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Re: [PSUBS-MAILIST] Unusual propulsion system
Tony,
The stuff you call Muscle Wires is also known as memory alloy,
because it memorises two different shapes depending on the
temperature it is in. You heat it (or cool it) beyond a certain temperature
and it snaps into a different shape. It goes through a hysteresis loop, which
means, when heating, the temperature where it changes to its new cristal
structure
is different from the temperature where it changes back to the old structure.
I wrote my thesis on this stuff at university, but at the time the number of
possible applications was pretty limited.
Firstly, it is quite expensive, secondly the efficiency is low in its
conversion from thermal into mechanical energy.
You would need a hell of a lot of these wires to develop the sort of
forces needed to propel a sub.
There is possible alternative, it is gels. This stuff is familiar to us all,
you find it in diaphers. When you add water it swells, but it also swells
if you apply an electric current.
Paul Flory got the Chemistry Nobel prize for the basic theory behind this,
but more interestingly, on the application side of things, a Japanese guy
called Tanaka (I hope I remember his name correctly) has done
extensive experiments with that.
He tried to build artificial limbs with artificial muscles consisting of gel and
got pretty far with his approach. Maybe also useful in subs?
Martin
|--------+----------------------->
| | TeslaTony@aol|
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| | |
| | 20/08/2000 |
| | 00:38 |
| | Please |
| | respond to |
| | personal_subm|
| | ersibles |
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| Subject: [PSUBS-MAILIST] Unusual propulsion system |
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A long time ago I read about using flippers (like those of a fish, shark or
whale) on a boat and how much more efficient they are, but I can't help
noticing that muscles are difficult to imitate with motors or selenoids
efficiently and you always get a side-to-side or up-down motion in the body
of the craft, plus it is rather difficult to go into reverse with.
The second problem isn't that hard to remedy, just imitate a Mantaray with
the wings on either side rippling to push itself along, which has some nice
advantages in the maneuverability department, but the thing still has to be
powered.
Next I found out about a material called "Muscle Wires," an alloy of Nickel
and Titanium developed by the Naval Ordinance Laboratory (hence another of
its names, NiTiNOL). The unusual property of this material is it contracts up
to 8% (prefereably only 4% though) when heated and expands when cooled,
meaning that properly thin wires can be heated with an electrical current to
act just like muscles.
Now there is a book out that has several projects that use muscle wires, and
one project is for a tube that has two muscle wires running through it and
one power wire, allowing the thing to bend in one of three directions on
command.
But suppose that there were several tubes made between one and five feet long
(or whatever size tilts your wagon), designed to go up and down then encased
in a gelatinous or rubbery plastic that isn't bothered by water or high
pressure, attached to a controller then strapped onto the sides of a sub,
creating a weed-free silent propulsion system for a sub that may negate the
need for a ballast tank (although some Mantarays might think the sub is
rather sexy and lead to some very interesting experiences for you, the Manta
and the sub.
What is all of your takes on this?
Anthony
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