"Nick Müller" wrote in message
...
Ed Huntress wrote:

ince you're into it this deep, I'd like to suggest something you may
want
to consider: magnetostrictive metals.
~~~~~~~~~~~~~~~~
The name says it all!

I have some (indirect) experience with them. They produce much more
force
than piezo, and they're good for (IIRC) 20 kHz. They activate very
simply,
with a solenoid-type coil, but they do have some mechanical hysteresis.

Now this sounds (pun intended) _very_ good! Thanks a lot for that hint!

Small bars of the material are reasonably priced.

Say, do you know how much they contract at about (%-wise)? Going to have
to google for a source (no success until now).


Have fun. It sounds like you've developed your work into something close
to
laboratory research.

Sometimes I do have the same impression. ;-)
Next, I will publish my tube-bender (it took me 50 hours of development
and two prototypes to be thrown away). Look at the tubes of the Ellwe to
see how good they are.


Thanks again for the magnetostrictive metal
Nick

Go to Google and look up Terfenol-D. Also, look up "magnetostrictive
transducer." Without the quotes, I got 20,000 hits.

You may run into one of my old articles about it. When I was at Wasino, we,
in cooperation with Etrema, who were the material experts, were developing
it for elliptical piston-turning.

The properties are well-known. The force is very high compared to any
comparable technology. When I Googled, I saw a technical paper about
modeling the hysteresis, but I didn't read it.

IIRC, some engine company was considering using it for fuel injection, but I
don't trust my memory that far.

Anyway, it's a great project for an experimenter. As for prices, go to:

http://www.etrema-usa.com/products/terfenol/

They'll give you a quote. You may find a similar material cheaper somewhere.
The US Navy uses it in sonar, so there must be other sources.

--
Ed Huntress