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To: <fork@example.com>
From: "R. A. Hettinga" <rah@shipwright.com>
Subject: Re: Electric car an Edsel...
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--- begin forwarded text


Status: RO
From: A guy who models plasma all day...
To: "R. A. Hettinga" <rah@shipwright.com>
Subject: Re: Electric car an Edsel...
Date: Tue, 3 Sep 2002 22:49:20 -0600

Bob,

This capacitor drive idea isn't completely stupid, but neither is it well
thought out.

Maxwell (www.maxwell.com) makes and sells high energy density capacitors,
called ultracapacitors.  They deliver them in an air-cooled, voltage
regulated module that will charge to 42 V and hold 128 kilojoules -- roughly
the energy in 2 teaspoons of sugar or a bite of a donut -- and weighs 16
kilograms.  If that electrical energy could all be converted to kinetic
energy, there's enough to get the capacitor module up to about 200 mph -- in
a vacuum.

Suppose you take the entire power density of the capacitor module -- 2.8
kw/kg (~4 hp/kg!) --  and punch it through an electric motor.  How much does
the 64 hp electric motor weigh?  If it were as little as 50 kg -- and I bet
it isn't -- that capacitor and motor would have a top speed of 100 mph --
the speed at which their energy is the 128 kJ that was initially stored
electrically in the capacitor.  And it's not at all obvious that the torque
vs. speed characteristic of 42 V DC motors will support this, or how they do
it without wheels, drive train, etc.

But if they can, they can only do it in a vacuum where there is no drag!

On to the Lunarnationals?  Or would you prefer the bite of donut?


<Somebody's .sig>

----- Original Message -----
From: "R. A. Hettinga" <rah@shipwright.com>
To: "Vinnie Moscaritolo" <vinnie@vmeng.com>; "Randolph Elliott"
<elliott@engineous.com>; <NicholasFC@aol.com>; "Duncan Goldie-Scot"
<dgs@btinternet.com>; "G. Gruff" <g_gruff@yahoo.com>;
<michael.frese@numerex.com>
Sent: Monday, September 02, 2002 11:15 PM
Subject: Re: Electric car an Edsel...


>
> --- begin forwarded text
>
>
> Status: RO
> Delivered-To: fork@example.com
> From: "Adam L. Beberg" <beberg@mithral.com>
> To: RossO <fork@ordersomewherechaos.com>
> Cc: <fork@example.com>
> Subject: Re: Electric car an Edsel...
> Sender: fork-admin@xent.com
> Date: Mon, 2 Sep 2002 21:24:47 -0700 (PDT)
>
> On 2 Sep 2002, RossO wrote:
>
> > John Waylan (who was interviewed in Wired a few years back) pulled out a
> > 14.4 second run in the quarter mile (91mph), on a battery pack that
> > hasn't been broken in yet. He expects to break his record next year
> > topping his 13.1sec/99mph run a couple of years ago. He's shooting for a
> > 12 second run.
>
> Battery pack, huh what???
>
> You dont use batteries for a 1/4 mile run, you use capacitors. MANY times
> the energy density, and you can get the energy out fast enough. Note that
> the battery packs are fully swapped out for recharging after each run
> anyway, just like a gas dragster is refueled, so this wouldnt be cheating.
> 200 MPH should be no problem.
>
> - Adam L. "Duncan" Beberg
>   http://www.mithral.com/~beberg/
>   beberg@mithral.com
>
> --- end forwarded text
>
>
> --
> -----------------
> R. A. Hettinga <mailto: rah@ibuc.com>
> The Internet Bearer Underwriting Corporation <http://www.ibuc.com/>
> 44 Farquhar Street, Boston, MA 02131 USA
> "... however it may deserve respect for its usefulness and antiquity,
> [predicting the end of the world] has not been found agreeable to
> experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'
>

--- end forwarded text


-- 
-----------------
R. A. Hettinga <mailto: rah@ibuc.com>
The Internet Bearer Underwriting Corporation <http://www.ibuc.com/>
44 Farquhar Street, Boston, MA 02131 USA
"... however it may deserve respect for its usefulness and antiquity,
[predicting the end of the world] has not been found agreeable to
experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'

