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From: jmuchow@SPAMMENOTcamlight.com (John Muchow)
Subject: Re: Reducing contact resistance for low volt use?
Date: Tue, 07 Jan 2003 06:26:10 GMT
Organization: MindSpring Enterprises
References: <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com>
X-Server-Date: 7 Jan 2003 06:28:02 GMT
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>>> Sure it is. If they get too hot, they stall because you have reached
>>>the currie point of the perm magnets in them. That is probably one of
>>>the main problems, when you overvoltage the motors. Actually the
>>>currie point poses a problem for steel and iron parts as well.
>>> Their makers could tell you about it, I'm sure. I don't think the
>>>windings like it a lot either. Having done it so much, I'm sure you
>>>already know this.
>>> If they are electrically excited fields, you are using juice on the
>>>batteries in two places, not just one. I was thinking they are perm
>>>mag motors. Still heat can pose serious problems inside those
I agree. I haven't experienced it yet, but others have demagnetized
their motors due to overcurrent conditions...hundreds of amps.
>>> It doesn't remain at 24 volts either, does it?
No, of course not. I don't need to keep the packs at 24V. The 'bot
is designed to run at my desired speed (approximately 15MPH) with the
cells at their plateau voltage, approximately 1.0V/cell.
>>> I'm just saying that the job could probably get done without
>>>stressing them at all.
This has been the Holy Grail of combat robot builders for years...to
create an *effective* (very important) fighting 'bot that doesn't fry
its components, much less stress them at all. You'd be the first one
ever to create such a bot...and that should tell you something about
I invite you to design such a bot. There are several competitions
nationwide every year and if you're that confident about your design,
you should have no qualms about the cost and time involved in making
such a desirable machine. The money you could make selling the plans
would more than pay for your time.
>>>>Even the R/C car and airplane builders use their cells at very high
>>>>discharge current levels
>>> I know. I make controller circuits for them. I stay inside the
I respect that. I'm involved with folks who rarely stay inside the
envelpe though. Anyone who has, has lost very badly, very quickly.
>>> Since you extend outside it, and work at low voltage levels, have
>>>you sought lower voltage motors that put out what your overvolted
>>>motors do? Those extra bits of efficiency are what you seek anyway.
>>>One step at a time.
The lower voltage motors often don't have the torque, speed, or
durability to do the job. And the extraordinary current requirements
of these lower voltage motors makes them even harder to use. Before
voltage limitations made it impossible, several builders were using 96
volt motors and enjoying the much lower current requirements.
>>> Just like the old days of drag racing with stock vehicles. It goes
>>>from parsing out pieces of the car to reduce weight to porting out the
>>>heads to increase flow. One step at a time.
>>> I merely suggested that power is power, and you should be able to
>>>find a motor that delivers your needs within the range it was designed
Thank you for the suggestion. An awful lot of research has been done
before I came along and became interested in combat robotics and R/C
vehicles. Though there are many great motors (electrically), they
often fail to measure up mechanically, or in size or weight. The
sport has been continuously evolving, in small and large ways, since
the beginning...as I guess all of them do. You wouldn't believe how
more robust everything has gotten, and how much more powerful
too...all making those one-step-at-a-time changes you mentioned.
This is an astoundingly destructive sport that requires an entirely
new way of thinking about the components being used. I welcome any
specific recommendations you have for motors, batteries, etc., and
invite you to join us at the Yahoo BattleBots forum. You can post
your design/component ideas and suggestions and get feedback from many
other builders who have been competing for years.
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