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Cornering - road car v F1 car
Re: Cornering - road car v F1 car
"APLer" <APLer@floor.tilde> wrote in message
news:Xns9A90913388B8APLer@127.0.0.1...
> "Dave Baker" <Null@null,com > wrote in news:fv6dn8$n1i$1@news.datemas.de:
> According to a first year university physics prof I had years ago,
> downforce adds nothing to grip, neither does tire width.
I think you'll find what he actually said was "coefficient of grip" not
"grip".
--
Dave Baker
Puma Race Engines
"APLer" <APLer@floor.tilde> wrote in message
news:Xns9A90913388B8APLer@127.0.0.1...
> "Dave Baker" <Null@null,com > wrote in news:fv6dn8$n1i$1@news.datemas.de:
> According to a first year university physics prof I had years ago,
> downforce adds nothing to grip, neither does tire width.
I think you'll find what he actually said was "coefficient of grip" not
"grip".
--
Dave Baker
Puma Race Engines
Re: Cornering - road car v F1 car
"Dave Baker" <Null@null,com > wrote in message
news:fv9dsl$hqf$1@news.datemas.de...
>
> "APLer" <APLer@floor.tilde> wrote in message
> news:Xns9A90913388B8APLer@127.0.0.1...
>> "Dave Baker" <Null@null,com > wrote in news:fv6dn8$n1i$1@news.datemas.de:
>
>> According to a first year university physics prof I had years ago,
>> downforce adds nothing to grip, neither does tire width.
>
> I think you'll find what he actually said was "coefficient of grip" not
> "grip".
> --
> Dave Baker
> Puma Race Engines
>
<average ignorant Joe>
OK, those two posts blew the logic circuits in my brain.
Please explain???
</average ignorant Joe>
AC
"Dave Baker" <Null@null,com > wrote in message
news:fv9dsl$hqf$1@news.datemas.de...
>
> "APLer" <APLer@floor.tilde> wrote in message
> news:Xns9A90913388B8APLer@127.0.0.1...
>> "Dave Baker" <Null@null,com > wrote in news:fv6dn8$n1i$1@news.datemas.de:
>
>> According to a first year university physics prof I had years ago,
>> downforce adds nothing to grip, neither does tire width.
>
> I think you'll find what he actually said was "coefficient of grip" not
> "grip".
> --
> Dave Baker
> Puma Race Engines
>
<average ignorant Joe>
OK, those two posts blew the logic circuits in my brain.
Please explain???
</average ignorant Joe>
AC
Re: Cornering - road car v F1 car
"AC" <xxxx@xxxx.xxx> wrote in message
news:IOXRj.46630$B83.42908@newsfe3-gui.ntli,net ...
>
> "Dave Baker" <Null@null,com > wrote in message
> news:fv9dsl$hqf$1@news.datemas.de...
>>
>> "APLer" <APLer@floor.tilde> wrote in message
>> news:Xns9A90913388B8APLer@127.0.0.1...
>>> "Dave Baker" <Null@null,com > wrote in news:fv6dn8$n1i$1@news.datemas.de:
>>
>>> According to a first year university physics prof I had years ago,
>>> downforce adds nothing to grip, neither does tire width.
>>
>> I think you'll find what he actually said was "coefficient of grip" not
>> "grip".
>> --
>> Dave Baker
>> Puma Race Engines
>>
>
> <average ignorant Joe>
>
> OK, those two posts blew the logic circuits in my brain.
>
> Please explain???
>
> </average ignorant Joe>
The coefficient of grip (cg) is a measure of the adhesion between two
surfaces 'for a given contact force'. The contact force in most situations
is the weight of the object. Contact force x cg = total grip. When just the
weight of an object is pressing it down onto a horizontal surface then
contact force = 1 and lateral grip in g force is the same number as the cg.
Downforce simply increases the contact force and the grip varies directly
with it. The coefficient of grip doesn't actually change much. In fact for
tyres it decreases slightly as contact force increases.
Put a box on a table and ask someone to move it by pressing laterally. Now
put your hand on it and push it down and ask them to try again. What changed
was not the cg but the contact force.
For road tyres in the dry the cg varies between about 0.85 for something
cheap and cheerful and just over 1 for the best rubber with a reasonable
life. In the wet between about 0.6 and 0.85. Very soft compound racing tyres
have a cg of about 1.3. The grooved F1 tyres might be a tad lower than this.
The maximum cornering g force possible is thus the same number as the cg for
road cars with no appreciable downforce and up to three times the cg for F1
cars that generate twice their own weight in additional downforce at top
speed. Downforce varies with the square of speed so at lower speeds it's a
very much smaller number.
--
Dave Baker
Puma Race Engines
"AC" <xxxx@xxxx.xxx> wrote in message
news:IOXRj.46630$B83.42908@newsfe3-gui.ntli,net ...
>
> "Dave Baker" <Null@null,com > wrote in message
> news:fv9dsl$hqf$1@news.datemas.de...
>>
>> "APLer" <APLer@floor.tilde> wrote in message
>> news:Xns9A90913388B8APLer@127.0.0.1...
>>> "Dave Baker" <Null@null,com > wrote in news:fv6dn8$n1i$1@news.datemas.de:
>>
>>> According to a first year university physics prof I had years ago,
>>> downforce adds nothing to grip, neither does tire width.
>>
>> I think you'll find what he actually said was "coefficient of grip" not
>> "grip".
>> --
>> Dave Baker
>> Puma Race Engines
>>
>
> <average ignorant Joe>
>
> OK, those two posts blew the logic circuits in my brain.
>
> Please explain???
>
> </average ignorant Joe>
The coefficient of grip (cg) is a measure of the adhesion between two
surfaces 'for a given contact force'. The contact force in most situations
is the weight of the object. Contact force x cg = total grip. When just the
weight of an object is pressing it down onto a horizontal surface then
contact force = 1 and lateral grip in g force is the same number as the cg.
Downforce simply increases the contact force and the grip varies directly
with it. The coefficient of grip doesn't actually change much. In fact for
tyres it decreases slightly as contact force increases.
Put a box on a table and ask someone to move it by pressing laterally. Now
put your hand on it and push it down and ask them to try again. What changed
was not the cg but the contact force.
For road tyres in the dry the cg varies between about 0.85 for something
cheap and cheerful and just over 1 for the best rubber with a reasonable
life. In the wet between about 0.6 and 0.85. Very soft compound racing tyres
have a cg of about 1.3. The grooved F1 tyres might be a tad lower than this.
The maximum cornering g force possible is thus the same number as the cg for
road cars with no appreciable downforce and up to three times the cg for F1
cars that generate twice their own weight in additional downforce at top
speed. Downforce varies with the square of speed so at lower speeds it's a
very much smaller number.
--
Dave Baker
Puma Race Engines
Re: Cornering - road car v F1 car
> The coefficient of grip (cg) is a measure of the adhesion between two
> surfaces 'for a given contact force'. The contact force in most situations
> is the weight of the object. Contact force x cg = total grip. When just the
> weight of an object is pressing it down onto a horizontal surface then
> contact force = 1 and lateral grip in g force is the same number as the cg.
>
> Downforce simply increases the contact force and the grip varies directly
> with it. The coefficient of grip doesn't actually change much. In fact for
> tyres it decreases slightly as contact force increases.
>
> Put a box on a table and ask someone to move it by pressing laterally. Now
> put your hand on it and push it down and ask them to try again. What changed
> was not the cg but the contact force.
>
> For road tyres in the dry the cg varies between about 0.85 for something
> cheap and cheerful and just over 1 for the best rubber with a reasonable
> life. In the wet between about 0.6 and 0.85. Very soft compound racing tyres
> have a cg of about 1.3. The grooved F1 tyres might be a tad lower than this.
>
> The maximum cornering g force possible is thus the same number as the cg for
> road cars with no appreciable downforce and up to three times the cg for F1
> cars that generate twice their own weight in additional downforce at top
> speed. Downforce varies with the square of speed so at lower speeds it's a
> very much smaller number.
> --
> Dave Baker
> Puma Race Engines- Hide quoted text -
I've never understood how a dragster can generate up to 4G in the
split second BEFORE any downforce aero occurs --- the old mantra used
to be that 1G "must" be the limit for grip. Odder still (less so
today), bygone dragsters were exceeding 1G even during massive
wheelspin at the start --- how can this be?
> The coefficient of grip (cg) is a measure of the adhesion between two
> surfaces 'for a given contact force'. The contact force in most situations
> is the weight of the object. Contact force x cg = total grip. When just the
> weight of an object is pressing it down onto a horizontal surface then
> contact force = 1 and lateral grip in g force is the same number as the cg.
>
> Downforce simply increases the contact force and the grip varies directly
> with it. The coefficient of grip doesn't actually change much. In fact for
> tyres it decreases slightly as contact force increases.
>
> Put a box on a table and ask someone to move it by pressing laterally. Now
> put your hand on it and push it down and ask them to try again. What changed
> was not the cg but the contact force.
>
> For road tyres in the dry the cg varies between about 0.85 for something
> cheap and cheerful and just over 1 for the best rubber with a reasonable
> life. In the wet between about 0.6 and 0.85. Very soft compound racing tyres
> have a cg of about 1.3. The grooved F1 tyres might be a tad lower than this.
>
> The maximum cornering g force possible is thus the same number as the cg for
> road cars with no appreciable downforce and up to three times the cg for F1
> cars that generate twice their own weight in additional downforce at top
> speed. Downforce varies with the square of speed so at lower speeds it's a
> very much smaller number.
> --
> Dave Baker
> Puma Race Engines- Hide quoted text -
I've never understood how a dragster can generate up to 4G in the
split second BEFORE any downforce aero occurs --- the old mantra used
to be that 1G "must" be the limit for grip. Odder still (less so
today), bygone dragsters were exceeding 1G even during massive
wheelspin at the start --- how can this be?
Re: Cornering - road car v F1 car
On Wed, 30 Apr 2008 04:33:23 -0700 (PDT), "brafield@hotmail,com "
<brafield@hotmail,com > wrote:
>> The coefficient of grip (cg) is a measure of the adhesion between two
>> surfaces 'for a given contact force'. The contact force in most situations
>> is the weight of the object. Contact force x cg = total grip. When just the
>> weight of an object is pressing it down onto a horizontal surface then
>> contact force = 1 and lateral grip in g force is the same number as the cg.
>>
>> Downforce simply increases the contact force and the grip varies directly
>> with it. The coefficient of grip doesn't actually change much. In fact for
>> tyres it decreases slightly as contact force increases.
>>
>> Put a box on a table and ask someone to move it by pressing laterally. Now
>> put your hand on it and push it down and ask them to try again. What changed
>> was not the cg but the contact force.
>>
>> For road tyres in the dry the cg varies between about 0.85 for something
>> cheap and cheerful and just over 1 for the best rubber with a reasonable
>> life. In the wet between about 0.6 and 0.85. Very soft compound racing tyres
>> have a cg of about 1.3. The grooved F1 tyres might be a tad lower than this.
>>
>> The maximum cornering g force possible is thus the same number as the cg for
>> road cars with no appreciable downforce and up to three times the cg for F1
>> cars that generate twice their own weight in additional downforce at top
>> speed. Downforce varies with the square of speed so at lower speeds it's a
>> very much smaller number.
>> --
>> Dave Baker
>> Puma Race Engines- Hide quoted text -
>
>I've never understood how a dragster can generate up to 4G in the
>split second BEFORE any downforce aero occurs --- the old mantra used
>to be that 1G "must" be the limit for grip. Odder still (less so
>today), bygone dragsters were exceeding 1G even during massive
>wheelspin at the start --- how can this be?
>
Dragsters cheat and accelerate with the use of 'extra gears', called
tyres. :)
--
Regards, Frank
On Wed, 30 Apr 2008 04:33:23 -0700 (PDT), "brafield@hotmail,com "
<brafield@hotmail,com > wrote:
>> The coefficient of grip (cg) is a measure of the adhesion between two
>> surfaces 'for a given contact force'. The contact force in most situations
>> is the weight of the object. Contact force x cg = total grip. When just the
>> weight of an object is pressing it down onto a horizontal surface then
>> contact force = 1 and lateral grip in g force is the same number as the cg.
>>
>> Downforce simply increases the contact force and the grip varies directly
>> with it. The coefficient of grip doesn't actually change much. In fact for
>> tyres it decreases slightly as contact force increases.
>>
>> Put a box on a table and ask someone to move it by pressing laterally. Now
>> put your hand on it and push it down and ask them to try again. What changed
>> was not the cg but the contact force.
>>
>> For road tyres in the dry the cg varies between about 0.85 for something
>> cheap and cheerful and just over 1 for the best rubber with a reasonable
>> life. In the wet between about 0.6 and 0.85. Very soft compound racing tyres
>> have a cg of about 1.3. The grooved F1 tyres might be a tad lower than this.
>>
>> The maximum cornering g force possible is thus the same number as the cg for
>> road cars with no appreciable downforce and up to three times the cg for F1
>> cars that generate twice their own weight in additional downforce at top
>> speed. Downforce varies with the square of speed so at lower speeds it's a
>> very much smaller number.
>> --
>> Dave Baker
>> Puma Race Engines- Hide quoted text -
>
>I've never understood how a dragster can generate up to 4G in the
>split second BEFORE any downforce aero occurs --- the old mantra used
>to be that 1G "must" be the limit for grip. Odder still (less so
>today), bygone dragsters were exceeding 1G even during massive
>wheelspin at the start --- how can this be?
>
Dragsters cheat and accelerate with the use of 'extra gears', called
tyres. :)
--
Regards, Frank
Re: Cornering - road car v F1 car
<brafield@hotmail,com > wrote in message
news:3d66073f-ca4b-416a-9006-29dc38be3874@q1g2000prf.googlegroups,com ...
> I've never understood how a dragster can generate up to 4G in the
> split second BEFORE any downforce aero occurs --- the old mantra used
> to be that 1G "must" be the limit for grip.
True, I recall people saying and writing that but they didn't understand the
grip mechanism of tyres and there's actually no theoretical limit on the
grip. It's just that for two relatively flat surfaces in contact it was long
thought that 1g was some sort of 'speed of light' barrier which could never
be crossed.
Odder still (less so
> today), bygone dragsters were exceeding 1G even during massive
> wheelspin at the start --- how can this be?
Burnouts to melt the tyre to the track, very soft rubber and wrinkle wall
technology which allows the car to start moving before the tread does.
Exactly how all of these things work at a physical or molecular level is
another matter. Beyond my area of detailed study to date I'm afraid although
it does interest me.
--
Dave Baker
Puma Race Engines
<brafield@hotmail,com > wrote in message
news:3d66073f-ca4b-416a-9006-29dc38be3874@q1g2000prf.googlegroups,com ...
> I've never understood how a dragster can generate up to 4G in the
> split second BEFORE any downforce aero occurs --- the old mantra used
> to be that 1G "must" be the limit for grip.
True, I recall people saying and writing that but they didn't understand the
grip mechanism of tyres and there's actually no theoretical limit on the
grip. It's just that for two relatively flat surfaces in contact it was long
thought that 1g was some sort of 'speed of light' barrier which could never
be crossed.
Odder still (less so
> today), bygone dragsters were exceeding 1G even during massive
> wheelspin at the start --- how can this be?
Burnouts to melt the tyre to the track, very soft rubber and wrinkle wall
technology which allows the car to start moving before the tread does.
Exactly how all of these things work at a physical or molecular level is
another matter. Beyond my area of detailed study to date I'm afraid although
it does interest me.
--
Dave Baker
Puma Race Engines
Re: Cornering - road car v F1 car
"Dave Baker" <Null@null,com > wrote in message
news:fv9ik2$nrs$1@news.datemas.de...
>
> "AC" <xxxx@xxxx.xxx> wrote in message
> news:IOXRj.46630$B83.42908@newsfe3-gui.ntli,net ...
>>
>> "Dave Baker" <Null@null,com > wrote in message
>> news:fv9dsl$hqf$1@news.datemas.de...
>>>
>>> "APLer" <APLer@floor.tilde> wrote in message
>>> news:Xns9A90913388B8APLer@127.0.0.1...
>>>> "Dave Baker" <Null@null,com > wrote in
>>>> news:fv6dn8$n1i$1@news.datemas.de:
>>>
>>>> According to a first year university physics prof I had years ago,
>>>> downforce adds nothing to grip, neither does tire width.
>>>
>>> I think you'll find what he actually said was "coefficient of grip" not
>>> "grip".
>>> --
>>> Dave Baker
>>> Puma Race Engines
>>>
>>
>> <average ignorant Joe>
>>
>> OK, those two posts blew the logic circuits in my brain.
>>
>> Please explain???
>>
>> </average ignorant Joe>
>
> The coefficient of grip (cg) is a measure of the adhesion between two
> surfaces 'for a given contact force'. The contact force in most situations
> is the weight of the object. Contact force x cg = total grip. When just
> the weight of an object is pressing it down onto a horizontal surface then
> contact force = 1 and lateral grip in g force is the same number as the
> cg.
>
> Downforce simply increases the contact force and the grip varies directly
> with it. The coefficient of grip doesn't actually change much. In fact for
> tyres it decreases slightly as contact force increases.
>
> Put a box on a table and ask someone to move it by pressing laterally. Now
> put your hand on it and push it down and ask them to try again. What
> changed was not the cg but the contact force.
>
> For road tyres in the dry the cg varies between about 0.85 for something
> cheap and cheerful and just over 1 for the best rubber with a reasonable
> life. In the wet between about 0.6 and 0.85. Very soft compound racing
> tyres have a cg of about 1.3. The grooved F1 tyres might be a tad lower
> than this.
>
> The maximum cornering g force possible is thus the same number as the cg
> for road cars with no appreciable downforce and up to three times the cg
> for F1 cars that generate twice their own weight in additional downforce
> at top speed. Downforce varies with the square of speed so at lower speeds
> it's a very much smaller number.
> --
> Dave Baker
> Puma Race Engines
>
Cheers.
About 10 re-reads, but I think I understand.
AC
"Dave Baker" <Null@null,com > wrote in message
news:fv9ik2$nrs$1@news.datemas.de...
>
> "AC" <xxxx@xxxx.xxx> wrote in message
> news:IOXRj.46630$B83.42908@newsfe3-gui.ntli,net ...
>>
>> "Dave Baker" <Null@null,com > wrote in message
>> news:fv9dsl$hqf$1@news.datemas.de...
>>>
>>> "APLer" <APLer@floor.tilde> wrote in message
>>> news:Xns9A90913388B8APLer@127.0.0.1...
>>>> "Dave Baker" <Null@null,com > wrote in
>>>> news:fv6dn8$n1i$1@news.datemas.de:
>>>
>>>> According to a first year university physics prof I had years ago,
>>>> downforce adds nothing to grip, neither does tire width.
>>>
>>> I think you'll find what he actually said was "coefficient of grip" not
>>> "grip".
>>> --
>>> Dave Baker
>>> Puma Race Engines
>>>
>>
>> <average ignorant Joe>
>>
>> OK, those two posts blew the logic circuits in my brain.
>>
>> Please explain???
>>
>> </average ignorant Joe>
>
> The coefficient of grip (cg) is a measure of the adhesion between two
> surfaces 'for a given contact force'. The contact force in most situations
> is the weight of the object. Contact force x cg = total grip. When just
> the weight of an object is pressing it down onto a horizontal surface then
> contact force = 1 and lateral grip in g force is the same number as the
> cg.
>
> Downforce simply increases the contact force and the grip varies directly
> with it. The coefficient of grip doesn't actually change much. In fact for
> tyres it decreases slightly as contact force increases.
>
> Put a box on a table and ask someone to move it by pressing laterally. Now
> put your hand on it and push it down and ask them to try again. What
> changed was not the cg but the contact force.
>
> For road tyres in the dry the cg varies between about 0.85 for something
> cheap and cheerful and just over 1 for the best rubber with a reasonable
> life. In the wet between about 0.6 and 0.85. Very soft compound racing
> tyres have a cg of about 1.3. The grooved F1 tyres might be a tad lower
> than this.
>
> The maximum cornering g force possible is thus the same number as the cg
> for road cars with no appreciable downforce and up to three times the cg
> for F1 cars that generate twice their own weight in additional downforce
> at top speed. Downforce varies with the square of speed so at lower speeds
> it's a very much smaller number.
> --
> Dave Baker
> Puma Race Engines
>
Cheers.
About 10 re-reads, but I think I understand.
AC
Re: Cornering - road car v F1 car
"Dave Baker" <Null@null,com > wrote in message
news:fv9ik2$nrs$1@news.datemas.de...
>
> "AC" <xxxx@xxxx.xxx> wrote in message
> news:IOXRj.46630$B83.42908@newsfe3-gui.ntli,net ...
>>
>> "Dave Baker" <Null@null,com > wrote in message
>> news:fv9dsl$hqf$1@news.datemas.de...
>>>
>>> "APLer" <APLer@floor.tilde> wrote in message
>>> news:Xns9A90913388B8APLer@127.0.0.1...
>>>> "Dave Baker" <Null@null,com > wrote in
>>>> news:fv6dn8$n1i$1@news.datemas.de:
>>>
>>>> According to a first year university physics prof I had years ago,
>>>> downforce adds nothing to grip, neither does tire width.
>>>
>>> I think you'll find what he actually said was "coefficient of grip" not
>>> "grip".
>>> --
>>> Dave Baker
>>> Puma Race Engines
>>>
>>
>> <average ignorant Joe>
>>
>> OK, those two posts blew the logic circuits in my brain.
>>
>> Please explain???
>>
>> </average ignorant Joe>
>
> The coefficient of grip (cg) is a measure of the adhesion between two
> surfaces 'for a given contact force'. The contact force in most situations
> is the weight of the object. Contact force x cg = total grip. When just
> the weight of an object is pressing it down onto a horizontal surface then
> contact force = 1 and lateral grip in g force is the same number as the
> cg.
>
> Downforce simply increases the contact force and the grip varies directly
> with it. The coefficient of grip doesn't actually change much. In fact for
> tyres it decreases slightly as contact force increases.
>
> Put a box on a table and ask someone to move it by pressing laterally. Now
> put your hand on it and push it down and ask them to try again. What
> changed was not the cg but the contact force.
>
> For road tyres in the dry the cg varies between about 0.85 for something
> cheap and cheerful and just over 1 for the best rubber with a reasonable
> life. In the wet between about 0.6 and 0.85. Very soft compound racing
> tyres have a cg of about 1.3. The grooved F1 tyres might be a tad lower
> than this.
>
> The maximum cornering g force possible is thus the same number as the cg
> for road cars with no appreciable downforce and up to three times the cg
> for F1 cars that generate twice their own weight in additional downforce
> at top speed. Downforce varies with the square of speed so at lower speeds
> it's a very much smaller number.
> --
> Dave Baker
> Puma Race Engines
>
Surely the "cg" of the road surface must come into this equation somewhere
too?
Chad
"Dave Baker" <Null@null,com > wrote in message
news:fv9ik2$nrs$1@news.datemas.de...
>
> "AC" <xxxx@xxxx.xxx> wrote in message
> news:IOXRj.46630$B83.42908@newsfe3-gui.ntli,net ...
>>
>> "Dave Baker" <Null@null,com > wrote in message
>> news:fv9dsl$hqf$1@news.datemas.de...
>>>
>>> "APLer" <APLer@floor.tilde> wrote in message
>>> news:Xns9A90913388B8APLer@127.0.0.1...
>>>> "Dave Baker" <Null@null,com > wrote in
>>>> news:fv6dn8$n1i$1@news.datemas.de:
>>>
>>>> According to a first year university physics prof I had years ago,
>>>> downforce adds nothing to grip, neither does tire width.
>>>
>>> I think you'll find what he actually said was "coefficient of grip" not
>>> "grip".
>>> --
>>> Dave Baker
>>> Puma Race Engines
>>>
>>
>> <average ignorant Joe>
>>
>> OK, those two posts blew the logic circuits in my brain.
>>
>> Please explain???
>>
>> </average ignorant Joe>
>
> The coefficient of grip (cg) is a measure of the adhesion between two
> surfaces 'for a given contact force'. The contact force in most situations
> is the weight of the object. Contact force x cg = total grip. When just
> the weight of an object is pressing it down onto a horizontal surface then
> contact force = 1 and lateral grip in g force is the same number as the
> cg.
>
> Downforce simply increases the contact force and the grip varies directly
> with it. The coefficient of grip doesn't actually change much. In fact for
> tyres it decreases slightly as contact force increases.
>
> Put a box on a table and ask someone to move it by pressing laterally. Now
> put your hand on it and push it down and ask them to try again. What
> changed was not the cg but the contact force.
>
> For road tyres in the dry the cg varies between about 0.85 for something
> cheap and cheerful and just over 1 for the best rubber with a reasonable
> life. In the wet between about 0.6 and 0.85. Very soft compound racing
> tyres have a cg of about 1.3. The grooved F1 tyres might be a tad lower
> than this.
>
> The maximum cornering g force possible is thus the same number as the cg
> for road cars with no appreciable downforce and up to three times the cg
> for F1 cars that generate twice their own weight in additional downforce
> at top speed. Downforce varies with the square of speed so at lower speeds
> it's a very much smaller number.
> --
> Dave Baker
> Puma Race Engines
>
Surely the "cg" of the road surface must come into this equation somewhere
too?
Chad
Re: Cornering - road car v F1 car
"Chad" <cbstun@safemail,com > wrote in message
news:481a0db6$0$30466$afc38c87@news.optusnet,com .au...
> "Dave Baker" <Null@null,com > wrote in message
> news:fv9ik2$nrs$1@news.datemas.de...
>>
>> "AC" <xxxx@xxxx.xxx> wrote in message
>> news:IOXRj.46630$B83.42908@newsfe3-gui.ntli,net ...
>>>
>>> "Dave Baker" <Null@null,com > wrote in message
>>> news:fv9dsl$hqf$1@news.datemas.de...
>>>>
>>>> "APLer" <APLer@floor.tilde> wrote in message
>>>> news:Xns9A90913388B8APLer@127.0.0.1...
>>>>> "Dave Baker" <Null@null,com > wrote in
>>>>> news:fv6dn8$n1i$1@news.datemas.de:
>>>>
>>>>> According to a first year university physics prof I had years ago,
>>>>> downforce adds nothing to grip, neither does tire width.
>>>>
>>>> I think you'll find what he actually said was "coefficient of grip" not
>>>> "grip".
>>>> --
>>>> Dave Baker
>>>> Puma Race Engines
>>>>
>>>
>>> <average ignorant Joe>
>>>
>>> OK, those two posts blew the logic circuits in my brain.
>>>
>>> Please explain???
>>>
>>> </average ignorant Joe>
>>
>> The coefficient of grip (cg) is a measure of the adhesion between two
>> surfaces 'for a given contact force'. The contact force in most
>> situations is the weight of the object. Contact force x cg = total grip.
>> When just the weight of an object is pressing it down onto a horizontal
>> surface then contact force = 1 and lateral grip in g force is the same
>> number as the cg.
>>
>> Downforce simply increases the contact force and the grip varies directly
>> with it. The coefficient of grip doesn't actually change much. In fact
>> for tyres it decreases slightly as contact force increases.
>>
>> Put a box on a table and ask someone to move it by pressing laterally.
>> Now put your hand on it and push it down and ask them to try again. What
>> changed was not the cg but the contact force.
>>
>> For road tyres in the dry the cg varies between about 0.85 for something
>> cheap and cheerful and just over 1 for the best rubber with a reasonable
>> life. In the wet between about 0.6 and 0.85. Very soft compound racing
>> tyres have a cg of about 1.3. The grooved F1 tyres might be a tad lower
>> than this.
>>
>> The maximum cornering g force possible is thus the same number as the cg
>> for road cars with no appreciable downforce and up to three times the cg
>> for F1 cars that generate twice their own weight in additional downforce
>> at top speed. Downforce varies with the square of speed so at lower
>> speeds it's a very much smaller number.
>> --
>> Dave Baker
>> Puma Race Engines
>>
>
> Surely the "cg" of the road surface must come into this equation somewhere
> too?
>
> Chad
>
Hmm, I took the "cg" to be the grip between 2 surfaces.
So, a tire on ice will be one number, and a tire on a road will be another
number.
AC
"Chad" <cbstun@safemail,com > wrote in message
news:481a0db6$0$30466$afc38c87@news.optusnet,com .au...
> "Dave Baker" <Null@null,com > wrote in message
> news:fv9ik2$nrs$1@news.datemas.de...
>>
>> "AC" <xxxx@xxxx.xxx> wrote in message
>> news:IOXRj.46630$B83.42908@newsfe3-gui.ntli,net ...
>>>
>>> "Dave Baker" <Null@null,com > wrote in message
>>> news:fv9dsl$hqf$1@news.datemas.de...
>>>>
>>>> "APLer" <APLer@floor.tilde> wrote in message
>>>> news:Xns9A90913388B8APLer@127.0.0.1...
>>>>> "Dave Baker" <Null@null,com > wrote in
>>>>> news:fv6dn8$n1i$1@news.datemas.de:
>>>>
>>>>> According to a first year university physics prof I had years ago,
>>>>> downforce adds nothing to grip, neither does tire width.
>>>>
>>>> I think you'll find what he actually said was "coefficient of grip" not
>>>> "grip".
>>>> --
>>>> Dave Baker
>>>> Puma Race Engines
>>>>
>>>
>>> <average ignorant Joe>
>>>
>>> OK, those two posts blew the logic circuits in my brain.
>>>
>>> Please explain???
>>>
>>> </average ignorant Joe>
>>
>> The coefficient of grip (cg) is a measure of the adhesion between two
>> surfaces 'for a given contact force'. The contact force in most
>> situations is the weight of the object. Contact force x cg = total grip.
>> When just the weight of an object is pressing it down onto a horizontal
>> surface then contact force = 1 and lateral grip in g force is the same
>> number as the cg.
>>
>> Downforce simply increases the contact force and the grip varies directly
>> with it. The coefficient of grip doesn't actually change much. In fact
>> for tyres it decreases slightly as contact force increases.
>>
>> Put a box on a table and ask someone to move it by pressing laterally.
>> Now put your hand on it and push it down and ask them to try again. What
>> changed was not the cg but the contact force.
>>
>> For road tyres in the dry the cg varies between about 0.85 for something
>> cheap and cheerful and just over 1 for the best rubber with a reasonable
>> life. In the wet between about 0.6 and 0.85. Very soft compound racing
>> tyres have a cg of about 1.3. The grooved F1 tyres might be a tad lower
>> than this.
>>
>> The maximum cornering g force possible is thus the same number as the cg
>> for road cars with no appreciable downforce and up to three times the cg
>> for F1 cars that generate twice their own weight in additional downforce
>> at top speed. Downforce varies with the square of speed so at lower
>> speeds it's a very much smaller number.
>> --
>> Dave Baker
>> Puma Race Engines
>>
>
> Surely the "cg" of the road surface must come into this equation somewhere
> too?
>
> Chad
>
Hmm, I took the "cg" to be the grip between 2 surfaces.
So, a tire on ice will be one number, and a tire on a road will be another
number.
AC
Re: Cornering - road car v F1 car
"Chad" <cbstun@safemail,com > wrote in message
news:481a0db6$0$30466$afc38c87@news.optusnet,com .au...
> Surely the "cg" of the road surface must come into this equation somewhere
> too?
There is only one cg for the interaction between two surfaces but obviously
the condition of both surfaces affects this which is why cg and grip are
less in the wet or on ice. Similarly, different road surfaces will affect
the cg for a given tyre in the dry. That Shellgrip stuff you get on
roundabouts and corners gives much higher adhesion than ordinary tarmac,
especially in the wet.
About ten years ago I went on holiday to Wales with a g/f and it pissed down
more or less non stop. The Pirellis on the car had plenty of tread left but
had gone 'weird' as they wore down and although still fine in the dry had
lost all semblance of wet grip. I mean to the point of being close to
dangerous just at normal speeds. I literally couldn't keep up with cars in
front that were just being driven steadily without losing adhesion in
corners. Mind you many of the roads in Wales were pretty poor and were
polished down smooth by traffic after years without resurfacing. However as
soon as we got onto a bit of Shellgrip the tyres stuck like that stuff to a
blanket. Every corner meant looking ahead to see what the surface was like
and then choosing speed accordingly. No Shellgrip meant scrubbing off 20 mph
and still probably having to correct a minor slide at some point and with
Shellgrip I could chuck it in almost as if the road was dry. It was a very
strange trip. Also the last time I ever buy Pirellis.
The closest analogy was those dreadful nylon tyres they used to put on
Japanese bikes in the 70s which were fine in the dry but had zero grip in
the wet and could kill you in a blink when you weren't even trying to go
fast. I remember falling off my Suzuki moped in the wet when I was 16 at no
more than walking pace round a bend at school and wondering what the hell
was going on. They got ditched for decent British tyres fairly smartly
before I ended up as a statistic.
--
Dave Baker
Puma Race Engines
"Chad" <cbstun@safemail,com > wrote in message
news:481a0db6$0$30466$afc38c87@news.optusnet,com .au...
> Surely the "cg" of the road surface must come into this equation somewhere
> too?
There is only one cg for the interaction between two surfaces but obviously
the condition of both surfaces affects this which is why cg and grip are
less in the wet or on ice. Similarly, different road surfaces will affect
the cg for a given tyre in the dry. That Shellgrip stuff you get on
roundabouts and corners gives much higher adhesion than ordinary tarmac,
especially in the wet.
About ten years ago I went on holiday to Wales with a g/f and it pissed down
more or less non stop. The Pirellis on the car had plenty of tread left but
had gone 'weird' as they wore down and although still fine in the dry had
lost all semblance of wet grip. I mean to the point of being close to
dangerous just at normal speeds. I literally couldn't keep up with cars in
front that were just being driven steadily without losing adhesion in
corners. Mind you many of the roads in Wales were pretty poor and were
polished down smooth by traffic after years without resurfacing. However as
soon as we got onto a bit of Shellgrip the tyres stuck like that stuff to a
blanket. Every corner meant looking ahead to see what the surface was like
and then choosing speed accordingly. No Shellgrip meant scrubbing off 20 mph
and still probably having to correct a minor slide at some point and with
Shellgrip I could chuck it in almost as if the road was dry. It was a very
strange trip. Also the last time I ever buy Pirellis.
The closest analogy was those dreadful nylon tyres they used to put on
Japanese bikes in the 70s which were fine in the dry but had zero grip in
the wet and could kill you in a blink when you weren't even trying to go
fast. I remember falling off my Suzuki moped in the wet when I was 16 at no
more than walking pace round a bend at school and wondering what the hell
was going on. They got ditched for decent British tyres fairly smartly
before I ended up as a statistic.
--
Dave Baker
Puma Race Engines
Re: Cornering - road car v F1 car
Dave Baker <Null@null,com > writes
>"Chad" <cbstun@safemail,com > wrote in message
>> Surely the "cg" of the road surface must come into this equation
>somewhere
>> too?
>
>Mind you many of the roads in Wales were pretty poor and were
>polished down smooth by traffic after years without resurfacing.
Thats the sort of surface we need for F1 tracks...not the high grip
stuff they use.
--
Peter
Dave Baker <Null@null,com > writes
>"Chad" <cbstun@safemail,com > wrote in message
>> Surely the "cg" of the road surface must come into this equation
>somewhere
>> too?
>
>Mind you many of the roads in Wales were pretty poor and were
>polished down smooth by traffic after years without resurfacing.
Thats the sort of surface we need for F1 tracks...not the high grip
stuff they use.
--
Peter
Re: Cornering - road car v F1 car
"peter" <scoular@blackhole.do-not-spam.me.uk> wrote in message
news:c4j+AaA3ZsGIFwLY@ntlworld,com ...
> Dave Baker <Null@null,com > writes
>>"Chad" <cbstun@safemail,com > wrote in message
>>> Surely the "cg" of the road surface must come into this equation
>>somewhere
>>> too?
>>
>>Mind you many of the roads in Wales were pretty poor and were
>>polished down smooth by traffic after years without resurfacing.
>
> Thats the sort of surface we need for F1 tracks...not the high grip stuff
> they use.
> --
> Peter
It would be exciting, but we might struggle to get 3 cars finishing to fill
the podium :D
Chad
"peter" <scoular@blackhole.do-not-spam.me.uk> wrote in message
news:c4j+AaA3ZsGIFwLY@ntlworld,com ...
> Dave Baker <Null@null,com > writes
>>"Chad" <cbstun@safemail,com > wrote in message
>>> Surely the "cg" of the road surface must come into this equation
>>somewhere
>>> too?
>>
>>Mind you many of the roads in Wales were pretty poor and were
>>polished down smooth by traffic after years without resurfacing.
>
> Thats the sort of surface we need for F1 tracks...not the high grip stuff
> they use.
> --
> Peter
It would be exciting, but we might struggle to get 3 cars finishing to fill
the podium :D
Chad
Re: Cornering - road car v F1 car
On Sat, 3 May 2008 02:42:11 +1000, "Chad" <cbstun@safemail,com > wrote:
>"peter" <scoular@blackhole.do-not-spam.me.uk> wrote in message
>news:c4j+AaA3ZsGIFwLY@ntlworld,com ...
>> Dave Baker <Null@null,com > writes
>>>"Chad" <cbstun@safemail,com > wrote in message
>>>> Surely the "cg" of the road surface must come into this equation
>>>somewhere
>>>> too?
>>>
>>>Mind you many of the roads in Wales were pretty poor and were
>>>polished down smooth by traffic after years without resurfacing.
>>
>> Thats the sort of surface we need for F1 tracks...not the high grip stuff
>> they use.
>> --
>> Peter
>
>It would be exciting, but we might struggle to get 3 cars finishing to fill
>the podium :D
>
Easy. Let's bring back traction control and introduce ABS, ESC,
venturis, skirts and auto levelling suspensions.. Or just lay rails.
;-)
--
Regards, Frank
On Sat, 3 May 2008 02:42:11 +1000, "Chad" <cbstun@safemail,com > wrote:
>"peter" <scoular@blackhole.do-not-spam.me.uk> wrote in message
>news:c4j+AaA3ZsGIFwLY@ntlworld,com ...
>> Dave Baker <Null@null,com > writes
>>>"Chad" <cbstun@safemail,com > wrote in message
>>>> Surely the "cg" of the road surface must come into this equation
>>>somewhere
>>>> too?
>>>
>>>Mind you many of the roads in Wales were pretty poor and were
>>>polished down smooth by traffic after years without resurfacing.
>>
>> Thats the sort of surface we need for F1 tracks...not the high grip stuff
>> they use.
>> --
>> Peter
>
>It would be exciting, but we might struggle to get 3 cars finishing to fill
>the podium :D
>
Easy. Let's bring back traction control and introduce ABS, ESC,
venturis, skirts and auto levelling suspensions.. Or just lay rails.
;-)
--
Regards, Frank
Re: Cornering - road car v F1 car
"Dave Baker" <Null@null,com > wrote in news:fv9dsl$hqf$1@news.datemas.de:
>
> "APLer" <APLer@floor.tilde> wrote in message
> news:Xns9A90913388B8APLer@127.0.0.1...
>> "Dave Baker" <Null@null,com > wrote in
>> news:fv6dn8$n1i$1@news.datemas.de:
>
>> According to a first year university physics prof I had years ago,
>> downforce adds nothing to grip, neither does tire width.
>
> I think you'll find what he actually said was "coefficient of grip"
> not "grip".
Ok, (sorry about the delay BTW - real life inc.) The lecturer - he
didn't actually have tenure - two levels below full prof if I recall
correctly, Used it as an aside in part of a lecture on angular momentum.
Since that time, I've never really dealt with the apparent disparity
(see previous parenthsized remark), so thanks for clearing that up.
"Dave Baker" <Null@null,com > wrote in news:fv9dsl$hqf$1@news.datemas.de:
>
> "APLer" <APLer@floor.tilde> wrote in message
> news:Xns9A90913388B8APLer@127.0.0.1...
>> "Dave Baker" <Null@null,com > wrote in
>> news:fv6dn8$n1i$1@news.datemas.de:
>
>> According to a first year university physics prof I had years ago,
>> downforce adds nothing to grip, neither does tire width.
>
> I think you'll find what he actually said was "coefficient of grip"
> not "grip".
Ok, (sorry about the delay BTW - real life inc.) The lecturer - he
didn't actually have tenure - two levels below full prof if I recall
correctly, Used it as an aside in part of a lecture on angular momentum.
Since that time, I've never really dealt with the apparent disparity
(see previous parenthsized remark), so thanks for clearing that up.
Re: Cornering - road car v F1 car
In article <fv6dn8$n1i$1@news.datemas.de>, "Dave Baker" <Null@null,com >
wrote:
> Another little exercise born of idle curiosity. I've calculated the
> cornering speeds of a decent average modern road car and an F1 car round
> bends of various radii. I've assumed the road car can generate 0.9g force
> which is quite do-able on good tyres for an average modern car like my
> Focus. 1g or even a tad over is possible for sports cars. For the F1 car
> I've assumed 1.3g static grip on the sticky rubber plus downforce of 1200kg
> at 200 mph. The main effect of downforce is it varies with the square of
> speed so it has little effect at low speeds and then very rapidly builds up.
> This means the F1 car struggles in tight radius bends and then abruptly
> reaches a point at which cornering speeds go off the scale as downforce
> glues it to the track. The bend radii are in feet and the speeds in mph.
An interesting exercise, but I am not sure how useful it really is.
Skidpad g-numbers are good for comparing tires if you use the same
care, or cars if you use the same tires, or even the same car and tires
with different suspension settings. How usefully the numbers translate
to use on a track is another question.
Case in point: for a few years I autocrossed a BMW M-Coupe. At SCCA
and some other events I used various R-compound, DOT certified tires
(Yokohama A032rs, Kumho 700 and 710s and Hoosiers), while at BMW club
events I used the street tires (Sumitomo HZRs and some Michelins, if I
recall correctly.) I also ran a G-Cube, so I got readouts on my
cornering forces, both peak and sustained.
All four of the various R-compound tires produced sustained lateral G
forces of around 1.35G. The G-Cube software defines 'sustained' as over
.1 second in duration. Race cars, or even autocross cars, seldom do 100
foot circles, and even if you do a perfect circle isn't likely to be the
fastest way around it.
The street tires varied more, but the various Max Performance street
tires all produces about 1.15G sustained.
By comparison, I recall a friend's M-Coupe (set up for One Lap Of
America with a *much* better than stock suspension) "only" pulled about
1G on the skid pad at Tire Rack. Ah:
Sat May 12 12:09:21 2007
Tire Rack - Dry Skid Pad - Results sorted by position Page 1
Pos Car # Vehicle Class Gs
1 25 Chevrolet Z06 Corvette SSGT1 BB 1.074 G
Dan Corcoran, Kyle Corcoran
2 3 Dodge Hennessey Viper SSGT1 BB 1.046 G
Brian Smith, Nick Arevalo
3 14 Toyota Supra SSGT2 SB 1.045 G
Greg Caloudas, Leh Keen
4 26 Ultima GTR SSGT1 BB 1.044 G
Carl Warren, Sam Kimberley-Bryant
5 40 World Class Mot S2K-SC SSGT2 SB 1.035 G
Loren Edwards, Kevin Boulton
6 8 Cheverolet Corvette SSGT1 BB 1.025 G
Steve Stubbs, Aaron Pfadt
7 45 Subaru Impreza STi MidPri Sed 1.020 G
Steven Rankins, Dale Teague, Jon Krolewicz
8 1 Porsche 996 TT SSGT1 BB 1.015 G
Mark DaVia, Drew Wikstrom
9 51 Dodge SRT-4 MidPri Sed 1.014 G
Douglas Wind, Devin Clancy, Ken Brewer
10 2 Dodge Viper SSGT1 BB 1.005 G
Ronald Adee, Rick Schopp
11 30 BMW M Coupe SSGT1 SB 0.992 G
Neil Simon, Woody Hair
So beware of the numbers: I trust the G-Cube, but realize that
'track' driving is different from 'skidpad' driving.
--
David W. James vnend(at)sff,net
"When all you have is a chainsaw, everything looks like the living dead."
TJ, age 11.
In article <fv6dn8$n1i$1@news.datemas.de>, "Dave Baker" <Null@null,com >
wrote:
> Another little exercise born of idle curiosity. I've calculated the
> cornering speeds of a decent average modern road car and an F1 car round
> bends of various radii. I've assumed the road car can generate 0.9g force
> which is quite do-able on good tyres for an average modern car like my
> Focus. 1g or even a tad over is possible for sports cars. For the F1 car
> I've assumed 1.3g static grip on the sticky rubber plus downforce of 1200kg
> at 200 mph. The main effect of downforce is it varies with the square of
> speed so it has little effect at low speeds and then very rapidly builds up.
> This means the F1 car struggles in tight radius bends and then abruptly
> reaches a point at which cornering speeds go off the scale as downforce
> glues it to the track. The bend radii are in feet and the speeds in mph.
An interesting exercise, but I am not sure how useful it really is.
Skidpad g-numbers are good for comparing tires if you use the same
care, or cars if you use the same tires, or even the same car and tires
with different suspension settings. How usefully the numbers translate
to use on a track is another question.
Case in point: for a few years I autocrossed a BMW M-Coupe. At SCCA
and some other events I used various R-compound, DOT certified tires
(Yokohama A032rs, Kumho 700 and 710s and Hoosiers), while at BMW club
events I used the street tires (Sumitomo HZRs and some Michelins, if I
recall correctly.) I also ran a G-Cube, so I got readouts on my
cornering forces, both peak and sustained.
All four of the various R-compound tires produced sustained lateral G
forces of around 1.35G. The G-Cube software defines 'sustained' as over
.1 second in duration. Race cars, or even autocross cars, seldom do 100
foot circles, and even if you do a perfect circle isn't likely to be the
fastest way around it.
The street tires varied more, but the various Max Performance street
tires all produces about 1.15G sustained.
By comparison, I recall a friend's M-Coupe (set up for One Lap Of
America with a *much* better than stock suspension) "only" pulled about
1G on the skid pad at Tire Rack. Ah:
Sat May 12 12:09:21 2007
Tire Rack - Dry Skid Pad - Results sorted by position Page 1
Pos Car # Vehicle Class Gs
1 25 Chevrolet Z06 Corvette SSGT1 BB 1.074 G
Dan Corcoran, Kyle Corcoran
2 3 Dodge Hennessey Viper SSGT1 BB 1.046 G
Brian Smith, Nick Arevalo
3 14 Toyota Supra SSGT2 SB 1.045 G
Greg Caloudas, Leh Keen
4 26 Ultima GTR SSGT1 BB 1.044 G
Carl Warren, Sam Kimberley-Bryant
5 40 World Class Mot S2K-SC SSGT2 SB 1.035 G
Loren Edwards, Kevin Boulton
6 8 Cheverolet Corvette SSGT1 BB 1.025 G
Steve Stubbs, Aaron Pfadt
7 45 Subaru Impreza STi MidPri Sed 1.020 G
Steven Rankins, Dale Teague, Jon Krolewicz
8 1 Porsche 996 TT SSGT1 BB 1.015 G
Mark DaVia, Drew Wikstrom
9 51 Dodge SRT-4 MidPri Sed 1.014 G
Douglas Wind, Devin Clancy, Ken Brewer
10 2 Dodge Viper SSGT1 BB 1.005 G
Ronald Adee, Rick Schopp
11 30 BMW M Coupe SSGT1 SB 0.992 G
Neil Simon, Woody Hair
So beware of the numbers: I trust the G-Cube, but realize that
'track' driving is different from 'skidpad' driving.
--
David W. James vnend(at)sff,net
"When all you have is a chainsaw, everything looks like the living dead."
TJ, age 11.
