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balancing. (long, sorry!)





-----Original Message-----
From: T. Reed [mailto:treed2@wsu.edu]
Sent: Sunday, November 02, 2003 4:21 AM
To: David Utley
Cc: Dan Bubb; scirocco-l@scirocco.org
Subject: RE: balancing. (long, sorry!)


"  I dunno what mail software you use, but it would make your replies a lot
  easier to read if you replied in the conventional fashion (maybe this is
  part of the reason that not many people responded to your earlier msg?)
  rather than just interspersing your comments in the message you're
  replying to. ]"
I am using MS Outlook...  During Biz hours, I use the browser/webmail that
my ISP gives me, so I will be sure to manually put that in there...  How can
I adjust it at home?  No need to irritate  when I am not trying to
deliberately...;-)

> 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...

"YES, especially when you have a heavy flywheel. See, you need a lot more
fuel to spin a heavy flywheel up to a particular speed than you do to spin
up a light flywheel. When you step on the brakes, that energy is dumped to
heat."
I understand that...  What I am speaking of is cruising, highway, prolonged
trips...  If you are in a highway cruiser with a heavy flywheel, it is to
your advantage... If you are in town, and want to terrorize Hondas/Toyotas,
then ti would not be to your advantage...
 My whole approach with modifying my car is to improve areas where it is
needed, and leave the rest alone... In other words, I like to build a car
that is built for its' purpose, which for me is occasional highway
cruiser/hauler/Honda terrorizer...  This is hard to do all at once, but is
what I strive for...
 "With a lightened flywheel you will get better gas mileage in this
scenario (ie. city driving) because you're dumping less energy. That
energy has to come from somewhere; fuel.. so the lightened flywheel is
using less fuel since its dumping less heat."
I agree...  My point DOES figure more into HIGHWAY driving...

"This is about potential energy- think of a heavy flywheel as a large
bucket. You scoop water out of a bathtub with this large bucket (ie. spin
up the flywheel). Then, lift it over your head and dump it out on the
bathroom floor. If you'd used a smaller bucket, you'd have wasted less
energy lifting the water."
Excellent analogy!  This will help me with my point, I hope...  With that
smaller bucket, it will take less effort...  However, if I need to dump a
bunch of water (as in, a trip to another state), then I would want a larger
bucket, so that I do not have to lift it as often...  Right?


"If you want to pace me in my lightened-flywheel car side by side with your
normal-flywheel car, you will have to burn more fuel to accelerate at the
same rate as me. And when you stop, your brakes will be hotter because you
will have more kinetic energy (because you burned more fuel)."
I agree...

"At a constant speed, the acceleration is zero, so the flywheel weight
does not matter. The bucket is already over your head so all you have to
do is keep it there; you're not expending any energy in lifting it. (Just
fighting gravity.. or friction in the engine example)"
Yes, but here is where the analogy fails us...  On the road, even at a
constant speed, it takes fuel to maintain that speed...  Greater inertia
slows deceleration, which is its only benefit...  That is my point almost in
its entirety...


"You can spin the flywheel up as fast as you want (within the power limits
of your engine and the shear strength of the flywheel bolts). To spin it
up from 1000 rpm to 3000 rpm in 2 seconds is possible for both an 8 lb
and a 12 lb flywheel. But it will take more power for the 12 lb flywheel.
This power has got to go somewhere, and it winds up as potential energy
in the flywheel. The 12 lb flywheel has more stored power."

Yes!


"Let's say the keg was too small.. ie. your flywheel was not heavy enough.
What happens? You don't get drunk! The engine stalls. This is why
you have to give cars with lightened flywheels a little more gas to get
going.. you have to store more potential energy in the smaller flywheel
by revving it slightly higher to make up for its small mass."

By Jove, I think you have it...


"I think part of the problem you're having here is that you're tackling the
lightened flywheel as a 'whole car' issue, rather than considering the
specific changes resulting from a change in weight of the flywheel. That
is the only part of the system that is changing, so it is best to focus on
the changes that are created by the change in weight and propogate them
outwards.

The change from a physics point of view is the energy storage potential of
the flywheel. I've already run :the results of this change: in to the
ground.. so I won't discuss them again (unless you want me to)."

No need...  Someone other than myself got the point, and that is all that I
was after...  :)


"I don't think it was so much that you were a relative new comer (you are?
that's news to me.. i figured you were just one of the quiet folk that
don't post often) than that Dan pretty much laid out a logical explanation
of his counter-arguments and you responded to his post with little
more than doubt and cynicism, and failed to really address any of his
arguments by further explaining your statement(s). The latter was probably
the most inflammatory part, contrary to what you might think. It's fine to
call someone wrong or even (what's that word for 'overly proud'?) but
you've got to state your position clearly and back it up or you just come
across as intentionally disrespectful rather than passionate."
I agree...  He and I have sorted things out, and we bear no ill-will...  We
both were having a rare Friday, I think...


"It took me a while to write that response but I felt like it was necessary
to try and create some understanding for Dan's position, as well as try
to clarify (what I thought was.. evidently I was wrong) your argument.

Now I'm responding because I'm trying to give you an opportunity to
explain yourself using my weird "laymen's terms" parallels so that I can
correct your explanation :)

(yes, that was a mild jab.. hehe)"
No sweat, I again appreciate the efforts...  And to explain, I am a longtime
lurker, but new poster, as of prolly tow months or so?  I have been involved
with dubs for at least 14 years...
Thanks again,
David

-Toby

BTW: when replying to this post, please trim the parts that don't matter
for the sake of our digest brethren.