Newsgroups: comp.robotics
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From: av574@FreeNet.Carleton.CA (Tim Sallans)
Subject: Re: Artifical Muscles
Message-ID: <D2sCCD.69r@freenet.carleton.ca>
Sender: av574@freenet3.carleton.ca (Tim Sallans)
Reply-To: av574@FreeNet.Carleton.CA (Tim Sallans)
Organization: The National Capital FreeNet
References: <3fpkph$72k@crl3.crl.com> <3fp4h7$lmg@crl6.crl.com> <D2oEvu.Bw7@cunews.carleton.ca> <3fot77$q6l@newsbf02.news.aol.com> <D2q97L.Jy7@freenet.carleton.ca>
Date: Sun, 22 Jan 1995 02:31:25 GMT
Lines: 44


In a previous posting, Darin L. Reed (dreed@crl.com) writes:
> Tim Sallans (av574@FreeNet.Carleton.CA) wrote:
> 
> : In a previous posting, Darin L. Reed (dreed@crl.com) writes:
> : > Centauri7 (centauri7@aol.com) wrote:
> : > : jpaulson@chat.carleton.ca (Jess Paulson) wrote:
> 
> : As I understand it, the nitinol contraction is caused by the
> : *thermal* change in the wire...a rather inefficient conversion
> : of thermal to mechanical energy, after the electrical energy
> : has been converted to thermal by an inefficient resistance
> : conversion.  For anything larger than a miniscule power contraction,
> : the wire must be heated even further (requiring higher current
> : and lower efficiency).  For mobile projects, I would think the size
> 
> Hmmm. As I understand it, these wires go full contraction at full strength
> at a key temperature. That temperature for the 250um muscle wire is 70
> degrees C. It takes 1000ma for approximately 7 seconds to achieve this. 
> I've done some checking and the batteries in my radio control airplanes
> can easily achieve this. 
> -- 
> Tracy Reed
> treed@ucssun1.sdsu.ed
> dreed@crl.com
> 

Really?  I didn't know this...perhaps I'm overestimating my knowledge.
<grin>  Then does that mean I've gotten it backwards, and the temperature
just catalyzes (the correct term for a non-chemical interaction?)
the release of mechanical energy stored while stretching the material?
Then that would mean that you would need some mechanism to stretch
the metal (a spring wouldn't work, or that would be a perpetual
motion machine :) )...the energy output of the metal must either come
from the heat or the stretching.  Which is it?  I really don't
know enough about this stuff, and would be interested in a quick
answer.

					--Tim

--
Tim Sallans                        "I've a plan so cunning, you
Ottawa, Ontario, Canada             could stick a tail on it and  
av574@freenet.carleton.ca           call it a weasel." -- Black Adder
