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Old 22nd July 2003, 08:55 PM   #81 (permalink)
LSR
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Tire choice does matter. If I had a Veyron 16/4, but on crap tires, I wouldn't get the top speed extracted. The tires need to cope with the performance. The Brabus SL55 AMG cannot hit its top speed, because the tires aren't designed for the job, and suitable tires are being designed. Traction also matters, because without it, you'd be wheelspinning all along. But then traction limits the power available?

CdA is basically taking into account the car's cross section, don't start getting too technical

Apparently the Skyline makes a 26% power loss, which is a lot. I thought it was 320hp ATC to 280hp ATW, which is just over 10%.

And without high speed stability, the car wouldn't be pushed to its top speed by the tester, unless there is some serious contigency plans.
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Old 22nd July 2003, 09:09 PM   #82 (permalink)
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The problem with talking to kids is just that, they're just kids.

Things are already given in the example, traction was dealt with by the equal G force in a constant radius.

You are wrong again, it is not a x-section it is a silhouete, you would lose points if you said x-section in an exam, because it shows a lack of learning. Use silhouette or keep schtum.

In trying to establish core values you must learn to dis-count things that just blur the picture.

Power loss and high speed stability merely serve to confuse and frankly illustrate unclear thinking.

You are young and enthusiastic, that is wonderful and to be applauded, but your mind will be best served by listening and reading for a little time yet.
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Old 22nd July 2003, 09:32 PM   #83 (permalink)
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Quote:
So what you are saying in your own uniquely mealy-mouthed way is that what I have been saying all along has been right.
In a way yes.

Quote:
in simple terms getting a 1 tonne car to corner at 1 g is very much easier than to make the 2 tonne car do the same trick...
But that makes two of us.

Paul
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Old 22nd July 2003, 09:48 PM   #84 (permalink)
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I agree with what you said mycroft.

Keep reading to learn - agreed. I am still doing that, after all I am 17 and I have been into all things cars for two years, so I still have a lot to learn. I will continue to do that, as I have done long before joining up to here, MLR, scoobynet and mkivsupra.net

I mentioned the power loss concept but that didn't have anything to do with what else I typed such as tires, I only typed it up as it was mentioned before.

You mentioned exam, but for what? Automotive engineering degree? Doing this course did cross my mind, but I am not going to do it. I've still got another year to go in A levels.

Quote:
You are young and enthusiastic, that is wonderful and to be applauded, but your mind will be best served by listening and reading for a little time yet.
Thanks for the complement and I will continue to read from your technical concepts. I also won't challenge your ideas, as they are most probably right, and I shall considery you my mentor hehe.

Quote:
The problem with talking to kids is just that, they're just kids.
What makes you think I am a kid?

Yes, I may not know everything.
Yes, I may be a bit ****y.
I am on the outer bounds of the "kid" age.
Yes, I may challenge your concepts.

But a typical kid would be someone who types in block CAPS with a lack of grammer/punctuation (yes, I know I just did that), makes a concept, but whether radical/true or not, there is insufficient justification. And that I do not do (fair enough, I may not backup my technical points completely on here or elsewhere, as I am still learning about the technicalities of a car and got a long way to learn, with a lot of terms/definitions etc, as you have kindly and strongly implied, with the same recommendation of reading, which I always have and always will.).
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Old 22nd July 2003, 10:11 PM   #85 (permalink)
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Now, may I kindly suggest that some more rational and reasonable posts return, I am very concious that I am an 'outsider' [non-skyline owner], Pavlo is an outsider for the same reason as is Simon de Banke and LSR, in the light of this I believe too much effort [by myself as much as others] has been expended trying to 'make points'.

PLEASE STOP NOW.
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Old 22nd July 2003, 11:04 PM   #86 (permalink)
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Well said Mycroft.

Now where has Mr Hyde got to?

Paul
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Old 23rd July 2003, 04:47 PM   #87 (permalink)
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Mycroft, I know you cant resist a reply so:

In your ideal example, I think you are right. But try to transfer it to the real world and I'll think you'll find lighter is better.
For example, you say:

Quote:
Following that... if you set the gearing so that both cars 'topped out' at [say] 150mph and both had 'boxes with similar ratios, which car would accelerate faster... this being a simple 'disposable' power question...
What you are saying is that the only reason the heavier car can accelerate better is due to a higher power to CdA ratio. Agreed this will make a big difference to terminal speed between the two cars but surely it wouldnt affect acceleration *too* much, especially if the conditions do not allow any where near terminal velocity.

The benefits achieved by this higher power to CdA ratio are far exceeded by the difficulty in getting the heavier car to corner at the same G-force as the lighter one. In reality it's easier to cut weight and increase cornering ability (and power to weigth ratio) rather than maintain cornering ability and increase power to CdA ratio (while maintaining power to weight ratio).
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Old 23rd July 2003, 05:33 PM   #88 (permalink)
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Quote:
Originally posted by roojai
In your ideal example, I think you are right. But try to transfer it to the real world and I'll think you'll find lighter is better.
Easier, not better.

That is why Lotus, TVR and all the other 'shed at the end of the Garden' UK car builders do not produce anything other than enthusiasts cars [ie faulty, smelly second rate tat] the density of engineering is beyond them.

Quote:
Originally posted by roojai
What you are saying is that the only reason the heavier car can accelerate better is due to a higher power to CdA ratio.
No. Re-read the postings .

Quote:
Originally posted by roojai
Agreed this will make a big difference to terminal speed between the two cars but surely it wouldnt affect acceleration *too* much, especially if the conditions do not allow any where near terminal velocity.
Re-read the post, and think about what acceleration actually is.

To help you, we must consider acceleration as merely a 'by-product', you must re-read the thread and see what it is a by-product of.

Quote:
Originally posted by roojai
The benefits achieved by this higher power to CdA ratio are far exceeded by the difficulty in getting the heavier car to corner at the same G-force as the lighter one.
Correct to some extent if you are a back-yard builder like Lotus, TVR then yes I suppose it would seem terribly difficult.

Quote:
Originally posted by roojai
In reality it's easier to cut weight and increase cornering ability (and power to weigth ratio) rather than maintain cornering ability and increase power to CdA ratio (while maintaining power to weight ratio).
Agreed, but I don't like cars that are merely a more salubrious Trabant!

I like my cars to have true Engineering integrity, not just in one or two aspects but in all of them.
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Old 24th July 2003, 09:07 AM   #89 (permalink)
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attempt to clear this up (who am I kidding?)

Mycroft

Like I say, your situtation, no matter how far fetch, does indeed have logic and accuracy behind it. But...

The fact remains, regardless of whether you term it as "easier", the weight of a car (when isolated from everything other factor) has a negative affect on its ultimate potential cornering performance. Surely you wouldn't disagree with that?

If you don't dissagree, the remainder of the conversation is irrelevant except to prove that if you have more power, you can overcome drag to a greater degree.

All the best

Simon
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Old 24th July 2003, 04:45 PM   #90 (permalink)
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Re: attempt to clear this up (who am I kidding?)

Quote:
Originally posted by SDB
The fact remains, regardless of whether you term it as "easier", the weight of a car (when isolated from everything other factor) has a negative affect on its ultimate potential cornering performance. Surely you wouldn't disagree with that?
If what you are saying is that effectively putting 100kilos onto a cars weight and doing nothing else will make it 'slower' then as far as acceleration is concerned yes, that would be the case, but a nice example that shows even that is not always the case comes from the past, for a while it was a good idea to put a bag of cement in the nose of some Beetles, it made them faster point to point, there have been many cars where ADDING weight has made them faster point to point.

So even though your point is to some extent right, yet again the reality is not quite so cut and dried as many would have us believe.
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Old 24th July 2003, 04:56 PM   #91 (permalink)
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Hi Mycroft

re-read. My point was very specific. :

"ultimate potential cornering performance"

Not point to point, not acceleration, nothing else. This relates directly to the title of this thread.

On a side note, please take care of the above prior to commenting on this (should you have any)...

The Beetle thing is interesting and I have heard of a number of situations like this. This specific situation however does not mean that adding weight makes a car go faster, it merely meant that the specific set-up of that car meant that adding weight to the front made the car more performant, for any number of combinations of reasons.

I think the point is that it's easy to confuse people by adding complex specific situations which are exceptions to the rule, rather than explaining the concepts and then adding a simple "however this does not ALWAYS work in the real world, because x, y, z".

All the best

Simon
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Old 24th July 2003, 06:05 PM   #92 (permalink)
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My point about the acceleration for the lighter car was not a summation of what has been said in this thread but rather, a disageement on how you have warped the truth in your recent posts.

Unfortunately I havent figure out the quote bit properly yet but:

Your logic implied that if a heavy more powerful car can achieve a higher terminal speed if the gearing allowed, then such a car with lower gearing, similar to the lighter car, would be able to achieve faster acceleration at lower speeds than the lighter car.

Perhaps this is not what you meant, but it is what you imply with your thread of posts.

I say that the acceleration of a car is directly related to it's power:weight ratio with it's power to CdA ratio being a factor only at very high speeds or continued long periods of high speed.

F=MA

A = F/M

or with air resistance

A = F-minus resisting force due to air resistance/M

thus giving you your advantage.

I dont fully understand the weight shift theory on corner exit so if it this that you are on about, my apologies.

All the Best

Roojai
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Old 24th July 2003, 06:21 PM   #93 (permalink)
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Groundhog posts.

So in keeping with them:-

###
2 cars... 1 weighs 1 tonne the other 2 tonnes they both have equal power-to weight ratios and torque curve/gearing coincide exactly for each... they are perfectly matched... even down to the 'G' force each can generate in any given curve...

In a race the 2 tonne car will eat the 1 tonner... quite easily...
###

Now, that is what I typed, and 7 pages later we get:-

###
Like I say, your situtation, no matter how far fetch, does indeed have logic and accuracy behind it. But...
###

Now, do I really need to do another 7 pages of this?

Answers on a post-card.
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Old 24th July 2003, 06:37 PM   #94 (permalink)
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Perhaps if you would like to answer what I think is Andys' underlying question then we would all be better served.

Is there an ideal weight or power to weight ratio for cornering?
If so, are there calculations for this whereby we can see the point where the true weight is maximised and the wing downforce takes over.

The answer to the 2 parts is Yes.
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Old 26th July 2003, 09:00 AM   #95 (permalink)
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Any thoughts on my last post Mycroft?

Then I would interested to go in to your last two questions.

All the best

Simon
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Old 26th July 2003, 10:14 AM   #96 (permalink)
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Quote:
Originally posted by SDB
Any thoughts on my last post Mycroft?
Yes.

Groundhog Post.



I don't want to labour the point Simon, but you really must try to move on, my point has been made and confirmed, even by such 'luminaries' as you.

Is there really much more to say on this?

Let's all try to avoid the conclusion that the 'D' in SDB means DULL.

What you say matey, move on or bore the pants off the entire forum?
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Old 26th July 2003, 10:27 AM   #97 (permalink)
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I thought we were done with "making points" mycroft?

You did not answer my question, and your "groundhog post" is irrelevant to my post at the top of this page.

It's a straight forward question, and I think we could make some progress if we are sure we're on the same wave-length.

To make it absolutely clear, I'll restate the question for you.

The hypothesis is this...

As a general rule and ignoring all far fetch or incredibly specific unusualities, adding weight to a car detrimentally affects its *ultimate cornering performance*.

Do you agree with this? Yes or No. If No, please explain.

Simon
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Old 26th July 2003, 10:35 AM   #98 (permalink)
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Apologies...
I mis-quoted myself! the above should read *ultimate potential cornering performance*
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Old 26th July 2003, 10:41 AM   #99 (permalink)
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Boring.

Move on son!
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Old 26th July 2003, 11:05 AM   #100 (permalink)
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I find it laughable that you are unwilling to simple say "yes I agree" to something so blatantly obvious. But I'll assume it is clear to all what that means.

Now on to your questions...

Quote:
Now, that is what I typed, and 7 pages later we get:-
###
Like I say, your situtation, no matter how far fetch, does indeed have logic and accuracy behind it. But...
###
Acutally, my very first post agreed that there was a loophole (which is the far fethced part) that meant you were correct in the specific thing you were saying. That is the reason that sentence (which was 5 pages after your statement, not 7) included the words "Like I say".

Unfortunately you chose to ignore the rest of my post and purely plucked out a sentence which had words to the affect of "you are right".

...

I also find it interesting that the following quote from your post a few back :
Quote:
I don't want to labour the point Simon, but you really must try to move on, my point has been made and confirmed, even by such 'luminaries' as you.

Is there really much more to say on this?

Let's all try to avoid the conclusion that the 'D' in SDB means DULL.

What you say matey, move on or bore the pants off the entire forum?
was added through an edit after both of my replies that followed. I prefer to stand by my words and retain the continuity of the thread. We can only speculate as to what kind of reasons someone would have for doing otherwise. My speculations include : at worst, a desire to make someone look stupid by not giving them the opportunity to discuss directly what you eventually edit in to your posts. At best, an inability to think clearly enough to come up with such a masterpiece the first time.

---

Now on to your next diversion from the topic you are unwilling to discuss (namely the topic this thread started asked about)...

Quote:
Is there an ideal weight or power to weight ratio for cornering?
No. There is no such thing as "ideal" when discussing vehicle dynamics in the real world. There are a number of papers which include extraordinarily simplified examples of figures (almost all from steady state physics) in an attempt to train the inexperienced accademic. I'm hoping (for fear of completely losing interest in this thread) that you are not going to start quoting them.

Regards

Simon
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