Subject:
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Re: Unique Gear Part - what is it 2.5 /5.0 in Motor Kit
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 14 Sep 1999 18:39:39 GMT
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Viewed:
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516 times
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In lugnet.robotics, Dave Baum writes:
> In article <FI1Ato.BEM@lugnet.com>, "Matt Silver"
> <silverm@tech-center.com> wrote:
>
> > What is the gear marked 2.5 /5.0 that comes with the Motor kit ?
> > The gear looks lie a 24 tooth, but is white and a bit thicker, and has a
> > grey hub inside that turns.
> >
> > [...] It slips pretty easily, so you need to
> gear down after it to get any reasonable amount of torque.
It starts slipping somewhere between 2.5 newton-cm and 5.0 newton-cm.
"newton-cm" is the SI unit of torque and corresponds to a force of 1 newton at
a radius of 1 cm, or a force of 0.1 newton at a radius of 10 cm, etc. [1]
The reason for the range 2.5 to 5.0 is that you can't be sure exactly what
torque it will start slipping at. It depends on how worn the internal surfaces
are and the usual randomness of static friction. [2] But you can be guaranteed
that it will always slip at torques over 5.0 n-cm and will never slip at
torques below 2.5 n-cm. You should set up the gear ratios in your gear train so
that the clutch gear is operating near but not above 2.5 n-cm under the maximum
reasonable load. You can't measure torque directly, but you can rebuild the
geartrain a few times and test it each time.
- Robert Munafo http://www.mrob.com/
LEGO: TC+++(8480) SW++ #+ S-- LS++ Hsp M+ A@ LM++ YB64m IC13
[1] Anyone remember high school physics? (-: A newton is the force necessary to
accelerate a mass of 1 kg at a rate of 1 meter per second per second. It is
also approximately equal to the force of the Earth pulling down on a motionless
102-gram mass at sea level.
[2] Does anyone know how the clutch gear works? I imagine it uses a magnet and
an iron disc, but I've never tried to take one apart.
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Message is in Reply To:
 | | Re: Unique Gear Part - what is it 2.5 /5.0 in Motor Kit
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| (...) Nope, that's the purpose of the gear. I think the Technic Element Registry calls it a "clutch gear". I find it handy to have around. It slips pretty easily, so you need to gear down after it to get any reasonable amount of torque. Even so, I (...) (25 years ago, 14-Sep-99, to lugnet.robotics)
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