anyone got a ballpark figure?
dry road. Force acting at 90 degrees to my direction of travel.
My little Corsa has been written off by some guy crashing into the side. He
managed to spin it through 360 degrees. Im trying to have a guesstimate of
the impact speed .
Ouch. Get one of those "heat up in a microwave" sausage shaped things, as
I suspect you`re going to be sore as hell within 2 days.
I was hit by a HGV in 2001 and still suffer now - leaning my head back to
relax is one thing I can`t do any more because the pain kicks in within 5
I was off for 6 or 7 weeks IIRC, and seriously couldn`t do a thing - i.e.
get dressed for the first 3 weeks or so. If it hadn`t been for internet
shopping we would have starved to death.
Please add "[newsgroup]" in the subject of any personal replies via email
--- My new email address has "ngspamtrap" & @btinternet.com in it ;-) ---
Key thing is what was the road condition. Downforce on back of a Corsa or
other small FWD hatchback can be as little as 0.1g (which is why the inside
wheel lifts in fast cornering) so it probably didn't take as much as you
Firstly, downforce is an aerodynamic term and very few road cars have any of
that. Most generate lift at speed.
If you meant weight distribution then still gibberish. The average FWD car has
55% to 65% weight on the front and 35% to 45% on the rear.
Finally, neither weight distribution nor downforce have anything to do with why
a FWD car lifts its inside rear wheel during fast cornering. That's to do with
the relative roll stiffness front to rear. FWD cars have high rear roll
stiffness to keep the front (driving wheels) on the ground in corners. RWD cars
have high front roll stiffness to keep the rear (driving wheels) on the ground
Dave Baker - Puma Race Engines (www.pumaracing.co.uk)
Downforce is the force acting downwards on the mass of the car. It could be
aerodynamic for a racing or performance car but in this case is just due to
gravity. Although there is 35% of the weight of a FWD though the back when
stationary, this drops to as low as 10% under dynamic conditions such as
heavy braking which is where ny 0.1g comes from. Do you understand now ?
I presume your pumas don't race too well then. A FWD lifts it's rear inside
wheel because the front outside is heavily loaded by cornering forces and
you get suspension compression. On a road car driven fast this is far in
excess of how fast the rear suspension can compensate as this is often
constrained by either a rear anti-roll system or some form of dead axle
connection and the wheel simply lifts. But if you can reduce forward weight
transfer under heavy cornering then the effect is reduced considerably - the
Focus RS is a prime example of how to do this correctly.
As for RWDs the high front roll stiffness is to keep both front wheels on
the ground during braking. Adjusted properly, squat is eliminated and
braking is optimal. It has no effect on the driven rear wheels in corners -
even on an old Mk2 Escort ! For a fully independent rear suspension the
position of the front wheels is nowadays almost irrelevant until you reach
the front suspension travel end point - which for a rally car is enormous
but for an F1 a few cm.
Oh stop being such a prat. You know very well what I mean - take the mass
of the car and multiply it by 0.1*9.81 to get the active downforce, then by
the co-efficient of friction of the tyre to the road (typically between 0.6
and 0.95) to get the level of grip needed to be overcome to start the spin.
Happy now ?
No. I don't like being called a prat by an arrogant arse who can't admit
to a simple mistake.
On the subject of 'downforce' I have always understood it to relate only
to aerodynamic forces but its usage is so new that none of the
dictionaries I can consult here (I am away from home atm) do so much as
mention it. I dare say that such usage would be useful to the pedants
who argue that 'weight transfer' is incorrect terminology on the dubious
grounds that the transfer involved is not actually weight but 'downforce
transfer' doesn't trip off the tongue quite so easily and, as you have
so amply proved, somewhat harder to calculate.
Then don't call other's people opinions gibberish.
I made a simplification often made in automotive circles. I agree it
wouldn't be obvious to all but should have been to most.
The two first mentions of aerodynamic forces I can find are in the 60s by
Dan Gurney referring to "an increase in downforce" and Colin Chapman
referring to an "aerodynamic gain", both referring to the wings added to the
rears of their cars.
To my mind, this implies the term downforce already applied to those cars,
i.e. the weight of the car. Also most school textbooks refer to the "force
down" through a wheel which isn't too far away.
Whatever your opinion of me the fact remains that what you posted was
not correct. Your explanation of why you used such wording was
unconvincing and I don't for a moment believe that your usage is common
usage in the automotive world except perhaps in the realms of car
salesmanship. I am surprised that you should consider this thread at an
end when your other fantasies are taking such a pounding but that is
your choice. I too have a choice - welcome to my killfile.
Except that my killfile refused to work on such a bland address.
Oh well it did at least give me the chance to see that Mike had started
a new thread to grovel to Dave, seemingly oblivious to the fact that it
was Dave who originally called his random noise gibberish.
That's the average IQ of those reading this lowered back down again then.
If you won't accept references to Dan Gurney or Colin Chapman on what
downforce is then there is little point.
Wonder if my killfile will accept you ?
Hardly. I checked his facts, compared them with mine and accepted that
modern road tyres do have a far sharp fall-off in performance on lockup than
I expected. If I could find some modern data on racing tyres I expect the
data would be different but that is rather beside the point.
You haven't made any as yet but if you post an easily accessed reliable
source I will look at it. But accept hearsay from you of all people, no
Why not try it. On the other hand we could call it a draw at this stage
and give both of us the chance to get on with what is left of our lives.
Seems like a grovel to me. Particularly that bit - "What I tried to say,
obviously not at all well..." but elementary tactics I suppose not
wanting to fight on 2 fronts but letting Dave get away with calling your
bit of nonsense gibberish smacks of lack of gumption.
Is it? F=MA so A=F/M but you are stretching the English language into
the absurd by claiming it is a way of expressing acceleration. It is a
way of calculating it when acceleration happens to be the single unknown
in the equation.
Anyway that is besides the point. The units of acceleration are length
per time^2. Not a lbf or a slug in sight. Ergo my statement above is
I haven't a clue what the op was doing when he came up with 0.1g. My
kindest interpretation is that he was just trying to be clever and had a
senior moment. (Don't we all from time to time?) 0.1g is 3.22 ft/sec^2.
What he meant was 0.1*(mass of vehicle)*g and omitting the mass is just
bizarre when calculating force.
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