balancing.

[mardak at cogeco.ca (Mark)]

Ok, another simple, somewhat offbase analogy.  Ask any professional
cyclist if he would prefer heavier wheels on his bike for his next race.
You get on a bike with 20 pound wheels, and I'll get on one with 10
pound wheels - there's no way you will expend less energy than me after
50 miles, even at a constant speed.

Mark.


> -----Original Message-----
> From: scirocco-l-bounces@scirocco.org [mailto:scirocco-l-
> bounces@scirocco.org] On Behalf Of David Utley
> Sent: November 1, 2003 10:55 PM
> To: T. Reed
> Cc: Dan Bubb; scirocco-l@scirocco.org
> Subject: RE: balancing.
> 
> Comments within...
> 
> -----Original Message-----
> From: T. Reed [mailto:treed2@wsu.edu]
> Sent: Friday, October 31, 2003 8:38 PM
> To: mr.utility@highstream.net
> Cc: Dan Bubb; scirocco-l@scirocco.org
> Subject: Re: balancing.
> 
> I'm gonna jump in here, against my better judgement..
> 
> > > So, if I understand this correctly, greater inertia helps you to
> maintain a
> > > constant speed better and because of this your throttle is more
> constant
> and
> > > therefore you get better mileage?
> >
> > To be more specific, this should read ---"greater inertia helps you
to
> > maintain a constant speed more easily, and therefore if your
throttle is
> > constant, the inertia of a weighted flywheel will be higher than a
> lilghtened
> > flywheel, therefore more mpg."
> 
> This is similar to the argument that has come up several times on the
> vortex - that cruise control hurts fuel economy because it is
constantly
> modulating the throttle, trying to maintain a fixed speed through
varying
> terrain.
> 
> My personal opinion is that it is in poor taste to make broad
> generalizations about the cruise control issue -- everyone's driving
style
> is different and an conculsive scientific analysis is not really
possible
> with so many variables. "it depends" would be my answer.
> 
> I do agree, however, that modulating the throttle expends more energy
> than holding it constant over the same amount of time and the same
stretch
> of road.
> 
> So as I understand it, David's argument is that the lumpier idle
resulting
> from a lightened flywheel results in modulation of the air flow plate
(ie.
> same effect as modulation of the throttle) and a decrease in fuel
economy.
> 
> Sort of...  Not so much a lumpier idle, as much as accelerating much
more
> than necessary....  You know like young drivers are often doing,
because
> they do not know how to coast well...  Constantly accelerating, then
> braking, then accelerating, etc...  Lots of wasted energy that is
vented
> through the brakes as heat...
> 
> I would tend to agree with this if the idle was excessively lumpy..
but
> I have a lightened flywheel and my idle is pretty close to rock solid.
> If other people have a rough idle it is my /opinion/ that it is due to
> something else in combination with the flywheel.
> 
> As I mentioned, you and I are on different pages here...  I appreciate
the
> help though, I think I need it...  :)
> 
> I'd say this falls under the 'negligible, if any' category. Kinda like
> that magnetic fuel saver thing.
> 
> Furthermore, the lumpy idle only occurs at.. well, idle. So whenever
> you're moving at a constant speed, the air flow through the engine
stays
> as constant as the position of your accelerator pedal.. regardless of
> flywheel weight. At a constant speed, there are no acceleration forces
> acting on the flywheel or your car, just frictional ones. Mass only
> influences acceleration and deceleration, not constant rotation. There
is
> a negligible effect on frictional force due to the difference in mass.
> 
> I'll stop here since I'm kinda repeating what Dan already said.
> 
> 
> Don't take Dan's arrogance personally. In the world of engineering,
> mistakes often mean people will die, and it will be 'your' fault.
Think
> about all the things in your daily life that were designed by
engineers
> that could kill you if they were designed improperly-- cars,
airplanes,
> missile silos, power transmission towers, electrical appliances,
bridges,
> dams, nuclear power plants, etc. In the engineering world, mistakes
are
> not tolerated(*), and when they happen, fellow engineers are quick to
> point them out.
> 
> A very good point, which is one reason why I chose to chill out a bit,
and
> take a moment to consider all sides a bit better...  I still contend
that
> I
> am right, and I still think he is a bit arrogant, but that is okay...
:)
> I
> can deal with arrogance, I deal with car salesmen all day...  :-P  I
just
> decided, and he confirmed, that he does not mean it personally, so
> therefore
> I should not take that on....  I apologize for the heat I sent out...
I
> could go on explaining my job these days, etc, but ultimately it does
not
> matter...  I am sorry for being a bit of a prick...  :(
> 
> 
> 
> (*) = this sounds a little gung-ho. mistakes do make it in to many
> designs, but you get my point.. it's essential that there be as few as
> possible.
> 
> There is so much misinformation circulating in the non-engineering
world
> about engineering topics that I think it begins to drive engineers a
> little crazy. Imagine going to a car show full of Honda drivers where
> everyone is saying "Sciroccos are slow and heavy, they don't handle
well
> and they always catch on fire when they crash". You'd probably feel
> compelled to speak up and try to correct them. It's the same thing
going
> on when people pipe up on the list to correct those who make
misinformed
> statements. Personal attacks they are not..
> 
> Yes...  Since I work at a VW dealership, and since I love VWs, I take
in
> personally anytime someone bad-mouths VWs...  Unfortunately, I have to
> admit
> that they seem a bit down in quality from where I would like to see
them...
> Fortunately, this does not affect us in this group too much, as we
know
> the
> older dubs rock!  I know where you are coming from...
> 
> > > flywheel may represent a significant amount of the rotational
inertia
> of
> the
> > > engine, but not a significant amount of the inertia (both linear
and
> > > rotational) of the whole car, especially in the higher gears where
the
> engine
> > > is only turning 3-3.5 times faster than the wheels.
> >
> > True, but the whole car does not push itself along, the engine
does...
> And if
> > you improve the ability of the engine to maintain a given speed,
then IF
> it
> > maintains a given speed, the efficiency is higher...  BTW, the whole
car
> does
> > not have any rotational inertia to speak of, unless it is rolling
end
> over
> > end...  :-)
> 
> The car *does* 'push itself along', it has mass and speed.. therefore
> forward momentum. At a constant speed, the engine only generates force
> to counteract the frictional forces that would otherwise slow the car
> down. The net force on the car at a constant speed is zero.
> 
> Yes, I agree...
> 
> > > >From a purely physics point of view, baring frictional effects,
if a
> mass is
> > > at a constant velocity (linear or rotational) it takes no energy
to
> maintain
> > > that velocity.
> >
> > Do you engineer rockets or something?  We are on earth, where
friction
> is
> > king, and gravity its' gueen...  If that were true, I could coast
from
> > Oklahoma City, to Dallas without any trouble...  Even if I do not
> include
> > friction, there is still gravity, prevailing winds, etc...  I am
> speaking
> of a
> > real world scenario here, or trying to...
> 
> It is standard scientific practice to abstract the real world to the
ideal
> (in this case frictionless) case in order to better understand the
forces
> at hand, THEN make adjustments to model the real case.
> 
> Agreed.  I guess I was a bit thrown by the indirect insults to see
where
> he
> was...
> 
> > Clearly it takes less energy to accelerate a lighter mass, but
> > > to maintain a constant speed requires no energy input so there is
no
> > > difference between a light flywheel and a heavy one.
> >
> > Ummm, like, what?!  We are talking about cars, not space ships...
It
> does
> > take less energy to accelerate a lesser mass, which is why we are
> talking
> > about all this mess...  To maintain a given speed DOES take energy,
as
> this is
> > the real world we live in, not space...
> 
> To maintain a given speed in and of itself does not take energy. To
oppose
> frictional (ie. surface friction as well as fluid and air resistance),
> magnetic, gravitational forces, etc -- energy is needed.
> 
> Yes...
> 
> > An engineer of what?!?  Perhaps instead of thinking about cars, you
> should
> 
> It really doesn't matter what kind of engineer he is; if he went to an
> accredited school and received an engineering degree then he has more
than
> just an idea of what he is talking about. Engineering school forces
you to
> abandon 'conventional wisdom' and develop olympic-athlete-like
critical
> thinking skills.
> 
> Yes...  I too have a degree...  In Philosophy, which if you have ever
> taken
> a course, can sometimes make you question not only why am I here, but
why
> did I take this friggin' class...  :)  I know about challenging
yourself
> mentally, everyday...  That is why I chose Philosophy, to do the right
> thing, at the right time, and to the right degree...  I fail at it all
the
> time, but as long as I admit my failure and try again, I have
ultimately
> succeeded...
> 
> [ Aside:  Critical Thinking - The disciplined ability and willingness
to
> assess evidence and claims, to seek a breadth of contradicting as well
as
> confirming information, to make objective judgments on the basis of
well
> supported reasons as a guide to belief and action, and to monitor
one's
> thinking while doing so (metacognition). The thinking process that is
> appropriate for critical thinking depends on the knowledge domain
(e.g.:
> scientific, mathematical, historical, anthropological, economic,
> philosophical, moral) but the universal criteria are: clarity,
accuracy,
> precision, consistency, relevance, sound empirical evidence, good
reasons,
> depth, breadth and fairness.  ]
> Cool definition...  And very true...
> 
> 
> > instead work on them , and experience a few things...  You seem a
bit
> too
> far
> > removed from working on them daily, as I do...  And are you
'implying'
> that
> > because you are an engineer, and I am not, that I am wrong?  I may
only
> have
> > two diplommas on my wall, but let's face it...  The most novel
invetions
> come
> > from those who were not trained to 'know better'...
> 
> Working on cars, while fun and definitely educational, unfortunately
does
> not make you any better at understanding the physics behind them. Let
me
> clarify as that sounds a little too broad - by physics I mean the mpg
> issue we're discussing. I'm not talking about the motion of pistons
and
> valves.. as there is certainly no better way to understand them than
to
> work on an engine. As we know from reading the Bentley the layout of
> things is much clearer when they're actually in front of you and not
just
> on the page of a book.
> 
> Yes...
> 
> > I applaud you on that, if that is what you are attempting to do...
I
> just
> > hope that you are looking for the 'truth' in its broadest terms, and
not
> just
> > in yours...
> 
> Engineering is not meteorology.. when applied correctly, it's about as
> close to 'truth' as you can get. Scientists sometimes get to ignore
the
> real world, but it is the playpen in which all engineers are locked.
They
> don't get to design and build things for an "ideal" world!
> 
> Yes, agreed...  I think the only problem we really have here "is a
failure
> to communicate".  No, beyond that...  It is a perception problem...
In
> some
> ways I think I have received this much flack because I am relatively a
new
> comer, and here I am standing up to  the one who (probably) is THE one
who
> would call BS or not...  If I could speak to Dan as an equal, in a
> language
> that he is more familiar with, I think he would agree...  However,
since
> we
> do not have that luxury, it will take longer to get my point across...
> And
> that is okay, as long as I do not get thrown off the list inbetween
now
> and
> then...  :)  I will either win my point, agree that I am wrong, or
agree
> to
> disagee and move on...
> 
> My 2 cents.. please take note that this e-mail is meant to have a
> light-hearted, informative tone. I'm not trying to instigate anything
> here.
> 
> Thank you Toby, for the friendly mediating...  I needed it, as I feel
that
> I
> have upset a few here with my comments...
> 
> Long live VWs!
> 
> Word...
> David
> 
> -Toby
> 
> 
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