Newsgroups: comp.robotics
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From: ccb8m@viper.cs.Virginia.EDU (Charles C. Bundy)
Subject: Re: nitinol underwater?
Message-ID: <CoIzGw.E70@murdoch.acc.Virginia.EDU>
Keywords: nitinol
Sender: usenet@murdoch.acc.Virginia.EDU
Organization: University of Virginia Computer Science Department
References: <2osgb1$bmn@birdie-blue.cis.pitt.edu> <nagleCoHvuM.6At@netcom.com>
Date: Tue, 19 Apr 1994 21:24:32 GMT
Lines: 44

In article <nagleCoHvuM.6At@netcom.com> nagle@netcom.com (John Nagle) writes:
>filip@alpha.smi.med.pitt.edu (Filip M Gieszczykiewicz) writes:
>>	Greetings. Has anyone tried to use nitinol wires as active 
>>	elements in underwater robots? If the robot is tethered, power
>>	is not a problem and due to the excellent cooling provided by
>>	water (especially when moving :-) would permit decent cycle
>>	times. And the winning factor for hobbyists like me is that it
>>	makes possible build robots that are inherenly water-proof :-)
>
>      That would be a good application.  The big problem with this stuff
>is that you get a contraction quickly when you apply power, but it takes
>time for wire in air to cool, so it takes a few seconds in air for the
>stuff to relax.  In water, or in a fast-moving air stream, this drops
>to a fraction of a second.  So the stuff should be much more effective
>in water.  In air, it's more of a curiosity than a useful actuator.

Has anybody done work on active/passive cooling systems?  Attach a little 
heat sink to the end of the wire :)

>
>      The other big problem is that you only get a few percent 
>contraction.  So you need some kind of mechanical leverage to get any
>significant travel.

What's wrong with mechanical leverage?  Aren't zylene's (sp) a type of
rachet in muscle tissue?

Hmm I've been wondering about spiral configs:

IE:
      <----------->  Say 5% contraction on 2" is .1" BUT

      Spiral wire around a core say 20" gives 1" of travel in the same
      2" space. (Probably not quite 50% but imagine an accordian folding)

      \  |\  |\  |
      |\ ||\ ||\ |  <-- Run active cooling fluid down core (or chill air)
      | \|| \|| \|

BTW: Are there any papers on Stiquito?

Thanks
Charles C. Bundy IV
ccb8m@virginia.edu
