but 10% more force on the tyres won’t equate to 10% more cornering force.
Andy
S1 or S2?
S1 … My contact retired 3-4 years ago …
Randy, a question for you
why does Simon Scuffman put a wing on the back of his elise if it has no benefit and causes more drag than downforce?
Sorry to keep harping on about this, but I just can’t understand where you’re coming from.
Basic physics again:
Ffric = m N (sorry, no mu symbol in this font).
In this equation the symbol m stands for the friction coefficient between tyres and the ground and N is the normal force on the tyres.
The frictional force is directly proportional to the normal force on the tyre. 10% extra in means 10% extra out. It really is as simple as that.
I should add of course that 10% more grip doesn’t mean 10% more speed through a corner. The cornering force is proportional to the square of the velocity.
I should add of course that 10% more grip doesn’t mean 10% more speed through a corner. The cornering force is proportional to the square of the velocity.
now you are just showing off
Does anyone else just drive the car and only worry about grip levels when they start to squeal whilst going round a corner?
Who’s “they”? Passenger, or driver?
Steve, just make an “anorak” your number 1 chrissie pressie, so you’ll feel at home on here
Oi Pesky, I resemble that remark!
Does anyone else just drive the car and only worry about grip levels when they start to squeal whilst going round a corner?
I found that after drivng and owning the car for a while the technical side of trackdays tends to suck you in like…well like a narrow tunnel under the side pod, shaped like an inverted wing, as air enters and is forced through the narrow center,its speed increases, creating a low pressure area between the bottom of the car and the track. This creates a suction effect, which holds the car to the track - a Venturi
Very good Brendan but you are assuming that a tyre gets its grip form simple friction - which it doesn’t. A tyre creates a chemical bond with the tarmac and hence does not act like it is in simple friction. I have some good books on tyres/aero which I will dig out at some stage and post up seeing as my personal experience seems of little value to you.
Randy, a question for you
why does Simon Scuffman put a wing on the back of his elise if it has no benefit and causes more drag than downforce?
Simon and I run a wing because the Elise has an aerodynamic imbalance - read my earlier post. This goes some way to rectifying the issue. On top of that it’s not just the wing on the Exige (which is a rubbish profile) which causes the drag and its not an Exige wing that we run, although the one we run is still not ideal. Ideally on a race car you try to generate the bulk of the downforce from the body as that the most efficient way of doing it and that�s what is rubbish on the Exige.
Anyway I�m getting fed up with posting technical info on here as all I get is people jumping down my throat� what I have learnt on the race track is obviously of little value.
Anyway I�m getting fed up with posting technical info on here as all I get is people jumping down my throat� what I have learnt on the race track is obviously of little value.
Randy - please continue posting. Your contributions are valued.
If there is any criticism I can raise (and the same can be equally true of a number of other people from time to time - myself included) it is in your delivery.
Perhaps you have been spending too much time in Scuffers company
No, Randy I made no such assumption. As I explained earlier, that equation is an over simplification, but it’s a reasonable appoximation for such a small amount of downforce.
I haven’t seen you post any technical info here, just opinions without any evidence or explanations.
I’m not doubting your experience, and I’m not trying to start an argument. I’m just trying to understand why you say the Exige doesn’t produce the downforce claimed by Lotus.
I know various Elises have been tested. Apparently a standard Elise has circa 50kg -ve at the front and 10kg +ve at the rear so maybe an Exige does have 80kg total. Maybe an Exige has been in the tunnel but I doubt any changes were made. If Lotus had even the slightest worry about aerodynamic performance they wouldn’t have made the rear clam with those silly overlapping bits.
Perhaps reading my posts would be a start.
Even if the Exige produces the 80kg Lotus claim, 80kgs is still bugger all.
I don’t agree that your approximations are relevant or even vaguely accurate. Personally I wouldn�t post anything like that unless it was quoted from a reliable source or if was an engineer in the appropriate field, otherwise its just hyperbole.
What’s next?
My race car’s got loads of power. The Exige has naff all power. I doubt you could even detect the power from that engine. It’ll never even move. Lotus claim 190bhp, but I bet it’s bugger all. They just designed the engine to look good. It’s rubbish.
I give up. I’ve read a number of books on vehicle dynamics, and a quick search of the 'net shows loads of examples backing up what I’ve learned. Unless you can give me some idea of where I’m wrong, we’ll just have to agree to disagree
Bollocks to it.
Seems like I’m the only one who is willing to call a spade a spade.
Shovel?
Anyway I thought this was a good thread. Learning loads of things from everyone’s posts. Don’t get the hump Randy, we are reading what you say (just don’t understand some of it, so will have to re-read later).
[quote]Learning loads of things from everyone’s posts[quote]
About all I’ve learnt so far about downforce is:
[image]http://fishki.net/podborka2/44/piccsat06.jpg[/image]
![http://fishki.net/podborka2/44/piccsat06.jpg[/image]](http://fishki.net/podborka2/44/piccsat06.jpg%5B/image%5D){kind=link}
That’s Randy’s Nissan on the left and Brendan’s Exige on the right