Em 15/2/2011 19:40, Chris McSweeny escreveu:
> On Tue, Feb 15, 2011 at 8:59 PM, Isaac Marino Bavaresco
> <isaacbavaresco@yahoo.com.br> wrote:
>> Em 15/2/2011 18:04, Olin Lathrop escreveu:
>>> Yigit Turgut wrote:
>>>> If you assume the start point is at sea level then you
>>>> should be right with your numbers 4 - 5 km's.
>>> OK, let's take this at face value.  Let's say the car weighed about 1 t=
on,
>>> which is light for a car.  That's 2000 pounds, or about 9000 Newtons.  =
If
>>> you take a 9000N car on a trip and it ends up 5000m higher at the end, =
45MJ
>>> had to have been expended somewhere somehow.  This has nothing to do wi=
th
>>> how curvey or not the path was, how long it took, or what exactly prope=
lled
>>> the car.  This is simply looking at resulting potential energy alone.
>>>
>>> Now let's look at a car battery.  Let's be generous and say it is rated=
 for
>>> 100 A-h, which means it can put out 100A at 12V for 3600 seconds.  That=
's
>>> 4.3MJ, or less than 1/10 of the absolute minimum it would take to move =
the
>>> car up 5000m.  4 such batteries simply can't do that, and that's assumi=
ng
>>> the entire energy of the battery can be converted to potential energy o=
f the
>>> car.  In reality there will be wind resistance (you said average speed =
was
>>> about 80km/h =3D 50 miles/h, so wind resistance is a factor), other sou=
rces of
>>> friction, and of course inefficiency in converting the battery energy t=
o
>>> motion.
>>>
>>> Clearly something is wrong somewhere.
>>
>> The site says that the 4 batteries are 150Ah for a total of 25.92MJ,
>> which is more than half the necessary energy. But still not enough.
> It also says the car is only 470kg, so 4600N, hence only 23MJ required
> in potential energy. So providing you can extract all that energy from
> the batteries with 100% efficient motors, and not too many other
> losses it is possible ;) The bigger problem is that the claim is a
> minimum speed of 70km/h - even if it was all done at that speed it
> would take 8.57 minutes or 514 seconds to cover the 10km, hence 44kW
> required power just against gravity, yet only 1.6kW of motors.
>
> Of course if we look at motor power, then consider that for a bicycle,
> 400W will get you close to 50km/h. Given almost all the power there is
> against wind resistance and that power required to overcome wind
> resistance goes with the cube of the speed, then 1600W would only get
> you close to 80km/h for a bicycle frontal area/Cd - now that car would
> appear to have a lot more than a bicycle worth of frontal area.
>
> Chris


I think his car is too heavy for its apparency. Four 150Ah truck
batteries  would mass something around 160kg to 180kg. The motors shown
in the site shouldn't mass more than a few units of kg each.
For just one person it surely should be possible to build a very light
weight vehicle. I would go for a tubular design, perhaps less than 100kg
in weight.

Isaac


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