Subject:
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Re: Avoiding motor stalls
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Newsgroups:
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lugnet.robotics
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Date:
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Sat, 9 Jul 2005 18:52:40 GMT
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Original-From:
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Mr S <szinn_the1@yahooNOSPAM.com>
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Viewed:
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1309 times
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Jordon,
Its hard to say for sure, but it looks like you are
losing torque in the gear conversions. The clutch is a
good idea, but will still strain the motor when it
comes to crunch time.
There are two things that I can think of to help you.
1 - with the same set up you have already, use an RCX
and rotation counter to determine when your drivechain
slows down, then let the program cut power to the
drive motor. That will eliminate > 95% of the chance
to burn out another motor.
2 - Keep the clutchgear on the motor, but make a
breakable/slipping link further down the drive chain
as well. Many of the LEGO wheels (with no tires on
them) will support using the rubber bands in the same
manner that you would use the gears and a chain. At
the point that you are using a big gear to drive a
small one, there is a lot of torque conversion
happening there, and that is the place to use the
rubber bands (assuming they are lose enough to slip if
needed)
3 - use a combination of both ideas
Hope that helps
Cheers
S
--- Jordan Bradford
<bradfj23REMOVE_THIS_SPAM_THINGY@uwosh.edu> wrote:
> I broke another 9V motor. See my
> <http://news.lugnet.com/technic/?n=14319
> original post> for the first story.
>
> I'm building what amounts to a pitching machine for
> the Great Ball Contraption.
> In most TECHNIC building you're building a gear
> train to produce lots of power
> at the expense of speed. But in this case I need to
> build one that has lots of
> speed and not much power.
>
> I have a tire that spins {very} quickly, and as the
> soccer balls roll past it
> they are accelerated and launched into the air. It's
> really cool, and I've been
> working with a prototype structure to hold it all
> together, so it's flimsy.
> Eventually I want to rebuild it to withstand
> day-long use, and that also means
> fixing the gear train, because I've broken two
> motors with it so far.
>
> In the prototype, I put a clutch gear right on the
> motor output, but even with
> that precaution the motor has a hard time turning if
> something completely stops
> the spinning tire. In both motors, something inside
> them eventually broke under
> the strain, so now they are very difficult to turn.
> I definitely want to avoid
> this in the future.
>
> I have no camera available at the moment to show you
> what it looks like, so I'll
> do my best to describe the gear setup.
>
> The motor has a clutch gear on its shaft. This is
> attached to a 40 tooth gear
> with a chain. On the other end of this gear's axle
> is another 40 tooth gear with
> another chain going to a 16 tooth gear on a third
> axle. This spins another 40.
> This 40 turns an 8 tooth gear on a fourth axle,
> which also turns a 24 tooth
> crown gear, which turns an 8 tooth gear on a fifth
> axle. This last axle has the
> tire on it.
>
> If you can sort that out in your mind, this means
> the tire is spinning
> {quickly}. Very, {very} quickly. It is fast enough
> that trying to stop it with
> your finger is very easy, and that's when the motor
> stalls. Actually, it doesn't
> technically stall; it still turns inside the clutch
> gear, but it has to work
> very hard to do so.
>
> What advice can you give me to avoid breaking any
> more motors? The clutch gear
> works in normal gear trains because the motor
> doesn't have to work very hard to
> begin with: it spins quickly and produces lots of
> torque farther down the line.
> But here I'm doing the opposite. If I had an RC
> motor I would try using that,
> since they are more powerful, but right now I'm
> stuck with normal 9V motors. Oh,
> I also have one of those weird motors (no axle, but
> an axle hole) from the
> monkey set, but I don't know how it compares to
> regular ones.
>
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