Re: [PSUBS-MAILIST] Horsepower

["Greg Teiber" <wolfe19@megsinet.net>]

You two are making assumptions electric people make.  Depending on the Motor, many are designed to work at peak efficany 100% of the time.  And can handle that withought a drop in lifespan. 

As electric motors go, the only relavant number is continous duty.  Their overpower settings are only good for 30sec-2mins.  And that just isn't a signifigant number for a slow moving boat like a Psub.  As for the batterys, that depends on what you use, LeadAcid a full discarge is down to 30-40%, but for nicads it's 98%  Well we are getting on a tangent here.  The proper method for Psub propulsoin is Sealed leadacid batterys, and a big, torquey electric motor, run at 5-10% power :)

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On 1/26/00, at 11:54 PM, Kenneth Schulze wrote: 

>Hi Doug,
>I think much of the confusion comes about because internal combustion engines are
>rated differently than electric motors.  Most gas/diesle engines are rated at
>their peak horsepower output, but are operated at 50 to 70 percent peak rpm.
>Electric motors are rated for continuous operation, but can be pushed to 200% for
>a limited time due to heat build up and possible overheating.
>Another "apples to oranges" comparison is made by not including the energy
>storage system, such at fuel storage volume and weight.  Batteries can only
>depleted to 30 or 40% of full capacity, any more will shorten the life of the
>battery system.
>Therefore, be careful how you compare internal combustion engines with electric
>motors.
>Take care,
>Ken Schulze
>
>SeaLordOne@aol.com wrote:
>
>> 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