Bicycle model [Archive] - FSAE.com Forums

BillCobb

03-31-2016, 07:59 PM

So:
According to your data, if I were to assume that your tire properties are PER WHEEL, then you can easily compute this vehicle's oversteer and understeer traits without simulation at all.

I get -0.55 deg/g or -.0095 rad sec^2/m for condition 1, and 1.84 deg/g or .00327 rad sec^2/m for condition 2. No need for any 'simulation' here. It's just algebra-I

If your 'tire stiffnesses' are for each axle, then the results are pretty close to yours.

1) This is your first post, so please introduce yourself so we know about the audience we are replying to (Name, school, student year, degree being pursued, Team name, birthday, Mother's middle name, etc.) Otherwise you will receive scorn, insults, comedy, sarcasm and equally puzzling replies. And that's just from me !

2) Always show plots with all axes labeled with parameter names, units, a legend, maybe some gridlines, really cool colors, thick lines and the source of the data. You're using Matlab, use Matlab's features to explain your case and methods.

3) I take it your coefficients are not from the TTC data library. I've never seen so many zeros in a tire cornering stiffness!

4) Just out of curiosity, how would you propose to get such different Cf and Cr stiffnesses from tires that are operating at the same wheel loads ?

5) Try to keep values for your input design parameters in units of the trade (N/deg, deg/g, etc.) all those fractional bits are sleep inducing and awkward to type into my phone's calculator.

6) Ask you question(s) again with a goal in mind. Different "WHAT" for front and rear (Masses, lengths, tire stiffnesses, dimensions ) ?

Then we can help you in small, understandable steps. You certainly are brave to get this far !

BTW: Your "Vehicle" as described as 'understeering' has 90% lateral acceleration response times of about 0.33 sec. and a yaw damping value (zeta) of 0.823. Values even the most simple of simulations ought to compute from the parameters you have provided here.

MaiUnaGioia

04-01-2016, 09:57 AM

I would said you can try to set this following coeffiicents to zero: PHY1,PHY2,PHY3,PVY1,PVY2,PVY3,PVY4

If looking at the equation you see they will shift the curve up & down and left&right.

Thanks.

https://s5.postimg.org/sfgflgo87/comparison3.png

So:
According to your data, if I were to assume that your tire properties are PER WHEEL, then you can easily compute this vehicle's oversteer and understeer traits without simulation at all.

I get -0.55 deg/g or -.0095 rad sec^2/m for condition 1, and 1.84 deg/g or .00327 rad sec^2/m for condition 2. No need for any 'simulation' here. It's just algebra-I

I know that I can say if the vehicle is oversteering or understeering simply using understeer coefficient.
I would make some simulation to see vehicle response to arbitrary control and disturbance inputs.
For example I would use different inputs for steering (step, ramp, sine).

Then I would like to compare results from these simulations with the ones from a more complex model, for example an Adams model with more d.o.f.
Vehicle data I posted are generic, found it in a book.

These are vehicle parameters I'm using for simulation:

m = 315.5; % kg vehicle mass
a = 0.78; % m distance from front tire to C.G.
b = 0.83; % m distance from rear tire to C.G.
Ca0 = 27537.5; % N/rad front cornering stiffness (single tyre)
Cp0 = 27537.5; % N/rad front cornering stiffness (single tyre)
Iz=34.42; % kg*m^2 moment of inertia about z axis

If your 'tire stiffnesses' are for each axle, then the results are pretty close to yours.

I took the cornering stiffness from Ky_alpha formula and then I multiplied it for 2 so I have axle stiffness.

1) This is your first post, so please introduce yourself so we know about the audience we are replying to (Name, school, student year, degree being pursued, Team name, birthday, Mother's middle name, etc.) Otherwise you will receive scorn, insults, comedy, sarcasm and equally puzzling replies. And that's just from me !

I'm sorry. When I registered I didn't find a section for introducing myself.
I'm a student. I'm part of formula student electric team at Sapienza uni.

3) I take it your coefficients are not from the TTC data library. I've never seen so many zeros in a tire cornering stiffness!

I'm using old data from a report of Stackpole Engineering Services.
Data are relative to Avon 7.2/20-13.

4) Just out of curiosity, how would you propose to get such different Cf and Cr stiffnesses from tires that are operating at the same wheel loads ?
6) Ask you question(s) again with a goal in mind. Different "WHAT" for front and rear (Masses, lengths, tire stiffnesses, dimensions ) ?

I'm assuming the same load on every wheel since in the 2 d.o.f model there is no load trasfer. Indeed I'm using the same value for front and rear cornering stiffness.
I asked this question to find out if there was some other parameter to consider, in addition to the normal load on the wheels, that maybe I was forgetting.
Maybe the error is to consider the same load on every wheel.
According to vehicle parameters maybe it's better using 797,8 N (front single tyre normal load) and 749,7 (rear single tyre normal load).
Then use this different values for calculation of cornering stiffness.
I should get Cf=32496,9 N/rad and Cr=33137,5 N/rad

04-06-2016, 09:15 PM

These are vehicle parameters I'm using for simulation:

m = 315.5 kg vehicle mass
a = 0.78 m distance from front tire to C.G.
b = 0.83 m distance from rear tire to C.G.
...
Iz = 34.42 kg*m^2 moment of inertia about z axis
...
I'm part of formula student electric team at Sapienza uni.

MaiUnaGioia,

"Sapienza", eh?

The "University of Wisdom"???

Yet ... so many mistakes... :)
~o0o~

The Yaw-Inertia (Iz) number is quite important for these simple bicycle model simulations. You say your Iz = 34.42 kg.m^2, which implies you think you have accuracy of 4 significant digits?

By my reckoning, the lowest practical mass of a tyre/wheel/axle/upright "corner-assembly" in FS/FSAE is around 10 kgs (taken as a round number of only 1 significant digit). The distance of this mass (again taken for simplicity as a point-mass) from the whole car's CG is around 1 metre (ie. your a, b = ~ 0.8 m, together with half-track = 0.6 m, gives radius = 1.0 m, thanks to Pythagorean 3/4/5 triangle).

So, your Iz, for the FOUR CORNERS ONLY, is AT LEAST Iz = 4 x 10 kg x 1 m^2 = 40 kg.m^2.

(Gee, I hope you are NOT factoring in some of Claude's "negative masses", that he claims you get by using pushrods-and-rockers!?)

Anyway, your four-significant-digit number has NONE of its digits close to correct. In fact, the whole number is close to an order of magnitude wrong.

Not wise.

Wiser is to try to get your order of magnitude right first, then maybe try for an accurate first digit.
~~~o0o~~~

Some More Comments About Pacejka's "Magic Formula".
=========================================
Back around Xmas-2015-New-Year-2016, Bill Cobb posted some "Step-Steer" simulations on various other threads. These used a simple four-parameter Pacejka MF, similar to the OP's above, together with Matlab code to solve the Laplace transforms of the step-steer. Spurred by the results of these simulations I had a go at doing similar, but with a "time-stepping" Classical Mechanics approach.

And given how easy all the coding was, I got a lot of very interesting results! I might post some of those results on the appropriate threads at a later date. But right now I am busy with other things, and I would like to dress-up the outputs a bit more so they are easier to follow (ie. better labels on graphs, more graphs, +++, all of which takes time...).

Anyway, one result that quickly became obvious is that in some areas of tyre behaviour, the Pacejka Magic Formula (and anything similar) is completely WRONG!

And, no, I am not referring to the "divide by zero velocity" error that gets many mentions on the first page of Google hits on the subject. Nope, this is actually a much bigger error, although I have yet to see any mention of it. This error is actually very easy to fix in the simulation code. But, in order to fix it, you must first be aware of it. So it should be clearly spelled out on page-one of any discussion of PMFs. But, I guess, this is just another example of the education system going down the drain.

Anyway, gold star to the first student to point out this fatal flaw. (It is "fatal" because it completely messes up a good simulation ... at certain times.)

Hints: This is a BIG-PICTURE thing. Forget about all the little details ... like using four parameters, or four-significant-digits when you are not even close on the first one. I ended up with very realistic simulations (albeit only of "bicycle model" cars) using only two parameters to specify the shape of each of the F&R tyre curves. But I did have to add that bit of big-picture code to make it work realistically.

This "feature" of tyre curves SHOULD be obvious, and it should be spelled out whenever tyre curves are discussed...

Z

Tim.Wright

04-07-2016, 03:35 AM

For steady state stuff I've always found the pacejka 4 parameter model to represent experimental/simulation data extremely well.

I'd be interested to find out what you have 'discovered'.

04-07-2016, 07:39 AM

Tim,

Hints:
* Assume the car is a tad oversteery. Or a lot oversteery...
* What happens to such a car when given a large-ish step-steer while travelling at significant speed?
* Also assume the fussy old-fart likes to see a reasonably realistic trajectory of the car after the step-steer, all the way until it rolls to a stop (note that "slip-angle drag" quickly drains the kinetic energy of the car, and I am assuming a "coasting" car during the test, with no "driving" forces).
* Perhaps too big a hint. => Under what circumstances does a OS car become a US car?

But when you get the answer, can you wait a while to see if any of the students can figure it out...? :)

Z

BillCobb

04-07-2016, 09:48 AM

There are actually several flaws in the Pacejka theory of tires, but you must farhten before you can go fig Newton. Old Hans lets a good one fly and 3:36

https://www.youtube.com/watch?v=DNFzYEih72g

Danschwind

04-07-2016, 10:00 AM

"Perhaps too big a hint. => Under what circumstances does a OS car become a US car?"

When it hits the wall.

Tim.Wright

04-08-2016, 05:33 AM

If you are trying to point at a combined operating condition (with lateral and longitudinal inputs) then this is covered in the full Pacejka parameterisation.

It's not perfect, but I would label it a fundamental flaw.

Clint T

04-08-2016, 02:13 PM

If I had to guess at what Z is referring to, it sounds like he's referring to when the car completely spins around? That's certainly liable to happen when you give an oversteery car a big step input at high speed.

EDIT:
Ha, it appears Bill beat me to it, I failed to watch his video. Funny stuff

BillCobb

04-08-2016, 03:47 PM

What you should notice in videos like this is that the yawrate drops off very quickly while the longitudinal velocity drops more slowly AND the remaining steering gain is just about zero. So when you have an oversteering vehicle that is above its critical speed, (hence 'unstable', your ability to control it diminishes rapidly. This is one big reason why some drivers prefer an absurdly high gain (low ratio) steering system. They are trying to crawl back quite a few degrees of slip angle to save their azz using adaptive moment control.

But that's not a Pacejka formulation issue as much as a Mu-limit coherence practice.

While we're at it:
A two term exponential model of a tire with the possibility of a standby 3rd term for load sensitivity makes a great tire model. Yes, you might need 2 different coefficient sets for front and rear tires if a weight differential is present.

And
The Laplace type algebraic solver for transient response demonstration I posted has no 'tires' (neither linear or nonlinear), its just a linear stiffness mechanism being portrayed using vehicle relevant parameters.

Also, the "nonlin" ISO4138 Constant Radius Test simulation I posted IS a time stepper with goal seeking (as in get me in a fixed radius turn at the posted speed). There's just nonlinear Fy and Mz. There's NO chassis compliance, no roll or camber, no large angle approximations, no longitudinal force vectoring, etc. Its just a sled. I leave if for the Student to show the additional complexities (linear and nonlinear) that would make this model compete with a real test car.
And there's no tire relaxation here for either steered or plunged tires. It's a process 'stimulator' for newbees.

04-10-2016, 08:50 PM

If I had to guess at what Z is referring to, it sounds like he's referring to when the car completely spins around?

Clint,

Congratulations! This may be the dawn of a new age in FSAE...

Or, perhaps, because you are a first-posting newbie you have not yet learnt to confuse yourself with trivial details, and instead have simply taken a step back and seen the obvious? :)
~o0o~

For those of you who still don't quite get it, watch Bill's video link between 3:06 and 3:13.

https://www.youtube.com/watch?v=DNFzYEih72g

How would you simulate this manoeuvre? What values would you give for the car's F&R "Slip-Angles" and "Lateral-Fy-Forces" (assuming a coasting bicycle-model car, with no longitudinal-Fx-forces)? In particular, how would you model the car from 3:06 to 3:11, and then from 3:11 to 3:13?

I have had another look at google's suggestions for how to do this (well, first page of hits only). Unsurprisingly, the suggestions are many and varied, and often contradictory. In particular, a clear, precise, and useful DEFINITION of "slip-angle" is sorely lacking!
~o0o~

So ... what is the allowable range of slip-angles?

In much of the technical world, "angles" can range from minus infinity to plus infinity. For fairly obvious reasons, most functions of these angles are cyclic (eg. see sine or cosine functions). At the very least, any angle that is restricted to a small range has its range clearly stated (or it should have!).

Based on the google advice I have seen so far, it seems there are several options for the above simulation.

* Option 1. Assume Slip-Angles can take any value, and assume Pacejka-like formulae return reasonable values for Lateral-Fy-Forces at any given SA. This gives a reasonable simulation for time 3:06 to about 3:10, but after 3:11 the Fy-Force is completely unrealistic. PMF gives a highish Fy at SA = ~Pi (=~180 degrees), when it should be close to zero!

* Option 2. Restrict the valid range of Slip-Angles to between -Pi/2 and +Pi/2 radians (ie. +/-90 degrees), and then either,
2a, never let cars "go backwards", or
2b, when a car does go backwards, somehow swap the various coordinate reference frames around so "Front" becomes "Rear" (or similar nonsense).
I have a hunch that this is how it is mostly done, but I have yet to see this restriction of SA range (ie. to +/- 90 deg) EXPLICITLY stated.

* Option 3. Let Slip-Angles take any value between +/- infinity (which is handy if you want to keep track of the number of times your car spins), and then make the Lateral-Fy curve look like a squared-off sinewave. That is, have Fy positive from 0 to Pi, negative from Pi to 2*Pi, positive from 2*Pi to 3*Pi, and so on, and opposite with the negative angles.

This last option seems most sensible to me, because it is most similar to most other angle functions (eg. sine waves, etc.). But I have yet to see this sinewave-like behaviour shown on any of the web pages devoted to this stuff. (An easy way to do this is to take something like the standard Pacejka curve, clip its SA range to +/- Pi/2, then copy and flip it left-to-right at every multiple of Pi/2. Or use other sinewave-like methods...).

I think it would be better for the general education of VD students if this behaviour of tyre-lateral-forces was made more clear, more often, say by something as simple as frequent use of "big-picture" sketches of this sinewave-like behaviour.
~o0o~

BTW, if the car in above video has F/R-mass% and F/R-cornering-compliances (and thus static-margin, etc.) that makes it "oversteery" from 3:06 to 3:11, then what is its handling-balance from 3:11 to 3:13? My simulations show that extreme-OS cars are very stable when step-steered in reverse (edit: and extreme-US cars are very UN-stable in reverse). Obvious, really! :)

Z

Tim.Wright

04-10-2016, 10:46 PM

Erik, unless you have raw test data over 360deg then the performance of the Pacejka model in this range is academic.

PAC models are all shipped with a validity range stated in the model which is usually the maximum slip angle used in the testing process.

Ignoring for a second that very few simulations call for accuracy in the range of >90deg, there are more physical models (i.e. not curve fitters) available which will simulate these extreme condition but they are expensive and complicated to setup and run.

For FSAE, there's no reason why you need accuracy over more than about 10deg of slip. Everywhere else, unless you are tuning an ESC system on the snow, there no reason why you would ever need more than 90deg of slip angle validity.

Maybe I'm missing something but it all seems like a pretty pointless revelation to me...

DougMilliken

04-10-2016, 11:53 PM

... How would you simulate this manoeuvre? ...
Since you are looking at an accident, I'd work with someone familiar with accident reconstruction--horses for courses. For example, our good friends at: http://www.mchenrysoftware.com/
The first video is mostly simulations of cars/trucks crashing and tumbling, but there are a few good spinouts with cars sliding/rolling backwards too. Obviously they have a vehicle dynamics model that works at any combination of angles.
Ray McHenry started on HVOSM (highway-vehicle-object simulation modeling) in the 1960's at CAL (now Calspan) and among other things used the Spiral Jump development as a way to correlate his work.
As well as the history on their website, we've also put a section into the history chapter in RCVD, page 458.

04-12-2016, 09:37 PM

Maybe I'm missing something but it all seems like a pretty pointless revelation to me...

Tim,

I made it clear that THIS IS NO "REVELATION". This is from the department of the BLEEDING OBVIOUS!

But, like too many people who have spent ages studying something in minute detail, you, and seemingly the entire VD world, have lost sight of this bleeding obvious, and very real, fact. So you call it "academic"!!!

And then you add...

...very few simulations call for accuracy in the range of >90deg... which [are] extreme conditions ... expensive and complicated to setup and run.
For FSAE, there's no reason why you need accuracy over more than about 10deg of slip... [+++]

HUH!? Such comments are (rock-solid) support for my argument that engineers should never be allowed near computers.

Have you never heard of the video game industry? The $ turnover of just the "racecar" sector of this industry far exceeds that of the entire automotive VD world. Which is why, I am sure, the game-makers never employ engineers to write their software!

As I explained earlier, it is exceedingly simple to simulate (with sufficient accuracy) the full range of slip-angles between +/- infinity. And for obvious reasons (again!) any FSAEers who are NOT getting well above "10deg of slip" during testing ... may as well stay at home! Groaaannn...
~o0o~

Anyway, to repeat my main point.

The OP took considerable effort to calculate and type-out his "Iz" number to the fourth-significant-digit. But (!), if he instead took a step back and thought the whole problem through, then he should have seen that ALL of his digits were wrong. In fact, his whole number is an ORDER-OF-MAGNITUDE WRONG!

Similarly, the vast majority of you FS/FSAEers spend way too much time obsessing over trivial little details, like what the 57th-special-Pacejka-parameter is, when more than half of the Pacejka curve is completely, and obviously, wrong (eg. half of the curve gives a large +ve number when it should be large -ve, or vice versa...)! And it is the same with your cars.

Large parts of your cars, probably well over half of each car in terms of "design" effort put in, is worthless junk!

Stop wasting time on worthless complications.

Stop listening to the "experts" who want you to add evermore complications to those already over-complicated, and worthless, complications.

Instead, take a step back, and look at the BIG-PICTURE!

Z

Tim.Wright

04-13-2016, 12:44 AM

I'll repeat the critical part of my reply which you are either avoiding or it went straight over your head.

What use is a pacejka model (which is a curve fitter - not a physical model) which calculates forces over a range outside of which it was fitted (i.e. the test data)??

The model works quite well in the range of slip/fz measured on the bench. And I believe that after they changed the belt material after the first round of testing, that that range now includes the peak of the Fy-slip curve.

By the way...

Instead, take a step back, and look at the BIG-PICTURE!
I agree that big picture stuff is important but if you want to actually build a car - at some point you need to go down into the details. Something you've clearly never done in the auto industry.

DougMilliken

04-13-2016, 08:28 AM

{cut from an earlier post} I have had another look at google's suggestions for how to do this (well, first page of hits only). ...
Have you never heard of the video game industry? ...
Z -- it seems that Google isn't your friend in this case?
For an overview of early work (c. 1960), see RCVD pages 266 and on. Google finds the first referenced paper, Radt, H. S. and W. F. Milliken, Jr. "Motions of Skidding Automobiles." SAE paper #205. 1960. And if anyone is interested in re-creating a similar model, the paper includes definitions and the math, Google links to the SAE page, http://papers.sae.org/600133/

The video game industry is well aware of vehicle dynamics, although in the early days it was hidden as a competitive advantage. Atari built what is probably the first arcade game that used "real physics" for the car and was issued patents on several important features. Jed Margolin, the hardware/computer designer on the team, tells the story on his website, http://jmargolin.com/schem/schems.htm Down a page or two from the top he writes:
When we started Hard Drivin' we wanted it to be as accurate as possible. That meant doing an accurate car model to mathematically describe the physics of how the parts of the car (engine, transmission, springs, shock absorbers, tires, etc.) react to each other, to the road, and to the driver's inputs. There is more detail on Jed's site.

04-13-2016, 10:57 PM

What use is a pacejka model (which is a curve fitter - not a physical model) which calculates forces over a range outside of which it was fitted (i.e. the test data)??

Tim,

Yes! Or, to put it another way, "What use is a Pacejka model which calculates forces on a different surface to that which it was fitted (i.e. the test data taken from a sandpaper-covered steel-belt ... which runs indoors ... and which has given Peak-Mu values ~50% higher than real FS tracks)???"

I wholeheartedly agree with your above reasoning. Namely that "assumption of good accuracy" from the TTC data and its derived Pacejka curves, is SHEER MADNESS! :)

It makes much more sense, ENGINEERING-WISE, to:
1. Try to find ALL the potential inaccuracies in your data, such as the massive errors in fully half of the Pacejka lateral-Fy curve, and the large inaccuracies of Peak-Mu in both Fy and Fx curves (<- these Mu errors are track-dependent, so always there).
2. Do your best to eliminate the biggest errors, such as by reworking the Fy-curve as I suggested before, and adjusting the "Mu" as necessary.
3. Finally, proceed with a caution that is directly proportional to your best estimates of the remaining "unknowns".

The UN-WISEST thing to do in engineering is to ignore things like "errors", "inaccuracies", or "tolerances". For example, believing that because the computer printed it out to four-(eight?, twelve?)-significant-digits, then all those digits "...must be true..."! <- STUPID!!!

Oh, and I certainly will never have the lobotomy necessary for me to work "...in the auto industry".
~o0o~

Doug,

The Radt paper was written in 1960, so I doubt it uses the Pacejka Magic Formula. And, despite being 56 years old, that paper is still hidden behind a pay-wall, so I ain't buying it! Anyway, if it gives any sort of reasonable model of a skidding car, then I am sure it uses something similar to the method I used in my simulation. To repeat, this is an extremely simple thing to do.

Also, my guess is that for a video game to be successful in the marketplace, it MUST be able to model a spinning car. Code that "crashes" when car spins = bad. Code that keeps working when car "crashes" = good.
~~~o0o~~~

For Students Contemplating "Obsess the Details" vs "Look at Big-Picture".
================================================== =====
In the earlier linked video there are 13 different cars that "lose it" at the same corner as the car at 3:06+ (it is #8). All these cars start to spin as they crest a small hump in the middle of the left-hand bend (the hump is just seen at top of screen). Although this sort of problem was well known over 50 years ago, and the cure was well understood back then, Tim's "auto industry" is still pumping out millions of cars that cannot handle it.

The reason for such poor handling cars is, IMO, too much compartmentalised thinking, with no one looking at the big-picture. The approach is to have many different isolated departments, each of which obsesses about the little details in their area of responsibility, but with next to no overall communication between departments (Bill may disagree with this, but...). The whole process works something like this.

Ride Department: "Well, for a comfortable ride over those sorts of humps, taken on a straight road of course, because we only deal with straight roads, we have to set the F&R-ride-frequencies to give a somewhat bouncy pitch, but not too pitchy a bounce. So we need F&R spring stiffnesses of..."

Handling Department: "Well, (Edit->) ... first up, let's be clear that we're the Handl'n Dept so we don't do any bumps, humps, or any other such nonsense. Oh, no, no, no... we're just about FLAT CORNER'N!!! So, ... (<-end edit) for sufficient US through those sorts of corners, so the guv'mnt doesn't jump on us again, like last time with that Corvair-Cock-Up..., we need a Buggeroff Understeer Index of N%. So we need ARB stiffnesses of..."

Customer: "My car keeps spinning-out when I hit this small hump on this particular corner. Can you help?"

Whole Car Industry in Unison: "NO WAY! It is all your fault for being so STUPID as to drive around a corner with a hump in it!!!"

Yep, no point designing better cars when you can blame the stupid customer. Or the stupid road...

(And, yes Bill, that is a BMW at 3:06+. Quite a tank-slapper it gets up, too...)

Z

Mitchell

04-14-2016, 12:18 AM

like last time with that Corvair-Cock-Up..., we need a Buggeroff Understeer Index of N%. So we need ARB stiffnesses of..."

The Corvair wikipedia page has made my day.

Handling issues
The first-generation Corvair featured a rear swing axle design similar to that of the Renault Dauphine and Volkswagen Beetle – a design which eliminates universal joints at the wheels and wherein the rear wheels are always perpendicular to the driveshafts. The design can allow rear tires to undergo large camber angle changes during fast cornering, leading to oversteer—a dynamically unstable condition where a vehicle can lose control and spin — and in extreme cases produce lift-off oversteer. Oversteer in both cases is due to more weight on the rear wheels than the front. Inertia would then cause the rear tires to lose traction and "spin". Understeer is common in front-engine cars, due to more weight, and inertia, on the front tires. Both conditions are dangerous when a car is driven at its cornering limits.

Tim.Wright

04-14-2016, 08:44 AM

"What use is a Pacejka model which calculates forces on a different surface to that which it was fitted (i.e. the test data taken from a sandpaper-covered steel-belt ... which runs indoors ... and which has given Peak-Mu values ~50% higher than real FS tracks)???"

Leaving the purely academic case of the lateral force calculation at 90deg of slip, yes - still open is the inaccuracy of the overal friction coefficient which comes from both flattrac and drum testing - but this isn't the biggest limitation of Pacejka*.

I have to say that your claim of 50% percent inaccuracy of the friction isn't something I've ever come across. You wouldn't be exaggerating things to prova a point now would you? I've never had to change friction levels more than about 15% to account for different track surfaces.

Furthermore I see this also as a perfectly valid modification because different tracks have different friction levels. Using the scaling factors of the Pacejka model this is acheived in a relatively correct way (i.e. without changing the cornering stiffness which is largely a function of the carcass mechanical properties and not the friction level).

I also see global friction as a parameter of secondary importance in simulations for a number of reasons. Firstly, the limit of a vehicle's grip performance is always a stability limit on the part of the driver - not the grip limit of the tyres. So identifying the peak grip level on the front and the rear axles and then designing your car to operate there will just result in an uncontrollable vehicle (objectively and subjectively) because of the lack or rear cornering stiffness.

Secondly, if you are comparing different tyres from different suppliers tested on different machines it's obvious that peak friction isn't a valid thing to be looking at.

Thirdly, and most importantly, in my opinion, the role of a tyre model is not just to tell you what the tyre forces are at any point but more importantly your CORNERING STIFFNESS and how does it change in the range of operation of the vehicle (from zero latacc to the limit).

The cornering stiffness of the front and rear axle are your fundamental handling parameters which determing your balance, controlability and stability. This effectively normalises the problem as you are merely focussing on the evolution of your front and rear cornering stiffness from zero to the limit - whereby your cornering stiffness goes from some static value to zero. If that limit is 1.5 or 1.6g it won't change so much (save from some load transfer effects which for FSAE tyres are usually tiny).

So, in light of this we have a Pacejka model fitted to test data created more or less in the operating range of the tyres which I believe now includes the lateral force limit range. If the fitting is done well, you can have a reasonable confidence that your cornering stiffness' in normal operating conditions will be correct. If your cornering stiffness' are correct then the handling behaviour of the vehicle will be correct in the range from straight line until limit cornering.

So basically to answer your question quoted above - a PAC formulation can be used to give you a very good idea of the handling properties of the vehicle provided it was fitted to test data which is representative of the loadcase seen on the vehicle. This means pressure, rim width and the range of vertical loads, slip and camber angles. This remains valid even after any required friction scaling but as I've mentioned this isn't really necessary to do.

Thoughts?

----------------------------------------------------------------------------------

*The biggest limitation of the Pacejka model in its native form is the lack of a thermal model. Rubber creates grip through a number of hysteretic and viscoelastic machanisms and these are highly sensitive to both sliding velocity and temperature. The Pacejka model takes care of the sliding velocity explicitly in the slip calculations but the temperature effects are only there implicitly. I.e. there is no thermal model but the fact that during the test the tyres are heating up means there is some temperature effect inside albeit uncontrolled.

However, these temperature effects can be pretty well approximated by adding a thermal model to an existing Pacejka model because in the end the temperature is merely changing the shape of your force vs slip curves. There are already quite a few of these models (Pacejka + thermal) on the market today. So this main limitation can be addressed.

DougMilliken

04-14-2016, 01:16 PM

...The Radt paper was written in 1960, so I doubt it uses the Pacejka Magic Formula.
I've been providing various links because I think the history is interesting, same reason we included the history chapter in the middle of RCVD.
These things have been done before, in many cases written up, and SAE has done a good job to digitize older papers (which are often available to students for free).

Pacejka worked at CAL/Buffalo as a grad student in about 1962 -- where the Vehicle Dynamics department (including Radt) had been looking at tire data from their on-road test rig for about 10 years. Pacejka returned to U. Delft, Netherlands, first paper on magic formula tire modeling, with Bakker and Nyborg, was from (iirc) 1987.

BillCobb

04-14-2016, 03:07 PM

Surface and surface temp adjustment procedures have been around for quite a while, just not published a lot because its usually a State Secret. Here's some examples of stuff found on Hillary's server:

I'll have more, but the weather is nice, the dogs are panting to go hunting, and my windmills need oiling. Has anyone given any thoughts to the eye opening notion that Pacejka's Magic Formula isn't the only game in town ? Sorry to get off on a tangent (actually an arc-tangent).

Oops, the uploads failed. The old FSAE.COM space-limit noose. Go to the Toyota R&D site and search "Pacejka thermal". The Honda R&D site has a trove of Pacejka fixer uppers too.

Tim.Wright

04-14-2016, 03:48 PM

PAC + thermal models are becoming quite popular in F1 today because the teams are prohibited from running tyre bench tests (to characterise a physical model) and therefore have to make do with the Pacejka coefficients received from Pirelli and add their own or a commercial thermal model to it.

Ones that I know of currently are Tametire which is a closed Michelin format. CDTire MF++ is a slightly more open model which can be parameterised by a number of people. Dufournier have such a model but I can't remember the name. In Chassissim there is a thermal model which is not based on Pacejka but a similar curve fitting non-physical model.

The problem is always the parameterisation. This stuff is pretty hard to measure so normally what's done is that the model is given the same test inputs as what is given on the test bench and an optimiser varies the thermal parameters in the model over many iterations until simulated tread temp matches the measured one.

04-17-2016, 09:19 PM

Tim,

Not much time for this, so I'll try and be brief.

Leaving the purely academic case of...
I have to say that your claim of 50% percent inaccuracy of the friction isn't something I've ever come across. You wouldn't be exaggerating things to prova a point now would you? I've never had to change friction levels more than about 15% to account for different track surfaces.

You have got to be kidding. Or you should get out of your ivory tower more often...

A change in aggregate shape, either in concrete or bitumen roads, from "sharp-squarish" to "smooth-rounded" can itself make a 50% change. Not to mention a thin layer of dust, especially with a bit of moisture in it. By my reckoning the two biggest Mu-killers are pea-gravel and black-ice, both of which drop Mu to ~zero in a heartbeat.

But the most relevant factor here, for all those 13 cars spinning out on that video corner, is BUMPS. Harsh corrugations can drop "effective" Mu to almost zero. Especially so on stiffly-sprung cars, but less so on those with good suspensions. All 13 of those cars are "losing it" because of their crappy suspensions crossing a relatively mild "hump". BTW, I edited my last post at bottom page 2 to clarify the reason for those failures. Namely, most "Handling" engineers are incapable of handling bumps.
~o0o~

... the limit of a vehicle's grip performance is always a stability limit on the part of the driver - not the grip limit of the tyres.

Huh? Try that on pea-gravel. Or black-ice. Or harsh corrugations. Or any real roads. (Yes ... you will have to go far away from your ivory tower.)
~o0o~

... most importantly, in my opinion ... CORNERING STIFFNESS
...
The cornering stiffness of the front and rear axle are your fundamental handling parameters which determing your balance, controlability and stability.
...
If your cornering stiffness' are correct then the handling behaviour of the vehicle will be correct in the range from straight line until limit cornering.
...
PAC formulation can be used to give you a very good idea of the handling properties ... provided it was fitted to test data which is representative ... This means pressure, rim width and the range of vertical loads, slip and camber angles ... valid even after any required friction scaling.

Thoughts?

Above is more evidence that you are spending too much time in ivory towers, rather than out in the real world. Because:
1. "Cornering stiffness" is an in-house jargon buzz-phrase, which is DERIVED from the measured Forces and Motions. It is the Fs and Ms that are fundamental to the problem. Inventing a plethora of buzzwords (usually poorly, or never, defined) only serves to obscure those fundamental F&Ms. All this VD stuff is much easier to undersatnd when it is boiled down to Forces and Motions.

2. The factor which gives by far the greatest variation to the Fs and Ms is THE ROAD! Test every tyre on the planet by running them over an identical section of road, and the resulting Fs and Ms are all within an order of magnitude. Probably only a spread of about 2:1, maybe 3:1 at most. But test the same tyre on very different road surfaces and the Fs and Ms change by many orders of magnitude. Bleeding obvious!

And real road surfaces have the habit of changing metre by metre. Good-grip, then bump (so more-grip, then less-grip), then no-grip (pea-gravel, but only for a metre), then back to really-good-grip...
~~~o0o~~~

Students,

Say you have that dream VD job, and your boss says "Fix our cars so they stop having those bummer-moments like that Bimmer at 3:06 in the video...".

What do you do, in big-picture terms?

What is the cause of the problem, in big-picture terms? (Importantly, what is wrong with the car's design, given that your eccentric boss reckons "humps in the middle of corners" is perfectly acceptable, and is NOT the problem.)

What changes do you make to the car, in big-picture terms *?

Z

(* Ie. don't suggest "tweak the ARB rates", or other ivory-tower-handling-twaddle...)

BillCobb

04-17-2016, 10:52 PM

Alright, I've been around a while, have tire data from TIRF, GM's MTS, Smithers, GDY, MIC, BRI and now even SoVa-Motion, also to the Eden Prairie Flat-Trac Roadway Simulator, also to the Aberdeen MTS Roadway Simulator, tested tires on machines with blank steel, etched steel (matches the parking lot asphalt), new and old 3M-Mite: honed, talced and virgin. I've also collected tire and vehicle test data at ALL levels of maneuvering severity (including rollover), have data from Cup cars on MTS and Michigan Scientific test wheels at full cornering under full power on Black Lake at the Milford PG, also measured dozens of cars and trucks for Holden and Opel at Millbrooke and Pferdsfeld, and I have had the luxury of racing around the 'Ring in an OPEL KADETT MINIVAN WHILE RUNNING BMWs and Fords and two 'scooters out of the way. Oh yeah, I took a fleet to the U.P. in Michigan for traction control evaluation stuff on 'controlled' and 'uncontrolled' ice. (That would be temp and sunshine control for the naive). And just about all that data and information still lives on my HP laptop, including pictures and videos, some also on a so called FreeAgent backup drive). There'a bit of variation in all testing, when you find a company that you can work with, you tend to stay with them and help them improve their techniques.

Here is all I want to say:

The Cornering Stiffness DERIVATIVEs for front and rear tires are the most important set of handling information that one can have, besides the front and rear axle weights. The values can be obtained via tests of vehicles, tests of tires and transcribed to virtually ALL operating conditions of roadway Mu and vertical PSD (long or short wavelength). The nature of 2D plots that are frequently used to represent what surfaces do is best described by using a cheese slicer on carpet plots of tire data. Unfortunately, they are universally presented at a fixed load or slip angle, Pairs of tires operate at different loads and slip angles during any cornering situation. You need a bent knife to carve this melon. Then: almost all tech-no wizards completely ignore the effects of tire aligning torque because they smoked out after the lateral force lecture. The BIG picture for MZ is the so called 'rigid body' net aligning torque's effect on the vehicle (and the driver's) attitude. Because MZ near or at the limits of adhesion is so obfuscating, no bookworm is ever going to live to tell about it.

So now we have some cool video showing all the boy racer wannabees who have run out of talent and who bought cars for their advertising more than their character and equipment content. Cars that have to put large tires on them because their mass distributions and chassis compliances are very unfavorable to fast transient response. Cars whose wheel houses are too small to allow decent linear ride travel and cars that must use shock valving to restrict wheel travel so they don't buckle the fender liners. Cars whose brake systems and load designations demand heavy front brake proportioning so that they snatch the rear wheels off the ground when the driver's butt runs out of courage. Cars whose owners read cool magazines and other folklore about adding another 10 to 20 psi to the manufacturers recomended tire pressures (that would be 69 to 138 kPa for all you propellerheads).

Now lets take the car's we've all been suckered into buying, add the tire pressure increases, maybe add that fat friend for extra unplanned ballast) and go for a spin. You overcook the posted speed, break the brakes, loose the azz end, travel the rear suspension into a few degrees of toe out, hit some marbles and release some fartfigNewtons. Your tires once had a recommended pressure for peak Mu, but you read on Facebook somewhere that a few extra psi will save your tires. Oh, and you know that radiator overflow from the car ahead of you (yeah, that guy read about putting some cardboard in front of his radiator to get more "dumbforce". Meanwhile you forgot to put a damper on your throttle return so that the dropped throttle decel didn't scare your boy/girlfriend.

What have I forgotten? Oh, maybe the best tires for the job were to rich for my food handlers celery, so I bought the "buy 3 get one free" deal at Uncle Fritz's Tire Shoppe.

Can't fool me with this shitte anymore. I've seen it all.

Its the driver operator's JOB to gauge the roadway, have equipment up to the task, creep up on the car's limit handling nature, solve the nonlinear differential equations of motion "on-the-fly" in your head while driving, "Feel" the cars response to your finger torque applicators instead of commanding a steer displacement, gauge the roadway's unfortunate displacement constraint, and respect the safety of your passenger and other drivers out there in front and behind you.

Don't mess with extra 'roll bars', especially rear ones. A roll bar's effect on big and fat tires is probably just the opposite of what your Mother told you.

And when you are drinking, don't drive, when driving, don't park, because accidents cause people...

They let just about ANYONE with a quarter into the 'ring, still? First turn at the German Grand Prix is the ONLY racing event that I've ever seen that completely spooked me. Somebodys breaking the laws of physics there.

Tim.Wright

04-18-2016, 02:56 AM

They let just about ANYONE with a quarter into the 'ring, still?

Costs a lot more than a quarter these days but noone stopped me a few years ago from doing a lap with a long wheelbase Ford Transit with 2 couches in the back for extra downforce.

It's a public road so I don't think they can really stop anyone.

Oh I did 16:30 BTG if anyone's wondering.

MCoach

04-18-2016, 04:59 PM

For anyone curious, "Tires, Suspension and Handling" by John Dixon compares Fy and Mz curves on scales of 0-9 deg and 0-90 deg on page 96. Decent book, really. And for anyone who isn't familiar with the guy, he also wrote "The Damper Handbook".

Forces and moments are products from the stress and displacements of the tire. When we talk about materials and their response, we talk about their yield strength, ultimate strength, and stiffness. Nothing different here, no buzzwords.

I also don't think the answer is as straight forward as these cars have "bad suspension" because they they have have little response at the limit once unsettled. There isn't much you can do once you reach a steering gain of 0. Since what Z has decided a "good suspension" is one that can take bumps and the boss man has declared that it is my problem to fix.
I would just tell him to bring a truck next time or a "magic carpet" Cadillac from the 60's. These are the toys people play with where I grew up:

https://www.youtube.com/watch?v=7WdhXlLCFgY

Something something, body control, target ride frequency of 0hz (I.E. constant force vs travel). Bonus points for twin I beam on that one....
If the road can't really affect your wheel loading, then it can't have an influence on your chassis handling. Then you just dumb it down to near 0 bumpsteer and near 0 camber gain and etc over that enormous travel range of 1+ meters.

However, there is still the trade off of response vs stiffness. You want a car to handle now, and always now, the answer is a go kart. Will a go kart get over a sleeping police man? Of course not. Do they enjoy taking bumps? Hell no.
You want bumps? Get some body isolation going. You want bigger bumps? Get more isolation! But now the ride is all soft and squishy, the car rolls all over the place, and when you put the pedal down, the inside front tire picks up off the ground.
Real roads don't necessary have to change meter by meter and consist of black ice and pea gravel. In fact I would class those as "Michigan test grade roads"...

MCoach

04-19-2016, 12:31 PM

Coming at it again with a little more realistic view of it...

another potential solution:
Some can steer with the rear wheels as well and when controlled well can target a yaw damping rate and body slip angle (or tire slip if you so prefer); essentially giving you more control when otherwise there would be little/none
in such cases of high lateral acceleration where the cornering stiffness drops to nil or negative at peak Fy or past out into the sliding range. Targets include Something, something "drives like its on rails".
Bill correct me if I'm seeing this incorrectly...

Another option would be to fit tires similar to the Hoosier LC0 (although less realistic) where "more slip, more grip" seems to be the rule. The tires peak lateral force somewhere out in the great beyond, past 15 degrees or so (outside test data range).
This type of Fy curve would allow a car design where there is almost always a positive rear cornering stiffness and even getting silly-sideways allows the car to remain stable. Again, correct me if I'm looking at this wrong. Eventually velocity will catch up with you though...

Speaking of rails...
The whole conversation took off without the instigator and haven't heard from him from page 1. It's time to back up and get the train back on the tracks.

BillCobb

04-19-2016, 06:40 PM

A vehicle with rear steer (usually meant to be mainly front steered with a relationship between the rear and front steer angles) does nothing to impove lateral grip. Measured max lateral g's on cars without and with in-phase and out of phase rear steer) present identical results. Vehicle understeer is also unchanged because the rear slip angles are mechanically affected and not by lateral acceleration factors. The body sideslip angle is of coarse affected, as is the vehicle gain (steering sensitivity), but the only thing that a tire listens to at the extremes shown here are loads and maybe some camber. Increased tire pressure also usually hurts you if the tires are set to the optimum hot pressure. Pressures would usually be increased to save the tires (get more runs), but putting rubber down is what the roadway interface wants. MX optimization for 'happy tires' (when they they sizzle) is the wheel and camber and travel component that would need to be fixed'. Cars spin because their level of oversteer exceeds the so called Ackerman Understeer value (9.8*57.3 * wheelbase /(speed^2) deg/g, watch your units. The (faster you go)^2, the more fun it becomes.

Riding on rails (the flanged tire precept) is IMHO a relaxation construct. If it takes 3 revolutions to transmit the sideforce, then the feedback to the driver is diminished. This is a high load and slip example). Keep in mind that a PAIR of tires is involved in all of these happy trails episodes. They need to work together. Running a simulation with various front and rear dynamic toe values can reveal a lot about lateral grip. That means there's sort of a rear Ackerman function to work out. And it's tire construction dependent. Some work with toe out tendencies and some with toe in.
Dampers need to be 'Q'ed to relaxation. This is called 'transmissibility' in the venues I've hung around in. Tires are not 'springs' they are velocity gizmos and thus work best when other velocity gizmos are in synch. A damper mount (think Spring) is there, too. A really cool science project is to activate a magneohydrodynamic damper (Think OEM Cadillac junk yard parts) and play with it constrained to behave like a passive shock. This is called hardware-in-the-loop optimzation. Run a quarter car suspension and tire on a Flat-Trac belt with your finest sandpaper made from virgin pubic hair clippings. Tell me what you find. BTW: Honda has already written a paper about this. Look on the Honda R&D site.

All cars have rear steer of some sort: deflection steer and camber, roll steer, plunge (lateral defection without steer angle changes but a deflection no less that affects the relaxation phenom.

Yes, pros like wide slip range tires. So do stability control systems. Think of them as high grip conventional tires. Linear range cornering stiffness is not exceptional but the slip at peak is large. It's these tires that are hard to Pacejka-ize because their midrange is usually very linear Arctangents don't like this trait. These tires are also more controllable when its time to apply forward bite: Pedal to the metal-file.

Disclaimer: As always, I will point out that my intent is not to offend anybody. It is to offend everybody. If you are offended walk it off princess.

Tim.Wright

04-20-2016, 07:07 AM

Disclaimer: As always, I will point out that my intent is not to offend anybody. It is to offend everybody. If you are offended walk it off princess.

I didn't get offended, I demand a refund.

MCoach

04-20-2016, 12:28 PM

I didn't get offended, I demand a refund.

Indeed. Likewise.

04-26-2016, 11:57 PM

Earlier in this thread (mid-p3) I asked about the car spinning out in the video...

What is the cause of the problem, in big-picture terms? (Importantly, what is wrong with the car's design,...

In the next post Bill answered (among other points)...

... Cars whose wheel houses are too small to allow decent linear ride travel and cars that must use shock valving to restrict wheel travel so they don't buckle the fender liners...

I agree 100% with Bill's answer above as the root cause of the particular problem here.

A lack of soft enough, and long enough, rear suspension travel is, IMO, undoubtedly the main cause of many cars "losing it" when they encounter bumps in the middle of corners. Certainly, BMWs are well known for having next to no suspension travel (F or R!), and there are quite a few Bimmers losing it on that same corner in the video.

Here are two of the main reasons, IMO, that too many OEM "Suspension Engineers" design bad suspensions. (There are exceptions here, but methinks too many of them have retired, or are long dead!)
~o0o~

Reason 1. "Rule 1 for Good Ride - Rear-frequency/stiffness must be higher than Front-frequency/stiffness". (<-Wrong!)

This rule-of-thumb goes back to the 1920-30s (eg. see Millikens' "Olley - Chassis Design..." book, chapter 5 - Ride). This rule is intended to give a "flat ride" to cars that have overly stiff, but UNDER-damped, suspension (ie. side-view "horizontal-bouncing" of the car is considered OK, but "pitching" is considered bad).

This rule-of-thumb becomes pointless with softer and better damped suspension. But as long as the rear suspension is stiffer than the front it is less able to absorb bumps/humps than the front, so the rear wheels are more likely to get bounced into the air while the fronts are still in good contact with the ground. And it matters nought how many of Pacejka's 57 special parameters you happen to know, because when the rear tyres are in the air they have NOUGHT lateral grip! A spin quickly follows.

This is also what I was getting at before with comments about "...Ride-Engineers only focus on straight-line travel, while Handling-Engineers only do flat corners with NO bumps...". Sadly, this lobotimizing of design responsibilities is all too common in modern corporations, and also in too many FS/FSAE Teams. NOT GOOD.
~o0o~

Reason 2. Most vehicles (ie. small cars through to big trucks) carry most of their "live-load" (ie. passengers/luggage/payload) on the rear wheels.

If follows that if such vehicles have very soft and long travel rear suspension, then any significant change in live-load gives a large change in rear ride-height, and hence also a large change in pitch-angle. So, if empty car starts off horizontal, then loaded car has bum on ground and headlights pointing to the sky! This is a "bad look" that the Marketing Dept simply cannot tolerate (... the car looks "broken").

So, the easiest fix all round, is simply to fit stiff rear springs! And we are back to the car spinning out on any corner with a bump in it. And OEM's lawyers saying "Well, it's your fault for driving too fast [at posted speed limit?] around a corner with a bump in it!!!".
~o0o~

Anyway, this second problem was well solved in 1950s when Citroen started fitting oleopneumatic suspension to their cars. The "pneumatic" allows extremely soft spring-rates with very low mass springs (normally softer rate = heavier spring), and the "oleo" makes it very easy to do the self-levelling that is necessary with soft-springs + variable-load. The trucking industry also wised up 50+ years ago, and many trucks nowadays run air-bag suspension for the above reasons (... often with normal leaf-springs at front, because minimal load change there).

Some of the luxury car makers (Merc, RR) also got on board with self-levelling air-suspension, but just as often they jumped off again. Most likely because it is a lot easier to tell the customer "Hey, it's a luxury car! So stay OFF bad roads!".

Another quick-fix for the problem, very widespread nowadays, and a natural for the luxury car makers, is simply to increase the dead-mass of the car. In the olden-days a car (eg. early Citroen ID/DS) designed to carry a live-load of, say, a half-ton, might have weighed ~one ton dry. Nowadays the same payload needs at least two tons of car to cart it around. The percentage change from empty to full-load is much less, so less ride-height change, so no need for Young-Executive-VP-of-Suspension-Design to bother "pushing the envelope" with softly sprung, self-levelling suspension (...despite that envelope being burst long ago...).

Yep, much easier to say "Back off! Look ... all the other OEMs' cars are spinning too!"

Z

CWA

04-27-2016, 12:29 PM

And we are back to the car spinning out on any corner with a bump in it. And OEM's lawyers saying "Well, it's your fault for driving too fast [at posted speed limit?] around a corner with a bump in it!!!".

Interesting thoughts Z.

But I can't help considering that the premise you've presented us is unrealistic. Cars aren't / shouldn't be driven on public roads as we have seen in this video. Most public roads by design do not require high levels of lat acc (speaking from my experience living in the UK / EU at least). The path curvature the corners have and the speed limits the roads are given are such that any bumps present should not cause loss of grip / spins as we have seen in your video at the 'ring.

Any legal proceedings brought about as a result of loss-of-control cases such as you've mentioned would therefore be quite justified in attributing loss of control to excessive speed before any vehicle design is considered un-fit for purpose.

I can't help but feel that if what you have presented as a problem facing the industry was actually so, ISO, the SAE and other regulatory bodies would have begun to address it. Real industry problems in the past, such as the Ford Explorers on Firestones, the Corvair, the A-class rightly stood out at the time, and were given plenty of negative attention with appropriate reforms made.

But for all other cars released into market, in recent past and currently, even though such vehicles conform to what you've called a poor design philosophy, they are perfectly acceptable to pretty much all customers and all use cases. This I suspect is why most VD requirements and tests do not consider the events you've suggested when vehicles are designed and eventually signed-off.

Show me the statistics that prove that the vehicles of today do not have sufficient roadholding capability for the customers that buy them to drive them safely, and that this is costing OEMs more money than it should in lost law suits, and I / our whole VD/OEM-cottage-industry may start to see the light. Until then, I think you are trying to sell a solution to a problem that just doesn't exist.

04-27-2016, 08:14 PM

Show me the statistics that prove that the vehicles of today do not have sufficient roadholding capability for the customers that buy them to drive them safely, and that this is costing OEMs more money than it should in lost law suits, and I / our whole VD/OEM-cottage-industry may start to see the light.

CWA,

It is NOT costing the OEMs ANY money, because, as I noted before, they have the perfect excuse of,

"... Look ... all the other OEMs' cars are spinning too!"

The way society works (and clearly also the way FSAE works) is that the first and foremost Rule is, "If everyone else is doing it, then IT MUST BE GOOD!" (witness push/pullrods&rockers+++ in FSAE).

A car that spins out at a certain speed on a poorly maintained country road is, in the view of nearly everyone on the planet, the fault of the driver. The fact that a car with a better suspension might potentially take the same corner at twice the speed is never considered. In fact, some people would call that "academic".

The fact that a certain 50+ year old car CAN take the corner at twice the speed is usually met with something like,
"Oh... well..., that's different. Err..., that doesn't count ... because it's too old. Anyway, we make modern cars much better nowadays. You know, with stuff like "bluetooth", and other stuff..., and that old car doesn't have bluetooth...".

The Merc A-class you mentioned was panned because it flipped during a manouevre that (almost) all other cars easily pass. It was panned because it was below "the standard". But "the standard" is really very low.

If the SAE/auto-industry really does want to raise the standard, then the first step is easy. I have been pushing it here for years.

PUT SOME REAL BUMPS ON THE AUTO-X AND ENDURO TRACKS!

Currently, FS/FSAE cars with "BMW suspension" (= next to none) can easily win these comps. Which, of course, is much easier for everyone, all around...

Z

(PS. Consider the upcoming Olympics. Wouldn't it be much easier if they lowered all those hurdles in the running races to, oh..., say, about 6 inches? And how about shortening the marathon to, say, a half-mile or so? (Then E-cars could compete in it!) Yeah, easier is better! :D)

BillCobb

04-27-2016, 10:07 PM

Having sat in hundreds (maybe even thousands of meetings concerning new car platform "Voice of the Customer" requirement settings, I can assure you of one central, key, unavoidable and universal truth: "Safety Doesn't Sell". Car buyers resisted purchasing seat belts, disc brakes, power steering, stronger bumpers, collapsible steering colums, air bags, anti-lock brakes, radial tires, unibody chassis, heated washer fluid, run-flat tires and daytime running lights. They had to be mandated by law or or made standard equipment usually at a negative cost factor (profit) by car makers. Given a choice between safety equiped models and a cheaper one, cheaper gets chosen. That's why most cars today can't be custom ordered.

So here are my observations from all this "V.O.C." (voice of the customer, remember??) Design Review meetings as to why the best suspensions aren't there:

1) Packaging: gas tank and spare tire locations, drop down into the floor rear seats, battery and jack compartments. Rear washer bottle volume. Gotta make it through Uncle Bob's Brushless car wash without getting stuck from a control arm caught in the track or drive chain.

2) Ride comfort: Buyers read ride quality after going 50 feet in a demo car. Even my dogs read this well. I get a different evaluation company car every week or so after a few years of slavery. There were some cars my dogs REFUSED to get into because the ride comfort "back there" of up front was a problem for them. This means locations of springs, bushings, brake lines, mufflers, rear seats and number of them. A suspension attachment bushing at a passengers hip point is a kiss of death for a good ride rating. 35 psi tire pressures are also a ride killer (harshness) but this is essentially mandated by the EPA for emissions/fuel economy.

3)Market for a performance car is not there. Few buyers will or could ever use the vehicle's potential. You need good tires for this, too. You can get good tires on the new purchase, but under the rules of "Forseeable Misuse", a customer will most likely replace the "good" OEM tires with the cheapest, solid carbon black baloney skined OddBall WifeBeaters of a smaller size if possible. Sure, not everyone, just the 1 or 2 who unfortunately you don't kill but turn into a drooling vegetable and has a loud, nationwide legal fraternity, nice suits and is good friends with the Clintons. 85 to 95% of any car model badged with 1 or more extra performance level options (motor, tires and wheels, steering feel, roll bars and springs, etc) will be sold only as base models. The rest are for dealer gambles and bought by a few car guys.

4)Emissions/fuel economy. Sales weighted average emissions and fuel economy requirements (by Law) requires a 4 cylinder (or less) motor to pass the California Emissions test. Even Knowledgeable Readers may not know that ONE spark plug misfire during the U.S. Federal Emissions Test procedure fails the vehicle. On the Max lat test procedures I've had run for me hundreds of times at Milford, a 0.72g measurement says just one thing to me: Its motor limited, not tires, understeer, driver skill, road surface temperature, or anything else. (This brings up one of my favorite anecdotes: Once while testing a Ferrari (308 maybe, it was YELLOW), on the skid pad, the car (it was a RENTAL) made just one lap of the 108' radius circle before puking its motor guts all over our fine tuned mu measured calibrated lined, divined, and grind asphalt. Lack of baffles in the crankcase meant the oiling "system" was never designed for sustained high cornering levels. Even Ferrari owners probably use their cars mostly for ornaments, chick magnets and planter boxes).

So, what is the incentive to produce a really high grip, linear, fast, pretty, elevation manager, wet, snow, ice and sand surface capable car ? Its easy to do with traction, anti-lock, yaw stability, variable steer ratio, speed sensitive effort, reference seer model, rheologoical shock, etc. electronic controls. But nobody wants to buy it. They don't check the box. They've never reached 0.3 gs in their whole life. The parking effort is too high. They run 20 psi in the tires and put tape over the pressure warning light. Its too complicated to switch all the level settings. It blew a fuse and put the car into limp home mode. And their ex-wife's nephew (the one with a high school night school degree in auto mechanics) has no freakin' idea of where to begin finding out what the problem is.

So that's why its balls out (that would be flywheel) on the 'ring. It feels so good when I crash into the barrier. I can now tell the oldlady we need a better car for the weekend of fun. Maybe an Panzer tank, (you know, the one with a 1/2 life in battle of 6 minutes?) Depleted uranium equipped. Hell, even the CD player has a track for squealing tires.

That's my opinion and I'm unanimous with it...

CWA

04-28-2016, 01:19 PM

A car that spins out at a certain speed on a poorly maintained country road is, in the view of nearly everyone on the planet, the fault of the driver.

This, this is what is not a realistic premise to the auto industry. Cars these days do not spin out, even on poorly maintained roads. This is not a problem, you think it is, but it just is not. There are pretty much no cases like these that result in a reduction of sales for any given company other than the extreme historic cases I’ve mentioned. Even if you think law suits result in unjust judgement in favour of the OEM over the driver, the bad publicity of such an issue if it is as you've described would contribute to some reduction in reputation and a resulting loss of custom (by the way I’m welcome to receiving any kind of evidence that moves towards proving me wrong here..). But this doesn't happen any more.

Here's some anecdotal evidence in an attempt to counter your argument, my VW Polo is the most benign car in the world, it will not spin ANYWHERE. And I road-rally and auto-test this car all the time, getting as close to the 'ring use case you've provided as any other 'average' customer will get. So already here is a huge modern day OEM who manufactures a car that does not fall under your self-professed design rules of stupidity or whatever, and has released a perfectly safe car despite all the cost, packaging etc compromises I'm sure it's development was faced with.

The fact that a car with a better suspension might potentially take the same corner at twice the speed is never considered. In fact, some people would call that "academic".

It does not need to be considered, because the cost required to deliver a system that would provide this ‘benefit’ will be greater than the value this performance increase will bring to a company through any resulting increase in sales or revenue. Your average customer does not need this capability, even if you try and dress it up as a ‘safety feature’.

If the SAE/auto-industry really does want to raise the standard, then the first step is easy. I have been pushing it here for years

It doesn't want to. It doesn't need to. If the cars adhere to the sign-off tests that have been developed in line with customer expectations and regulatory bodies, why does it need to achieve more? And if it did want to do this, why do you think it does not already know how? (I'm sure Bill does for a start)

(PS. Consider the upcoming Olympics. Wouldn't it be much easier if they lowered all those hurdles in the running races to, oh..., say, about 6 inches? And how about shortening the marathon to, say, a half-mile or so? (Then E-cars could compete in it!) Yeah, easier is better! )

Conversely (also with sarcasm) wouldn't it be better if all governments around the world made no effort to build smooth roads. So OEMs can be faced with more interesting design challenges for their vehicle's suspensions, to distract them from the apparently less important issues they face, such as pressures to address sustainability, global emissions, and the ever present need to be competitive against competitors..

We haven't even begun to discuss active systems yet, which dilute any argument you have even further.

Active systems may be a band-aid for base chassis compromises, but with increasing electrical complexity leading to eventual autonomy, active systems are not going to go away, and are surely likely to be implemented with even greater reliance in the future. I wonder why you think the NHTSA mandated all new vehicles be equipped with ESC systems in 2012? Ignorance I suppose. Active systems may not be the most elegent or romantic solution to a mechanical designer, but they give flexibility during the development phase without reliance on components, and are arguably more cost-effective in achieving a safe vehicle whilst maintaining performance in other areas of compromise. In this light, demand for your perfect suspension is now even less, probably non-existent.

CWA

04-28-2016, 01:23 PM

Bill you paint a good picture, my relatively limited experience so far aligns exactly with what you've described.

BillCobb

04-28-2016, 04:03 PM

Honey, do you love me, or is that the hand-brake ?

https://www.youtube.com/watch?v=tjJi50Z9I4c

In a Round-About-Way...

Claude Rouelle

04-28-2016, 04:29 PM

OK Bill if you go this way here we go...

Steady state (well.... "quasi" steady-state) : https://www.youtube.com/watch?v=JOBZc2ccK80

Transient: https://www.youtube.com/watch?v=yAcmUmPch8U

A good illustration about getting the yaw moment you want when you want it. Also a good illustration on where the yaw axis is (or could be, or should be).

I use these videos (and several others) in the OptimumG seminars as a debate opening on the priorities (I say priority more than importance) between grip, balance, stability and control.

BillCobb

04-29-2016, 08:15 PM

Ok lets see how all of you react to this classroom exhibit:

https://www.youtube.com/watch?v=2shK4XfA2L8

Things I watch for in this and many other videos like it (don't care for the 'fails' just those with great execution), are:

Note how maintaining front grip at just about all costs introduces a notion missed by most in the VD Field: The yaw rate of the vehicle is being controlled by rotation about the central front axle by means of the so-called 'rigid body aligning moment'. The turning is excited by the steering wheel using the scrub torques still available. You can experience this phenomenon by putting grease plates (or better yet air bearings) under the rear wheels only. As you turn the steering wheel, the car yaws about the central steer axis. If the mass distribution is favorable to provide low inertia about THIS rotation axis, you get a car great for the hairpins. These so-called 'handbrake' turns (You'll have to guess why), are quite handy to avoid having to manage large rear tire slip angle forces. They are just about zero. Moment control is via steering. Then you can add the front wheel air bearings and experience the same phenom if the geometry settings are favorable.

BTW: The problem with most handling simulations is that this extra yaw moment is usually missing from the formulations. Its an understeering effect, so your car will measure higher understeer than you predict from simulation. But, you can always blame it on the tires or the surface porosity.

I also like the aerials shown in the vids. Note how little toe and camber change occurs as they go into full droop. Same for compression. No nightmares for their tires as they land.

https://www.youtube.com/watch?v=2shK4XfA2L8

Claude Rouelle

04-30-2016, 07:30 PM

There are 3 causes for slip angle: Beta (CG slip angle), r (yaw velocity) and delta (steering)

This video will show you that these 3 causes do not happen at the same time or at the same rate.
https://www.youtube.com/watch?v=kacfwj71iCw
Look very carefully and replay between 0.28 and 0.33 and between 1:35 and 1:39.
Sometimes the driver steers, sometimes he is not. Sometimes the car slides sideways, sometimes it doesn’t (or it is not noticeable). Sometimes it rotates, sometimes it is not (or it is not noticeable)

Just for fun see to 0.36 to 0.39; the shortest line between 2 points is a straight.

Look at the whole video and appreciate the driver skills; a bit different than Nascar....

This an another video that will help to understand the compromise between lateral acceleration and yaw moment

https://www.youtube.com/watch?v=ewxrNSOKFow

The driver pulls the handbrake, loose lateral rear grip (so total grip too of course) but at the benefit of the yaw moment.
Yaw moment = (front tires grip * distance front axle to CG ) - (rear tires grip * distance CG to rear axle) also written as as Fyf*a-Fyr*b.
(There are 13 causes for the yaw moment: 4 tire Fy, 4 tires Fx and 4 tires Mz and the car aero yaw moment but in this simplified explanation we only look at the 4 Fy)
When there isn't any available front grip anymore the only way to rotates the car is to decrease the rear grip.
You would like max lateral G and speed at the apex, yeah but you need to enter the corner, so you need a yaw moment. Too little of it, you have under-steer. Too much of it, you have over-steer.

Everybody knows that V=rR (V being the speed, r yaw velocity and R the turn Radius). And everybody know that A = V2/R.
But many do not realize that r = A/V and that the Yaw moment is the Yaw Inertia Izz * the derivate of r
r can be measured with a gyro
Less people know that the r = A/V is only valid for a mass point. On a real car the Yaw moment is Izz * [d(A/V)/dt + d2(beta)dt2]

And, for fun too, if you like Van Halen and vertical accelerations.....

https://www.youtube.com/watch?v=kXhw3LEcJkQ

05-02-2016, 10:45 PM

Cars these days do not spin out, even on poorly maintained roads...
...
... my VW Polo is the most benign car in the world, it will not spin ANYWHERE. And I road-rally and auto-test this car all the time...

Posted by Bill:
Say it Ain't so.
===========
https://www.youtube.com/watch?v=tjJi50Z9I4c

CWA,

I rest my case (namely that young auto-execs are utterly clueless!).
~o0o~

I don't have time for more waffle on "un-spinable" cars, but students might ask:

Why did that VW spin so easily on that roundabout?
Was it an unintended application of the handbrake, as suggested by Bill?
Or something else?
Is there a much quicker, easier, way to get a naturally understeering front-drive car to turn sharply into corners?
Perhaps something all rally-drivers know?

I suspect the spin might have been an unintended application of the "other" technique.
~~~~~o0o~~~~~

More importantly,

IS THE CUSTOMER ALWAYS RIGHT???
================================
Bill's earlier post (~mid page 4) seems to suggest that the auto-industry is building cars the way that customers want. Namely, el-cheapos that get the owner from A to B, with no particular need for high performance. I agree, to some degree*.

(* One exception here is that the OEMs actually build the cars that the OEM's "Stylists" (<- they call themselves "Designers", haha...) think that the OTHER OEM-Stylists are going to be building their cars, next year. For example, see the ~40 years from 1950+ when we were force fed cars that each year were "longer, lower, and wider" than last year's cars. This, even though everyone really wanted "shorter, taller, narrower" cars, like back in the pre-WWII days, that are easier to get into and out of, and park. It took until the ~1990s before the Stylists eventually caught on to this "SUV" shape, mainly because for ~30 years the customers were moving in droves to commercial-vans and light-trucks.

* Also, I have never heard a customer ask for a car that falls apart the minute the warranty expires. But the OEM Bean-Counters demand "built-in-obsolescence", so that is what we get. A genuinely cheap car, which has low full-life-cycle costs, is what customers want, but never get...)

But the really troubling thing here is;
Why is it that the "Captains of the Auto-Industry", who to some degree can rightly call themselves "Leaders" of our society, carry out their LEADERSHIP roles by FOLLOWING the dim-witted hordes!?

Is that what they are teaching you in all your Universities? You know, the way your Unis are always advertising how they are producing the next generation of "Creative and Innovative ... LEADERS!!!", blah, blah, blah...
~o0o~

Anyway, the auto-industry is simply doing the same as too many other industries in our decaying modern society. Namely, NOT giving any well-thought-through "leadership".

Consider, as another industry example, the food-industry. Anyone with a shred of understanding of this industry knows that to be "successful" here, you MUST put maximum focus on The Three Essential Food Groups. These "essential groups" are ... FAT, SALT, and SUGAR!

Interestingly, extensive study (namely the whole history of the industry) has found that the optimal ratios of these essentials is ~30% each, with the final 10% made up of carefully selected old newspapers, and your own special blend of artificial colours and flavours. Oh, and really snazzy packaging!

There is absolutely no doubt about this. Any food company that strays from this recipe does poorly in the market place. The more they stray, the worse they do. Stray too far, and they go broke. So, all successful Captains of the Food Industry continually repeat this mantra, unanimously,
"The customer is always right! We must give the customer what they want! We ARE giving the customer what they want!
YES, THE CUSTOMER IS ALWAYS RIGHT!!!" (<- repeat, ad nauseam).

And, off they "successfully" go to the bank, with their many bags of gold...

Now, personally, I have no problem with people eating whatever they want. I just object to having to pay too much of MY hard-earned, just to keep these dimwits waddling along, somewhere between the junk-food-joint, and the diabetes/liver/heart-disease++ treatment centres.

Let them eat whatever they want, but when they fall over ... either recycle them as Big-Macs, or plough them into "organic" farm yards. Problem solved! The customers get what they want, and society in general can spend its taxes on better things. :)
~o0o~

So, back to FS/FSAE. Which way to go? It seems that the current direction is:

Design Judge, "Interesting car you have here. Tell me how this car is going to solve our societies' problems."

Student (soon-to-be Future-OEM-Executive), "Well, as you can see, it is huge and weighs over two tons, which is just what customers of these single-seaters want. It is also all-electric, which the customer sees as "the future", and they are always right. So it has all these pretty flashing lights. Look, lots and lots of lights. And, although some critics have said that its one-ton-of-coal-per-mile fuel-consumption might be a slight downside, we note that the customer has no complaints about this, as long as the power-station is just out of town."

DJ, "Yes, yes..., but can I get a super-big, family-sized, version (although I do prefer to drive by myself...)?"

S, "Oh yes, sure. And here, try some of our Extra-Special-Sweet-n-Spicy-Double-Cheese-Sauce..."

DJ, "Umm... delicious! I am awarding you 899 points out of the 900 for Design Event, because you are exactly the sort of clever Young Engineer the auto-industry needs!"
~o0o~

Yep..., just like boiling a frog.

Turn the heat up slow enough, and they never notice what is happening to them...

Z

05-02-2016, 11:42 PM

There are 3 causes for slip angle: Beta (CG slip angle), r (yaw velocity) and delta (steering).

Claude,

The above quote, and much of the rest of the cogitatio caeca* in your post, is somewhere between misleading and very WRONG. I hope you do NOT teach it that way in your seminars.

But, then again, you have showed in the past that you do not want to learn how to do these things correctly. So...
~o0o~

Any students care to correct the above quote?

(Hints:
1. * "Cogitatio caeca" refers to the "blind thinking" inherent in Descartes' algebraic approach to understanding these sorts of (Classical) Mechanical problems. It was a popular discussion topic in the 1600+s. It was also called "mechanical" or "imagineless" thinking, in that manipulation of the algebraic equations can be done with NO knowledge of the underlying problem, and thus with no meaningful connection to it. So, for example, an equation which starts with "cause" on the LHS, and "effect" on the RHS, can be scrambled willy-nilly until it loses all sense of "cause and effect".

2. There is (a big) something missing from the "equation". There is no way that you can get the correct LHS (slip-angle) from the terms on the RHS (beta, r, delta). This, no doubt, because some big assumptions are left UN-stated. Very sloppy...)

Z

CWA

05-03-2016, 03:11 PM

I rest my case (namely that young auto-execs are utterly clueless!).

What case? You think because there is a link to a single instance of a car spinning, that I'm an idiot, everything I've said is wrong, and that it certainly proves that you know better than the whole automotive industry? My Ford Focus currently spins just as Bill's particular Polo did, because the front ARB has failed (car was sold to me in this way).

The truth is there are plenty of noise factors that could be present in this case and any others (any others?) like it, noise factors that it is impossible for OEMs to exercise full control over when a car has for years been in the hands of a customer who is supposed to have taken responsibility for maintenance. Prove to me that in this case of this Polo..
1. There was no oil on the road
2. Tyres are at correct pressure and have suitable tread depth
3. The rest of the car is fully functioning mechanically and has not been neglected
4. The handbrake wasn't pulled
..and perhaps I could concede that the video has highlighted a combination of car setup, road conditions and driver inputs that result in a vehicle response that VW's current sign-off tests do not expose.

My issue with you is that you're trying to stretch this into an argument that the whole industry is building cars that are unfit for purpose (and that all OEM engineers should be fired for being incapable and that you should be deferred to on all matters relating to vehicle dynamics.. or some other egotistical nonsense).

(* One exception here is that the OEMs actually build the cars that the OEM's "Stylists" (<- they call themselves "Designers", haha...) think that the OTHER OEM-Stylists are going to be building their cars, next year. For example, see the ~40 years from 1950+ when we were force fed cars that each year were "longer, lower, and wider" than last year's cars. This, even though everyone really wanted "shorter, taller, narrower" cars, like back in the pre-WWII days, that are easier to get into and out of, and park. It took until the ~1990s before the Stylists eventually caught on to this "SUV" shape, mainly because for ~30 years the customers were moving in droves to commercial-vans and light-trucks.

You twist the 'late' movement of the industry towards SUVs into some kind of failure on its part. I would in the same way twist the fact that as you previously quoted, the industry no longer makes cars that can handle rough roads like 50 years ago. Why do you think cars like this aren't made any more? As I've already said (which you've not been able to contest) - it is because people do not need them. People aren't prepared to pay extra shilling for this capability. They would rather spend the money on in-car entertainment or creature comforts (surprise me by not trying to twist this into some kind of flaw in humanity).

By the way, I see you have no comment on active systems, why not?

Do you think it coincidence that SUV's began to become more prevalent at the same time that active systems became available to support them? A brake-based roll stability control algorithm can stop an SUV rolling by saturating the contact patch with longitudinal force when triggered by inertial measurement and vehicle state estimation signals. How exactly did the excellent legacy mechanical systems in use beforehand give the same capability?

IS THE CUSTOMER ALWAYS RIGHT???

Yes. And your failure to accept this, despite your technical ability, is quite staggering. Your ridiculously irrelvant FSAE premise adds no value to this discussion, and in no way disproves that the customer, or rather that market demand, is always right.

What customers do with the products they buy, be it at the expense of civilisation or the retardation of the progression of society or whatever you claim, is completely up to the customer. You can try and twist the reality into something complicated and more meaningful than it is but why bother. At the end of the day, customers buy cars to better their day to day lives or to make themselves feel good. And companies must simply respond to what customers seem to want. Those companies that do not recognise this in time fail to exist.

That is why no-one cares for your clever, expensive suspension solutions. They've all been tried in the past, and dismissed because they are inferior in the eyes of customers. Has it ever occurred to you that what you consider important is meaningless to the hordes of other punters, whose money is exactly the same colour?

On a personal note, I have to ask, have you ever worked with anyone in the automotive industry, Eric? I don't mean recent graduates, I mean engineers with a few years under their belts. Would you be willing to share personal experiences that have lead you to believe that "young auto-execs" are "utterly clueless"? You seem intent on insulting anyone associated with the industry, so I don't feel too forward in testing your frankly rather extreme and offensive views. Do you believe everyone employed by any OEM in the world is ignorant, useless and incapable of doing anything of value?

..but students might ask.. ..So, back to FS/FSAE. Which way to go?..

Ha! Well you've insulted students and their education enough already, at least don't insult them further by pretending that your tirade against the auto industry (and the food industry.. and society in general) is somehow for their benefit.

Jay Lawrence

05-03-2016, 11:18 PM

Classic Z!!!

I happen to agree (not that it matters) that the customer is WRONG. How can someone rely on complex algorithms to fix their obvious mistakes (the first of which was to buy a car based on its high seating position and its colour) and claim to be in the right? How can an industry tolerate bull bars and lift kits on road cars but not roll cages and claim to be right? All you have to do is witness a typical conversation on speeding to see how wrong the customer generally is ("oh that biker was doing 100mph, that's insane!" Meanwhile, muppet has no problem sharing the road with a 20t truck). How could someone who consciously buys chrome wheels and cheap tyres ever be right? It goes on and on.

However, to me, this doesn't mean that the industry and the professionals within it are stupid. It would be like saying that F1 engineers are dumb because they're not using bigger/better (but illegal) aero components. Or, on a less related level, it would be like saying that teachers are stupid for trying to implement a given curriculum.

How to fix this? I don't know, but I imagine there would be a great many committees involved, so it would take a long time. In the mean time, how could anyone blame an engineer for trying to come up with new ways to save some fool who never learnt how to drive and has no interest, and yet holds the future prospects of that engineer in their hands?

CWA

05-04-2016, 12:36 AM

How can someone rely on complex algorithms to fix their obvious mistakes (the first of which was to buy a car based on its high seating position and its colour) and claim to be in the right?

High seating position is desirable, for practicality and looks (as Z already mentioned).
The average customer probably doesn't even know algorithm's exist on their modern, because most probably don't even realise that the CH height is an issue.
But they don't have to know any of this. Most customers aren't interested in physical issues or limitations, nor the engineering required to overcome them.
They only care about the capability that these solutions give them, and how much it costs for the pleasure. They are not 'wrong' for buying in this way.

Jay Lawrence

05-04-2016, 10:12 PM

I guess the difference of opinion that we are having here is in the definition of what is 'wrong.' To me, if a person has no knowledge on a given subject (and hence buys a car because it has a high seat and is a nice shade of plum), then they cannot make in informed choice. To my reckoning, an uninformed choice is about the same as being 'wrong.' When there is a majority of customers who are unable to make an informed choice, then of course the industry that supplies them is going to 'dumb itself down' to suit. If you want a great example of this, check out the Sprotor...

Charles Kaneb

05-04-2016, 10:55 PM

CWA,

Nominate any car you want as "un-spinnable", and bring it up to Farmington Hills, Michigan.

I will bet you a pair of tires that my friend Mike Ogren can spin it between cones spaced three feet wider than the length of the car in a parking lot without use of the handbrake or gross abuse of the transmission.

Z,

How do you reconcile consumers no longer wanting high performance with my being able to rent a 15-second car that pulls over .8g on the skidpad from the minivan category at the airport?
How do you reconcile having the bean counters demand cars that fall apart after the warranty, with no cars in my local junkyard newer than ten years old apart from those completely obliterated by crashes? Most of the GM and Honda cars in there are between MY1995 and MY2000 with ~200,000 Michigan miles on the clock. We have billiard-table roads up here, a pocket every five feet!
How do you reconcile saying that consumers cannot get manufacturers to deliver vehicles with low life-cycle cost with the existence of the Ford Fiesta, the Fiat 500, the Honda Fit, the Chevrolet Sonic, the Toyota Corolla, etc? What exactly is expensive to maintain on a Fiesta?

CWA

05-05-2016, 12:12 PM

Nominate any car you want as "un-spinnable", and bring it up to Farmington Hills, Michigan.

I will bet you a pair of tires that my friend Mike Ogren can spin it between cones spaced three feet wider than the length of the car in a parking lot without use of the handbrake or gross abuse of the transmission.

If it was at all a feasible possibility, I would love to, even pay to see someone convincingly spin this polo of mine. I'm not a bad hand behind a steering wheel, I've had my fair share of seat time, and I've tried all the tricks in my book to no avail. I'm curious to learn what your associate's technique is..

By the way, I didn't claim that cars these days are "un-spinnable", I said cars don't spin on the roads these days. In my view, with as little pedanticism as can be tolerated, these are different things. Cars spinning off roads are not problems like they used to be, is what I meant, and is hopefully what I conveyed.

I guess the difference of opinion that we are having here is in the definition of what is 'wrong.' To me, if a person has no knowledge on a given subject (and hence buys a car because it has a high seat and is a nice shade of plum), then they cannot make in informed choice. To my reckoning, an uninformed choice is about the same as being 'wrong.' When there is a majority of customers who are unable to make an informed choice, then of course the industry that supplies them is going to 'dumb itself down' to suit. If you want a great example of this, check out the Sprotor...

Sorry Jay, I think this is very poor reasoning. If you say a customer is 'wrong' to buy an SUV, you are saying SUVs are 'wrong'. Please explain how an SUV is 'wrong'. Because early versions used to roll? Early cars used to have all kinds of failures, often resulting in deaths, but this didn't stop more and more 'dumb' people buying them.

We can agree, the market generally dictates how technology develops. After it became clear to OEMs that lots of customers like having tall vehicles (because they are practical and visually appealling - as Marketing established), engineers adapted these products to ensure they are safe, and ensure that CG height no longer compromised capability.

This is in no way a 'dumbing-down' of the industry, it is in fact the industry focusing on what is clearly important in order to progress, remain profitable and survive.

It is no different to an OEM recognising that customers buy vehicles with good in-car-entertainment, and focussing on improving their ability to deliver electrical systems. Market pull, not technology push, in this case as with most others.

You say buyers are dumb for buying what they want, I say engineers are dumb if they do not make things that buyers want. Look at reality, at what is actually happening in the global car market right now, and think again about which is closer to the truth.

Charles Kaneb

05-05-2016, 04:49 PM

The entire "light truck" thing happened because they were (and still are) not subjected to passenger-car fuel economy standards. They were given an immense freebie advantage over anything that didn't have 8" ground clearance and a flat load floor.

If the EPA had followed up with the rules they wanted in 1981, "light trucks" would have required commercial licensing, DOT numbers on the sides, and a non-bypassable speed governor. Unfortunately, a gas-waster government appeared and now I can't see past or over half the cars on the road.

DougMilliken

05-05-2016, 05:49 PM

The entire "light truck" thing happened because they were (and still are) not subjected to passenger-car fuel economy standards. ...
In addition to the items you noted, "light trucks" were also subject to less safety regulation for awhile (also, emissions? not sure on that one). IIRC, there were some years where some of the cheapest vehicles on the market in USA were stripped down, small pickups. Just another aspect of the market distortion in the USA that has given us all these stupid useless vehicles.

Almost forgot, "Just say NO to SUV's" -- with apologies to Nancy Reagan who used to say, "Just say no to drugs".

BillCobb

05-05-2016, 07:22 PM

Just so you will know, the small stripper trucks were part of the overseas campaign to avoid tarrifs put on to try to protect the hurting US industry. So, foreign manufacturers, avoided tariffs by unloading small trucks where the pickup bed, or fenders, or spare tires had been removed an the transport ships. The collection of unassembled parts were then reassembled in local 'Assembly Parks' and labeled as "Made in U.S.A."

I worked on a small SUV project to convert them to RHD. No problems until unloading them in Japan. Each and every vehicle coming onto the island must have an accompanying "sideslip" measurement before it could leave the ship. Sideslip referred to a 4 wheel alignment validation that must be witnessed by a Japanese government official. Sideslip measuring machines are only allowed to be from Japan and were surprisingly in short supply. Needless to say, these inspector guys were nowhere to be found and often wrote stuff on the approval certificates that was not noticed by the GM car stewards. The symbols usually stated "Not Passed, machine out of specification" even though the toe and camber numbers were within the band range.

Now you see why the protectionism of other countries is resented so much here, and is worked in their favor ? We gave up. People looked at the Blazers and admired them, but were afraid to buy them because they might lose their jobs, homes, and benefits.

Jay Lawrence

05-05-2016, 10:52 PM

CWA, it sounds like you are saying that people who don't know what's going on, even at a basic level, are 'right'? I agree with this to the extent that 'the customer is always right' and the customer wants SUVs with USA-worthy cup holders. To me, SUVs are 'wrong' for the reasons listed by others above, and I don't agree that they are practical (and certainly disagree on them being visually appealing!!!). To me, the industry is dumbed down by having to deal with the whims of clueless people (why spend decades developing complex electric rescue systems when you could just buy a well suspended car of low mass and CG?). As mentioned, I don't intend to label the engineers/designers as dumb, and I certainly admire the development that goes into such things, but it feels a bit like solutions to problems that shouldn't exist in the first place.

It's all a matter of perspective I suppose. For me, as a car/driving enthusiast, the market is full of morons with no clue and it annoys me that their buying habits are doing what they can to destroy what I love about cars. Fortunately, as a motorcyclist, there is still plenty of motoring purity left. Unfortunately, the safe undertaking of such is often at the whims of the aforementioned clueless morons who, in my opinion, should be confined to public transport.

CWA

05-06-2016, 12:34 AM

Claude Rouelle

05-06-2016, 07:56 AM

Bill,

You wrote "People looked at the Blazers and admired them". Can you elaborate a bit?. I wonder from what country(ies) where the "people" who did admire the Blazers? What was it that they like in the Blazers?

Claude

Pat Clarke

05-06-2016, 03:25 PM

Claude,

Having had very similar 'Protection Obstacles' placed in my way, with of all things, wheel alignment equipment, I am sure Bill is talking about the Land of Nippon.
I was reminded of a pyramid of frustrations trying to do business there.
They have no actual laws against foreign competition, but they sure throw some obstacles in the way...and then put obstacles in the obstacles!

Pat

Claude Rouelle

05-06-2016, 07:15 PM

Pat

I worked in Japan with the Volvo work team in 1986 and I learned a lot from Volvo Japan about it worked when it was about homologation and import of passengers cars in Japan.
Also was the technical representative for Reynard racing cars in Japan in the early 90's.
I know how much custom, bureaucratic, cultural "chicanes" there were.

On the other end, I do not remember the number, but at that time the number of cars that Toyota and Honda could sell in the European community was extremely limited.
That is also another side of the picture side westerners do not often speak about.

But that was not my main point neither my main question to Bill. My main question was: what was it to admire in the Blazer?

Claude

BillCobb

05-06-2016, 08:20 PM

I'm talking about a 1996 model Chevrolet Blazer, 2wd. RHD, leather, A/C, abs, auto trans, alloy wheels, killer audio power, V6, Summer L# Bridgestone tires (not the M+S US versions), REALLY good Fit & Finish, clear lacquer, a real RHD steering system unlike the aftermarket job shopped cars which often ran a cross shaft from the RH colunm to the LH steering gear.

Preview customer clinics here on all the 'island countries' (You know what that means, right), indicated it was a winner. Yes you could roll marbles down the hood seam.

It was viewed as a 'status' ownership model, not a daily beater.

But when all was said and done, the cost to a buyer was more than double the MSRP because of the duties, inspection fees, certification delays, emissions sniffing, dealer surcharges for maintenance parts inventory, door stickers and the list goes on. Your 1986 experiences are too early for the import war games.

When we threw in the towel, the exquisite expalnation was simply : "Japan is a rocky island, and unable to feed its people without exporting everything it can. Import food only. That is our way."

BillCobb

05-06-2016, 09:04 PM

So Doug, my 'Vette was my last SUV, but not the best farm vehicle. Windrowed hay gets balled up in front of the air dam and even under the car. Delivery in winter is a real beach because most horse stables don't plow really good, and of course you really need 4WD when pulling a farm tractor out of a field weep.

My Tahoe with "Displacement on Demand" (That would be rotating 4 cylinder mode) does a much better job. And it gets 22 mpg with the 6,000 lbs of hay trailer in tow along I-96 at 65 mph on regular gas. With the boat in tow, the mpg is down because we can do 75 mph.

My .jpg s won't load, jealousy, I guess...

DougMilliken

05-06-2016, 10:35 PM

Hi Bill, I have nothing against trucks and SUVs when they are used for doing real work, pulling trailers, etc.
But when they carry one person around the 'burbs I think they are pretty stupid and useless.

Tim.Wright

05-07-2016, 08:26 AM

The same could be said about any sports car though.

Anyway, why are we talking about vehicles with a non zero track width in this thread??

DougMilliken

05-07-2016, 10:41 AM

The same could be said about any sports car though.
Sort of -- but the sports car is probably a lot lighter and lower drag, not such a waste when carrying one person.

Felice Bianchi Anderloni of Carrozzeria Touring -- "Il peso è il nemico, la resistenza dell'aria è l'ostacolo" (Weight is the enemy, air resistance the obstacle).

Anyway, why are we talking about vehicles with a non zero track width in this thread??
Not sure, maybe "pair analysis"? <grin>

Jay Lawrence

05-08-2016, 10:58 PM

It sounds like historically there is more to the US market of 'pickups' than I was aware of. I assume that somewhere along the line this equally translates into justification of the country's thirst for 'SUVs' too.

My comments have been made with other markets in mind, where in fairly recent years the trend of consumers in many market segments moving away from saloons into SUVs (moves based on the merits of physical attributes, rather than phoney incentivisation) is undeniable.

So you scorn fellow consumers (who are no worse than you, by the way, assuming they spend the same amount of money or more on new cars as you) because they don't buy cars that you like. You must recognise that you as a 'car enthusiast' and your kind are a minority and that is why OEMs will not maintain their portfolios to suit 'purists' like yourself. Cars to other people are just commodities and fashion accessories, hence why their purchase decisions are driven by baser instincts, rather than by engineering considerations. If you can't see the business case for SUVs then it's probably just as well you remain an engineer.

Because there are plenty of people who would rather pay (considerably more) money for a tall vehicle. Pandering to this gives an OEM a competitive advantage, I'm sure it's not that hard to understand. I suppose you have the same blinkered view of electrification and autonomy in the industry too. And as we are on an FSAE forum, let's remind ourselves, why do race teams spend so much money making cars drive around in circles as fast as possible? We both know the answer, because people love to watch this, because of the spectacle, nothing more sensible than than. There's nothing less rational about what drives the decisions of SUV buyers than this motivation for motorsport.

Ahhh yep, that's pretty much it! I know full well that I'm in the minority, but I would have assumed that most on this forum would also be a member of that group. As I've said a couple of times now, the engineers/marketers are not 'wrong' for giving the customer what they want, but that doesn't mean that the customer has the resources to comprehend what they are doing. Of course I can see the business case for SUVs (mind you, SUVs were not the target of my initial comment, but you latched onto them. Sore spot?). Are there more ways I need to say it? I agree with you. I agree that OEMs will supply what the customer wants. I agree that people who have no idea what they are talking about are good at wanting things that are worse for society. I fully support electrification (though I feel it's stupid to put all our eggs in that one basket, for reasons Z is always going on about), and I fully support autonomy (I'm hoping that autonomous cars become a version of public transport in which the non-caring/image-enthusiast crowd can get carted around, allowing motoring enthusiasts to have some space (though I fear the reality will be quite different)). I'm really not sure where your point of difference is coming from

05-09-2016, 12:18 AM

Many other things to do, but I feel obliged to give some replies...

CWA,

(From your post back on page 5...)

"You think ... you know better than the whole automotive industry?"

Everything I have said on this Forum for the last 10+ years was known to at least some parts of the auto-industry at least 60+ years ago. Sadly, nowadays much of it is forgotten.
~o0o~

"My issue with you is that you're trying to stretch this into an argument that the whole industry is building cars that are unfit for purpose..."

My issue is that the whole industry is building junk-food, while OEM Engineers are kidding themselves that they are MasterChefs.

CWA, you are flipping burgers. Nothing wrong with that, but it ain't Engineering!
~o0o~

"... the industry no longer makes cars that can handle rough roads like 50 years ago. Why? ...it is because people do not need them. People aren't prepared to pay extra shilling for this capability."

Rubbish. My local friendly bush-mechanic always has his front paddock full of "SUVs" that need fixing. The ones from the town-side of the river usually last about the ten allocated years before Built-In-Obsolescence (BIO) dictates major repairs. The SUVs (big Toyotas, mostly) from the other side of the river are often in the shop after only ~3 years of driving on the FEW dirt roads over there! The major weakness is a front-lower-outer-BJ that snaps-off due to fatigue of a criminally negligent design (neck-of-BJ is in tension+bending). Consider the consequences of this failure!

But the customers:
1. Have no options here, given that Tojo is supposed to be the most reliable, ruggedly built, such vehicle, and the alternatives are at least as bad.
2. Are idiots who have long ago lost the ability to protest such incompetence, mainly because they are too busy shoving that umpteenth deep-fried cholestrol burger down their gobs.
~o0o~

"... I see you have no comment on active systems, why not?'

From the department of the bleeding-obvious. -> "Active-electronic doo-dads" CANNOT SWALLOW BUMPS!!!

For a car to cope with real roads (ie. with real bumps in them) requires sufficient SUSPENSION TRAVEL to swallow said bumps (this already covered several pages back, and more below). Once that travel is there, there is no need for any extra electronic gimmickry, other than for BIO reasons:

Customer Relationship Engineer, "That light on your dash is from a failed wheel-speed sensor. It will cost you about $2,999 to fix it, because we have to change the whole hub/bearing/axle/sensor-unit. Yeah, we make it an "integrated-unit" to save you money. :)".
~o0o~

"Do you think it coincidence that SUV's began to become more prevalent at the same time that active systems became available to support them?"

Utter rubbish. See below for just one example.
~o0o~

"... market demand, is always right. ...
... customers buy ... to make themselves feel good."

You should set up business outside your local Primary School selling "recreational drugs" to the kiddies. You have just given yourself the moral justification to make a fortune!

(And BTW, the junk-food industry is simply the legal version of the illicit rec-drug industry.)
~o0o~

"... companies must simply respond to what customers seem to want. Those ... that do not recognise this ... fail to exist."

More rubbish. Wrong, wrong, wrong... A good example of how wrong is the recent 2008+ history of the US "Big-Three". Very briefly, it went something like this:

Big-Three, "Aww, it's not fair. Those Japs keep building small, economical cars, and OUR customers keep buying 'em. We demand the taxpayer give us $50 BILLION!!!"

US-Congress, "Well, you guys are IDIOTS. You haven't been "responding to what customers seem to want". You should "fail to exist"."

B-3, " Waa-waa-waaaaa... Not fair... LOST JOBS... Waaaaa..."

US-C, "Oh, ok... here's $25 billion. Don't do it again."

B-3, "Hehehe..."

In a (western) world flooded with food, no person, or company, has to work hard, or even think hard, in order to survive. Like pigs at a trough, the very worst that can happen is that the truly unfit waddle over after everyone else has finished, and then gorge themselves on the leftovers. Look at all the execs of the many banks that "failed to exist" during the GFC. How tough are those execs doing it now?
~o0o~

"... no-one cares for your clever, expensive suspension solutions. ... all been tried in the past, ...and dismissed because ... inferior..."

I think most everyone here will agree that I have spent the last 10+ years pushing the SIMPLEST, CHEAPEST suspension solutions, that also happen to have the BEST PERFORMANCE. These solutions have been "tried in the past", and were loved by the customers because they are so superior. And CHEAP too! See more below on "World's Cheapest Car".

But it is also very apparent that those on this Forum who object most vocally to my suggestions (namely, of the old and well-proven ideas), are those who have absolutely NO IDEA how that stuff works. Methinks the many objections are primarily an excuse to avoid having to learn how that stuff works.

My philosophy -> "A good Engineer is someone who can do with one dollar, what any fool can do with a hundred."
~o0o~

"... have you ever worked with anyone in the automotive industry, [followed by bad spelling]..."

Yes. They were poorly paid, worked long hours at boring tasks, and while they were "passionate" about cars, they were, indeed, mostly "clueless".
~o0o~

And, finally, from CWA's reply to Jay.

"Cars ... are just commodities and fashion accessories, hence why their purchase decisions are driven by baser instincts, rather than by engineering considerations. If you can't see the business case for SUVs then it's probably just as well you remain an engineer."

CWA, good to see you agree that you are just a burger-flipper, and NOT AN ENGINEER!

Z

05-09-2016, 12:27 AM

Charles,

"How do you reconcile having the bean counters demand cars that fall apart after the warranty, with no cars in my local junkyard newer than ten years old apart from those completely obliterated by crashes? Most of the GM and Honda cars in there are between MY1995 and MY2000 ..."

Well...,

1. I am guessing that you, personally, are a bit older than a MY1995? Do you feel ready for the junkyard? :)

2. In the previous post I gave the example of a wheel-speed sensor integrated into the hub/bearing/axle unit as one way that BIO works (ie. a single failed sensor, or frayed wire, costs big-bucks). There are many other examples, mainly these days involving "graceful degradation" of electronic and plastic junk so customer can keep driving, but gradually feels more pressure to buy new car. Rubber suspension bushes are another good example, in that they gradually get hard, then later crack and get sloppy, all of which makes that new car ride/handling feel oh-so much better.

But even the above wheel-bearings themselves are now so close to "the limit" that one big pot-hole, or mild curb-strike, costs you the whole hub-assembly. The old-fashioned tapered-rollers were much more durable, adjustable with wear, and cheaply changeable in worst case (which was usually water ingress -> rust -> pitting).

Modern cars are designed to gradually start failing after ~10 years of "medium-duty" loading (eg. "off-road" SUV taking kids to school or to local shops, on smooth roads). They fail much more quickly under "heavy-duty" conditions, such as SUVs actually going off-road (like in all their ads!). But if such cars had maybe ~10 kgs of steel (total, maximum) added in crucial areas (eg. hub-bearings, axles, susp-pick-ups, gearboxes, etc...), then they would have a medium-duty lifetime (= "MTBF") of hundreds of years, or heavy-duty life of many decades.

The extra cost of this 10 kgs would be negligible to the customer, but the longevity of the cars would send sales figures plummeting for the OEMs. The OEMs say that they are "giving the customer what they want", but, in fact, the OEMs (and all other such industries) work only to maximise their profits. Whether it is the food-industry selling fat-salt-&-sugar to the fatties, or big-pharma selling drugs to dimwits (it works the same way with both licit and illicit drugs), or the auto-industry selling blinking-lights to bone-heads, one thing is sure, the whole game is only about making that short term buck, with no one thinking in the long term.

We nowadays live in a "garbage economy". Everyone spends ~40 hours a week making junk so they can earn enough money to temporarily RENT the other junk that the other people are making. BORING!!!

3. My local friendly town-mechanic, Jason, who normally specialises in Citroens, is now driving a Merc. A middle-aged, gentle-driving, woman came to him with her 2008 C-class "Kompressor" Merc, with its busted engine. She had all the car's required services done at the same Merc dealership where she bought the car (for ~$70+K). After the engine went bang the dealership said "... it'll cost ~$12+K to fix the engine, or we can buy the whole car back off you for $4K...". The cam-chain had stretched, and cam-sprockets were nearly completely worn down, which resulted in valves hitting pistons. I have forgotten the exact number, but this ~8 year old car had done well under 100k miles!!!

Anyway, Jason (edit: bought the car for ~$4.4k) and fixed the engine for a few grand, and has yet another car. But ... the Merc is now up for sale ... because ride is much too harsh. He has been spoiled by all his Citroens!

And have you heard about all the Merc engine-wiring-looms of late-1990s/early-2000s? They are well known for insulation that gets very brittle after 5-10 years, then cracks up and causes endless shorts. A replacement loom, plus fitting, costs many thousands...
~o0o~

"... vehicles with low life-cycle cost..."

Hmmm, let me think of an example...

What about The World's Cheapest Car? (<- Many other OEMs reverse-engineered this car and gave it this name. Some concluded it cost HALF as much as their cheapest car to make.)

This car is also one of the original "Utility Vehicle"s, especially in its use of a "shorter, higher, narrower" overall shape. For those who missed it last time I posted this link, here is a Sports version of this UV:

http://www.youtube.com/watch?v=hAocmae9vyE

More here:

http://www.sparrowautomotive.co.uk/citroen2cvbmw.html

Some notes on the original, and slightly slower, UV predecessor (these notes from memory, so corrections welcome):

1. It is a quite spacious "Compact UV", with four doors, four seats, plus luggage area. Interior height is sufficient to "...allow French farmer and wife to drive to church while wearing their best Sunday hats". Total empty running mass of the original versions was 520 kg (!), with payload of 320 kg. Later, larger, plastic-bodied versions (eg. Ami 6) had mass of 660 kg.

2. Design-spec insited on extremely soft ride to cope with very rough French rural roads of the time. The problem of "change in ride-height with change in live-load" solved by simply letting tail be quite high in air when car empty, then car low and horizontal when fully loaded.

3. Engine started as 375 cc air-cooled flat-twin, but eventually grew to big-block 602 cc with ~30 hp. Real world fuel consumption on poor quality (very low-octane post WWII) fuel was ~5 litres/100 km, or 50+ mpg (imp). See "Coccinelle" prototypes for lightweight/reduced-aero-drag version with about half this fuel consumption from same engine, but still carburettored.

4. This was NOT a design-spec that came out of some Marketing-Focus-Group. On the contrary, it was the sole vision of the head of Citroen at the time, Pierre Boulanger. Fact is that during its development it was much UN-loved by nearly everyone. Certainly, all the "experts" considered such a backwards step as, well, certain failure. Boulanger had to work hard to push it through, including constantly having to pull back the many attempts to overcomplicate it.

5. BUT (!) when it eventually hit the market it sold like hot-cakes. From memory (?), over its 40+ year production life it sold 7 - 9 million of all versions, including the delivery-van, twin-engine-4WD, Ami, Dyane, etc. Obviously, the marketplace liked it. And they and still do, because at the local classic(=old)-car auctions these World's-Cheapest-Cars often fetch much higher dollars than top-of-range Mercs/BMWs/Jags/+++ of same vintage.

Over the first half of its life this car, and the DS, kept Citroen well and truly in the black. But then the talent started leaving the company. The key figures behind these cars got old and retired, or died (just like with many successful FS/FSAE Teams!). The new "Leaders" thought they have to "...give the customers what they want".

Many disastrous decisions followed. Many fantastic opportunities were missed. See the cheap-to-build "Panhard-DS prototypes" for a potentially huge money-spinner that was dropped at the last minute in favour of the more upmarket, and much more expensive-to-build, SM. So, as inevitably happens when many bad decisions are made in succession, the black ink turned red. And, no doubt, much of the blame for the gradually developing troubles was directed at "the other guys" (preferably people recently retired or dead...).

So, did Citroen "fail to exist"?

Of course NOT! It was simply absorbed into Peugeot. And I am sure that all the Grand-Fromages of the time patted each other on the back for the great Leadership skills they showed in saving such a Creative and Innovative marque. (<- Yep, got all the key buzzwords in there... :))

Z

Charles Kaneb

05-09-2016, 10:04 AM

1) I'm a MY86, and my grandmother is not ready for the junkyard.
2) The lifespan of a modern vehicle isn't limited by odd component failures or integration. Even that Merc got an engine rebuild and kept going. A modern car lasts ONE BIG SMASH and that's it. That's why ~2/3 of the cars in US Auto in Sterling Heights are there. The rest? Worse than planned obsolescence is "NLA" - parts no longer available. I would pay the new-part price to get a new HVAC control box for my CRX but Honda won't sell me one anymore.
In addition, some components aren't worth rebuilding anymore. My mother's old-school ex complained about our local mechanic replacing a leaking caliper on her Subaru for $97 instead of rebuilding it. If a rebuild would've taken half an hour, cost $30 in parts, and not been under warranty against the new parts being bad from day 1 like the caliper, how likely does a failed rebuild (bore won't clean up, secondary leak actually through a crack in caliper body, Junko-brand rebuild kit NFG) have to be to make it worse than buying a new one?
3) You hit a sore spot here with that Citroen. I have long admired them and agree that both the DS/ID and 2CV are a vastly superior solution to rough/dirt roads than anything else I've driven. At the same time, with a range of DS/ID and 2CV derivatives from 1955-on, they did not make enough money to design and build the (2.5 liter belt cam OHC straight six) engine the DS needed. That and some rust traps in the body were the only things that kept it from being salable as long as the 2CV! It's not as if they were wasting their money at the time, either; the Ami-6 and Ami-8 were close 2CV derivatives and the best-selling cars in France.
The closest anyone comes nowadays is... Citroen! They have a 940kg CUV with some innovative features and a mildly reduced part count. I saw one on the streets of Michigan recently parked next to a Grand Cherokee and my thoughts recalled Gen. Ducrot's statement at the battle of Sedan!

Charles Kaneb

05-09-2016, 10:16 AM

Outside of Michigan, where else in the US is severely-rough-road-at-speed capability needed? Everywhere else (TX, OH, NC, MA) even the dirt roads are smooth. I guess out in Australia they may need it, which is why UWA's awesome -05 car was built, but most of these cars are sold in the West where smooth-road handling takes priority over bad-road work.

CWA

05-09-2016, 02:24 PM

I'm really not sure where your point of difference is coming from

I said customers are right whatever they buy, you seem to think they are wrong and stupid if they don't buy cars that you like. Bla bla.

The major weakness is a front-lower-outer-BJ that snaps-off due to fatigue of a criminally negligent design

Since responding to your initial moans about hatchbacks spinning at the Nurburgring, I have only ever been talking about road-holding, not component durability.

From the department of the bleeding-obvious. -> "Active-electronic doo-dads" CANNOT SWALLOW BUMPS!!!

They are not made for this purpose, at least the systems you know that I am referring to are not. But if you are going to pretend you don't understand how they work nor their benefits in relation to the topic of our original discussion then I won't bother correcting you.

Utter rubbish. See below for just one example.

The 2CV? So the western automotive industry is a failure because it produces cars with rubber bushings and electronics and are no longer anything like the Citroen 2CV. Here endeth the lesson, I suppose.

You should set up business outside your local Primary School selling "recreational drugs" to the kiddies. You have just given yourself the moral justification to make a fortune!
(And BTW, the junk-food industry is simply the legal version of the illicit rec-drug industry.)

The difference is the role of the government in providing laws and legislation to protect anyone harmed by such hedonism. Giving drugs to children certainly results in harm. A mother buying a new SUV instead of a Citroen 2CV is not at all comparable. Laws and legislation reflect this, and until all the poor victims of SUVs start to cry out against them, it will remain this way.

Methinks the many objections are primarily an excuse to avoid having to learn how that stuff works.

Not true, speaking for myself at least, I've spent plenty of hours reading your technical threads, even if I don't post in all of them.

CWA, you are flipping burgers. Nothing wrong with that, but it ain't Engineering!

You know as much about what I do for a living as I know about what you do.