Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!wuarchive!emory!att!att!watmath!mwtilden
From: mwtilden@watmath.waterloo.edu (M.W.Tilden, Hardware)
Newsgroups: comp.robotics
Subject: Nitenol msg for cphoenix@csli.stanford.edu
Message-ID: <1990Nov11.205704.24949@watmath.waterloo.edu>
Date: 11 Nov 90 20:57:04 GMT
Distribution: comp
Organization: University of Waterloo
Lines: 38


Mail bounced.  Relevant to recent posting about nitenol, so 
I'm posting.

   ----- Transcript of session follows -----
Subject: Re: Memory Metals

Well, the other problem I found is that nitenol distortions do slowly
accumulate over time as you flex nitenol from room temperature up
(I grant the distortion point probably is not room temperature,
but that's what I found with my tests).  All the kids toys you might 
have seen using nitenol use ice as the flex medium.  Sub 
room-temperature mediums help nitenol keep it's 'memory' but 
are very difficult to implement in a robot limb (unless you pump 
freon through it, but to what point.  If you're going to do all
that plumbing, why not just go hydralic?).

The nichrome covering is a good idea, but it would only lengthen 
the efficiency decay, not prevent it.  Would nichrome be able to 
stand the mechanical distortions of the wire?  Hmmm.

Actually, now that I think of it, it might be possible to make sub-zero
robots for work in, say, artic environments with a relatively high 
reliability. Very little electrical energy would be needed to overcome
the latent heat of the wire muscles which could be cooled by the clever
application of external heat sinks.  It'd be a bitch to design, however.

In any case, I won't be impressed until I saw a nitenol robot walk to the 
North pole.  Now that'd be an interesting demonstration.

Is all.


-- 
Mark Tilden: _-_-_-__--__--_      /(glitch!)  M.F.C.F Hardware Design Lab.
-_-___       |              \  /\/            U of Waterloo. Ont. Can, N2L-3G1
     |__-_-_-|               \/               (519) - 885 - 1211 ext.2454,
"MY OPINIONS, YOU HEAR!? MINE! MINE! MINE! MINE! MINE! AH HAHAHAHAHAHAHAHAHA!!"