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Science Forum Index » Nanotechnology Forum » unbalanced nano motor rotor
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| MCAS NV |
 Posted: Sat Aug 30, 2003 10:32 pm |
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saw a picture of the nano electric motor. the rotor is odd-shaped, obviously
not balanced, spinning on a nano-tube bearing. They said it could spin at
millions of rpm's--question: with such an unbalanced rotor, how could the
device keep from disintegrating at high rpm? |
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| dopecoder |
| Posted: Tue Sep 02, 2003 8:17 am |
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where did you see the picture? if you found it on the net pass me the
link, i would be interested in taking a look at it
muffy
mcasnv@aol.com (MCAS NV) wrote in message
news:<birtoh02d7f@enews4.newsguy.com>...
Quote: saw a picture of the nano electric motor. the rotor is odd-shaped, obviously
not balanced, spinning on a nano-tube bearing. They said it could spin at
millions of rpm's--question: with such an unbalanced rotor, how could the
device keep from disintegrating at high rpm? |
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| J. Damon Hoff |
| Posted: Tue Sep 02, 2003 11:56 am |
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mcasnv@aol.com (MCAS NV) wrote in message
news:<birtoh02d7f@enews4.newsguy.com>...
Quote: saw a picture of the nano electric motor. the rotor is odd-shaped, obviously
not balanced, spinning on a nano-tube bearing. They said it could spin at
millions of rpm's--question: with such an unbalanced rotor, how could the
device keep from disintegrating at high rpm?
Your macroscale intuition is getting in the way -- scaling laws make
inertial forces negligible at very small size scales.
Let's do a very broad first-order estimate of the force involved in
this case. We'll assume the rotor is a 300nm x 500nm x 50nm
rectangular prism of gold, revolving 100nm from it's center of mass.
Then, the static imbalance at 1 million RPM is:
F = Mhw^2
= (1.48E-13 g) (100nm) (2700 rad/s)
= 4E-20 N
Assume this force is distrubuted across an area 300nm x 10nm:
F/A = 4E-20 N / 300E-17 m^2
= 13 E-6 N/m^2 = 13uPa
The yield strength of a single-walled carbon nanotube is on the order
of GPa -- many, many orders of magnitude above any forces generated by
this imbalance.
--Damon |
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| Calin |
| Posted: Tue Sep 02, 2003 7:15 pm |
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I assume you are referring to the nanomotor announced by the Zettl
Research Group at University of California, Berkeley.
In their publication they state "Although in principle very high
frequency operation should be possible (restricted only by the stripline
bandwidth of
the leads and, ultimately, inertial effects of the rotor plate), our SEM
image capture rate limited direct real-time observations of rotor
plate oscillations to frequencies of typically several hertz."
A.M. Fennimore, T.D. Yuzvinsky, Wei-Qiang Han, M.S. Fuhrer, J. Cumings
and A. Zettl, Rotational actuators based on carbon nanotubes. Nature
424, 408-410 (2003):
http://www.physics.berkeley.edu/research/zettl/pdf/285.Nat424fennimore.pdf
Original PR, with the SEM picture sequence animation:
http://news.nanoapex.com/modules.php?name=News&file=article&sid=3637
-Calin
--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG |
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| J. Damon Hoff |
| Posted: Tue Sep 02, 2003 7:15 pm |
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Quote: F = Mhw^2
= (1.48E-13 g) (100nm) (2700 rad/s)
Oops... working too quickly -- forgot to square the radial velocity.
Should be: F = 1.1E-13 N
Making F/A = 1.1E-13/300E-17 m^2
= 36 Pa
Which is still orders of magnitude less than a SWNT's yield strength.
BTW, muffy, I believe this is the motor he's refering to:
http://www.scienceagogo.com/news/20030627221223data_trunc_sys.shtml |
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| Will Ware |
| Posted: Sun Sep 07, 2003 8:18 am |
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"J. Damon Hoff" wrote:
Quote: Oops... working too quickly -- forgot to square the radial velocity.
Should be: F = 1.1E-13 N
Here's some Python code I use for doing physical calculations. It
automatically keeps track of all the units, which will often warn
about math mistakes:
http://tinyurl.com/mhcd |
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