Re: [PSUBS-MAILIST] Horsepower

["D. Blake" <dblake@bright.net>]

Yeah, and that peaky power-curve is why internal combustion engines need a
transmission and clutch.  Both of which suck enormous amounts of available
horsepower and energy through friction.  The electric motor develops torque
the instant you apply power, and maintains a more or less linear power curve
throughout the RPM range.  No need to rev the motor to obtain power, and no
need to waste energy by idling.
Pull your front tires up against the curb.  See if that 60hp internal
combustion engine will push you over the top without a few revs of the motor
and dumping the clutch.  Do the same with a 20hp series-wound DC motor with
direct-drive to the rearend, and you will go immediatly over the top.
The stuff I have read says it's not uncommon to go zero to sixty and more
without ever having to shift gears.  That is how linear the power-curve is
with electric motors.
Big Dave
-----Original Message-----
From: Marsee Skidmore <heyred@email.msn.com>
To: personal_submersibles@psubs.org <personal_submersibles@psubs.org>
Date: Wednesday, January 26, 2000 11:28 PM
Subject: Re: [PSUBS-MAILIST] Horsepower


>The difference is in how the ratings are done. Electric motors have a
fairly
>linear power curve (hp vs. rpm), and are derated for continuous duty. In
>other words, the rated horsepower of an electric motor is on the low end of
>the output curve, just to be conservative. Internal combustion engines have
>a very peaky power curve, and are rated by the peak output. Conservative,
>conshmervative, let's sell cars! Race car drivers like to run at the peak
of
>the power curve, but those of us who pay for their own gas and overhauls
>operate a little bit further down on the curve. Three to one sounds about
>right. A 60 hp Volkswagen runs just fine with a 20 hp electric motor. - Joe
>----- Original Message -----
>From: <SeaLordOne@aol.com>
>To: <personal_submersibles@psubs.org>
>Sent: Wednesday, January 26, 2000 5:59 PM
>Subject: [PSUBS-MAILIST] Horsepower
>
>
>> Teammates,
>>
>> Please help me with this one.  According to an article in BOAT/U.S.
>Magazine
>> (January 2000, pages 24-25), electric motors somehow provide three times
>the
>> performance of internal combustion engines.  How can this be?  Horsepower
>is
>> horsepower is horsepower, isn't it?
>>
>> The article (Electric Boats Charging Back) is about coverting gasoline or
>> diesel boats into electric ones.  The author (Ryck Lydecker) says: "He
>> calculates that to replace internal combustion engines, particularly in
>> sailboats, the power ratio is about three-to-one.  That is, a 3-hp
>electric
>> motor is adequate to replace a 9-hp outboard."  I thought a 3-hp diesel =
>a
>> 3-hp gasoline = a 3-hp electric = a 3-hp anything.  Yes?  No?  Please
help
>me
>> out here.  Does this guy know something I don't?
>>
>> Thanks,
>>
>> Doug
>>
>
>
>