspension(equivalently we could look at the whole car with zero roll stiffness on one axle), the total load transfer on each wheel will be equal but opposite in magnitude:

Total Load Transfer = FL elastic + FL inelastic = FR elastic + FR inelastic

However typically because the outside tire is generating a higher lateral force the inelastic load transfer on the outside tire will be much greater than that of the inside tire. Thus

FL elastic is not equal to FR elastic
Fl inelastic is not equal to FR inelastic

Extending this to four wheels there would also be diagonal load transfer since the front and rear axles are not independent, but are connected by a hopefully somewhat rigid chassis.

[exFSAE]

Think we're essentially in agreement, you probably said it better. The force is still there which is why the end effect is the sprung body displacing to some new position to resolve the force imbalance.

The imbalance itself, is transient condition.

[Pete Marsh]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Total Load Transfer = FL elastic + FL inelastic = FR elastic + FR inelastic

However typically because the outside tire is generating a higher lateral force the inelastic load transfer on the outside tire will be much greater than that of the inside tire. Thus

FL elastic is not equal to FR elastic
Fl inelastic is not equal to FR inelastic
</div></BLOCKQUOTE>

So jacking displacement is not trivial, and must not be ignored. If the inside spring is responsible for a greater proportion of the elastic transfer it MUST displace more than the outside spring = jacking. In steady state these forces and displacements need to resolve.

The importance of this is that your kinematic simulation does not account for this, so it's roll centre prediction, and hence jacking force, is way off.

This, I believe, is why SPMM roll centre, and roll stiffness results are consistently higher than predicted values. (even allowing for estimated/observed tyre deflection)

It's about time another good VD thread popped up.

Pete

[Buckingham]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">This, I believe, is why SPMM roll centre, and roll stiffness results are consistently higher than predicted values. (even allowing for estimated/observed tyre deflection) </div></BLOCKQUOTE>

One thing to be cautious about with SPMM testing is that jacking mode is different. With the chassis constrained on the test rig, jacking will cause a change in Fz at the contact patch and not a change in chassis attitude (changing Fz at the contact patch will also cause incorrect tire deflection).

Additionally, most SPMM testing is done with 4 clamps to the chassis, which can significantly increase the torsional rigidity of the chassis.

[exFSAE]

I'm not convinced the net axle jacking forces aren't trivial on these cars. Maybe displace the sprung mass somewhere on the order of a tenth of an inch? The stiffer the ride rate of the car (and seemingly teams love to have them way stiff for what platform control they need), the less movement you have.

Relative to everything else going on, for example outrageous compliance rates, I think it's a second order effect.

But, for the sake of completeness... also don't forget to include the tire's overturning moment in your load transfer calculations. In addition to any track width change from kinematics and compliances, there is a pneumatic component as well.

[Pete Marsh]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> One thing to be cautious about with SPMM testing is that jacking mode is different. With the chassis constrained on the test rig, jacking will cause a change in Fz at the contact patch and not a change in chassis attitude (changing Fz at the contact patch will also cause incorrect tire deflection). </div></BLOCKQUOTE>

Not the case with the machine we used, Fz was corrected for.

Pete

[Zac]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Buckingham:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">This, I believe, is why SPMM roll centre, and roll stiffness results are consistently higher than predicted values. (even allowing for estimated/observed tyre deflection) </div></BLOCKQUOTE>

One thing to be cautious about with SPMM testing is that jacking mode is different. With the chassis constrained on the test rig, jacking will cause a change in Fz at the contact patch and not a change in chassis attitude (changing Fz at the contact patch will also cause incorrect tire deflection).

Additionally, most SPMM testing is done with 4 clamps to the chassis, which can significantly increase the torsional rigidity of the chassis. </div></BLOCKQUOTE>

How significant of an effect is this though? My experience has been that jacking forces on a FSAE car are fairly low. You also have to keep in mind that since the tire isn't rolling, the tire's lateral stiffness will be artificially high anyway. You could also see as much as a 20% variation in lateral stiffness just due to the clock position of the tire (it depends on how the various splices line-up).

I also wouldn't worry about a significant increase in torsional chassis rigidity when testing FSAE vehicles on the SPMM. For starters you're looking at a single axle test due to the short wheel base which changes both how the load is input into and reacted by the chassis. There's also the question of how rigidly mounted the bracket is to the car. I've seen a range from noodles to girders.

The biggest thing with these cars is compliance. There is a very good correlation between rear toe compliance and lap time.

[ZAMR]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by flavorPacket:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JT A.:
Distribution of inelastic weight transfer- Logic says to make it the same as the distribution of your elastic weight transfer. Unless I'm missing something, I don't see any reason to make it different. </div></BLOCKQUOTE>

The car needs to do 2 things to get around a corner: 1) rotate and 2) translate. Given the difference in speed of weight transfer between inelastic and elastic kinds, one can influence how fast each of these things occurs.The same rationale can be applied to having different low speed damping ratios. </div></BLOCKQUOTE>

Think you hit the nail on the head here, along with your comment asking if it is worth it to include in a model a 10lb jacking force.

Everyone saying that jacking forces on an FSAE vehicle are too low to account for much of anything are probably right for most of the cars out there that, as a kinematics design goal, try to limit KRC migration and limit jacking forces. I don't see this as a wrong way to go about things (if there is such thing as a right way in vehicle design, I haven't heard it!), as long as you understand how this will effect your car and you know what you are doing with different damping ratios. Most FSAE cars probably implement this methodology for this reason. It certainly makes modeling things, and hence predicting a decent suspension setup, easier.

However, there are other cars out there, for example GFR, that I think (I don't know for sure, its just a guess based on how their car responds and a look at their shocks and kinnnys) make good use of inelastic/elastic weight transfer to achieve the same goal as different damping ratios. This would require an good vehicle model that incorporated jacking forces or inelastic weight transfer whatever you want to call it. So in this case, you are modeling more than 10lbs of jacking (not saying you are wrong flavorpacket, on the contrary, modeling jacking on a car with very low KRC's might not be worth it).

Stuff to think about if you ever want to have a good conversation with Billings... Mine went very poorly haha...

[flavorPacket]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ZAMR:

However, there are other cars out there, for example GFR, that I think (I don't know for sure, its just a guess based on how their car responds and a look at their shocks and kinnnys) make good use of inelastic/elastic weight transfer to achieve the same goal as different damping ratios. This would require an good vehicle model that incorporated jacking forces or inelastic weight transfer whatever you want to call it. So in this case, you are modeling more than 10lbs of jacking (not saying you are wrong flavorpacket, on the contrary, modeling jacking on a car with very low KRC's might not be worth it). </div></BLOCKQUOTE>

This is one of the fundamental differences between professionals and most students right here. Achieving this sort of behavior actually doesn't "require" any simulation. It requires the car to behave that way, which can happen as a result of development/tuning, or by blind luck. Far more cars have been made fast using these methods than with complicated simulations.