In article ,
Clive George wrote:
Then they need to read the original thread that started this.

I did, and what I said is correct. You may think the discussion is still
about one thing, but for most people it's moved on - thread drift is a
perfectly normal thing. You're talking about one thing, everybody else
is talking about something else. Both sides are correct about what
they're talking about, which is why this argument has gone on quite so
long - it's not a physics problem, it's a communication problem.

Not so. Plenty are still saying the best acceleration occurs at peak BHP.
It doesn't and never has.

That is what started the original discussion. With idiots throwing in
gearboxes, etc.

--
*Being healthy is merely the slowest possible rate at which one can die.

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

On 01/04/2016 14:58, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
Then they need to read the original thread that started this.

I did, and what I said is correct. You may think the discussion is still
about one thing, but for most people it's moved on - thread drift is a
perfectly normal thing. You're talking about one thing, everybody else
is talking about something else. Both sides are correct about what
they're talking about, which is why this argument has gone on quite so
long - it's not a physics problem, it's a communication problem.

Not so. Plenty are still saying the best acceleration occurs at peak BHP.
It doesn't and never has.

If you define best acceleration as "how to get from speed A to a higher
speed B as fast as possible", which is an entirely reasonable definition
IMO, it does.

That is what started the original discussion. With idiots throwing in
gearboxes, etc.

I've pointed out that nobody in this discussion is being an idiot WRT
the technical bits. A big part of the problem of this discussion is
people dismissing what others have said out of hand, when actually what
has been said is correct, only applying to a different thing the first
person thinks it does.

When you're talking about the best acceleration in the way I and various
others are talking about it, gear boxes are very relevant indeed.

On 01/04/2016 15:12, Clive George wrote:


When you're talking about the best acceleration in the way I and various
others are talking about it, gear boxes are very relevant indeed.


Indeed they are. The rate of acceleration is dependent on gearbox
*output* torque - not on engine torque. At a given road speed, output
torque will *always* be higher when the engine is at max power in a
lower gear than when it's at max torque in a higher gear.

Forget acceleration for a moment, and think about steady state thrust
when (say) climbing a steep hill. If you want to make the most progress
do you slog it out in a high gear with the engine at max *torque*, or do
you change down to let the engine develop more *power*?

I know what I do!
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 01/04/2016 12:23, bert wrote:
In article , Roger Mills
writes

Next time, take an accelerometer with you, and tell us what happens in
the higher gear.


That would be more scientific but I don't feel sufficient desire to
prove my point to justify the investment.

If you've got a smart-phone you'll already have one. There are lots of
free apps for displaying the output in graphical form. [I don't know how
useful they are for this sort of thing - but maybe worth a try.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 3/31/2016 5:01 PM, Dave Plowman (News) wrote:
In article ,
newshound wrote:
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've been trying to get that point across for some weeks now. But it is
obviously beyond many. ;-)

I'm giving up and killing the thread now. At least there are a few of us
who understand.

:-)

On 01/04/2016 12:29, bert wrote:
In article , Roger Mills
writes


Yes, it would. But you'd still have less thrust at the wheels because
of the higher gearing.


Where does one measure thrust at a wheel? Presumably at the hub, or do
you mean torque?

No, I mean thrust. The torque which the drive shaft imparts to the wheel
is converted into thrust at the contact patch. That's what accelerates
the vehicle - and why it doesn't go quite so well when driving on ice.

You don't normally measure it directly[1] - you calculate it from the
known parameters - torque, wheel radius, etc.

[1] Motor manufacturers do, though - by running the vehicle on a rolling
road and restraining it via a force measuring system attached to the tow
hitch. That's what I did in my Rover Research days, anyway.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

In article ,
Clive George wrote:
Not so. Plenty are still saying the best acceleration occurs at peak
BHP. It doesn't and never has.

If you define best acceleration as "how to get from speed A to a higher
speed B as fast as possible", which is an entirely reasonable definition
IMO, it does.

No it doesn't. Acceleration is never uniform from rest to top speed. It
will obviously be better in a low gear than high, and also within any one
gear range. So it then comes down to when it is best in any single gear.
Which started off this discussion.

--
*Horn broken. - Watch for finger.

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

In article ,
Roger Mills wrote:
Indeed they are. The rate of acceleration is dependent on gearbox
*output* torque - not on engine torque.

And the two are directly related.

Why is it impossible to see this? A gearbox simply multiplies the torque
of the engine.

--
*Eschew obfuscation *

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

In article ,
Roger Mills wrote:
[1] Motor manufacturers do, though - by running the vehicle on a rolling
road and restraining it via a force measuring system attached to the tow
hitch. That's what I did in my Rover Research days, anyway.

And that rolling road - same as an engine test bed - measures torque. It
then calculates the BHP from that. And with most rolling roads adds on a
fiddle factor to give the car owner a nice rosy glow. ;-)

--
*I'd kill for a Nobel Peace Prize *

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

On 01/04/2016 17:14, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
Not so. Plenty are still saying the best acceleration occurs at peak
BHP. It doesn't and never has.

If you define best acceleration as "how to get from speed A to a higher
speed B as fast as possible", which is an entirely reasonable definition
IMO, it does.

No it doesn't. Acceleration is never uniform from rest to top speed. It
will obviously be better in a low gear than high, and also within any one
gear range. So it then comes down to when it is best in any single gear.
Which started off this discussion.

Now that's where I'm going to disagree with you, and I suspect several
others are too.

When people say "car X accelerates faster than car Y", they'll be
looking at the acceleration to get from one speed to another, eg 0-60,
50-70, etc, not the single point of maximum acceleration in first gear.

But that's a semantic point, not a physics one.

On 01/04/2016 17:14, Dave Plowman (News) wrote:
In ,
Clive wrote:
Not so. Plenty are still saying the best acceleration occurs at peak
BHP. It doesn't and never has.

If you define best acceleration as "how to get from speed A to a higher
speed B as fast as possible", which is an entirely reasonable definition
IMO, it does.

No it doesn't. Acceleration is never uniform from rest to top speed. It
will obviously be better in a low gear than high, and also within any one
gear range. So it then comes down to when it is best in any single gear.
Which started off this discussion.


Did anyone say that acceleration *was* uniform across the speed range -
I certainly didn't?!

In general, acceleration is highest at a low road speed and decreases
by some function with increasing speed.

Power at the road is thrust x road speed. If you could maintain a
constant power at the road, thrust would reduce as the inverse of speed.
You try to do that by selecting the most appropriate gear. A
continuously variable transmission would be ideal if one could be made
to work reliably.

But the fact remains that the more power you can get to the road, the
greater the acceleration. And you get that by operating the engine as
near to its maximum power point as you can. Can you not *see* that?

[I don't believe that you're stupid - I rather suspect that you realise
that you've backed yourself into a corner and find it difficult to
retreat with any dignity].
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

I spent 23 years in an Engine Laboratory, testing engines for Performance, Economy, Durability and Emissions. There's been quite a few misconceptions been aired in this thread; you guys need to sit down and look at some performance curves and make your own calcs.. Some of you are confusing Max Power with Max Throttle Opening; to maintain a given road speed at Max Power, the load on the car must equal the Torque at that engine speed; any reduction in load will cause the car to speed up.

On 01/04/2016 17:16, Dave Plowman (News) wrote:
In ,
Roger wrote:
Indeed they are. The rate of acceleration is dependent on gearbox
*output* torque - not on engine torque.

And the two are directly related.

Why is it impossible to see this? A gearbox simply multiplies the torque
of the engine.


The two *are* indeed directly related - but the actual relationship
depends on what gear is selected. At any given road speed you'll get
more output torque by using a lower gear and a higher engine speed.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 01/04/2016 00:29, Dave Plowman (News) wrote:
Which is were we came in. I was talking about accleration*in any one gear*

Nobody else has been.

Admit it, you're just trolling.

On 01/04/2016 17:19, Dave Plowman (News) wrote:
In ,
Roger wrote:
[1] Motor manufacturers do, though - by running the vehicle on a rolling
road and restraining it via a force measuring system attached to the tow
hitch. That's what I did in my Rover Research days, anyway.

And that rolling road - same as an engine test bed - measures torque. It
then calculates the BHP from that. And with most rolling roads adds on a
fiddle factor to give the car owner a nice rosy glow. ;-)


The setup I'm talking about had 5' diameter rollers and - in the
configuration which I described - measured thrust by means of an A-frame
fitted with strain gauges. The non-driven wheels were on air bearings so
as not to influence things.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

In article ,
Clive George wrote:

When people say "car X accelerates faster than car Y", they'll be
looking at the acceleration to get from one speed to another, eg 0-60,
50-70, etc, not the single point of maximum acceleration in first gear.

Decent car mags like Autocar tested 10mph increments in top gear. As a
measure of how soon you'd have to change gear on a hill, or to overtake.

--
*What do little birdies see when they get knocked unconscious? *

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

In article ,
Roger Mills wrote:
The two *are* indeed directly related - but the actual relationship
depends on what gear is selected. At any given road speed you'll get
more output torque by using a lower gear and a higher engine speed.

That depends on the torque curve and the gear ratios and the speed. It's
perfectly possible to have more torque at the wheels in the higher gear.
Not that common, but possible.

--
*I started out with nothing... and I still have most of it.

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

In article ,
Vir Campestris wrote:
On 01/04/2016 00:29, Dave Plowman (News) wrote:
Which is were we came in. I was talking about accleration*in any one gear*

Nobody else has been.

Admit it, you're just trolling.

Oddly, I was thinking that of you bringing back the subject.

From the very start of all this nonsense, I said that you'll get maximum
acceleration at peak torque in any one gear. Others said at peak BHP. Then
started taking about different gears.

I'll make this simple.

Choose a gear where the car can reach peak BHP. Say second gear.
In that gear only, log the time taken for each 5mph increment in speed at
full throttle.

The time taken for that 5 mph increase will be shortest at peak torque.
Not peak BHP.

--
*You are validating my inherent mistrust of strangers

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

On Fri, 01 Apr 2016 17:16:40 +0100, Dave Plowman (News) wrote:

In article ,
Roger Mills wrote:
Indeed they are. The rate of acceleration is dependent on gearbox
*output* torque - not on engine torque.

And the two are directly related.

Why is it impossible to see this? A gearbox simply multiplies the torque
of the engine.

I think we can all accept that as "A Given". However, for a given road
speed where the selected gearbox ratio matches the peak engine power
revs, you will gain a modest increase in torque applied to the driven
wheels compared to a ratio selected to allow the engine to run at peak
torque revs.

If we assume the theoretical case of a perfect stepless gearbox which
can automatically adjust the ratio to hold the engine to its peak torque
rpm as the road speed increases, you'll find that the resulting
acceleration will be less than one configured to hold the engine to its
peak power output rpm (it will operate at a larger reduction ratio in
this case which increases the torque applied to the road wheels compared
to the ratio range used to keep the engine operating at its maximum
torque rpm).

In the case of a manual gearbox, we approximate this mode of operation
by choosing max power rpm as the next change up point rather than the
lower peak torque rpm point.

--
Johnny B Good

On Sat, 02 Apr 2016 00:55:15 +0100, Dave Plowman (News) wrote:

In article ,
Vir Campestris wrote:
On 01/04/2016 00:29, Dave Plowman (News) wrote:
Which is were we came in. I was talking about acceleration*in any one
gear*

Nobody else has been.

Admit it, you're just trolling.

Oddly, I was thinking that of you bringing back the subject.

From the very start of all this nonsense, I said that you'll get maximum
acceleration at peak torque in any one gear. Others said at peak BHP.
Then started taking about different gears.

I'll make this simple.

Choose a gear where the car can reach peak BHP. Say second gear.
In that gear only, log the time taken for each 5mph increment in speed
at full throttle.

The time taken for that 5 mph increase will be shortest at peak torque.
Not peak BHP.

You can gain an even greater acceleration over that particular range of
road speeds (let's say 40 to 45 mph) by using a slightly higher gearing
(less taller) ratio that results in higher engine rpms which results in a
higher accelerating torque being applied to the driven wheels simply as a
direct result of the higher reduction ratio magnifying the torque
available at the gearbox output shaft.

Although the engine torque will be a little less than at peak torque
output revs, the larger reduction ratio will still provide a net gain in
torque at the driven wheels.

--
Johnny B Good

On 02/04/2016 01:56, Johnny B Good wrote:
On Fri, 01 Apr 2016 17:16:40 +0100, Dave Plowman (News) wrote:

In ,
Roger wrote:
Indeed they are. The rate of acceleration is dependent on gearbox
*output* torque - not on engine torque.

And the two are directly related.

Why is it impossible to see this? A gearbox simply multiplies the torque
of the engine.

I think we can all accept that as "A Given". However, for a given road
speed where the selected gearbox ratio matches the peak engine power
revs, you will gain a modest increase in torque applied to the driven
wheels compared to a ratio selected to allow the engine to run at peak
torque revs.

If we assume the theoretical case of a perfect stepless gearbox which
can automatically adjust the ratio to hold the engine to its peak torque
rpm as the road speed increases, you'll find that the resulting
acceleration will be less than one configured to hold the engine to its
peak power output rpm (it will operate at a larger reduction ratio in
this case which increases the torque applied to the road wheels compared
to the ratio range used to keep the engine operating at its maximum
torque rpm).


I couldn't have put it better myself!

In fact, I invited Mr Plowman to consider these two scenarios - with a
stepless transmission holding the engine either at its max torque point
or at its max power point - but he ruled it invalid because such
transmissions don't exist. My likely because it proved a point against
which he had no valid argument.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 02/04/16 08:40, Roger Mills wrote:
In fact, I invited Mr Plowman to consider these two scenarios - with a
stepless transmission holding the engine either at its max torque point
or at its max power point - but he ruled it invalid because such
transmissions don't exist. My likely because it proved a point against
which he had no valid argument.

Lefty****s always avoid losing arguments


--
To ban Christmas, simply give turkeys the vote.

In article ,
Johnny B Good wrote:
On Fri, 01 Apr 2016 17:16:40 +0100, Dave Plowman (News) wrote:

In article ,
Roger Mills wrote:
Indeed they are. The rate of acceleration is dependent on gearbox
*output* torque - not on engine torque.

And the two are directly related.

Why is it impossible to see this? A gearbox simply multiplies the
torque of the engine.

I think we can all accept that as "A Given". However, for a given road
speed where the selected gearbox ratio matches the peak engine power
revs, you will gain a modest increase in torque applied to the driven
wheels compared to a ratio selected to allow the engine to run at peak
torque revs.

Of course A gearbox simply multiplies the torque of the engine.
Regardless of the engine or road speed. But if it increases the torque at
peak BHP, it will also do the same at peak torque, so you'll have more
torque at the wheels at peak torque. Therefore better acceleration...


If we assume the theoretical case of a perfect stepless gearbox which
can automatically adjust the ratio to hold the engine to its peak torque
rpm as the road speed increases, you'll find that the resulting
acceleration will be less than one configured to hold the engine to its
peak power output rpm (it will operate at a larger reduction ratio in
this case which increases the torque applied to the road wheels compared
to the ratio range used to keep the engine operating at its maximum
torque rpm).

The type of gearbox makes no difference to the principle.

In the case of a manual gearbox, we approximate this mode of operation
by choosing max power rpm as the next change up point rather than the
lower peak torque rpm point.

A decent box will then plonk you at or near the peak torque point in the
next higher gear - to give you the best acceleration.

--
*Be more or less specific *

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

In article ,
Roger Mills wrote:
In fact, I invited Mr Plowman to consider these two scenarios - with a
stepless transmission holding the engine either at its max torque point
or at its max power point - but he ruled it invalid because such
transmissions don't exist.

Sigh. Only because the transmission type makes not a scrap of difference
to my original statement. If you did want to discuss different types of
transmissions I'd be happy to join in.

However, I did have access to a DAF van many years ago. On full belt it
went to approximately the peak torque point and stayed there. Not maximum
revs.

My likely because it proved a point against
which he had no valid argument.

Was simply trying to stick to the original point. Which despite all this,
many still disagree with.

--
*Sometimes I wake up grumpy; Other times I let him sleep.

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

In article ,
The Natural Philosopher wrote:
On 02/04/16 08:40, Roger Mills wrote:
In fact, I invited Mr Plowman to consider these two scenarios - with a
stepless transmission holding the engine either at its max torque point
or at its max power point - but he ruled it invalid because such
transmissions don't exist. My likely because it proved a point against
which he had no valid argument.

Lefty****s always avoid losing arguments

Nice one. Now explain how you know so little about basic mechanics?
Probably because the likes of you think it beneath them. You might have to
get your hands dirty.

--
*Beware - animal lover - brakes for pussy*

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

On 02/04/2016 11:20, Dave Plowman (News) wrote:


A decent box will then plonk you at or near the peak torque point in the
next higher gear - to give you the best acceleration.


IN THAT GEAR.

But almost certainly a LOWER acceleration than you experienced at the
same road speed immediately before changing up.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 02/04/16 13:11, Roger Mills wrote:
On 02/04/2016 11:20, Dave Plowman (News) wrote:


A decent box will then plonk you at or near the peak torque point in the
next higher gear - to give you the best acceleration.


IN THAT GEAR.

But almost certainly a LOWER acceleration than you experienced at the
same road speed immediately before changing up.


Even then what Plowperson said is plain wrong.

You want to arrange gear shifts symmetrically around peak *power*.


--
"I am inclined to tell the truth and dislike people who lie consistently.
This makes me unfit for the company of people of a Left persuasion, and
all women"

On 02/04/2016 11:26, Dave Plowman (News) wrote:
In ,
Roger wrote:
In fact, I invited Mr Plowman to consider these two scenarios - with a
stepless transmission holding the engine either at its max torque point
or at its max power point - but he ruled it invalid because such
transmissions don't exist.

Sigh. Only because the transmission type makes not a scrap of difference
to my original statement. If you did want to discuss different types of
transmissions I'd be happy to join in.


Maybe you'd better remind us what your original statement was, since it
got lost in the mists of time!

Seems to me that we are arguing over semantics and may even be in
agreement over the engineering principles (though I'm not 100%
convinced!). So let's try again.

Q1: How do you maximise the acceleration of a car in a given gear?

A1: By using full throttle and running the engine at its maximum torque
speed.

Q2: How do you maximise the acceleration of a car at a given speed?

A2: By using full throttle and by choosing a gear which enables the
engine to develop its maximum power (or as near to it as the choice of
gearing permits).

Unless I misunderstand you, you are saying that the answer to Q2 is A1.
If so, you are simply WRONG!
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

In article ,
Roger Mills wrote:
On 02/04/2016 11:20, Dave Plowman (News) wrote:


A decent box will then plonk you at or near the peak torque point in
the next higher gear - to give you the best acceleration.


IN THAT GEAR.

And you think I meant anything else?

But almost certainly a LOWER acceleration than you experienced at the
same road speed immediately before changing up.

Given the gearbox multiplies the torque from the engine, what else would
you expect?

Have we now got to the point where everyone agrees that *in any one gear*
the best acceleration is at peak torque, not peak BHP?

That is and was the crux of the matter. Before all the red herrings and
moving of goal posts started.

--
*Xerox and Wurlitzer will merge to market reproductive organs.

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

In article ,
Roger Mills wrote:
On 02/04/2016 11:26, Dave Plowman (News) wrote:
In ,
Roger wrote:
In fact, I invited Mr Plowman to consider these two scenarios - with
a stepless transmission holding the engine either at its max torque
point or at its max power point - but he ruled it invalid because
such transmissions don't exist.

Sigh. Only because the transmission type makes not a scrap of
difference to my original statement. If you did want to discuss
different types of transmissions I'd be happy to join in.


Maybe you'd better remind us what your original statement was, since it
got lost in the mists of time!

Can't be bothered. Many seem unable to read or understand a simple
statement.

Seems to me that we are arguing over semantics and may even be in
agreement over the engineering principles (though I'm not 100%
convinced!). So let's try again.

I'm not arguing over semantics.

Q1: How do you maximise the acceleration of a car in a given gear?

A1: By using full throttle and running the engine at its maximum torque
speed.

If you ran the car at maximum torque there'd be no acceleration, since
that occurs at specific revs.

Q2: How do you maximise the acceleration of a car at a given speed?

A2: By using full throttle and by choosing a gear which enables the
engine to develop its maximum power (or as near to it as the choice of
gearing permits).

And that's where you're wrong.

Unless I misunderstand you, you are saying that the answer to Q2 is A1.
If so, you are simply WRONG!

As I said before, some seem totally incapable of understanding a very
simple and basic condition.

--
*Parenthetical remarks (however relevant) are (usually) unnecessary *

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

On 02/04/2016 14:15, Dave Plowman (News) wrote:
In ,
Roger wrote:
On 02/04/2016 11:26, Dave Plowman (News) wrote:
In ,
Roger wrote:
In fact, I invited Mr Plowman to consider these two scenarios - with
a stepless transmission holding the engine either at its max torque
point or at its max power point - but he ruled it invalid because
such transmissions don't exist.

Sigh. Only because the transmission type makes not a scrap of
difference to my original statement. If you did want to discuss
different types of transmissions I'd be happy to join in.


Maybe you'd better remind us what your original statement was, since it
got lost in the mists of time!

Can't be bothered. Many seem unable to read or understand a simple
statement.

Seems to me that we are arguing over semantics and may even be in
agreement over the engineering principles (though I'm not 100%
convinced!). So let's try again.

I'm not arguing over semantics.

Q1: How do you maximise the acceleration of a car in a given gear?

A1: By using full throttle and running the engine at its maximum torque
speed.

If you ran the car at maximum torque there'd be no acceleration, since
that occurs at specific revs.

Of course there would. It would only be at its max value at the max
torque point itself - which may actually cover a range of speeds since
some engine torque curves are flatish rather than peaky at max torque.
We're talking about a dynamic rather than static situation anyway.
Acceleration is the RATE OF CHANGE of speed and is a continuously
variable function. If you're defining acceleration as a step change in
speed it's little wonder that you're living on a different cloud from
everyone else.

Maybe I need to change A1 for your benefit, thus:

A1: By using full throttle and allowing the car to accelerate over a
speed range which encompasses the max torque speed of the engine.
Maximum acceleration will occur as the engine passes through its max
torque point.

[In actual fact, it may not! As the car speed increases, the aerodynamic
drag increases as the square of the speed. The effect of this - which we
have so far ignored in this discussion - is that maximum acceleration
MAY occur slightly below the max torque speed because the increase in
drag may more than offset the increase in torque.]


Q2: How do you maximise the acceleration of a car at a given speed?

A2: By using full throttle and by choosing a gear which enables the
engine to develop its maximum power (or as near to it as the choice of
gearing permits).

And that's where you're wrong.

Unless I misunderstand you, you are saying that the answer to Q2 is A1.
If so, you are simply WRONG!

As I said before, some seem totally incapable of understanding a very
simple and basic condition.


I think we agree on THAT! What we DON'T agree on is who those people ARE!!!!
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 02/04/16 18:01, Roger Mills wrote:
On 02/04/2016 14:15, Dave Plowman (News) wrote:
In ,
Roger wrote:
On 02/04/2016 11:26, Dave Plowman (News) wrote:
In ,
Roger wrote:
In fact, I invited Mr Plowman to consider these two scenarios - with
a stepless transmission holding the engine either at its max torque
point or at its max power point - but he ruled it invalid because
such transmissions don't exist.

Sigh. Only because the transmission type makes not a scrap of
difference to my original statement. If you did want to discuss
different types of transmissions I'd be happy to join in.


Maybe you'd better remind us what your original statement was, since it
got lost in the mists of time!

Can't be bothered. Many seem unable to read or understand a simple
statement.

Seems to me that we are arguing over semantics and may even be in
agreement over the engineering principles (though I'm not 100%
convinced!). So let's try again.

I'm not arguing over semantics.

Q1: How do you maximise the acceleration of a car in a given gear?

A1: By using full throttle and running the engine at its maximum torque
speed.

If you ran the car at maximum torque there'd be no acceleration, since
that occurs at specific revs.

Of course there would. It would only be at its max value at the max
torque point itself - which may actually cover a range of speeds since
some engine torque curves are flatish rather than peaky at max torque.
We're talking about a dynamic rather than static situation anyway.
Acceleration is the RATE OF CHANGE of speed and is a continuously
variable function. If you're defining acceleration as a step change in
speed it's little wonder that you're living on a different cloud from
everyone else.

Maybe I need to change A1 for your benefit, thus:

A1: By using full throttle and allowing the car to accelerate over a
speed range which encompasses the max torque speed of the engine.
Maximum acceleration will occur as the engine passes through its max
torque point.

[In actual fact, it may not! As the car speed increases, the aerodynamic
drag increases as the square of the speed. The effect of this - which we
have so far ignored in this discussion - is that maximum acceleration
MAY occur slightly below the max torque speed because the increase in
drag may more than offset the increase in torque.]


Q2: How do you maximise the acceleration of a car at a given speed?

A2: By using full throttle and by choosing a gear which enables the
engine to develop its maximum power (or as near to it as the choice of
gearing permits).

And that's where you're wrong.

And that's where the staggerring incompetence of Plowperson emerges.



Unless I misunderstand you, you are saying that the answer to Q2 is A1.
If so, you are simply WRONG!

As I said before, some seem totally incapable of understanding a very
simple and basic condition.


I think we agree on THAT! What we DON'T agree on is who those people
ARE!!!!

You and Dave, basically.


--
"It is an established fact to 97% confidence limits that left wing
conspirators see right wing conspiracies everywhere"

In article , Roger Mills
writes
On 01/04/2016 12:23, bert wrote:
In article , Roger Mills
writes

Next time, take an accelerometer with you, and tell us what happens in
the higher gear.


That would be more scientific but I don't feel sufficient desire to
prove my point to justify the investment.

If you've got a smart-phone you'll already have one. There are lots of
free apps for displaying the output in graphical form. [I don't know
how useful they are for this sort of thing - but maybe worth a try.
Yes and No - Windows smart phone I'll have a look for an app.
--
bert

On 02/04/2016 18:11, The Natural Philosopher wrote:
On 02/04/16 18:01, Roger Mills wrote:
On 02/04/2016 14:15, Dave Plowman (News) wrote:


As I said before, some seem totally incapable of understanding a very
simple and basic condition.


I think we agree on THAT! What we DON'T agree on is who those people
ARE!!!!

You and Dave, basically.



Pray what simple and basic condition have *I* failed to understand?
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 02/04/16 22:53, Roger Mills wrote:
On 02/04/2016 18:11, The Natural Philosopher wrote:
On 02/04/16 18:01, Roger Mills wrote:
On 02/04/2016 14:15, Dave Plowman (News) wrote:


As I said before, some seem totally incapable of understanding a very
simple and basic condition.


I think we agree on THAT! What we DON'T agree on is who those people
ARE!!!!

You and Dave, basically.



Pray what simple and basic condition have *I* failed to understand?

Gearboxes. The relationship between power torque acceleration and speed.
Basic mechanical engineering.
Take your pick.



--
All political activity makes complete sense once the proposition that
all government is basically a self-legalising protection racket, is
fully understood.

On 02/04/2016 22:57, The Natural Philosopher wrote:
On 02/04/16 22:53, Roger Mills wrote:
On 02/04/2016 18:11, The Natural Philosopher wrote:
On 02/04/16 18:01, Roger Mills wrote:
On 02/04/2016 14:15, Dave Plowman (News) wrote:


As I said before, some seem totally incapable of understanding a very
simple and basic condition.


I think we agree on THAT! What we DON'T agree on is who those people
ARE!!!!

You and Dave, basically.



Pray what simple and basic condition have *I* failed to understand?

Gearboxes. The relationship between power torque acceleration and speed.
Basic mechanical engineering.
Take your pick.


Rubbish! I challenge to you quote anything I wrote which backs up your
statement.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 02/04/2016 18:01, Roger Mills wrote:
Of course there would. It would only be at its max value at the max
torque point itself - which may actually cover a range of speeds since
some engine torque curves are flatish rather than peaky at max torque.
We're talking about a dynamic rather than static situation anyway.
Acceleration is the RATE OF CHANGE of speed and is a continuously
variable function. If you're defining acceleration as a step change in
speed it's little wonder that you're living on a different cloud from
everyone else.

Maybe I need to change A1 for your benefit, thus:

A1: By using full throttle and allowing the car to accelerate over a
speed range which encompasses the max torque speed of the engine.
Maximum acceleration will occur as the engine passes through its max
torque point.

[In actual fact, it may not! As the car speed increases, the aerodynamic
drag increases as the square of the speed. The effect of this - which we
have so far ignored in this discussion - is that maximum acceleration
MAY occur slightly below the max torque speed because the increase in
drag may more than offset the increase in torque.]

I've given up on Plowman, he must be trolling. Or too embarrassed to
admit he's wrong.

Your A1 as it is written is perfectly true, but irrelevant for performance.

To get the greatest acceleration for a car you need to maximise the
amount of power that the engine generates.

If you think of acceleration as increasing your kinetic energy this
should be obvious.

If you follow through some of the examples I gave earlier it should also
help.
To remind you:

400nM at 2000 RPM geared down to 1000RPM - 800nM at the wheel.
200nM at 5000 RPM geared down to 1000RPM - 1000nM at the wheel.

Andy

On 03/04/2016 21:44, Vir Campestris wrote:
On 02/04/2016 18:01, Roger Mills wrote:
Of course there would. It would only be at its max value at the max
torque point itself - which may actually cover a range of speeds since
some engine torque curves are flatish rather than peaky at max torque.
We're talking about a dynamic rather than static situation anyway.
Acceleration is the RATE OF CHANGE of speed and is a continuously
variable function. If you're defining acceleration as a step change in
speed it's little wonder that you're living on a different cloud from
everyone else.

Maybe I need to change A1 for your benefit, thus:

A1: By using full throttle and allowing the car to accelerate over a
speed range which encompasses the max torque speed of the engine.
Maximum acceleration will occur as the engine passes through its max
torque point.

[In actual fact, it may not! As the car speed increases, the aerodynamic
drag increases as the square of the speed. The effect of this - which we
have so far ignored in this discussion - is that maximum acceleration
MAY occur slightly below the max torque speed because the increase in
drag may more than offset the increase in torque.]

I've given up on Plowman, he must be trolling. Or too embarrassed to
admit he's wrong.

Your A1 as it is written is perfectly true, but irrelevant for performance.

Yes, I'm aware of that - and was simply trying to explain to Mr Plowman
that his assertion only applies if you restrict yourself to one gear.

To get the greatest acceleration for a car you need to maximise the
amount of power that the engine generates.


Yes, indeed. That's what I've been saying all along. That's why I gave
the example of using a continuously variable transmission to hold the
engine at its max power (*NOT* max torque) speed as the car accelerates.

It's obvious when you consider that power = thrust x speed. At any given
speed, the higher the power the higher the thrust.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

In article ,
Vir Campestris wrote:
On 02/04/2016 18:01, Roger Mills wrote:
Of course there would. It would only be at its max value at the max
torque point itself - which may actually cover a range of speeds since
some engine torque curves are flatish rather than peaky at max torque.
We're talking about a dynamic rather than static situation anyway.
Acceleration is the RATE OF CHANGE of speed and is a continuously
variable function. If you're defining acceleration as a step change in
speed it's little wonder that you're living on a different cloud from
everyone else.

Maybe I need to change A1 for your benefit, thus:

A1: By using full throttle and allowing the car to accelerate over a
speed range which encompasses the max torque speed of the engine.
Maximum acceleration will occur as the engine passes through its max
torque point.

That's fair enough, but how is that any different from saying 'in any one
gear' as I've constantly stipulated in this discussion?

[In actual fact, it may not! As the car speed increases, the
aerodynamic drag increases as the square of the speed. The effect of
this - which we have so far ignored in this discussion - is that
maximum acceleration MAY occur slightly below the max torque speed
because the increase in drag may more than offset the increase in
torque.]

Adding in drag etc is simply attempting to move the goalposts yet again.
Drag depends on speed. And that is irrelevant to the discussion.

I've given up on Plowman, he must be trolling. Or too embarrassed to
admit he's wrong.

You've been wrong all the time and have attempted every trick in the book
to try and prove yourself right.

Your A1 as it is written is perfectly true, but irrelevant for
performance.

Totally relevant to the original point. And perfectly accurate.

To get the greatest acceleration for a car you need to maximise the
amount of power that the engine generates.

Right. Once again it seems you don't understand what power is.
You need to maximise the torque at the driven wheels under all conditions.
If talking about through the gears, the same applies.



If you think of acceleration as increasing your kinetic energy this
should be obvious.

Why would you think of it as that?

If you follow through some of the examples I gave earlier it should also
help.
To remind you:

400nM at 2000 RPM geared down to 1000RPM - 800nM at the wheel.
200nM at 5000 RPM geared down to 1000RPM - 1000nM at the wheel.

Congratulations. You've discovered that a gearbox multiplies the torque.

--
*No word in the English language rhymes with month, orange, silver,purple

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

In article ,
Roger Mills wrote:
On 03/04/2016 21:44, Vir Campestris wrote:
On 02/04/2016 18:01, Roger Mills wrote:
Of course there would. It would only be at its max value at the max
torque point itself - which may actually cover a range of speeds since
some engine torque curves are flatish rather than peaky at max torque.
We're talking about a dynamic rather than static situation anyway.
Acceleration is the RATE OF CHANGE of speed and is a continuously
variable function. If you're defining acceleration as a step change in
speed it's little wonder that you're living on a different cloud from
everyone else.

Maybe I need to change A1 for your benefit, thus:

A1: By using full throttle and allowing the car to accelerate over a
speed range which encompasses the max torque speed of the engine.
Maximum acceleration will occur as the engine passes through its max
torque point.

[In actual fact, it may not! As the car speed increases, the aerodynamic
drag increases as the square of the speed. The effect of this - which we
have so far ignored in this discussion - is that maximum acceleration
MAY occur slightly below the max torque speed because the increase in
drag may more than offset the increase in torque.]

I've given up on Plowman, he must be trolling. Or too embarrassed to
admit he's wrong.

Your A1 as it is written is perfectly true, but irrelevant for performance.

Yes, I'm aware of that - and was simply trying to explain to Mr Plowman
that his assertion only applies if you restrict yourself to one gear.


If talking about the maximum accleration point in an engine's output over
its speed range, why would you not restrict it to one gear? Surely you
realise that what applies in one gear will also apply to another?

To get the greatest acceleration for a car you need to maximise the
amount of power that the engine generates.


Yes, indeed.

No it's ********. You need to maximise the torque. Not power.

That's what I've been saying all along. That's why I gave
the example of using a continuously variable transmission to hold the
engine at its max power (*NOT* max torque) speed as the car accelerates.

Care to explain why a CVT holds the engine at maximum torque, then?

It's obvious when you consider that power = thrust x speed. At any given
speed, the higher the power the higher the thrust.

I've no idea what you mean by 'thrust' That's something usually associated
with a jet engine. Power is a function of torque and RPM. And the higher
the power does *not* mean the higher the torque.

--
*If work is so terrific, how come they have to pay you to do it?

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