It's all about mu

[jvincent]

Originally Posted by maloney2

.... maloney2 gets all physicsy .....

Waiting for our great Oracle's reply to this.

[mrceltic]

Originally Posted by jvincent

Waiting for our great Oracle's reply to this.

I'm sure THIS time the light will go on and he'll recognize that if he closed his mouth and opened his ears he might actually learn something.

[husker741]

Titties.

[PMPB]

Originally Posted by mrceltic

I'm sure THIS time the light will go on and he'll recognize that if he closed his mouth and opened his ears he might actually learn something.

Actually, I'm fairly certain, his majesty will declare Maloney's paper to be crap, that his degree should be rescinded, and that he fears for us all because in his opinion Maloney is absolutely wrong (for some reason or another).

[drewbot]

[jvincent]

Originally Posted by mrceltic

I'm sure THIS time the light will go on and he'll recognize that if he closed his mouth and opened his ears he might actually learn something.

I'll take that bet.

[KPDoubleX]

Just get rid of your car already so we can all go back to talking about how much we love ours....thanks!

[Suberman]

For a guy on so many people's ignore list this is perversely gratifying. It's hard to know where to begin.

None of the posters actually understood what I wrote. I'm not sure if anyone understood what they thought I wrote. I have implemented a policy of never responding to wparsons as he is clearly an idiot, or so good at imitating an idiot no one can tell he's not really an idiot.

Most hilarious was the comment on Stig's lap in the 458. About the only places the Stig does allow a bit of oversteer is at the apex of hammerhead (logical, it's a tight bend and a transition bend, hence the name) and on the exit to hammerhead. All the remaining corners clearly show the 458 with the front wheels turned somewhat into the corner, as you would expect from an expert driver. I believe that's Ben Collins. I don't think many drivers in the world could beat Collins on that track although Rubens Barrichello did....

The engineer must know that mu is a constant by definition. He failed to note my qualifier when my little play on words caught him out. That's ok. His post at least confirms much of what I've been saying and with nifty charts. Thanks for the info, your text is not so useful and although your thesis is somewhat interesting and one can glean relevant information it isn't very helpful to the topics at hand. Engineers still avoid taking English at university except the mandatory course. Thanks anyway.

As for mu not being constant even though it is a constant this article goes some way to explaining my "oversimplification":

http://bsesrv214.bse.vt.edu/Hop/Pape...oefficient.pdf

I haven't read it but I have a pretty good idea what it does say.

I did like the perceptive if technically inaccurate suggestion that tire friction is non-Newtonian. It is true that tires don't behave strictly speaking as we might expect. Automotive engineers have not been troubled by the need to fudge the numbers a tad to match real world measurements though. It is perfectly correct that tire rubber meets the road surface in complex ways and also that considering mu to be constant as well as a constant means the actual performance of any given tire may be a bit different than the maths might predict but it is still obedient to Newtonian physics.

Use of the gravitational constant g isn't useful in analyzing oversteer relative to understeer because it is assumed to act through the imaginary CG. Use of g and fractions of g (which is actually absurd if one considers things properly) began with the aeronautics industry who do need to measure vertical g so it makes sense to use g for all accelerations in the pilot's 3D world. However, even there g is used for the entire vehicle and the entire pilot, not one end or the other. I'm pretty sure yaw, pitch or roll is neither measured nor displayed to the pilot in g, but I'm not a pilot.

Just as an amusing aside, a pilot or driver must fly by the sensations in his inner ear as compared to what he is seeing with his eyes. Neither pilots nor drivers can really "drive by the seat of their pants" that's all illusory. Without vision to coordinate with the acceleration your inner ear is experiencing you can neither drive nor fly. This is due to your inner monkey ....

I was particularly amused by the poster who suggested I get rid of understeer by pumping up my front tires and letting some air out of the rear tires...no, I won't be doing that.

I do note that Whiteline offers a 24 mm front bar (substantially stiffer than the stock 18 mm) which is really odd if much of what others have said about this car is correct. Please note that whiteline suggests this is your best bang for your buck:

http://www.whiteline.com.au/search_2011_4.php

I suspect they are right.

For my purposes I would consider fitting rear springs from the GT86 instead, if indeed the rest of the world gets a more softly sprung car than we do in North America. The gt86 apparently has softer rear springs than either the BRZ or the FRS but, squidgier front springs than the BRZ. In the wet softer rear springs should help but apparently not the gt86 as all testers report the gt86 is a real handful in the wet, as we have all discovered it is in the dry. No doubt that whiteline bar would be even more effective on a gt86.

Again, this is odd tuning if oversteer is faster.

I really was hoping for more reasoned posts. Just have to try again I guess. I'm patient and persistent.

Maybe somebody will actually quote a specific refutation from an actual suspension engineer? What an idea? We now apparently have one, or at least a wannabe one, but he still has difficulty reading and writing, and with a Masters degree (don't ask a practicing engineer what he thinks of engineers with masters degrees, just btw, they may suggest only incompetent engineers stay in school longer than they need to ...just sayin'. That's the basis for all those Howard jokes on Big Bang: no PhD AND "just" a Master's degree. All the engineers with only a bachelors degree roll on the floor laughing at that continual running double joke.)

[husker741]

Originally Posted by Suberman

For a guy on so many people's ignore list this is perversely gratifying. It's hard to know where to begin.

None of the posters actually understood what I wrote. I'm not sure if anyone understood what they thought I wrote.

Most hilarious was the comment on Stig's lap in the 458. About the only place the Stig does allow a bit if oversteer is at the apex of hammerhead (logical, its a tight bend and a transition bend, hence the name) and on the exit to hammerhead. All the remaining corners clearly show the 458 with the front wheels turned somewhat into the corner, as you would expect from an expert driver. I believe that's Ben Collins. I don't think many drivers in the world could beat Collins on that track although Rubens Barrichello did....

The engineer must know that mu is a constant by definition. He failed to note my qualifier when my little play on words caught him out. That's ok. His post at least confirms much of what I've been saying and with nifty charts. Thanks for the info, your text is not so useful. Engineers still avoid taking English at university except the mandatory course.

I did like the perceptive if technically inaccurate suggestion that tire friction is non-Newtonian. It is true that tires don't behave strictly speaking as we might expect. Automotive engineers have not been troubled by the need to fudge the numbers a tad to match real world measurements though. It is perfectly correct that tire rubber meets the road surface in complex ways and also that considering mu to be constant as well as a constant means the actual performance of any given tire may be a bit different than the maths might predict but it is still obedient to Newtonian physics.

Use of the gravitational constant g isn't useful in analyzing oversteer relative to understeer because it is assumed to act through the imaginary CG. Use of g and fractions of g (which is actually absurd if one considers things properly) began with the aeronautics industry who do need to measure vertical g so it makes sense to use g for all accelerations in the pilots 3D world. However, even. There g is used for the entire vehicle and the entire pilot, not one end or the other. I'm pretty sure yaw is neither measured nor displayed to the pilot in g, but I'm not a pilot.

I was particularly amused by the poster who suggested I get rid of understeer by pumping up my front tires and letting some air out of the rear tires...no, I won't be doing that.

I do note that Whiteline offers a 24 mm front bar (substantially stiffer than the stock 18 mm) which is really odd if much of what others have said about this car is correct. Please note that whiteline suggests this is your best bang for your buck:

http://www.whiteline.com.au/search_2011_4.php

I suspect they are right.

For my purposes I would consider fitting rear springs from the GT86 instead, if indeed the rest of the world gets a more softly sprung car than we do in North America. The gt86 has softer rear springs than either the BRZ or the FRS but, squidgier front springs than the BRZ.

Again, this is odd tuning if oversteer is faster.

I really was hoping for more reasoned posts. Just have to try again I guess. I'm patient and persistent.

Maybe somebody will actually quote a refutation for a suspension engineer? What an idea? We now apparently have one, but he has difficulty reading and writing.

[jvincent]

Originally Posted by Suberman

For a guy on so many people's ignore list this is perversely gratifying. It's hard to know where to begin.

None of the posters actually understood what I wrote. I'm not sure if anyone understood what they thought I wrote. I have implemented a policy of never responding to wparsons as he is clearly an idiot, or so good at imitating an idiot no one can tell he's not really an idiot.

Most hilarious was the comment on Stig's lap in the 458. About the only places the Stig does allow a bit of oversteer is at the apex of hammerhead (logical, it's a tight bend and a transition bend, hence the name) and on the exit to hammerhead. All the remaining corners clearly show the 458 with the front wheels turned somewhat into the corner, as you would expect from an expert driver. I believe that's Ben Collins. I don't think many drivers in the world could beat Collins on that track although Rubens Barrichello did....

The engineer must know that mu is a constant by definition. He failed to note my qualifier when my little play on words caught him out. That's ok. His post at least confirms much of what I've been saying and with nifty charts. Thanks for the info, your text is not so useful and although your thesis is somewhat interesting and one can glean relevant information it isn't very helpful to the topics at hand. Engineers still avoid taking English at university except the mandatory course. Thanks anyway.

As for mu not being constant even though it is a constant this article goes some way to explaining my "oversimplification":

http://bsesrv214.bse.vt.edu/Hop/Pape...oefficient.pdf

I haven't read it but I have a pretty good idea what it does say.

I did like the perceptive if technically inaccurate suggestion that tire friction is non-Newtonian. It is true that tires don't behave strictly speaking as we might expect. Automotive engineers have not been troubled by the need to fudge the numbers a tad to match real world measurements though. It is perfectly correct that tire rubber meets the road surface in complex ways and also that considering mu to be constant as well as a constant means the actual performance of any given tire may be a bit different than the maths might predict but it is still obedient to Newtonian physics.

Use of the gravitational constant g isn't useful in analyzing oversteer relative to understeer because it is assumed to act through the imaginary CG. Use of g and fractions of g (which is actually absurd if one considers things properly) began with the aeronautics industry who do need to measure vertical g so it makes sense to use g for all accelerations in the pilot's 3D world. However, even there g is used for the entire vehicle and the entire pilot, not one end or the other. I'm pretty sure yaw is neither measured nor displayed to the pilot in g, but I'm not a pilot.

Just as an amusing aside, a pilot or driver must fly by the sensations in his inner ear as compared to what he is seeing with his eyes. Neither pilots nor drivers can really "drive by the seat of their pants" that's all illusory. Without vision to coordinate with the acceleration your inner ear is experiencing you can neither drive nor fly. This is due to your inner monkey ....

I was particularly amused by the poster who suggested I get rid of understeer by pumping up my front tires and letting some air out of the rear tires...no, I won't be doing that.

I do note that Whiteline offers a 24 mm front bar (substantially stiffer than the stock 18 mm) which is really odd if much of what others have said about this car is correct. Please note that whiteline suggests this is your best bang for your buck:

http://www.whiteline.com.au/search_2011_4.php

I suspect they are right.

For my purposes I would consider fitting rear springs from the GT86 instead, if indeed the rest of the world gets a more softly sprung car than we do in North America. The gt86 apparently has softer rear springs than either the BRZ or the FRS but, squidgier front springs than the BRZ. In the wet softer rear springs should help but apparently not as all testers report the gt86 is a real handful in the wet, as we have all discovered it is in the dry.

Again, this is odd tuning if oversteer is faster.

I really was hoping for more reasoned posts. Just have to try again I guess. I'm patient and persistent.

Maybe somebody will actually quote a refutation for a suspension engineer? What an idea? We now apparently have one, but he has difficulty reading and writing.

There's so much fail in this post I don't even know where to start. So I won't.

@mrceltic, I told you so.

[maloney2]

The engineer must know that mu is a constant by definition

Mu is a variable not a constant. g, the acceleration due to gravity on earth's surface, is also not a constant. It is another example of a variable. G, the universal gravitational constant, however, is a constant. Some examples of other constants would be;

e, euler's number
Pi, the ratio of a circle's circumference to its diameter
L, Avogadro's number

variables such as g and mu are often assumed to be constant values, because in many real world applications this assumption is perfectly valid. With respect to tires however, the effective coefficient of friction cannot be assumed to be a constant.

He failed to note my qualifier when my little play on words caught him out. That's ok.

Perhaps I missed your play on words due to your misunderstanding that Mu is not a constant. That's ok

His post at least confirms much of what I've been saying and with nifty charts.....

...Because mu is a constant and identical for all four tires (one reason you must never mix tires) all four tires have the potential to develop the same grip. Axle weight distribution isn't as important as people think because total force is proportional to vertical load. Total grip varies but so does the loading the grip is required to deal with. This is why lighter people don't slip and fall any more readily than heavier people. Were mu not a constant the world would be a weird place.

My post in no way confirms what you have been saying. I was specifically trying to help you understand that axle distribution is critically important because the coefficient of friction is not a constant with respect to tires.

Slip angle results from mu. The distortion of the tire exhibited as slip angle is the reason static mu is the only relevant factor unless and until the car is overdriven and slides. Kinetic mu is markedly lower than static mu, and, kinetic mu has nothing to do with slip angle. Only while the contact patch grips the road statically does the tire produce slip angle forces. Once the grip is lost, slip angles decrease as does total traction and cornering grip.

First of all, the tire is both sliding and gripping simultaneously within the contact patch at all times. There is not some step where the tire goes from gripping to sliding. The relative quantity of gripping or slipping within the contact patch depends on the demands on the tire.

The dynamic coefficient of friction also has a large effect on the tires performance. In fact at very low normal loads, as seen in the provided data, the effective coefficent of dynamic friction can actually be larger than the static coefficient of friction.

The slip angle the tire is undergoing does not magically decrease when the tire begins to slide. If this were the case, the tire would self correct for excessive steer angles and always settle in a position that optimized grip.

This is why oversteering cars are slower, they reach kinetic mu earlier than cars which understeer.

This is entirely untrue. Over/Under steering behavior is related to the yaw angle of the vehicle relative to its heading. Given an equivalent deviation from the optimal path, whether it is one that tends to increase the cornering radius, as in understeering, or decrease the cornering radius, as in oversteering; the forward speed lost from scrubbing the tires is the same.

Maybe somebody will actually quote a specific refutation from an actual suspension engineer? What an idea? We now apparently have one, or at least a wannabe one, but he still has difficulty reading and writing, and with a Masters degree (don't ask a practicing engineer what he thinks of engineers with masters degrees, just btw, they may suggest only incompetent engineers stay in school longer than they need to ...just sayin'. That's the basis for all those Howard jokes on Big Bang: no PhD AND "just" a Master's degree. All the engineers with only a bachelors degree roll on the floor laughing at that continual running double joke.)

I have no idea why you feel the need to attack and belittle me, nor why you feel I lack literary ability. I have said nothing hostile towards you and have only tried to provide sound information. I am by no means a "wanna be" engineer. I chose to continue my education because I had both the talent to acquire scholarships and desire to better understand exactly this topic.

As a gainfully employed practicing engineer in the automotive industry, I have no concerns observing some of my fellow engineers with bachelors degrees spending their days detailing drawings. I can assure not all the engineers with bachelors feel as you have described. Typically those that convey that opinion do so in frustration over their own lack of ability to do so.

There is so much crap spread over the internet with regards to vehicle dynamics that I simply wanted to correct some of your misinformation. Your attacks are clearly in an attempt to incite some type of hostility, however, I in no way have any interest in attacking a persons character and for someone of your qualifications I cannot understand why you do.

[mrceltic]

Originally Posted by Suberman

Also, this arrogant and egotistical rejoinder is to a ridiculously personal criticism that has no place in this thread or on this board. If you're going to get personal at least be amusing or clever about it.

I never cast the first stone, ever.

Except of course when it's a new user on the boards who takes the time to share his knowledge and expertise with a stranger...

Originally Posted by Suberman

Maybe somebody will actually quote a specific refutation from an actual suspension engineer? What an idea? We now apparently have one, or at least a wannabe one, but he still has difficulty reading and writing, and with a Masters degree (don't ask a practicing engineer what he thinks of engineers with masters degrees, just btw, they may suggest only incompetent engineers stay in school longer than they need to ...just sayin'. That's the basis for all those Howard jokes on Big Bang: no PhD AND "just" a Master's degree. All the engineers with only a bachelors degree roll on the floor laughing at that continual running double joke.)

Hypocrisy, irrationality, and loneliness; all the requirements to be a troll. All you're missing is a bit of originality.

[mrceltic]

Originally Posted by jvincent

There's so much fail in this post I don't even know where to start. So I won't.

@mrceltic, I told you so.

Double or nothing; Suberman apologizes to Maloney for his personal attack and admits he's a paralegal of average intelligence.

[PMPB]

Originally Posted by mrceltic

Double or nothing; Suberman apologizes to Maloney for his personal attack and admits he's a paralegal of average intelligence.

I'm almost willing to bet my car. However, I've seen too much evidence that Suberman is willing to say anything to nettle us. In fact, this last week, his posts have been so over the top with ignorance and blatant misconstruing of facts, that I'm positive he's just trolling.




I'm just so glad there is another engineer in here, saying the same thing as the rest of us, so I know I'm not losing my mind.

Originally Posted by Suberman

We now apparently have one, or at least a wannabe one, but he still has difficulty reading and writing, and with a Masters degree (don't ask a practicing engineer what he thinks of engineers with masters degrees, just btw, they may suggest only incompetent engineers stay in school longer than they need to ...just sayin'. That's the basis for all those Howard jokes on Big Bang: no PhD AND "just" a Master's degree. All the engineers with only a bachelors degree roll on the floor laughing at that continual running double joke.)

Are you really basing real life on a TV show?

BTW Suberman. I have nothing but respect for M. Eng. In my field, I feel like doing a masters isn't going to get you very far, because the vast majority of our work is more dependant on experience.

With that said, certain fields, like Electrical, Mechanical, Software, Chemical, the new guys with the most education are typically the most valued and trusted, and if a B. Eng or a practicing engineer is laughing behind their back, it's because they are jealous. I know it's been a long time since you've been to school Suberman, but very few are qualified to be taken on as Masters or Doctoral candidates. Too few spots for too many students.

For somebody who says they are wise enough to step outside when the monkeys are flinging shit, you are always there to throw the first volley...