Subject:
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Re: new Mindstorms servos?
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 9 Jan 2006 03:18:52 GMT
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Viewed:
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1977 times
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In lugnet.robotics, steve <sjbaker1@airmail.net> wrote:
> The problem with gearing down motors in order to exchange
> RPM for torque is that if you actually NEED RPM rather than
> torque then you have to gear them back up again.
And the problem with not gearing down the motors is that for anyhting
requiring more than the motors "native" torque, you have to gear them down with
those inefficient plastic gears.
> On the face of it, therefore it ought not to matter whether
> you provide a geared-down motor or leave the motor operating
> at it's raw RPM because whatever you do, half of the people
> will have to add a gear train in order to get the motor to
> do what they want.
That assumes that all possible torque/speed combinations are equally likely.
Far more common is that there are reasonable ranges for torque/speeds that the
end users often try to derive. For me, that's more commonly gearing slower than
gearing faster. That's not saying I don't gear for faster output sometimes - I
certainly do. But far more commonly I gear for a slower speed even with the
standard gear motors (and certainly for the old "standard" motor I have).
> However, in a system like Lego where you can't possibly
> predict how the motor will be used in practice...
Predict, no. But you can play the odds. And most people, *especially* most of
the target audience for something like Mindstorms, use the motors first and
foremost to drive wheels on a mobile platform - they build moving robots. And
for that, I usually have to gear for a slower speed using the gear motors,
either for control issues or pushing power (sumo, hill climbing, moving over
carpet, etc.). I suspect LEGO is trying to drive the motor towards the most
commonly used torque/speed combo for the core user here.
> So if I had to choose just one style of motor, I'd prefer
> one with no gearing at all to one that has been pre-geared
> down for torque.
You prefer the old-style 9V over the Mindstorms gear motors?
> For that reason (and others), I predict that the NXT motors
> will be less useful than the RCX style motors.
My biggest worry is the size and how to attach them firmly. But that could be
because I'm not an expert on studless construction. Buti'm willing to learn :-).
--
Brian Davis
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Message is in Reply To:
 | | Re: new Mindstorms servos?
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| The problem with gearing down motors in order to exchange RPM for torque is that if you actually NEED RPM rather than torque then you have to gear them back up again. If you have a high RPM motor to start with, you have to gear it down in order to (...) (18 years ago, 9-Jan-06, to lugnet.robotics)
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