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From: "Bob J" <Bob-at-ezworks.net>
Subject: Re: Electric Motor
Date: Fri, 5 Sep 2003 23:24:14 -0700
Reply-To: tanks-at-rctankcombat.com

Hey  Bill
        Theres no problem with talking to your self.  You may be like me,
enjoy intelligent conversation.  How ever be very carefull about lying
to your self as thats geting close to NOT GOOD.  But when you lye and
then go ahead and believe it, your in deep do-do....   OK?
Bob

----- Original Message ----- 
From: "William and Melissa Johns" <gizmology-at-gizmology.net>
To: <tanks-at-rctankcombat.com>
Sent: Friday, September 05, 2003 4:57 PM
Subject: Re: Electric Motor


> By the way, this assumes it's a permanent magnet DC motor.  If it's
> series-wound or whatever, then all bets are off.
>
> Bill
>
> (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
>
>
>
>