Muscle Wires

AIman

Has any one used muscle wires with a stamp?
For that matter has anyone used muscle wires?

If so were the results favorable?

Phil Pilgrim (PhiPi)

I tried them only briefly several years ago. I needed to be able to trip a shutter release remotely and rigged up a little device to do so. Muscle wires provide a lot of force but over a short throw distance. So to get much movement, you need to leverage their output somehow. For the shutter release, I used a small lever cut out of FR4 with about a 1:5 ratio, and it was enough to do the job.

You can't solder to muscle wires. All connections must be mechanical. Also, they don't react as fast as a servo or solenoid, and you have to have some kind of countervailing force (e.g. a spring) to return them to their relaxed state. Finally, you need some way to limit the current going through them, else they'll get too hot and lose their "muscle" properties. Even then, they're not as efficient as a servo might be.

In short, the plain wires are a bit difficult to work with. But if you understand their limitations and operate within them, there are some apps that they're well suited for. In my mind, their biggest advantage is compactness. The shutter release I described fit in a space about .6" x .3" x .3". Try doing that with a solenoid or servo!

-Phil

AIman

I am running into a space issue so the wires might be the way to go. From what you said it sounds like it might work out.

Thanks.

Yendor

I was interested in muscle wire years ago, and put together this kit (a pre-solar version). The pdf has some schematics that may be useful to you.

http://www.robotstore.com/store/product.asp?pid=383&catid=1634
http://www.robotstore.com/download/3-619_Solar_SW_Instr.pdf

Basically, the muscle wire looped over the wings that simulated·a slight butterfly flapping effect -·very gentle and slow.· It also shows that it needs some force to go back to its initial state when relaxed, as Phil stated above.

Overall it was interesting, but the movement was so slight that it proved to me you would need quite a few wires to generate any force or distance.

Rodney

Post Edited (Yendor) : 12/5/2006 5:00:16 AM GMT

AIman

I am thinking about using several of them together in the place of a push rod on my R/C airplane. The alerons don't need much to move them and unless I am doing aerobatics (which are very fun) the speed isn't needed.

My thinking was to remove the aleron servos and use the wires because the equvilant weight in wires should be a much greater force then a servo of about the same power use.

Robert Kubichek

AIman said...
I am thinking about using several of them together in the place of a push rod on my R/C airplane. The alerons don't need much to move them and unless I am doing aerobatics (which are very fun) the speed isn't needed.

My thinking was to remove the aleron servos and use the wires because the equvilant weight in wires should be a much greater force then a servo of about the same power use.

Well, correct me if I am wrong, but using servos, you send em the control pulse and the servo arm moves to the porportional position,
and stays there until the next pulse.

How are you going to accomplish the same acuracy of movement with muscle wires?
Muscle wires by their very nature use MUCH more energy than a servo, which is NOT good in RC planes....
Also to get full movement back/forward, you have to have double the M wires for both directions. or one set with a spring return..
It would not be as fine a contro as a servo would provide..

Bob

LoopyByteloose

Muscle wires work on a thermal change in the metal due to electrical current, while other motors work in response to a magnetic field. With the newer alloys of magnets getting lighter and more intense, it is really hard for the muscle wire to compete. Response is slower and current to convert energy to heat is more demanding.

I suppose there are some instances where slowness is good as a way of governing speed without having the bulk of a geared down motor and there are situations where the higher current may not be a problem, but in general I keep returning to magnetic devices.

If you have a spring controled centering on the airplane and a minimun of need to have the muscle wire powered up to overcome the springs, it may be a substantally lower weight load that can compensate for heavier batteries. But, I would not expect ultra-responsive control. In some cases, that may be a non-issue.

In other words, it really is going to require some thoughtful engineering to get the muscle wire into a superior configuration for RC flight.

Since amperage is a function of cross section, I suspect that you can only increase speed somewhat by increasing voltage. But that only works in one direction.· In the other direction, you have to rely on ambient cooling.

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Post Edited (Kramer) : 12/5/2006 4:44:49 PM GMT

Mike Green

Some other things to think about:

Muscle wire takes quite a bit of power to activate and must continue to be heated to maintain its position. With servos, there's gearing involved and it takes quite a bit of force to move a servo off position even if unpowered. The servo mechanism will expend power to keep it positioned properly if there's something forcing it to move. The biggest advantage to muscle wire is that it's very very simple and light weight. If you can arrange some kind of mechanical latch or ratchet, it can be very useful. One piece of muscle wire can move a ratcheting device to tighten or rotate something and another piece of muscle wire can release the catch.

Phil Pilgrim (PhiPi)

Google is your friend. I found these:

0.1g Muscle Wire Actuator
Plane built with above

'Also discovered a certain familiar G.S. haunting those forums as well.

-Phil

AIman

Phil,

Very cool airplane.