In article ,
Grimly Curmudgeon wrote:
On Sun, 09 Sep 2012 00:06:44 +0100, "Dave Plowman (News)"
wrote:

In article ,
Grimly Curmudgeon wrote:
And if someone offered you an unused (and I don't mean dry-charged) LA
battery that was four years old would you pay any money for it?
I wouldn't.

If it had not been allowed to go flat at any point, I'd buy it - at the
right price. Obviously not full price since that would be pointless.

I would pay nothing and only pay something once it'd been proven under
load for a while. Even then I'd only pay a fiver.

I bought a Halfords 'calcium' for the central heating system backup some 6
years ago, and it's the correct one for my old Rover. It lived in a
kitchen cupboard at a near constant temp and kept on a maintenance charge.
Was never used in anger.
It's now in the car after that battery died, and before installing it I
checked it with my posh tester. Which showed it as perfect. If I test a 6
years old car battery which has been used in a car, it usually shows some
degradation.

BTW, if it's a reasonably big car battery, the scrap value is more than a
fiver. ;-) Got 7 quid for the old Rover one.

--
*A fine is a tax for doing wrong. A tax is a fine for doing well*

Dave Plowman London SW
To e-mail, change noise into sound.

In article
,
harry wrote:
A lot depends on where the price of petrol goes in the next few years.

Natural gas - which provides most of our electricity - tends to track the
price of crude. Or the other way round. And although there is currently
no taxation on the fuel for an electric car, you can be sure this will
change if they become common. Probably in the form of road use taxation.

--
*There are 3 kinds of people: those who can count & those who can't.

Dave Plowman London SW
To e-mail, change noise into sound.

In article , Dave Plowman (News)
scribeth thus
In article
,
harry wrote:
A lot depends on where the price of petrol goes in the next few years.

Natural gas - which provides most of our electricity -


Not quite Dave its still King Coal, nuclear a 8 GW base load and the
rest filled in with Gas plus the of bit of Hydro and the ever fickle
wind;!...

http://www.gridwatch.templar.co.uk/


tends to track the
price of crude. Or the other way round. And although there is currently
no taxation on the fuel for an electric car, you can be sure this will
change if they become common. Probably in the form of road use taxation.


Indeed thats a bigger cert than electric cars becoming an everyday
thing..

Which won't happen till they get the prime mover power sorted out..
--
Tony Sayer

In article
..com, harry scribeth thus
On Sep 8, 8:37*am, tony sayer wrote:
In article
.com, harry scribeth thus

On Sep 7, 6:45*pm, Andy Cap wrote:
On 07/09/12 18:40, harryagain wrote:

Drove an electric car today.
Uncanny experience but good.
http://www.mitsubishi-cars.co.uk/imiev/technology.aspx

... and the batteries last how long and cost what to replace?

Andy C

Range is 83 miles. Batteries guaranteed for 5-10 years (Dependingon
how you treat them.). Replacement cost around £4,000

Well it does say range 93 miles, but how expensive is that to run
compared to petrol?..

It gives a consumption figure that looks like miles per watt hour which
doesn't seem right?..

Mind you if thats 28 K to buy then thats all rather academic..

--
Tony Sayer

A lot of the energy expended (potential, kinetic) is recovered by
regeneration.
Only frictional losses can't be recovered.

Yes regen , been used on the tube railway since god knows when, isn't
that much of a factor..
--
Tony Sayer

In article , Dave Plowman (News)
scribeth thus
In article
,
harry wrote:
... and the batteries last how long and cost what to replace?

Andy C


Range is 83 miles. Batteries guaranteed for 5-10 years (Dependingon
how you treat them.). Replacement cost around £4,000

Treat them? Leave it in the garage on charge but never driven to get the
10 year warranty? And is the warranty free replacement or a proportional
cost according to age?

Tesla, for example, won't do a warranty replacement if the car is unused
and not on charge for a few weeks - like say left at an airport carpark
while on holiday.


Hrump!, The car under discussion wouldn't get me to the main Two London
airports and its very marginal if it could do a return trip to the
nearest one!..

--
Tony Sayer

tony sayer wrote:
In article
.com, harry scribeth thus
On Sep 8, 8:37 am, tony sayer wrote:
In article
.com, harry scribeth thus

On Sep 7, 6:45 pm, Andy Cap wrote:
On 07/09/12 18:40, harryagain wrote:
Drove an electric car today.
Uncanny experience but good.
http://www.mitsubishi-cars.co.uk/imiev/technology.aspx
... and the batteries last how long and cost what to replace?
Andy C
Range is 83 miles. Batteries guaranteed for 5-10 years (Dependingon
how you treat them.). Replacement cost around £4,000
Well it does say range 93 miles, but how expensive is that to run
compared to petrol?..

It gives a consumption figure that looks like miles per watt hour which
doesn't seem right?..

Mind you if thats 28 K to buy then thats all rather academic..

--
Tony Sayer
A lot of the energy expended (potential, kinetic) is recovered by
regeneration.
Only frictional losses can't be recovered.

Yes regen , been used on the tube railway since god knows when, isn't
that much of a factor..

most car losses are tyre rolling resistance and air resistance. Neither
of which I would describe as friction, though that;s more a matter of
precise definition.


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

In article ,
The Natural Philosopher wrote:
Yes regen , been used on the tube railway since god knows when, isn't
that much of a factor..

most car losses are tyre rolling resistance and air resistance.

So that's how to improve the range of any car - get rid of the tyres. And
of course drive very slowly where air resistance is minimal. Or drive with
the wind where it helps things.

Neither
of which I would describe as friction, though that;s more a matter of
precise definition.

It's the major factor. In still water a single person can move a ship
weighing many tons. You'll not do that with a similar weight vehicle.

--
*Middle age is when work is a lot less fun - and fun a lot more work.

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article ,
The Natural Philosopher wrote:
Yes regen , been used on the tube railway since god knows when, isn't
that much of a factor..

most car losses are tyre rolling resistance and air resistance.

So that's how to improve the range of any car - get rid of the tyres.

Indeed.

Trains have much less rolling resistance as do bicycles with very small
high pressure tyres.

And
of course drive very slowly where air resistance is minimal. Or drive with
the wind where it helps things.


Absolutely. an electric bicycle is far better than a car in terms of
miles/Kwh..


Neither
of which I would describe as friction, though that;s more a matter of
precise definition.

It's the major factor. In still water a single person can move a ship
weighing many tons. You'll not do that with a similar weight vehicle.


Due to the tyre rolling resistance.

I can in fact push a van weighing several toinnes on well pumped up
tyres on a dead smooth flat road.

remember that what you BELIEVE is not the truth, necessarily. Its what
you believe, that's all.

Measuring the effects of things independently is the key to getting an
accurate understanding, not relying on religion.


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

In article ,
The Natural Philosopher wrote:
It's the major factor. In still water a single person can move a ship
weighing many tons. You'll not do that with a similar weight vehicle.


Due to the tyre rolling resistance.

I can in fact push a van weighing several toinnes on well pumped up
tyres on a dead smooth flat road.

I'm talking about a small ship like say a trawler where I've seen it done.

I'll bet you'll not move a truck weighing anywhere near as much.

--
*A closed mouth gathers no feet.

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article ,
The Natural Philosopher wrote:
It's the major factor. In still water a single person can move a ship
weighing many tons. You'll not do that with a similar weight vehicle.


Due to the tyre rolling resistance.

I can in fact push a van weighing several toinnes on well pumped up
tyres on a dead smooth flat road.

I'm talking about a small ship like say a trawler where I've seen it done.

I'll bet you'll not move a truck weighing anywhere near as much.

As I said, that's because of the tyres.

Whether you call that friction is up to you. Personally I dont.
Friction to me is sliding contact between hard surfaces, or fluid over
a surface.

If you did in fact have a classic frictional case as a boat hull in
water, you very quickly find that cars go faster than boats of the same
weight for the same power

Tyre rolling resistance represents almost a fixed drag component
irrespective of speed.


Boat hull resistance is purely a function of wetted area and speed.

Air resistance is more complex, because air is more compressible. Its a
function of frontal area and shape.





--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

In article ,
Dave Plowman (News) wrote:
In article ,
The Natural Philosopher wrote:
It's the major factor. In still water a single person can move a ship
weighing many tons. You'll not do that with a similar weight vehicle.


Due to the tyre rolling resistance.

I can in fact push a van weighing several toinnes on well pumped up
tyres on a dead smooth flat road.

I'm talking about a small ship like say a trawler where I've seen it done.

I'll bet you'll not move a truck weighing anywhere near as much.

You only need to look at how much load a single horse could pull on a canal
barge.

--
From KT24

Using a RISC OS computer running v5.18

charles wrote:
In article ,
Dave Plowman (News) wrote:
In article ,
The Natural Philosopher wrote:
It's the major factor. In still water a single person can move a ship
weighing many tons. You'll not do that with a similar weight vehicle.


Due to the tyre rolling resistance.

I can in fact push a van weighing several toinnes on well pumped up
tyres on a dead smooth flat road.

I'm talking about a small ship like say a trawler where I've seen it done.

I'll bet you'll not move a truck weighing anywhere near as much.

You only need to look at how much load a single horse could pull on a canal
barge.


Indeed, but it does NOT support his thesis that its 'friction'


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

In article , The Natural Philosopher
wrote:
charles wrote:
In article , Dave Plowman (News)
wrote:
In article , The Natural Philosopher
wrote:
It's the major factor. In still water a single person can move a
ship weighing many tons. You'll not do that with a similar weight
vehicle.


Due to the tyre rolling resistance.

I can in fact push a van weighing several toinnes on well pumped up
tyres on a dead smooth flat road.

I'm talking about a small ship like say a trawler where I've seen it
done.

I'll bet you'll not move a truck weighing anywhere near as much.

You only need to look at how much load a single horse could pull on a
canal barge.


Indeed, but it does NOT support his thesis that its 'friction'

but if it wasn't for friction, the wheels would simply spin on the ground.

--
From KT24

Using a RISC OS computer running v5.18

On Sun, 09 Sep 2012 17:06:08 +0100, charles
wrote:

In article , The Natural Philosopher
wrote:
charles wrote:
In article , Dave Plowman (News)
wrote:
In article , The Natural Philosopher
wrote:
It's the major factor. In still water a single person can move a
ship weighing many tons. You'll not do that with a similar weight
vehicle.


Due to the tyre rolling resistance.

I can in fact push a van weighing several toinnes on well pumped up
tyres on a dead smooth flat road.

I'm talking about a small ship like say a trawler where I've seen it
done.

I'll bet you'll not move a truck weighing anywhere near as much.

You only need to look at how much load a single horse could pull on a
canal barge.


Indeed, but it does NOT support his thesis that its 'friction'

but if it wasn't for friction, the wheels would simply spin on the
ground.


T'aint necessarily so. The non-flatness at a macro scale would be
sufficient without any 'real' friction being needed.

--
Rod

charles wrote:
In article , The Natural Philosopher
wrote:
charles wrote:
In article , Dave Plowman (News)
wrote:
In article , The Natural Philosopher
wrote:
It's the major factor. In still water a single person can move a
ship weighing many tons. You'll not do that with a similar weight
vehicle.

Due to the tyre rolling resistance.
I can in fact push a van weighing several toinnes on well pumped up
tyres on a dead smooth flat road.
I'm talking about a small ship like say a trawler where I've seen it
done.
I'll bet you'll not move a truck weighing anywhere near as much.
You only need to look at how much load a single horse could pull on a
canal barge.


Indeed, but it does NOT support his thesis that its 'friction'

but if it wasn't for friction, the wheels would simply spin on the ground.

that's not what slows you down. Friction between surfaces that are not
moving relative to one another wastes no power.


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

In message , The Natural Philosopher
writes
Boat hull resistance is purely a function of wetted area and speed.

Air resistance is more complex, because air is more compressible. Its
a function of frontal area and shape.


A displacement boat has a "natural" maximum speed (the hull speed)
dependent on the hull length. I've often wondered if something similar
applies to cars in air.

It might explain why in the old Omega, fuel consumption on the motorway
only went skywards over 70, but my current vehicle is bad over 60.
--
Bill

On Sun, 09 Sep 2012 17:15:14 +0100, polygonum
wrote:

but if it wasn't for friction, the wheels would simply spin on the
ground.


T'aint necessarily so. The non-flatness at a macro scale would be
sufficient without any 'real' friction being needed.

Take it small enough and that's all friction is. So, without friction,
you'd be ****ed. We'd all be ****ed.
What's 'real' friction when it's at home?

On Sep 9, 11:18*am, tony sayer wrote:
In article
.com, harry scribeth thus





On Sep 8, 8:37*am, tony sayer wrote:
In article
.com, harry scribeth thus

On Sep 7, 6:45*pm, Andy Cap wrote:
On 07/09/12 18:40, harryagain wrote:

Drove an electric car today.
Uncanny experience but good.
http://www.mitsubishi-cars.co.uk/imiev/technology.aspx

... and the batteries last how long and cost what to replace?

Andy C

Range is 83 miles. Batteries guaranteed for 5-10 years (Dependingon
how you treat them.). Replacement cost around £4,000

Well it does say range 93 miles, but how expensive is that to run
compared to petrol?..

It gives a consumption figure that looks like miles per watt hour which
doesn't seem right?..

Mind you if thats 28 K to buy then thats all rather academic..

--
Tony Sayer

A lot of the energy expended (potential, kinetic) is recovered by
regeneration.
Only frictional losses can't be recovered.

Yes regen , been used on the tube railway since god knows when, isn't
that much of a factor..
--
Tony Sayer- Hide quoted text -

- Show quoted text -

It is in electric cars.. The battery is only 17Kwh, Pretty
insignificanr really.
Electric trains don't have hills to climb and descend. Not significant
ones anyway. Niether do they run in traffic.

On Sep 9, 11:57*am, The Natural Philosopher
wrote:
tony sayer wrote:
In article
.com, harry scribeth thus
On Sep 8, 8:37 am, tony sayer wrote:
In article
.com, harry scribeth thus

On Sep 7, 6:45 pm, Andy Cap wrote:
On 07/09/12 18:40, harryagain wrote:
Drove an electric car today.
Uncanny experience but good.
http://www.mitsubishi-cars.co.uk/imiev/technology.aspx
... and the batteries last how long and cost what to replace?
Andy C
Range is 83 miles. Batteries guaranteed for 5-10 years (Dependingon
how you treat them.). Replacement cost around £4,000
Well it does say range 93 miles, but how expensive is that to run
compared to petrol?..

It gives a consumption figure that looks like miles per watt hour which
doesn't seem right?..

Mind you if thats 28 K to buy then thats all rather academic..

--
Tony Sayer
A lot of the energy expended (potential, kinetic) is recovered by
regeneration.
Only frictional losses can't be recovered.

Yes regen , been used on the tube railway since god knows when, isn't
that much of a factor..

most car losses are tyre rolling resistance and air resistance. Neither
of which I would describe as friction, though that;s more a matter of
precise definition.

Hysteresis
I-Meiv is fitted with low rolling resistance tyres.

harry wrote:
On Sep 9, 11:57 am, The Natural Philosopher
wrote:
tony sayer wrote:
In article
.com, harry scribeth thus
On Sep 8, 8:37 am, tony sayer wrote:
In article
.com, harry scribeth thus
On Sep 7, 6:45 pm, Andy Cap wrote:
On 07/09/12 18:40, harryagain wrote:
Drove an electric car today.
Uncanny experience but good.
http://www.mitsubishi-cars.co.uk/imiev/technology.aspx
... and the batteries last how long and cost what to replace?
Andy C
Range is 83 miles. Batteries guaranteed for 5-10 years (Dependingon
how you treat them.). Replacement cost around £4,000
Well it does say range 93 miles, but how expensive is that to run
compared to petrol?..
It gives a consumption figure that looks like miles per watt hour which
doesn't seem right?..
Mind you if thats 28 K to buy then thats all rather academic..
--
Tony Sayer
A lot of the energy expended (potential, kinetic) is recovered by
regeneration.
Only frictional losses can't be recovered.
Yes regen , been used on the tube railway since god knows when, isn't
that much of a factor..
most car losses are tyre rolling resistance and air resistance. Neither
of which I would describe as friction, though that;s more a matter of
precise definition.

Hysteresis
I-Meiv is fitted with low rolling resistance tyres.

Golly. Harry got something right!
Almost anyway

--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

On Sep 9, 5:34*pm, The Natural Philosopher
wrote:
charles wrote:
In article , The Natural Philosopher
wrote:
charles wrote:
In article , Dave Plowman (News)
* wrote:
In article , The Natural Philosopher
* wrote:
It's the major factor. In still water a single person can move a
ship weighing many tons. You'll not do that with a similar weight
vehicle.

Due to the tyre rolling resistance.
I can in fact push a van weighing several toinnes on well pumped up
tyres on a dead smooth flat road.
I'm talking about a small ship like say a trawler where I've seen it
done.
I'll bet you'll not move a truck weighing anywhere near as much.
You only need to look at how much load a single horse could pull on a
canal barge.

Indeed, but it does NOT support his thesis that its 'friction'

but if it wasn't for friction, the wheels would simply spin on the ground.

that's not what slows you down. Friction between surfaces that are not
moving relative to one another wastes no power.

--
Ineptocracy

(in-ep-toc’-ra-cy) – a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.- Hide quoted text -

- Show quoted text -

If no power was wasted, there would be no friction.
Hysteresis is what wastes power in tyres. (ie flexing them).
The higher the tyre pressure the less flex and less energy lost.

harry wrote:


If no power was wasted, there would be no friction.


Oh dear. Now you are back to talking ********


iu can have friction but no slip and then no power is wasted.

power loss is friction force times slip speed.

Isdf slei[ seed is zero, mno power loss.


Hysteresis is what wastes power in tyres. (ie flexing them).
The higher the tyre pressure the less flex and less energy lost.

Well that is correct, at least.


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

On Sun, 09 Sep 2012 18:02:51 +0100, Grimly Curmudgeon
wrote:

On Sun, 09 Sep 2012 17:15:14 +0100, polygonum
wrote:

but if it wasn't for friction, the wheels would simply spin on the
ground.


T'aint necessarily so. The non-flatness at a macro scale would be
sufficient without any 'real' friction being needed.

Take it small enough and that's all friction is. So, without friction,
you'd be ****ed. We'd all be ****ed.
What's 'real' friction when it's at home?

Sure there are the 'asperities' where the surfaces are imperfectly smooth
- but there are interactions between, say, the tyre and the asphalt which
are at the inter-atomic level.

What was going through my mind was a sort of rack and pinion system - as
if the lumps on the tyres 'fitted' the gaps between projections of the
stones. That would allow movement even if both tyre and road were made of
teflon or even a mythical frictionless material.

--
Rod

On Sun, 09 Sep 2012 17:34:49 +0100, The Natural Philosopher
wrote:

but if it wasn't for friction, the wheels would simply spin on the ground.

that's not what slows you down. Friction between surfaces that are not
moving relative to one another wastes no power.

But they are moving relative to one another, all the time.

On Sun, 9 Sep 2012 17:57:57 +0100, Bill wrote:

A displacement boat has a "natural" maximum speed (the hull speed)
dependent on the hull length. I've often wondered if something similar
applies to cars in air.

It might explain why in the old Omega, fuel consumption on the motorway
only went skywards over 70, but my current vehicle is bad over 60.

A helluva lot to do with overall gearing and torque characteristics of
the engine, too.

Grimly Curmudgeon wrote:
On Sun, 09 Sep 2012 17:34:49 +0100, The Natural Philosopher
wrote:

but if it wasn't for friction, the wheels would simply spin on the ground.

that's not what slows you down. Friction between surfaces that are not
moving relative to one another wastes no power.

But they are moving relative to one another, all the time.

not at the pint of contact. That's the whole point

Unless you are in a wheelspin mode

hardly likely if you are towing or pushing a van.


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

On 09/09/2012 15:27, The Natural Philosopher wrote:
Whether you call that friction is up to you. Personally I dont.
Friction to me is sliding contact between hard surfaces, or fluid over
a surface.

If you did in fact have a classic frictional case as a boat hull in
water, you very quickly find that cars go faster than boats of the same
weight for the same power

That depends. At very low speed the friction of a floating object is
negligible; that isn't true of a car. I'll happily push a 10 tonne boat
off from a jetty, but I wouldn't even try with a truck.


Tyre rolling resistance represents almost a fixed drag component
irrespective of speed.


Boat hull resistance is purely a function of wetted area and speed.

I see you don't sail much.


Air resistance is more complex, because air is more compressible. Its a
function of frontal area and shape.

.... and you won't notice the compressibility of air until you get to a
substantial fraction of the speed of sound.

Andy

Bill wrote:

A displacement boat has a "natural" maximum speed (the hull speed)
dependent on the hull length. I've often wondered if something similar
applies to cars in air.
It might explain why in the old Omega, fuel consumption on the motorway
only went skywards over 70, but my current vehicle is bad over 60.

Stick a bulbous prow on it and see what happens ...

On 09/09/2012 17:57, Bill wrote:

A displacement boat has a "natural" maximum speed (the hull speed)
dependent on the hull length. I've often wondered if something similar
applies to cars in air.

It might explain why in the old Omega, fuel consumption on the motorway
only went skywards over 70, but my current vehicle is bad over 60.

Or it might not.

Hull speed is when you are travelling at about the same speed as a wave
of the same length. Increase speed and your stern wave falls behind, so
you are climbing a wave at the front but not getting pushed by the stern
wave behind - and power needed goes up.

In a car air resistance is proportional to the square of the speed. (and
power to the cube). So go faster, use much more fuel. And you get odd
effects in engine efficiency too - petrol engines are really inefficient
at low power settings, so go a little faster and you may get better fuel
economy especially on a large petrol engine. I'm guessing the Omega
wasn't a diesel? And that the current car has a smaller engine?

Andy

Andy Champ wrote:
On 09/09/2012 15:27, The Natural Philosopher wrote:
Whether you call that friction is up to you. Personally I dont.
Friction to me is sliding contact between hard surfaces, or fluid over
a surface.

If you did in fact have a classic frictional case as a boat hull in
water, you very quickly find that cars go faster than boats of the same
weight for the same power

That depends. At very low speed the friction of a floating object is
negligible; that isn't true of a car. I'll happily push a 10 tonne boat
off from a jetty, but I wouldn't even try with a truck.


Tyre rolling resistance represents almost a fixed drag component
irrespective of speed.


Boat hull resistance is purely a function of wetted area and speed.

I see you don't sail much.

Au contraire getting a boat to plane is about getting the wetted area down


Air resistance is more complex, because air is more compressible. Its a
function of frontal area and shape.

... and you won't notice the compressibility of air until you get to a
substantial fraction of the speed of sound.

I see you dont do physics or aeronautics. OR have a car with tyres that
are inflated.

Andy


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

In message , Grimly
Curmudgeon writes
On Sun, 9 Sep 2012 17:57:57 +0100, Bill wrote:

A displacement boat has a "natural" maximum speed (the hull speed)
dependent on the hull length. I've often wondered if something similar
applies to cars in air.

It might explain why in the old Omega, fuel consumption on the motorway
only went skywards over 70, but my current vehicle is bad over 60.

A helluva lot to do with overall gearing and torque characteristics of
the engine, too.

ISTR many years ago someone put forward a figure of 2hp needed to move a
pair of wing mirrors at 70mph.

--
Tim Lamb

The Natural Philosopher wrote:
Grimly Curmudgeon wrote:
On Sun, 09 Sep 2012 17:34:49 +0100, The Natural Philosopher
wrote:

but if it wasn't for friction, the wheels would simply spin on the
ground.

that's not what slows you down. Friction between surfaces that are
not moving relative to one another wastes no power.

But they are moving relative to one another, all the time.

not at the pint of contact. That's the whole point

Unless you are in a wheelspin mode

hardly likely if you are towing or pushing a van.


Look closely at the part of a tyre which is in contact with the ground,
and you will see that due to the way the rolling radius varies along the
flat part, there must always be a small amount of slippage between the
tyre and the ground which may or may not be absorbed by the elasticity
of the tyre material. This applies to all wheel/ ground interactions
where the wheel and ground are not perfectly rigid.

Incidentally, in the 19th Century, experiments were done which gave the
hauling capacity of a horse at walking speed on a level surface as
(roughly) 4 tons on a metal tyred, thin wheeled cart on a good hard road
surface, 7 tons on a railway waggon and 10 tons on a narrowboat. The
road figures may have changed slightly when the pneumatic tyre was
invented and came into use.

--
Tciao for Now!

John.

Tim Lamb wrote:
In message , Grimly
Curmudgeon writes
On Sun, 9 Sep 2012 17:57:57 +0100, Bill wrote:

A displacement boat has a "natural" maximum speed (the hull speed)
dependent on the hull length. I've often wondered if something similar
applies to cars in air.

It might explain why in the old Omega, fuel consumption on the motorway
only went skywards over 70, but my current vehicle is bad over 60.

A helluva lot to do with overall gearing and torque characteristics of
the engine, too.

ISTR many years ago someone put forward a figure of 2hp needed to move a
pair of wing mirrors at 70mph.

seems a lot. I built a model plane that would move 24" span at 70mp on
only 100W...

Mind you, that was edge on..
--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

John Williamson wrote:
The Natural Philosopher wrote:
Grimly Curmudgeon wrote:
On Sun, 09 Sep 2012 17:34:49 +0100, The Natural Philosopher
wrote:

but if it wasn't for friction, the wheels would simply spin on the
ground.

that's not what slows you down. Friction between surfaces that are
not moving relative to one another wastes no power.

But they are moving relative to one another, all the time.

not at the pint of contact. That's the whole point

Unless you are in a wheelspin mode

hardly likely if you are towing or pushing a van.


Look closely at the part of a tyre which is in contact with the ground,
and you will see that due to the way the rolling radius varies along the
flat part, there must always be a small amount of slippage between the
tyre and the ground

No, it doesn't mean that at all.

which may or may not be absorbed by the elasticity
of the tyre material. This applies to all wheel/ ground interactions
where the wheel and ground are not perfectly rigid.


No, it doesnt.

What counts with tyres is deformation, not slip


Incidentally, in the 19th Century, experiments were done which gave the
hauling capacity of a horse at walking speed on a level surface as
(roughly) 4 tons on a metal tyred, thin wheeled cart on a good hard road
surface, 7 tons on a railway waggon and 10 tons on a narrowboat. The
road figures may have changed slightly when the pneumatic tyre was
invented and came into use.

a lot. about 10 times as much rolling resistance for a tyre on concaret


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

On 9 Sep,
"Dave Plowman (News)" wrote:

Natural gas - which provides most of our electricity


Eh? about 20%. Coal and nuclear are usually a higher percentage.

See http://www.gridwatch.templar.co.uk/ which has been discussed here
before.

--
B Thumbs
Change lycos to yahoo to reply

wrote:
On 9 Sep,
"Dave Plowman (News)" wrote:

Natural gas - which provides most of our electricity


Eh? about 20%. Coal and nuclear are usually a higher percentage.

See http://www.gridwatch.templar.co.uk/ which has been discussed here
before.


Gas used to...but gas got expensive

coal is running far more of the baseload, and RWEs
converted-to-imported-biofuel coal plants (see 'other' )

Gas is now only being sold into peak demand periods, or as hot standby
for when the wind drops again..and again..and again...


If you look at the time graphs gas has lost out to coal over the last year.

Nuclear is actually increasing slightly - EDF have spent money doing
preventative maintenance on the old AGRs and they are running at better
capacity factor now.

Almost makes up fort the last but one Magnox that's closed..




--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

On Sun, 09 Sep 2012 19:54:37 +0100, The Natural Philosopher
wrote:

But they are moving relative to one another, all the time.

not at the pint of contact. That's the whole point

They are. Rubber squirming under load put on and taken off and even in
the contact patch there is movement.

On Sep 9, 7:54*pm, The Natural Philosopher
wrote:
Grimly Curmudgeon wrote:
On Sun, 09 Sep 2012 17:34:49 +0100, The Natural Philosopher
wrote:

but if it wasn't for friction, the wheels would simply spin on the ground.

that's not what slows you down. Friction between surfaces that are not
moving relative to one another wastes no power.

But they are moving relative to one another, all the time.

not at the pint of contact. That's the whole point

Unless you are in a wheelspin mode

hardly likely if you are towing or pushing a van.

--
Ineptocracy

(in-ep-toc’-ra-cy) – a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.


There is always "microslippage" between wheel and road. Even more when
cornering.

On Mon, 10 Sep 2012 01:16:38 -0700 (PDT), harry
wrote:

There is always "microslippage" between wheel and road. Even more when
cornering.

TNP has a fizziks degree; he knows better than everyone who doesn't.

Grimly Curmudgeon wrote:
On Mon, 10 Sep 2012 01:16:38 -0700 (PDT), harry
wrote:

There is always "microslippage" between wheel and road. Even more when
cornering.

TNP has a fizziks degree; he knows better than everyone who doesn't.


No I have an engineering degree, which means I talk about whats
important, not what might theoretically be one ten thousandth of the
observed and meausured result.


The dominant rolling resistance of a tyred car is down to deformation
and hysteresis. That is not normally called 'friction'. Nor is what
'friction' the tyre generates due to pico slippage in any way more than
such an infinitesimal fraction that it makes any sense to talk about it
unless of course you are in danger of looking a prat and losing an argument.



End of.


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.