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From: JOHN PITTELLI <jplily-at-yahoo.com>
Subject: Re: Electric Motor
Date: Fri, 5 Sep 2003 22:01:00 -0700 (PDT)
Reply-To: tanks-at-rctankcombat.com

Bill: Only when answering your own query.  :-)
                                     John
--- William and Melissa Johns
<gizmology-at-gizmology.net> wrote:
>
> 
> (I'm replying to myself.  Is that like talking to
> yourself?)
> 
> 
> At 07:45 PM 9/5/2003 -0400, you wrote:
> >Well, according to my EXTREMELY SUSPECT
> calculations, your motor is best 
> >run at around 12,000 rpm, where it should draw
> around 13 amps.  Assuming 
> >that the motor is 50% efficient, it should be
> generating around 0.05 
> >ft-lbs of torque and 0.10 horsepower.  If the motor
> is 75% efficient, it 
> >should be generating 0.07 ft-lbs of torque and 0.15
> horsepower.
> >
> >You can tell how efficient a motor is by measuring
> the stall torque - the 
> >higher the torque, the more efficient.  In your
> case, 0.23 ft-lbs works 
> >out to about 50% efficient, and 0.35 to 75%. 
> (Efficiency is good not just 
> >for battery life, but also HEAT - potentially
> enough to let the smoke out.)
> >
> >I hope this helps.  (I also hope it's right!)
> >
> >Bill
> >
> >
> >
> >At 05:08 PM 9/5/2003 -0500, you wrote:
> >
> >>I would like to see if any of you could help me
> with some electric motors 
> >>I bought at a local surplus store. They are 12
> volt ,  4.100"  overall 
> >>length ,  2.030" Dia. ,  5MM (.1969) Dia. shaft., 
> Internal fan 
> >>cooling   , 14,500  RPM free speed. It pulls 3.4
> Amps at no load. Pulls 
> >>50 Amps at stall. Any idea what an average load
> RPM and AMP draw might 
> >>be? Given a gear reduction of 25 to 30 to 
> >>one.                                              
>            Thanks Randy
> >
> >--
> >
> >"Forgive your enemies, but never forget their
> names" -- John F. Kennedy
> >
> >
> >
> >
> >
> 
> --
> 
> "Forgive your enemies, but never forget their names"
> -- John F. Kennedy
> 
> 
> 
> 


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