| Re: Why are SUVs and Christianity similar?
Joe Fischer wrote:
> On Fri, "R.H. Allen" <kkarie@hotmail.com> wrote:
>
>> I made a bit of an error there -- the heavier car would require 480kJ of
>> extra energy compared to the lighter car, not 32kJ (assuming 600N and
>> 300N are required to keep the heavy and light cars, respectively, at
>> constant speed). Assuming 30 mpg and 25% conversion efficiency, that's
>> 40MJ/mile for the light car and 41.92MJ/mile for the heavy one, so the
>> added weight produces a 4.8% increase in fuel consumption. Considering
>> that we're talking about a *doubling* in weight -- essentially a fully
>> loaded one-ton pickup that itself only weighs a ton, or about a third of
>> what such vehicles usually weigh -- that's still pretty small. A more
>> realistic figure for such a vehicle would be more like 1.5% more
>> gasoline (though of course the whole analysis is so simplified that the
>> only real-world conclusion you can draw is that weight has a negligibly
>> small effect).
>
> That sounds -real world-, if it were much different
> a train or even a big semi truck would not be able to
> do what they do, some big trucks don't have engines
> with much more displacement that a big car.
That small engine thing sounds counter-productive for a serious work
truck like a semi. A small engine would have to pull some serious RPMs
to get enough power, and I don't think the fleet managers want to
rebuild the engine every 100,000 miles. I think the large trucks have a
built in red line of about 3,000 RPM and are meant to cruise at 1,500 or
so. If anyone knows the exact numbers please chip in. I met a trucker at
a motel who said his truck was just "Broken in" at 150,000 miles.
>
>> I suspect something like rain-slickened roads or a difference in the
>> direction of the wind are enough to cause more than a 0.1 mpg difference
>
> Maybe much more, there was a true story in
> Flying magazine about a guy trying to fly a Piper Cub
> along the highway from the Salton Sea toward L.A.,
> and was running low on gas, and tried to land, but
> was flying backwards.
> He ran out of gas and had to land backwards,
> and when he jumped out, the plane flipped over
> backwards.
I have seen the same thing at an airport between Bakersfield and
Modesto, where the pilot just turned into the wind and rose straight up,
then backwards. Strange thing to watch, but it had my attention since I
was about to fly out and that didn't give me warm fuzzies.
>
> I watched US Army spotter planes flying
> backwards or holding stationary in north Texas
> in 1946, and aircraft are probably better than
> cars aerodynamically, so wind would seem to
> make a difference.
>
> Perhaps the moral of this story is that
> automobile engines are greatly oversized so
> those in a hurry can accelerate fast.
Total lead foot between stop signs or lights. Little wonder we have so
much dependence on oil when everybody drives like it's a drag race.
>
> Joe Fischer
>
Cheers,
Bill Baka
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