On 30/03/2016 00:37, Dave Plowman (News) wrote:
In ,
Roger wrote:
This clearly shows you get more force by choosing peak power in a low
gear over peak torque in a higher one.


That's a no-brainer, anyway. Just as you can express engine power in
terms of engine speed (times) engine torque (divided by) a suitable
constant, you can also express propulsive power as road speed (times)
thrust at the contact patch (divided by) a different constant - but they
should equate to the same thing apart from transmission losses. So when
the engine is developing its peak power, you'll get peak thrust at the
wheels.

Are you at it too? ;-)

Peak torque at the wheels happens when the engine is at peak torque - not
peak BHP, unless the two coincide. Regardless of which gear you choose.


See my previous post. At any given road speed the max available thrust
at the wheels occurs when the engine is developing its max *power* not
its max *torque*. You choose the gearing to suit.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 30/03/2016 13:42, Dave Plowman (News) wrote:
In article ,
The Natural Philosopher wrote:
On 30/03/16 00:30, Dave Plowman (News) wrote:
You get the best acceleration with the maximum torque*at the wheels*.
And in any given gear, this will be when the engine develops maximum
torque.

In the one sentence is encapsulated Lefty's are inevitably stupid
politics

I'm sure you think that a very pithy comment. Now try it again in English.

'in any given gear' is irrelevant, when you can choose your gear.

Thanks from proving once more you can't follow a discussion.

Let me see if I can put it in terms even you can understand.

Regardless of the gear chosen, the peak acceleration *in that gear* will
occur when the engine is developing peak torque.

Are we still doing this? What you've said there is true, however it is
not the way to accelerate the car the fastest.

On 30/03/2016 11:20, Dave Plowman (News) wrote:


Infinitely variable is a misnomer. It has a limit to the ratios available.
But is variable between the lowest and highest.

It has an upper and lower limit of course. But it is continuously
variable between those limits - in an infinite number of infinitesimal
steps!

The concept first appeared in the Austin Hayes transmission
http://www.austinmemories.com/styled-23/index.html in the 1930's - long
before Daf's belt drive system.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 30/03/2016 13:42, Dave Plowman (News) wrote:


Regardless of the gear chosen, the peak acceleration *in that gear* will
occur when the engine is developing peak torque.


No-one would argue with that.

But that only occurs at one road speed which corresponds to the engine's
peak torque speed in that gear.

I'm sure you would agree that you could more acceleration at that road
speed by choosing a different gear which allowed the engine to operate
at its max power speed. If you *don't*, please explain what's wrong with
that statement.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 30/03/16 16:54, Roger Mills wrote:
On 30/03/2016 00:30, Dave Plowman (News) wrote:



You get the best acceleration with the maximum torque *at the wheels*.
And in any given gear, this will be when the engine develops maximum
torque.


That is true of *that* gear at *that* road speed.

HOWEVER, the engine won't be developing its maximum power when running
at its max torque speed. So - at that roadspeed - you could actually get
*more* thrust and *more* acceleration by choosing a different gear which
allowed the engine to run at at its max power speed. The engine would be
producing less torque than in the first case, but this would be more
than offset by extra torque multiplication from the lower gearing.

Tell me, in your boy racer days, how did you decide when to change gear
in order to achieve the best possible 0-100 time?

Do you seriously think Dave ever did anything that much fun?



--
How fortunate for governments that the people they administer don't think.

Adolf Hitler

On 3/30/2016 11:53 AM, The Natural Philosopher wrote:
On 30/03/16 00:37, Dave Plowman (News) wrote:

Peak torque at the wheels happens when the engine is at peak torque - not
peak BHP, unless the two coincide. Regardless of which gear you choose.

No, it doesn't, because we have a car at speed and a gear box.

No wonder you vote Labia.

Peak torque at the wheels is when the gear ratio is lowest.

If you ignore car speed.

Which is 'as true' as your original fatuous statement


I think you are being deliberately obtuse. It's obvious to me that Dave
means that, *in each gear*, peak torque at the wheels occurs at peak
engine torque.

On 30/03/16 17:48, newshound wrote:
On 3/30/2016 11:53 AM, The Natural Philosopher wrote:
On 30/03/16 00:37, Dave Plowman (News) wrote:

Peak torque at the wheels happens when the engine is at peak torque -
not
peak BHP, unless the two coincide. Regardless of which gear you choose.

No, it doesn't, because we have a car at speed and a gear box.

No wonder you vote Labia.

Peak torque at the wheels is when the gear ratio is lowest.

If you ignore car speed.

Which is 'as true' as your original fatuous statement


I think you are being deliberately obtuse. It's obvious to me that Dave
means that, *in each gear*, peak torque at the wheels occurs at peak
engine torque.

Yes, but that's only because he CLAIMED that the 'best acceleration of
the *car* would always be at peak *engine* torque' and cant bear to be
proved wrong...


--
Future generations will wonder in bemused amazement that the early
twenty-first centurys developed world went into hysterical panic over a
globally average temperature increase of a few tenths of a degree, and,
on the basis of gross exaggerations of highly uncertain computer
projections combined into implausible chains of inference, proceeded to
contemplate a rollback of the industrial age.

Richard Lindzen

In article ,
Roger Mills wrote:
You get the best acceleration with the maximum torque *at the wheels*.
And in any given gear, this will be when the engine develops maximum
torque.


That is true of *that* gear at *that* road speed.

There can only be one road speed in one gear and at one engine speed.

Of course the rate of change of speed (acceleration) depends on the gear
in use and where the engine is in its torque curve.

But the maximum rate of change happens at peak torque. I really can't see
how so many fail to understand this very simple thing.

--
*Don't sweat the petty things and don't pet the sweaty things.

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

In article ,
Roger Mills wrote:
On 30/03/2016 00:37, Dave Plowman (News) wrote:
In ,
Roger wrote:
This clearly shows you get more force by choosing peak power in a low
gear over peak torque in a higher one.


That's a no-brainer, anyway. Just as you can express engine power in
terms of engine speed (times) engine torque (divided by) a suitable
constant, you can also express propulsive power as road speed (times)
thrust at the contact patch (divided by) a different constant - but
they should equate to the same thing apart from transmission losses.
So when the engine is developing its peak power, you'll get peak
thrust at the wheels.

Are you at it too? ;-)

Peak torque at the wheels happens when the engine is at peak torque -
not peak BHP, unless the two coincide. Regardless of which gear you
choose.


See my previous post. At any given road speed the max available thrust
at the wheels occurs when the engine is developing its max *power* not
its max *torque*. You choose the gearing to suit.

The discussion was about accleration - rate of change of speed - at any
one point in an engine's range.

--
*A nest isn't empty until all their stuff is out of the attic

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

In article ,
Clive George wrote:
Regardless of the gear chosen, the peak acceleration *in that gear*
will occur when the engine is developing peak torque.

Are we still doing this?

I'd long since given up. But someone decided to revive it.


What you've said there is true, however it is
not the way to accelerate the car the fastest.

We're not talking 0-60 times here. Just the best rate of change of speed.
No vehicle with an IC engine gives a linear rate of increase in speed from
0 to top speed. It will obviously produce the best acceleration in the
lowest gear, slightly less in the next one up, and so on. But that is a
red herring as regards when the engine produces the best acceleration in
any one gear.

--
*The statement above is false

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

In article , Roger Mills
writes
On 30/03/2016 00:37, Dave Plowman (News) wrote:
In ,
Roger wrote:
This clearly shows you get more force by choosing peak power in a low
gear over peak torque in a higher one.


That's a no-brainer, anyway. Just as you can express engine power in
terms of engine speed (times) engine torque (divided by) a suitable
constant, you can also express propulsive power as road speed (times)
thrust at the contact patch (divided by) a different constant - but they
should equate to the same thing apart from transmission losses. So when
the engine is developing its peak power, you'll get peak thrust at the
wheels.

Are you at it too? ;-)

Peak torque at the wheels happens when the engine is at peak torque - not
peak BHP, unless the two coincide. Regardless of which gear you choose.


See my previous post. At any given road speed the max available thrust
at the wheels occurs when the engine is developing its max *power* not
its max *torque*. You choose the gearing to suit.
If you chose the correct gearing would the car achieve maximum seed at
maximum power output? In which instant the acceleration would be zero.
--
bert

In article , Thomas Prufer
writes
On Tue, 29 Mar 2016 22:21:52 +0100, Roger Mills wrote:

Having said that, it's not particularly useful unless you've got an
infinitely variable transmission because fixed gearing will only allow
max power to be applied at the road at a few discrete speeds - not over
the whole speed range.

Well...

https://en.wikipedia.org/wiki/Variomatic

(Not that DAFs were known for neck-snapping acceleration,
Mine (DAF44 could easily out accelerate my Renault 18 (1.8) over the
first few hundred yards.
or anything other than
going backwards real fast...)

As fast as it could go forwards :-)

Thomas Prufer

--
bert

On 30/03/16 19:53, bert wrote:
In article , Roger Mills
writes
On 30/03/2016 00:37, Dave Plowman (News) wrote:
In ,
Roger wrote:
This clearly shows you get more force by choosing peak power in a low
gear over peak torque in a higher one.


That's a no-brainer, anyway. Just as you can express engine power in
terms of engine speed (times) engine torque (divided by) a suitable
constant, you can also express propulsive power as road speed (times)
thrust at the contact patch (divided by) a different constant - but
they
should equate to the same thing apart from transmission losses. So when
the engine is developing its peak power, you'll get peak thrust at the
wheels.

Are you at it too? ;-)

Peak torque at the wheels happens when the engine is at peak torque -
not
peak BHP, unless the two coincide. Regardless of which gear you choose.


See my previous post. At any given road speed the max available thrust
at the wheels occurs when the engine is developing its max *power* not
its max *torque*. You choose the gearing to suit.
If you chose the correct gearing would the car achieve maximum seed at
maximum power output? In which instant the acceleration would be zero.

Peak power is always the place of maximum speed and maximum
acceleration, given suitable choices of gears



--
Ideas are more powerful than guns. We would not let our enemies have
guns, why should we let them have ideas?

Josef Stalin

On 3/30/2016 8:03 PM, The Natural Philosopher wrote:
On 30/03/16 19:53, bert wrote:
In article , Roger Mills
writes
On 30/03/2016 00:37, Dave Plowman (News) wrote:
In ,
Roger wrote:
This clearly shows you get more force by choosing peak power in a low
gear over peak torque in a higher one.


That's a no-brainer, anyway. Just as you can express engine power in
terms of engine speed (times) engine torque (divided by) a suitable
constant, you can also express propulsive power as road speed (times)
thrust at the contact patch (divided by) a different constant - but
they
should equate to the same thing apart from transmission losses. So
when
the engine is developing its peak power, you'll get peak thrust at the
wheels.

Are you at it too? ;-)

Peak torque at the wheels happens when the engine is at peak torque -
not
peak BHP, unless the two coincide. Regardless of which gear you choose.


See my previous post. At any given road speed the max available thrust
at the wheels occurs when the engine is developing its max *power* not
its max *torque*. You choose the gearing to suit.
If you chose the correct gearing would the car achieve maximum seed at
maximum power output? In which instant the acceleration would be zero.

Peak power is always the place of maximum speed and maximum
acceleration, given suitable choices of gears



Not convinced. Peak power is certainly the place of max speed, I would
have said that peak torque is the place of max acceleration.

On 30/03/2016 18:39, Dave Plowman (News) wrote:


We're not talking 0-60 times here. Just the best rate of change of speed.
No vehicle with an IC engine gives a linear rate of increase in speed from
0 to top speed. It will obviously produce the best acceleration in the
lowest gear, slightly less in the next one up, and so on. But that is a
red herring as regards when the engine produces the best acceleration in
any one gear.


OK, can we agree on this?

In a given gear, the maximum rate of change of road speed will be
achieved at the engine's maximum torque speed. The road speed at which
that occurs will be determined by the engine speed and the gearing.

At a given road speed, the maximum rate of change of road speed will be
achieved at the engine's maximum power point. The necessary gear ratio
to achieve this will be determined by the chosen road speed and the
engine's maximum power speed.

Yes or no please - no equivocation!
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 30/03/2016 18:39, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
Regardless of the gear chosen, the peak acceleration *in that gear*
will occur when the engine is developing peak torque.

Are we still doing this?

I'd long since given up. But someone decided to revive it.


What you've said there is true, however it is
not the way to accelerate the car the fastest.

We're not talking 0-60 times here. Just the best rate of change of speed.

Ok. Which is achieved with the gear chosen so the engine at its maximum
power, not maximum torque.

No vehicle with an IC engine gives a linear rate of increase in speed from
0 to top speed. It will obviously produce the best acceleration in the
lowest gear, slightly less in the next one up, and so on. But that is a
red herring as regards when the engine produces the best acceleration in
any one gear.

I think people aren't concerned about when the engine produces the best
acceleration in any one gear, they're concerned about what is necessary
to accelerate the car the fastest, which means choosing gears which will
put the engine closest to maximum power, not maximum torque.

In article ,
newshound wrote:
On 3/30/2016 11:53 AM, The Natural Philosopher wrote:
On 30/03/16 00:37, Dave Plowman (News) wrote:

Peak torque at the wheels happens when the engine is at peak torque -
not peak BHP, unless the two coincide. Regardless of which gear you
choose.

No, it doesn't, because we have a car at speed and a gear box.

No wonder you vote Labia.

Peak torque at the wheels is when the gear ratio is lowest.

If you ignore car speed.

Which is 'as true' as your original fatuous statement


I think you are being deliberately obtuse. It's obvious to me that Dave
means that, *in each gear*, peak torque at the wheels occurs at peak
engine torque.

Don't think Rees-Turnip is being obtuse. He genuinely doesn't understand
basic mechanics.

--
*Born free - taxed to death *

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

In article ,
The Natural Philosopher wrote:
Peak power is always the place of maximum speed and maximum
acceleration, given suitable choices of gears

At least now you've come out with a definitive statement. No more crap
about gears. Definitive, but wrong. No surprise there.

--
*A conclusion is the place where you got tired of thinking *

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

In article ,
Roger Mills wrote:
On 30/03/2016 18:39, Dave Plowman (News) wrote:


We're not talking 0-60 times here. Just the best rate of change of
speed. No vehicle with an IC engine gives a linear rate of increase in
speed from 0 to top speed. It will obviously produce the best
acceleration in the lowest gear, slightly less in the next one up, and
so on. But that is a red herring as regards when the engine produces
the best acceleration in any one gear.


OK, can we agree on this?

In a given gear, the maximum rate of change of road speed will be
achieved at the engine's maximum torque speed. The road speed at which
that occurs will be determined by the engine speed and the gearing.

Yes.

At a given road speed, the maximum rate of change of road speed will be
achieved at the engine's maximum power point. The necessary gear ratio
to achieve this will be determined by the chosen road speed and the
engine's maximum power speed.

Yes. Assuming you have a gear which allows that road speed at maximum BHP.
That would by nature be a lower gear than one which place the engine at
peak torque at that road speed. And a lower gear multiples the torque.

Yes or no please - no equivocation!

Doesn't need any equivocation. Of course a lower gear multiplies the
engine's torque.

--
*Acupuncture is a jab well done*

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

In article ,
Clive George wrote:
We're not talking 0-60 times here. Just the best rate of change of
speed.

Ok. Which is achieved with the gear chosen so the engine at its maximum
power, not maximum torque.

You should join Turnip in some basic mechanical theory lessons.

--
*Heart attacks... God's revenge for eating his animal friends

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

On 31/03/2016 00:43, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
We're not talking 0-60 times here. Just the best rate of change of
speed.

Ok. Which is achieved with the gear chosen so the engine at its maximum
power, not maximum torque.

You should join Turnip in some basic mechanical theory lessons.

The weird thing is you've just agreed with my statement in your previous
post.

At a given road speed, the maximum rate of change of road speed will
be achieved at the engine's maximum power point. The necessary gear
ratio to achieve this will be determined by the chosen road speed
and the engine's maximum power speed.

is a longer way of saying what I've just said, and you replied saying "Yes".

Why agree with one yet disagree with the other?

In article ,
Clive George wrote:
On 31/03/2016 00:43, Dave Plowman (News) wrote:
In article , Clive
George wrote:
We're not talking 0-60 times here. Just the best rate of change of
speed.

Ok. Which is achieved with the gear chosen so the engine at its
maximum power, not maximum torque.

You should join Turnip in some basic mechanical theory lessons.

The weird thing is you've just agreed with my statement in your previous
post.

At a given road speed, the maximum rate of change of road speed will
be achieved at the engine's maximum power point. The necessary gear
ratio to achieve this will be determined by the chosen road speed
and the engine's maximum power speed.

is a longer way of saying what I've just said, and you replied saying
"Yes".

Why agree with one yet disagree with the other?

Sigh. If you measure the time taken for say 5 mph increments in speed in
any one gear, the shortest time will be at peak torque. Not peak BHP.

You decided to choose a road speed where the engine was at peak BHP in
that gear. The only way to get the same road speed at peak torque would be
by using a higher gear, since peak torque is always at lower RPM than peak
BHP.

--
*There's two theories to arguing with a woman. Neither one works *

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

On 31/03/2016 01:22, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
On 31/03/2016 00:43, Dave Plowman (News) wrote:
In article , Clive
George wrote:
We're not talking 0-60 times here. Just the best rate of change of
speed.

Ok. Which is achieved with the gear chosen so the engine at its
maximum power, not maximum torque.

You should join Turnip in some basic mechanical theory lessons.

The weird thing is you've just agreed with my statement in your previous
post.

At a given road speed, the maximum rate of change of road speed will
be achieved at the engine's maximum power point. The necessary gear
ratio to achieve this will be determined by the chosen road speed
and the engine's maximum power speed.

is a longer way of saying what I've just said, and you replied saying
"Yes".

Why agree with one yet disagree with the other?

Sigh. If you measure the time taken for say 5 mph increments in speed in
any one gear, the shortest time will be at peak torque. Not peak BHP.

You decided to choose a road speed where the engine was at peak BHP in
that gear. The only way to get the same road speed at peak torque would be
by using a higher gear, since peak torque is always at lower RPM than peak
BHP.

That doesn't explain why you disagree with what I said yet not with what
Roger said. None of what you've said just there disagrees with what I
said - best rate of change of speed is achieved with the gear chosen so
the engine at its maximum power, not maximum torque.

Or is this entire argument about you saying that the fastest instant
acceleration at all the road speeds between 0 and maximum speed will be
at the road speed where the engine is at peak torque in 1st gear? I
won't disagree with that, but don't think it's terribly useful, because
generally people are concerned with the fastest way of getting between
two road speeds (eg 20-60). And for that, the fastest way is to choose
the gear such that the engine is at or closest to maximum power, not
maximum torque. Ie change up late, not early.

On 30/03/16 23:01, newshound wrote:
On 3/30/2016 8:03 PM, The Natural Philosopher wrote:
On 30/03/16 19:53, bert wrote:
In article , Roger Mills
writes
On 30/03/2016 00:37, Dave Plowman (News) wrote:
In ,
Roger wrote:
This clearly shows you get more force by choosing peak power in a
low
gear over peak torque in a higher one.


That's a no-brainer, anyway. Just as you can express engine power in
terms of engine speed (times) engine torque (divided by) a suitable
constant, you can also express propulsive power as road speed (times)
thrust at the contact patch (divided by) a different constant - but
they
should equate to the same thing apart from transmission losses. So
when
the engine is developing its peak power, you'll get peak thrust at
the
wheels.

Are you at it too? ;-)

Peak torque at the wheels happens when the engine is at peak torque -
not
peak BHP, unless the two coincide. Regardless of which gear you
choose.


See my previous post. At any given road speed the max available thrust
at the wheels occurs when the engine is developing its max *power* not
its max *torque*. You choose the gearing to suit.
If you chose the correct gearing would the car achieve maximum seed at
maximum power output? In which instant the acceleration would be zero.

Peak power is always the place of maximum speed and maximum
acceleration, given suitable choices of gears



Not convinced. Peak power is certainly the place of max speed, I would
have said that peak torque is the place of max acceleration.

Well you are simply WRONG.

Consider: at a given speed you want to maximise thrust. Thrust is
linearly related to torque, so what you want is to maximise the product
of torque and the speed, which happens to be the dimension of POWER.


In order to get the best acceleration you set the engine at peak POWER
and use a particular gear ratio to match its RPM to the desired road speed.

Knowing when to stop thinking in terms of force and or torque, and start
thinking in terms of power and energy, is actually a key thing you learn
as an engineer.

Acceleration is adding kinetic energy, to get best acceleration you need
to deploy the best deployment of energy with time, that's power.

The mere mechanical detail of whether that energy is being deployed at a
wholly inappropriate crankshaft speed is why you employ mechanical
engineers to design gearboxes.



--
"In our post-modern world, climate science is not powerful because it is
true: it is true because it is powerful."

Lucas Bergkamp

On 30/03/16 23:16, Roger Mills wrote:
On 30/03/2016 18:39, Dave Plowman (News) wrote:


We're not talking 0-60 times here. Just the best rate of change of speed.
No vehicle with an IC engine gives a linear rate of increase in speed
from
0 to top speed. It will obviously produce the best acceleration in the
lowest gear, slightly less in the next one up, and so on. But that is a
red herring as regards when the engine produces the best acceleration in
any one gear.


OK, can we agree on this?

In a given gear, the maximum rate of change of road speed will be
achieved at the engine's maximum torque speed. The road speed at which
that occurs will be determined by the engine speed and the gearing.

At a given road speed, the maximum rate of change of road speed will be
achieved at the engine's maximum power point. The necessary gear ratio
to achieve this will be determined by the chosen road speed and the
engine's maximum power speed.

Yes or no please - no equivocation!

Yes.


--
You can get much farther with a kind word and a gun than you can with a
kind word alone.

Al Capone

On 30/03/16 23:46, Clive George wrote:
On 30/03/2016 18:39, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
Regardless of the gear chosen, the peak acceleration *in that gear*
will occur when the engine is developing peak torque.

Are we still doing this?

I'd long since given up. But someone decided to revive it.


What you've said there is true, however it is
not the way to accelerate the car the fastest.

We're not talking 0-60 times here. Just the best rate of change of speed.

Ok. Which is achieved with the gear chosen so the engine at its maximum
power, not maximum torque.

No vehicle with an IC engine gives a linear rate of increase in speed
from
0 to top speed. It will obviously produce the best acceleration in the
lowest gear, slightly less in the next one up, and so on. But that is a
red herring as regards when the engine produces the best acceleration in
any one gear.

I think people aren't concerned about when the engine produces the best
acceleration in any one gear, they're concerned about what is necessary
to accelerate the car the fastest, which means choosing gears which will
put the engine closest to maximum power, not maximum torque.

Well yes, if they have a need for peak acceleration.


--
You can get much farther with a kind word and a gun than you can with a
kind word alone.

Al Capone

On 31/03/16 00:54, Clive George wrote:
On 31/03/2016 00:43, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
We're not talking 0-60 times here. Just the best rate of change of
speed.

Ok. Which is achieved with the gear chosen so the engine at its maximum
power, not maximum torque.

You should join Turnip in some basic mechanical theory lessons.

The weird thing is you've just agreed with my statement in your previous
post.

At a given road speed, the maximum rate of change of road speed will
be achieved at the engine's maximum power point. The necessary gear
ratio to achieve this will be determined by the chosen road speed
and the engine's maximum power speed.

is a longer way of saying what I've just said, and you replied saying
"Yes".

Why agree with one yet disagree with the other?

He's a Lefty****.

Its called 'Doublethink' Read your George Orwell, Its all about winning
the (political) argument by holding two completely contradictory notions
in the head simultaneously. Its a form of mental illness that is very
common, and all its victims become Lefty****s.

"The power of holding two contradictory beliefs in one's mind
simultaneously, and accepting both of them... To tell deliberate lies
while genuinely believing in them, to forget any fact that has become
inconvenient, and then, when it becomes necessary again, to draw it back
from oblivion for just as long as it is needed, to deny the existence of
objective reality and all the while to take account of the reality which
one denies €“ all this is indispensably necessary. Even in using the word
doublethink it is necessary to exercise doublethink. For by using the
word one admits that one is tampering with reality; by a fresh act of
doublethink one erases this knowledge; and so on indefinitely, with the
lie always one leap ahead of the truth."


--
You can get much farther with a kind word and a gun than you can with a
kind word alone.

Al Capone

On Thu, 31 Mar 2016 11:15:39 +0100, The Natural Philosopher
wrote:

Consider: at a given speed you want to maximise thrust. Thrust is
linearly related to torque, so what you want is to maximise the product
of torque and the speed, which happens to be the dimension of POWER.

Eh?

Consider: at a given speed you want to maximise thrust.

Ok...

Thrust is linearly related to torque,

ok...

so what you want is to maximise the product
of torque and the speed, which happens to be the dimension of POWER.

Why don't you want to maximize the torque --hence the thrust-- anymore, like you
did above?


Thomas Prufer

On 31/03/16 11:47, Thomas Prufer wrote:
On Thu, 31 Mar 2016 11:15:39 +0100, The Natural Philosopher
wrote:

Consider: at a given speed you want to maximise thrust. Thrust is
linearly related to torque, so what you want is to maximise the product
of torque and the speed, which happens to be the dimension of POWER.

Eh?

Consider: at a given speed you want to maximise thrust.

Ok...

Thrust is linearly related to torque,

ok...

so what you want is to maximise the product
of torque and the speed, which happens to be the dimension of POWER.

Why don't you want to maximize the torque --hence the thrust-- anymore, like you
did above?


Because torque does not stay constant with SPEED.

So to get the best torque at any given speed, you need the most power
out of the engine.

If that's too hard, think of energy and power and the relationship of
rate of change of kinetic energy to them

I.e to move from say 50 mph to 70 mph requires an *energy* input of 1/2
mass x (70^2-50^2) (excluding drag)

The faster that energy goes in, the faster you get that job done, and
the rate of energy is POWER.


Consider a water wheel which gives as much torque as a formula one
engine, but rotates once every 10 seconds. Which do you think would
accelerate a block of whatever the fastest?

You want torque? How about a worm drive. Given a couple of worm drives I
can by hand generate more torque than a car engine.

Does that mean I can out accelerate the car on a bike?

At anything faster than 1/10 mph?

You are not alone in the confusion. I spent years patiently explaining
that 'static thrust' on a model aeroplane propellor is only useful if
you want it to emulate a helicopter, because static thrust drops away at
speed.

Power delivery at the speed you want is what you want.





Thomas Prufer



--
Those who want slavery should have the grace to name it by its proper
name. They must face the full meaning of that which they are advocating
or condoning; the full, exact, specific meaning of collectivism, of its
logical implications, of the principles upon which it is based, and of
the ultimate consequences to which these principles will lead. They must
face it, then decide whether this is what they want or not.

Ayn Rand.

On 30/03/2016 23:46, Clive George wrote:


I think people aren't concerned about when the engine produces the best
acceleration in any one gear, they're concerned about what is necessary
to accelerate the car the fastest, which means choosing gears which will
put the engine closest to maximum power, not maximum torque.


Indeed. If you want to accelerate the car as fast as possible, you need
to maximise the power available at the wheels. This invariably means
taking the engine up to at least its maximum power speed before changing
up to the next gear. I say "at least" because quite often - unless you
have lots of closely spaced gears - you still get more acceleration in
the gear you're in by keeping going beyond max power speed until you run
our of revs than by changing to the next gear which drops you a long way
back down the power curve.

To see this properly, you need - using the engine torque curve and the
gearing - to plot thrust vs road speed in each of the gears.

In each gear the thrust drops off when you're above the max torque point
- but it's invariably higher than it would be if you were to change up
to the next gear.

[I mis-spent a lot of my youth doing this sort of thing in the motor
industry many decades ago!]
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

In article ,
Clive George wrote:
On 31/03/2016 01:22, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
On 31/03/2016 00:43, Dave Plowman (News) wrote:
In article , Clive
George wrote:
We're not talking 0-60 times here. Just the best rate of change of
speed.

Ok. Which is achieved with the gear chosen so the engine at its
maximum power, not maximum torque.

You should join Turnip in some basic mechanical theory lessons.

The weird thing is you've just agreed with my statement in your
previous post.

At a given road speed, the maximum rate of change of road speed
will be achieved at the engine's maximum power point. The
necessary gear ratio to achieve this will be determined by the
chosen road speed and the engine's maximum power speed.

is a longer way of saying what I've just said, and you replied saying
"Yes".

Why agree with one yet disagree with the other?

Sigh. If you measure the time taken for say 5 mph increments in speed
in any one gear, the shortest time will be at peak torque. Not peak
BHP.

You decided to choose a road speed where the engine was at peak BHP in
that gear. The only way to get the same road speed at peak torque
would be by using a higher gear, since peak torque is always at lower
RPM than peak BHP.

That doesn't explain why you disagree with what I said yet not with what
Roger said. None of what you've said just there disagrees with what I
said - best rate of change of speed is achieved with the gear chosen so
the engine at its maximum power, not maximum torque.

Then you haven't understood what I've written. Many many times.

Or is this entire argument about you saying that the fastest instant
acceleration at all the road speeds between 0 and maximum speed will be
at the road speed where the engine is at peak torque in 1st gear?

Can I not get through to anyone that the gear used is irrelevant -
assuming it allows the vehicle to reach maximum BHP in that gear?

I
won't disagree with that, but don't think it's terribly useful, because
generally people are concerned with the fastest way of getting between
two road speeds (eg 20-60). And for that, the fastest way is to choose
the gear such that the engine is at or closest to maximum power, not
maximum torque. Ie change up late, not early.

The discussion was about where on the *engine's* output maximum
acceleration occurs. Not about achieving the best 0-60 mph or anything
else.

--
*A bartender is just a pharmacist with a limited inventory.

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

In article ,
The Natural Philosopher wrote:
Peak power is always the place of maximum speed and maximum
acceleration, given suitable choices of gears



Not convinced. Peak power is certainly the place of max speed, I would
have said that peak torque is the place of max acceleration.

Well you are simply WRONG.

No, You're wrong. For one who claims to have a degree of engineering
knowledge, it's unforgivable. There is no opinion involved. Just facts.

--
*I wish the buck stopped here. I could use a few.

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

In article ,
The Natural Philosopher wrote:
Why don't you want to maximize the torque --hence the thrust--
anymore, like you did above?


Because torque does not stay constant with SPEED.


But BHP does? You're excelling yourself with this one...

--
*Kill one man and you're a murderer, kill a million youand 're a conqueror.

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

In article ,
Roger Mills wrote:
Indeed. If you want to accelerate the car as fast as possible, you need
to maximise the power available at the wheels. This invariably means
taking the engine up to at least its maximum power speed before changing
up to the next gear. I say "at least" because quite often - unless you
have lots of closely spaced gears - you still get more acceleration in
the gear you're in by keeping going beyond max power speed until you run
our of revs than by changing to the next gear which drops you a long way
back down the power curve.

And idea set of gearbox ratios would allow you to change up round about
peak BHP and the next higher gear would plonk you at near enough maximum
torque...

--
*Dancing is a perpendicular expression of a horizontal desire *

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

In article ,
Thomas Prufer wrote:
On Thu, 31 Mar 2016 11:15:39 +0100, The Natural Philosopher
wrote:

Consider: at a given speed you want to maximise thrust. Thrust is
linearly related to torque, so what you want is to maximise the product
of torque and the speed, which happens to be the dimension of POWER.

Eh?

Consider: at a given speed you want to maximise thrust.

Ok...

Thrust is linearly related to torque,

ok...

so what you want is to maximise the product
of torque and the speed, which happens to be the dimension of POWER.

Why don't you want to maximize the torque --hence the thrust-- anymore,
like you did above?

I'd guess you're wasting your breath. ;-)

--
*Few women admit their age; fewer men act it.

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

On 31/03/2016 14:25, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
On 31/03/2016 01:22, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
On 31/03/2016 00:43, Dave Plowman (News) wrote:
In article , Clive
George wrote:
We're not talking 0-60 times here. Just the best rate of change of
speed.

Ok. Which is achieved with the gear chosen so the engine at its
maximum power, not maximum torque.

You should join Turnip in some basic mechanical theory lessons.

The weird thing is you've just agreed with my statement in your
previous post.

At a given road speed, the maximum rate of change of road speed
will be achieved at the engine's maximum power point. The
necessary gear ratio to achieve this will be determined by the
chosen road speed and the engine's maximum power speed.

is a longer way of saying what I've just said, and you replied saying
"Yes".

Why agree with one yet disagree with the other?

Sigh. If you measure the time taken for say 5 mph increments in speed
in any one gear, the shortest time will be at peak torque. Not peak
BHP.

You decided to choose a road speed where the engine was at peak BHP in
that gear. The only way to get the same road speed at peak torque
would be by using a higher gear, since peak torque is always at lower
RPM than peak BHP.

That doesn't explain why you disagree with what I said yet not with what
Roger said. None of what you've said just there disagrees with what I
said - best rate of change of speed is achieved with the gear chosen so
the engine at its maximum power, not maximum torque.

Then you haven't understood what I've written. Many many times.

I'm not alone in this.

Or is this entire argument about you saying that the fastest instant
acceleration at all the road speeds between 0 and maximum speed will be
at the road speed where the engine is at peak torque in 1st gear?

Can I not get through to anyone that the gear used is irrelevant -
assuming it allows the vehicle to reach maximum BHP in that gear?

It would help if you weren't assuming everybody in the discussion is an
idiot. Pretty much none of the people are, not even you.

I
won't disagree with that, but don't think it's terribly useful, because
generally people are concerned with the fastest way of getting between
two road speeds (eg 20-60). And for that, the fastest way is to choose
the gear such that the engine is at or closest to maximum power, not
maximum torque. Ie change up late, not early.

The discussion was about where on the *engine's* output maximum
acceleration occurs. Not about achieving the best 0-60 mph or anything
else.

To most of the people in this discussion, the discussion is about how to
achieve maximum acceleration during normal (or rather 'spirited')
driving, at whatever start and end speed the situation requires - and
the answer to that is to choose the right gear to get as near to maximum
power as you can, not maximum engine torque.

To you it seems to be only about at which point when you're racing from
0 to whatever are you accelerating fastest - which I agree is max torque
in first gear.

Is that an adequate summary of the two positions?

In article , Roger Mills
writes
On 30/03/2016 18:39, Dave Plowman (News) wrote:


We're not talking 0-60 times here. Just the best rate of change of speed.
No vehicle with an IC engine gives a linear rate of increase in speed from
0 to top speed. It will obviously produce the best acceleration in the
lowest gear, slightly less in the next one up, and so on. But that is a
red herring as regards when the engine produces the best acceleration in
any one gear.


OK, can we agree on this?

In a given gear, the maximum rate of change of road speed will be
achieved at the engine's maximum torque speed. The road speed at which
that occurs will be determined by the engine speed and the gearing.

At a given road speed, the maximum rate of change of road speed will be
achieved at the engine's maximum power point. The necessary gear ratio
to achieve this will be determined by the chosen road speed and the
engine's maximum power speed.

Yes or no please - no equivocation!
I did a little test with my Defender which has max torque at about 2000
rpm and max power at about 3500 rpm.
Going up the gears and accelerating as fast as I could I never got
anywhere near max power in any gear before I could feel the acceleration
dropping off.
--
bert

On 31/03/2016 15:39, bert wrote:

I did a little test with my Defender which has max torque at about 2000
rpm and max power at about 3500 rpm.
Going up the gears and accelerating as fast as I could I never got
anywhere near max power in any gear before I could feel the acceleration
dropping off.

But did changing to a higher gear result in faster acceleration?

On 3/31/2016 3:33 PM, Clive George wrote:
On 31/03/2016 14:25, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
On 31/03/2016 01:22, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
On 31/03/2016 00:43, Dave Plowman (News) wrote:



I
won't disagree with that, but don't think it's terribly useful, because
generally people are concerned with the fastest way of getting between
two road speeds (eg 20-60). And for that, the fastest way is to choose
the gear such that the engine is at or closest to maximum power, not
maximum torque. Ie change up late, not early.

The discussion was about where on the *engine's* output maximum
acceleration occurs. Not about achieving the best 0-60 mph or anything
else.

To most of the people in this discussion, the discussion is about how to
achieve maximum acceleration during normal (or rather 'spirited')
driving, at whatever start and end speed the situation requires - and
the answer to that is to choose the right gear to get as near to maximum
power as you can, not maximum engine torque.

To you it seems to be only about at which point when you're racing from
0 to whatever are you accelerating fastest - which I agree is max torque
in first gear.

Is that an adequate summary of the two positions?

Peak power revs is normally a point where your acceleration is dropping
right off. For the best 0-60, standing quarter, or whatever you would
normally change up before you reach peak power (as long as you have
another gear available). You change up somewhere beyond peak torque so
that in the next gear you are going back through the torque peak again.
Exactly where you change is also partly determined by how much time you
lose in the gearchange; you might decide to start in second if you have
a low first ratio, or to reduce wheelspin. If you are drag racing in a
Landy you probably would not use low ratios!

Power, revs, and torque are inextricably linked but I think that most
mechanical engineers who go back to the basics think of it being the
torque which provides the mechanical force at the wheels (and hence the
acceleration).

On 31/03/2016 16:15, newshound wrote:

Peak power revs is normally a point where your acceleration is dropping
right off. For the best 0-60, standing quarter, or whatever you would
normally change up before you reach peak power (as long as you have
another gear available).

I don't think that is true. Peak power will give you the fastest change
in speed - if you have a choice of gear X at peak power and a higher
gear Y at peak torque for that road speed, you will accelerate fastest
by being in gear X.

Power, revs, and torque are inextricably linked but I think that most
mechanical engineers who go back to the basics think of it being the
torque which provides the mechanical force at the wheels (and hence the
acceleration).

I don't find any of the relationships confusing.

Power = engine torque * RPM

Acceleration = wheel torque * constant

wheel torque = engine torque / gear ratio

(where higher gear = higher gear ratio)

That's all there is. The available torque at various RPM is of course
unknown, depending on the engine itself.