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| 25 new of 81 responses total. |
rcurl
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response 25 of 81:
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Apr 28 00:32 UTC 2002 |
My point about motorcycles concerned safety more than efficiency, but
they are still pretty efficient.
How do you propose to make the electricity for those hybrids? From
natural gas, I presume. But that can be used directly as fuel with
greater efficiency. Hybrids are most efficient when using electricity
generated and used in the vehicle itself, especially by recovering
energy when braking.
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senna
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response 26 of 81:
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Apr 28 03:18 UTC 2002 |
There was just an article mentioning that auto insurance is spiking right now,
partly due to maintenance of artificially low premiums and partly due to the
prevalence of SUVs. A quote of one insurance rep mentioned that if an SUV
runs a red light (and I've seen them come awfully close), the car they crash
into is a complete write-off, and the SUV is still expensive to repair.
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jazz
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response 27 of 81:
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Apr 28 05:29 UTC 2002 |
If everyone drove them, it wouldn't kick driving fatalities through
the roof, nor insurance costs, however.
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jmsaul
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response 28 of 81:
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Apr 28 05:45 UTC 2002 |
Why are people assuming I'm advocating SUVs? I'm not, I'm just advocating
against ultralight cars like the ones Russ was talking about.
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bdh3
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response 29 of 81:
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Apr 28 05:48 UTC 2002 |
re#27: Not practical so long as semis share the roadways.
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mdw
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response 30 of 81:
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Apr 28 05:56 UTC 2002 |
Hybrids run off the same fuels as conventional cars -- that's one of
their big attractions. Hybrids are a neat idea, and I hope they become
more popular. Main problems include considerable extra complexity (&
initial cost/maintenance), and less practical as an overall car (at
least part of the overall efficiency of this latest batch of hybrids is
due to them being designed as an extremely streamlined 2-seater -- a
hybrid SUV would not be nearly as impressive in terms of efficiency &
performance.)
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janc
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response 31 of 81:
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Apr 28 12:25 UTC 2002 |
The Honda hybrid is a 2-seater, but the Toyota is a fairly normal
4-seater, I think.
I'm not sure if the existance of semis on the road is an argument
against ultra-light cars. If you are hit dead-on by a semi, the
advantage of being in a Mazda Protege rather than a well-built
utlra-light car are probably marginal. You're toast either way. The
bigger difference is probably in hitting things more SUV sized.
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jmsaul
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response 32 of 81:
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Apr 28 14:07 UTC 2002 |
The difference is that if you're in an ultra-light car, being hit by a Mazda
Protege has the same effect as being hit by a semi.
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bdh3
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response 33 of 81:
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Apr 28 17:05 UTC 2002 |
In addition, an ultra light is much more effected by the 'draft'
caused by a moving semi.
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rcurl
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response 34 of 81:
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Apr 28 18:18 UTC 2002 |
Why? They would presumably be smaller, so would have decreased forces
on them from the wake. As long as the tires hold it should not make
much difference what is the mass of the veehicle.
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senna
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response 35 of 81:
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Apr 28 19:15 UTC 2002 |
They might not be that much smaller, though, given that they still have to
hold passengers. A lot of it depends on design, of course, but in general
lighter cars are a lot more vulnerable to aerodynamic problems.
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slynne
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response 36 of 81:
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Apr 28 19:44 UTC 2002 |
Wouldnt an ultra-light car be very useful for city driving though. It
seems that one of those would be at least as safe as riding a bike or a
moped on the street? If gas prices got high enough, you would see
people choosing those kinds of vehicles more. Heck, you'll see people
riding their bicycles more too.
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rcurl
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response 37 of 81:
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Apr 28 21:09 UTC 2002 |
But WHY would a light car be more vulnerable to aerodynamic problems?
I can see that they would be more easily rocked (tilted), but should
that be a problem?
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russ
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response 38 of 81:
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Apr 28 21:41 UTC 2002 |
Re #25: You're wrong about efficiency. An auto engine can get perhaps
30% efficiency, but a combined-cycle gas-turbine powerplant can easily
beat 50% and at least one has been specced to hit 60%. In theory, you
could get twice as many miles from natural gas burned in a stationary
powerplant than from natural gas burned in a vehicle.
Co-generated electricity has an effective efficiency of nearly 100% minus
transmission losses; if you are using space heat, it makes a huge amount
of sense to generate electricity from the fuel and then heat with the
waste of the generator. Otherwise you just burn fuel in one place to make
electricity and throw the waste heat away, then burn more fuel for the
heat you need. This is also true of use in a vehicle; it's more efficient
to burn fuel where you can use heat and send electricity to run a vehicle
than it is to burn fuel in a vehicle and throw the waste heat away.
And did I mention that grid-charged hybrid vehicles could run on energy
from coal, nuclear, wind, hydro and solar? All of these could displace
oil, and at least one of the above is bound to please some constituency.
Re #28: Ultralights are one thing, but the PNGV was supposed to produce
a FULL SIZE 4-door sedan that would get 80 MPG. You'd get a full measure
of crash-worthiness out of something that size, on less than 1/3 of the
fuel consumption of the average US vehicle. If you charged from the grid
you could cut oil consumption much further, up to 100% on short trips.
Re #30: Funny, but the auto companies disagree with you regarding
performance. The Dodge Ram Contractor Edition has the same performance
with a 4.6 liter as the 5.7 liter standard version, and the Ford Escape
hybrid would have achieved what, 40 MPG with the same performance?
One thing people don't seem to get is that electric powertrains often
have sparkling performance; the GM EV-1 can out-run many Corvettes up
to 60 MPH. The only problem is energy storage (range), and a hybrid
option deals with that.
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gull
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response 39 of 81:
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Apr 28 21:43 UTC 2002 |
Re #31: The new hybrid Honda Civic is also a four-seater. The Insight was
just their first effort, not the end of the program.
Re #35: My experience is that problems with semi wakes have more to do with
the surface area to weight ratio of a car than weight by itself.
My Honda Civic is pushed around a little by semi wakes, but not
dramatically. Wakes were much more of a problem in full-sized vans and
minivans I've driven, in spite of their much higher weight, because they
have so much surface area. They would literally rock from side to side when
following a semi, because of the eddies thrown off by the back of the
trailer. Crosswinds also were troublesome.
When a solar car race was held in Australia, one of the safety checks the
cars had to pass was they had to tolerate being passed by a "road train"
without becoming unstable. Australian road trains often have four or five
trailers and travel at up to 80 mph. If those dinky 300 pound solar cars
could be made to handle being passed by one of those beasts, it should be
possible to make a lightweight passenger car that can handle our
garden-variety semis.
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gull
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response 40 of 81:
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Apr 28 21:49 UTC 2002 |
Re #38: You're forgetting that the battery charge/discharge cycle in a car
is going to be less than 100% efficient, especially if you're trying to
quick-charge the batteries to get acceptable 'refueling' times. The faster
you try to pump in a charge, the more current you'll use and the more power
you lose as heat. You've also got transmission losses, and losses in the
charger itself. (Ever noticed how well-ventilated battery chargers are?)
The inductive paddle 'magnechargers' that seem to be popular for safety
reasons probably also have significant hysterisis losses.
I agree with your about electric powertrains. They have extremely wide
torque bands that tend to give better performance than the raw horsepower
figures suggest. A lot of the raw horsepower from an IC engine is lost in
the transmission, and the time you spend shifting from gear to gear is time
when you can't apply full power to the wheels. It's possible to cover 0 to
80 mph in one or two gears, depending on the design RPM of the motor and how
much starting torque you want.
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senna
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response 41 of 81:
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Apr 29 01:54 UTC 2002 |
Obviously, objects of equal size and shape will be subjected to identical
aerodynamic forces, but objects that are much lighter have (obviously) less
mass to resist movement. Basic newtonian principles. Additionally, the
vehicle's weight is what maintains tire contact with the ground, and if that
force is reduced, the vehicle is more likely to lose traction.
Like gull said, large vehicles have similar difficulties, some of which small
ultralights will also have, some (such as center of gravity) that they
probably won't.
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gull
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response 42 of 81:
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Apr 29 02:24 UTC 2002 |
Re #41: While it's true that a lighter car will have less of a downward
force on the tires, resulting in less traction, a lighter car also has less
inertia to resist when changing direction. The result is lighter cars tend
to have *higher* skidpad grip figures than heavier ones.
That doesn't mean a small car has to have 'twitchy' handling, of course.
How stable a car feels on the highway has more to do with the steering
geometry than anything else.
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russ
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response 43 of 81:
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Apr 29 03:35 UTC 2002 |
Just to illustrate the possibilities of cogeneration, let's try a
back-of-the-envelope calculation.
Suppose you have a Tzero car, which can go 90 miles on a charge
of 16 KWH (and does 0-60 in 4.03 seconds, but that's another
story). It uses about 180 watt-hours per mile. Let's suppose
you're running this in the winter, so you're using your furnace.
Your furnace puts out 30,000 BTU's per hour (about 9000 watts
of heat) when it's running, and it runs 1/3 of the time for an
average of 10000 BTU/hr (about 3000 watts). Assuming zero losses
(modern furnaces just about get there), that's 10 cubic feet of
gas per hour, or 240 cubic feet per day. At 48 cents per hundred
cubic feet (the rate on my last bill), that about $1.15 per day.
Now replace the furnace with a 30%-efficient cogenerator with the
same heat output. You'd burn 1.429 times as much fuel, or 14290
BTU/hour of gas. This gas would cost you $1.64 a day, and you'd
produce an average of 1260 watts of electricity. You could charge
your Tzero's batteries from flat to full in under 13 hours, giving
you 90 miles a day for an added fuel cost of forty-nine cents.
That's a bit over half a penny per mile in fuel cost for the car,
and none of it derived from oil. You'd also have about 12
kilowatt-hours of juice per day left over for other purposes.
Begin to get an idea of what we *could* do, if we wanted to?
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jmsaul
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response 44 of 81:
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Apr 29 03:38 UTC 2002 |
Have you seen the film of the TZero, by the way? They'll have to make those
things noisier, or pedestrians and cyclists will die. ;-)
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russ
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response 45 of 81:
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Apr 29 12:44 UTC 2002 |
Re #40: "Refueling" the batteries is only an issue in a pure
electric; a hybrid might charge off the grid but doesn't have to
sacrifice efficiency for charge rate. Besides, the efficiency
gained from never having to idle the engine compensates for what
you lose in the batteries.
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gull
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response 46 of 81:
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Apr 29 12:56 UTC 2002 |
Re #45: I agree, but it sounded like we were talking about pure electrics.
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jmsaul
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response 47 of 81:
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Apr 29 13:29 UTC 2002 |
The TZero he's talking about is a pure electric, I think.
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russ
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response 48 of 81:
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Apr 29 22:23 UTC 2002 |
Re #44: I've heard of that; the GM EV-1 (formerly Impact) is said to be
quiet enough to catch birds unawares. I've wondered about directional
high-frequency noisemakers, to put warning noise only where it's needed.
Driving a five-speed a lot means I get to play. Going downhill I can
shut down the engine; the car is very pleasantly quiet even moving at
45 MPH, making the radio a much better experience. I doubt that electric
cars would be much noisier. I think that people would love driving on
electric power if they could only try it.
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jmsaul
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response 49 of 81:
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Apr 29 23:00 UTC 2002 |
Impact. Heh.
The video clip of the TZero shows it accelerating hard -- and the most obvious
noise is tire squeal. Very little else, as far as I can tell.
When I can get one with a 300-mile range that seats four plus luggage and I
can fill it up as conveniently as, say, diesel, I'll want one. The tech isn't
mature enough for me yet, though.
(Oh yeah, and I want comparable power and acceleration to our M3... but I'm
not worried about their ability to deliver that.)
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