Suspension Design

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Originally posted by Z:
But the thing that really irks me is that the whole auto industry (production and racing) has promoted the 2-D theory as being the "absolutely" correct kinematic theory.

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Having worked in both the consumer and motorsport areas of the auto industry, I don't agree with this statement... specifically not agreeing that the 2D approach has promoted as "absolutely correct." I'd say it is viewed as one tool, of many.

Not to mention that in the real world where you are sometimes faced with kinematically overconstrained dependent suspensions (i.e. if rigid would be impossible to move), all the discussion of the pro's and con's of 2D vs 3D kinematic approach is pure masturbation.

Well I worked in the industry for 40 years and with 4 top echelon racing teams and I don't recall any proponents of "2-D" theory. When you have a K&C machine to use as readily as a copy machine, a top notch Adams group to support the latest international theories, and an Instrumentstion and Test group to analyze and evaluate the latest legends, lore, and hocus-pocus, you can get to the bottom of of vehicle dynamics pretty quickly. Getting Purchasing, Manufacturing, Marketting, Safety, Rules and Regulations, Durability and Dealer Support to accept "optimum", "refined", or "acceptable" chassis, steering and tire specifications, now that takes some serious magic.

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Originally posted by BillCobb:
When you have a K&C machine to use as readily as a copy machine, a top notch Adams group to support the latest international theories, and an Instrumentstion and Test group to analyze and evaluate the latest legends, lore, and hocus-pocus, you can get to the bottom of of vehicle dynamics pretty quickly.

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Bill,

Why do you need all that equipment? It is a very easy subject to understand.

And what are these "latest international theories"? Are they any better than the "hocus-pocus" developed by Euclid, Galileo, Newton, d'Alembert, Euler, Chasles, Ball, and a great many other very clever men, hundreds of years ago?
~~~o0o~~~

Anyway, it is perhaps pointless trying to reason with the angry mob...

"Heresy!!! It is heresy!!!!!!!
That blasphemer Z is saying that the world is NOT flat! He claims it is a globe, and it moves around the sun!!!!!
Bring the firewood and torches. He must be burnt at the stake...!!!!"

Bring on the next Dark Ages! http://fsae.com/groupee_common/emoti...on_biggrin.gif

Z

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Originally posted by Z:
Why do you need all that equipment? It is a very easy subject to understand.

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You seriously just said this?

http://www.burdandkeyz.com/wp-conten...on-300x224.jpg

But I will bow down to thee Z, who hath eclipsed us in professional motorsport experience and championship victories by thine screw axis method.

Just keep going, you only need to dig a little bit deeper to hit that magic 6ft mark

A few very amusing anecdotes come to mind when I read your question back to me.

1). When GM got together with Saab, a very loud and self centered 'expurt' went to all the GM execs spouting about how rear lateral force oversteer was a key ingredient to the superb handling of Saab cars. (You know what 'Saab' stands for, right? Still Ain't A BMW). OK, so we test and analyze and guess what? No Saab car has lateral force deflection oversteer. Their Panhard bar twist axle has a little on one rear wheel and deflection understeer on the other. Just like the 3-D theory says it ought to be. In other words, Dr. Shitforbrains is an ignorant fool, but with a big mouth and a bigger lame audience. Saabs need very unusual tire sizes and constructions because their suspensions are sloppy and require high cornering stiffnesses to achieve just 'average' transient response characteristics.

2). Lotus lovers would be horrified if they could see the k&C measurements on ANY of their cars. Probably never has been a single one build the same. No wonder they all have their 'unique' British flavor and distinction. Use of 3-D suspension analysis allows you to perform build tolerance studies. You use Monte Carlo techniques to statistically build suspensions and identify what locations are critical and what tolerances you must have to maintain consistency, alignment, safety, forseeable misuse, aftermarket tire use and durabilty concerns. If the plant can't hold the tolerance, you can't use that design. Lotus uses the Monte Python technique (IMHO) to slap their cars together. Good grief Charlie Brown. Of course, the world adores their products because of all the inebriated exuberance of their own verbosity. (You know what Lotus stands for, right? Lots of Technically Useless Shit).

3) The Holden G8 turned into the Pontiac Grand Prix was another reason to go to testing and analysis. When turned over to GM N.A. as a Finished product (not to be confused with the Swedish products), the G8 was release on a tire that was absurd for stopping distance, wet traction and fuel economy requirements. Any other brand of tire (Bridgstone would never even have had enought to meet US production volumes) made the car extremely unmanageable, failed NHTSA stopping tests and STBed its fuel economy requirements. GM exeecs who drove them lost control of a few cars in normal driving maneuvers. Analysis and testing forces a redesign of the head and azz end of the car by N.A. to make it LEGAL to sell here, in spite of the Aussie 'ex-purr-tease'. So much for Erector Set vehicle dynamics. (You know what Pontiac stands for, right? Penniless Old Nigerians Think Its A Continental).

If BMW's are so great, why does it take so long to put out a new model? and why does every generation of BMW have a different roll steer gradient? Yes, they are very close per given model year (unlike Lotus). Can't they stick with a great recipe, or don't they have one in mind yet. Analysis would tell you this. Testing would validate the analysis. (You know... Bite My Wieney).

If Porsche could add just abit more roll understeer to their cars, it would steer more than it rolls. But wait, that not what I read about those Black Forest gnomes. Back to the very expensive tires and now we need two different sizes on the car. Buddy can you spare a spare tire? (You know what Porsche stands for, right? Proof Only Rich Suckers Can Have Everything).

Want to know who does the most supurb, consistent, fun to drive, technically brilliant, blah, blah, blah best in all classes? You already know, eh? (Historically Orientals Never Drove Automobiles). And I've still got the DATA to prove it. When I saw a K&C summary sheet or a road test set of plots and metrics, any Honda car hits you like a DaVinci viewed in a museum.

I could go on, but I'd like not to resurrect old nightmares about how the Lords of Vehicle Dynamics get away without the triad of synthesis/analysis, lab tests, and road tests.

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Originally posted by Z:
It is a very easy subject to understand.


Z

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Now your just being facile. Tennis is just hitting a ball over a net - can I be a Grand Slam winner please?

Understanding the underlying engineering concept is often a tiny part of the battle, particularly when you're working with partners from different companies and cultures.

You never have all the data, so you have to make assumptions. When those assumptions conflict with those made by another engineer with the same incomplete set of data you have a problem that's no longer about engineering. Every engineering situation I've been in is like that from aerospace to mainstream OEM automotive to motorsport.

The reality Z is that you're a smart guy, but you're also likely to be the guy in a meeting that people will want to ignore and marginalise simply because you're arrogant and annoying. You might be right (you might be right all the time!!), but that's often not the point.

Ben

Z,

1. You cannot compare the seminar you came to more than 10 years ago with the one taught today. You should come for a refresh.

2. Whether you speak about the heave, roll, pitch and steering induced chassis Vs the ground movement (force or displacement input) or one wheel movement Vs the chassis there will (or could) be track, camber, caster, steer, wheelbase variations so implicitly in a good 3D geometry you describe these movements as a "screw axis" whether you call it or demonstrate it this way or not.

3. "You then made a career of teaching this talk to many of the "newbies" of the industry"
First my company is not only about teaching. That is 1/3, the 2 other 1/3 are consulting and simulation.
Second, think again Z. Not later than last week I gave seminar #347 at Chrysler to 100 engineers: 30 engineers from the vehicle dynamics group, 9 tire engineers, 10 “chassis controls” engineers (think ESP, ABS, etc...), 5 engineers from the testing group (K&C and instrumented handling), 23 Chassis Virtual Analysis engineers (modeling & simulation), 11 steering & suspension engineers, 7 people from SRT (ALMS Vipers) and a handful of other engineers, supervisors & managers. Not bad for somebody who "kept teaching the same nonsense"

4. You can be provocative but you need to adapt your words to your audience chose and your expression mode (written or spoken). It is a fine border. You use good judgment. If you don't people will. At your expense. I am sure you know things I don't and many other people don't. I am sure the community would benefit from both your knowledge and perspectives. Write more article, give seminars, become a teacher or a faculty adviser. Make the world benefiting from you but for God sake Z show some respect for others' experience and yes.. credentials. Maybe the whole education system is wrong, maybe the whole world is wrong but you are not helping anything and surely not yourself by being unnecessarily so aggressive. Time to unscrew your own axis Z. If you want a face to face meeting, I will be in Australia Melbourne area from December 6th to 15th. Not tie required for the meeting http://fsae.com/groupee_common/emoticons/icon_smile.gif just respect and desire to improve both knowledge and communication.

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Originally posted by Claude Rouelle:
If you want a face to face meeting, I will be in Australia Melbourne area from December 6th to 15th.

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If this actually happens, please please please put a camera in the room to record the conversation!

-Kirk

Z,

It seems a little one-sided when you critique forum members and then don't give said members the opportunity to critique you... What's your claim to fame besides book smarts and an acid tongue?

As Claude implied, think about your audience... this is a forum for a student engineering competition, with the bulk of us being undergraduates, alumni, volunteers and judges.

What category do you fit in? Maybe you don't...