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Discussion Starter #381 (Edited)
l0ki said:
Your latest.
It is about this... and again I am paraphrasing... Simon said something like, #I think we can all agree, grip does not not double as we double the weight# to which [paraphrasing] I said, # No, I can't a gree with that.#

Now we all know why... it was wrong.

Since then we have had a the shameful edited Graphs and the extra-ordinary 'Multiple centres of Gravity' debacle. In all instances I have been proved to be correct, it has just taken 300 posts to correct some thing to the satisfaction of the majority.

Mooseracer said:
Your latest.
You have it the wrong way round, they are not my words but Simons, I have not subtly changed them, they remain his and his alone.

I do catch people out, it is part of my job.

SDB said:
Your latest.
Yet again you seem to want to attach the words that you uttered to me, they are your own, it is YOU who has made all the innaccurate statements in this thread, you and your little claque.

It is you that has squirmed and danced around the truth.

I have put forward very little except in those first 3 posts of mine on Page 1, all the rest has been spent trying to correct your corrections of those posts... and it seems that finally you agree that your statement that:-
'Doubling the weight on a tyre, does not double it's grip.''
is wrong.

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

To whom it may concern...

It can be seen from this entire thread, apart from the first few posts, has not been about truth or the veracity of intellect or even the gainful seeking or passing on of knowledge, it has been about something far more important than that, it has been about Simons fragile Ego and my much larger, more robust one. :D

So far Simon has accepted all my offers of an Olive branch and has promptly burnt it the next day.

I leave this thread in the morning hope that sanity breaks out in the mean time only to return to find [often] 4 pages of bile and vomit all over my once lovely thread.

I posted way back after one of Simons [lets be charitable] more inane graphs the single word... 'Laughable' in hindsight, perhaps that is the best thing that can be said of this entire thread except for those first few posts...

That is the last possible attempt at an Olive branch I am gonna offer.

Cue: Thorin, Ayling and other assorted trolls adding to the mix in an effort to prolong this...
 

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I suprised myself by finding the initial goals of this thread quite interesting. Despite it going downhill, I've carried on reading, partially out of ghoulish curiosity, but also because I did still hope to learn something (even if I may never get to put it into practice).

I'm now left confused by several matters, and disappointed that it's unlikely they'll be answered. My attempts to find answers elsewhere have not helped. For example, I'll admit that I'm no physicist :) but these two points seem to be at complete odds to this thread:-

1. "If you apply twice the load to the tyre, you do not get twice the cornering force." - that quote is from Smithees Race Car Technologies, but seems to be echoed in the majority of sources.

2. I (like many others it seems) always believed that wider tyres=more contact=more grip, whereas my (admittedly amateurish) searching seems to point to engineers and physicists alike saying that this is not the case.

These seem to be just a couple of the points that go against the information in this thread, and just when I think they've been answered, the contributors come back and contradict them, leaving me thinking that there's more to it or I'm missing something.

For me as an average Joe, the precise difference between things like "slip" and "grip" is irrelevant. As far as I'm concerned, they're two areas on the same scale, like hot and cold, wet and dry - different, but all terms I can understand and relate to in subjects without being bogged down for pages in the actual terms themselves. I appreciate that many of the regulars on here are far more advanced than me and they probably wouldn't appreciate it being dumbed down, but doesn't the more people who find the information accessible make the thread more worthwhile, or is it all just navel probing, the elite telling each other what they all already know?

Anything beneath here is worthless general whinging, sorry. Apologies if anyone feels I'm attacking them, I'm just trying to say it as I see it as one who hasn't seen all that's gone before.

However this thread started out, it seems to me that Simon is willing to discuss with everyone who posted (regardless of their level of knowledge) their questions or statements, and I've seen him conceed quite happily a couple of times when making informed guesses. I even understood most of the stuff he wrote :D

For me, the vast majority of Mycroft's posts have been aimed AT "SDB", and almost all have been concerned with defining terms and what I see (as a layman) as nit-picking and point scoring. I'm unsure whether the concentration on using technical phrases where plain speak would suffice is because the subject is too complex for the likes of me and I'm on the wrong board, or whether it's being done on purpose. Either way, it's not given me anything, and his confrontational attitude is what has put me off posting until (what appears to be) too late.

To be honest I think that several of your differences could have been resolved quickly with some sensible dialogue, and while I don't know the history and cause of the obvious animosity between you two, viewing this thread in isolation I have to blame Mycroft's attempts at oneupmanship, word trickery and plain rudeness for that not happening. The need to be right or just prove someone else wrong seems to be the driving force, and far more important than actually giving anyone anything worthwhile.

Cheers,

Deano
 

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Discussion Starter #383
Originally posted by Beemer_Deano
1. "If you apply twice the load to the tyre, you do not get twice the cornering force." - that quote is from Smithees Race Car Technologies, but seems to be echoed in the majority of sources.
It is a phrase that I have no problem with so long it forms part of a greater sentence or paragraph.

Originally posted by Beemer_Deano
2. I (like many others it seems) always believed that wider tyres=more contact=more grip, whereas my (admittedly amateurish) searching seems to point to engineers and physicists alike saying that this is not the case.
The size contact patch for a given load governs the sum of the grip [that is the correct term] it does not govern the rate of slip, which is in the thrall of many variables.
 

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Hi Deano

Thank you for you comments, especially the suggestion that my explanations are accessible (something I place importance on). I also accept my part of your criticism.

To pick up on your questions (and I'm glad you decided to post them in the end)...

- The statement you found about doubling the grip is accurate and accepted throughout the world of vehicle dynamics, so you can take it as being an accurate description of a working car.

- "Bigger tyres = More grip"?

This is a cool one.

Ignoring the fact that the *area* of the contact patch isn't affected directly by the width of the tyre (I'll explain this if you wish)....

A wider tyre creates a wider contact patch, which (this is a blanket statement which cuts through a lot of the complexities) effectively gives you more cornering grip.

But... More rubber does not ACTUALLY mean more grip in the scientific sense. If you double the amount of rubber on the road, you end up halving the average "load per square cm" (if you like) on the contact patch, so there is no more actual friction.

But again, tyres are WAY more complicated than that, so having a wider tyre allows the load to be spread more evenly around the tyre, creating less heat build up (due to friction - not necessarily hysteresis) and less demand on each area of the tyre. So you do end up getting (to some degree, or in some way) more grip. But again it's not clear cut..

The problem is... If a tyre is too big for the application, it will never reach operating temperature, or will not be able to be run at low enough pressures to provide enough of a contact patch "length" (as oposed to width) for acceleration (meaning longitudinal acceleration) grip.

So it's not a straight forward question / answer I'm afraid. Like the majority of vehicle dynamics, it is a trade-off situation, where you will end up with an ideal (or best compromise) for your specific application.

Hope this helps

All the best

Simon
 

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Discussion Starter #385
Originally posted by Beemer_Deano
For me as an average Joe, the precise difference between things like "slip" and "grip" is irrelevant.
It would be nice to think so wouldn't it!, and if you keep your car entirely un-modified then so it will remain, all that 'work' has been done.

Originally posted by Beemer_Deano
As far as I'm concerned, they're two areas on the same scale, like hot and cold, wet and dry - different, but all terms I can understand and relate to in subjects without being bogged down for pages in the actual terms themselves
They are on the same line but at one end of that line you have 'GRIP' and at the other you have '100% SLIP' which effectively means Airborne!!!

Terms are very important if you are to get across any information correctly, to me a wrong term is like being told by a shopkeeper that will be '5' now 5 yen is a lot less than £5. So even to you in your own World terms are important.

Rather than addressing every point in the style above i will just add them as a 'running commentary'

Originally posted by Beemer_Deano
However this thread started out, it seems to me that Simon is willing to discuss with everyone [except me, the one person making serious corrections] who posted (regardless of their level of knowledge) their questions or statements, and I've seen him conceed quite happily a couple of times when making informed guesses. I even understood most of the stuff he wrote :D

For me, the vast majority of Mycroft's posts have been aimed AT "SDB", [In deed they have] and almost all have been concerned with defining terms and what I see (as a layman) as nit-picking and point scoring. I'm unsure whether the concentration on using technical phrases where plain speak would suffice is because the subject is too complex for the likes of me and I'm on the wrong board, or whether it's being done on purpose. Either way, it's not given me anything, and his confrontational attitude is what has put me off posting until (what appears to be) too late.

It is never too late to join in, but debate will always have some degree of confrontation, the Scientific World I inhabit is full of fights and bust ups put downs etc. this has been more refined than I am used to frankly, hence its dragging on for so long, if allowed to behave as on some forums Simons fragile ego would have been squashed like the tiny delicate blossom it is, I'm afraid to get nasty in case he cries his damned eyes out!
 

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hey up!

I see this is still going.

I thought we had some resolution on this?

Helloooooooo, get a life people.

Paul
 

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Discussion Starter #389 (Edited)
Where have you been?

You are not much of a shadow are you?

Slacker!

:D

Simon needed your help and you were not at hand in his hour of need.

Anyways up!

How you doin'?

Would you like to talk co-effs of friction or would you like to talk about grip?

As I believe you believe you are 'one smart cookie' perhaps you can answer the simple next question to be dealt with here:-

''Could you tell us all when a disc brake has a pad with a Co-eff friction of 0.45 and is slowed down by it does it mean, assuming flat ground, when the driver has stopped and is holding the car stationary with his foot on the brake, is that same co-eff or is it infinite?''
 

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Whilst I would be happy to be proved wrong...

And ignoring all silly complications like the fact that the suspension / diff binding, etc, etc may be exherting a force on the wheels... In effect assuming there is no turning force acting on the wheels at all....

I would suggest that the coefficient of friction of the pad / disk would be unaffected. It would just be that you would be measuring the static coefficient rather that kinetic.

Cheers

Simon
 

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Discussion Starter #391
You can ignore all those silly things, I never 'go' for things like that.

Perhaps, looking at it this way may lead you to getting the right answer.

When does friction actually happen?

You could describe friction as the ACTION of resisting movement by means of abrasion, in the absence of movement do you have any friction at all or a huge amount?

:D
 

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You can ignore all those silly things, I never 'go' for things like that.

Perhaps, looking at it this way may lead you to getting the right answer.

When does friction actually happen?

You could describe friction as the ACTION of resisting movement by means of abrasion, in the absence of movement do you have any friction at all or a huge amount?
hmmm..

3 major problems I have with what you're getting at.

1) Abrasion is CAUSED by friction, not the other way around
2) Friction is a force, not an event
3) Static friction coefficients would not be of any interest as they would all be infinite.

Please explain.

Regards

Simon
 

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Discussion Starter #393
Originally posted by SDB
1) Abrasion is CAUSED by friction, not the other way around
2) Friction is a force, not an event
3) Static friction coefficients would not be of any interest as they would all be infinite.
1/. Agreed, and nothing I have written contradicts this.
2/. Agreed, and nothing I have written contradicts this.
3/. So, we have gone from 0.45 to infinite, yes?
 

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Oh dear, I sense another one.

I'll post the reason for my first two items and a clarfication of what I meant by the third, then if you would be so good as to explain why you think that it goes to infinite, that would be great and would save a stream of posts arguing the toss (probably about wording again).

You could describe friction as the ACTION of resisting movement by means of abrasion
1) Abrasion is CAUSED by friction, not the other way around

You could describe friction as the ACTION of resisting movement by means of abrasion
2) Friction is a force, not an event

---
3) Static friction coefficients would not be of any interest as they would all be infinite.

What I mean by this is that, if the brake disc has no other force acting on it, the pad / disc interface is static. If it were true that this would mean that the coefficient of friction was infinite, there would not be a need for the term "Static Friction Coefficient", and all measurements would be "infinite".

So, I don't personally think that it would go to infinite, but (as I said) would be happy to be proved wrong.

As you can see I have not tried to be clever, disruptive, awkward, cryptic, etc, etc. So I hope you will just post your explanation now.

Regards

Simon
 

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Discussion Starter #395
Originally posted by SDB
I'll post the reason for my first two items and a clarfication of what I meant by the third, then if you would be so good as to explain why you think that it goes to infinite....
I haven't said it is either, have I?

Show me... :D
 

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I've given you my answer Mycroft, if you have a point, please make it, otherwise..

Take care, speak soon
 

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Discussion Starter #398
So, what is your answer to this simple question... 0.45 or Infinite?

You have apparently given mine...

''would be so good as to explain why you think that it goes to infinite....''
 

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Discussion Starter #400
You're here, perhaps if you were at work like me then you could be right, if you are however at home then it is you, sonny jim, that needs to do something more useful with your life.

Would you care to hazard a guess at this?
 
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