xpensive wrote:As I said at the very start of this thread Richard, we had quite a number of simplifications, mu being one of them. Static friction is obviously higher than dynamic such, one of the reasons for traction-control and anti-lock brakes, but I think the dynamic friction should stay pretty constant regardless of amount of wheel-spin?
Mu is clearly not constant with contact-pressure, Load over area, which is why cars have wide tyres in the first place. But on the other hand, contact area, or patch, increases with load, why there is a trade-off I think.
xpensive wrote:"Static friction is obviously higher than dynamic such,..."
"Given that rate of deceleration reduces when the tyres are locked up, I'm inclined to disagree with your statement."
Xcuse me Scot, but isn't that what I said, when dynamic friction is what you get after lock-up or wheel-spin?
Scotracer wrote:Here's what I came up with:
I had to use a larger frontal area than you, Ciro, as 0.9m^2 was giving me very small values.
*Ignore the stupid unit mess up in the last column
Coefficient of Lift: -2.3
Coefficient of drag: 1.0
Planform area: 3.5m^2
Frontal area: 1.5m^2
Coefficient of Rolling Resistance: 0.05
Here are some pretty graphs:
Total drag including rolling resistance and aero drag
Power comparison. Top speed is the cross-over point, obviously - High Downforce Setup
^ Shows how efficient these cars are, given that they have open wheels.
To calculate the wheelspin problem we need to know the torque about the back wheel and the force resisting that torque (which will be a function of mu, wheel radius and downforce I reckon...).
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