Memory wire

[Anonymous]

Did you hear about it [?] Sounds like a joke but it isn't.
Try this link http://users.skynet.be/pro-rail/ukcafam0.htm
I'm eager for your impressions.
Regards,

Andre INGELS
Brussels, Belgium (The beer country[:I])...and no, I'm not drunk!

[cacole]

That's nothing new. Memory wire has been available for at least 10 years and has been used to control railroad signals and turnouts that long, too.

Memory Wire, also known as Muscle Wire, Flexinol, or Nitlinol, is a nickel-titanium wire that contracts when an electrical current is applied, and expands when the current is removed. It's used a lot in robotics.

[Anonymous]

OK Cacole, I’m quite new in the hobby and never saw it used before.
I wonder why ‘cause it seems to be a inexpensive way to create movement.
Neither, so far as I remember, there was been written about it in MR.
So is there something wrong with it?

Regards,

Andre

[cacole]

Muscle Wire hasn't been used very much in model railroading because it is more expensive than a small solenoid or motor when you add in the other items that must be used in conjunction with it, such as linkages, return springs, and batteries.

One source of Flexinol in the U.S., Jameco Electronics, for example, sells a kit of 3 one-meter lengths of muscle wire of sizes 100, 150, and 375 microns plus a project book, for $59.95 plus shipping. You can get 4 Tortoise slow-motion switch machines for that price and have money left over.

The project book may help, but you'd have to do a lot of hit-and-miss experimentation to determine the correct length of wire and the voltage necessary to move a turnout or signal a certain distance, and there may be no guarantee that two pieces of Flexinol of the exact same length are going to contract exactly the same when voltage is applied.

I've never used Flexinol, but it may weaken over time.

[Anonymous]

I didn’t consider it that wise and will certainly establish a serious price comparison.
In order to balance your standpoint; hereunder you’ll find what Pro-Rail tells about it.
OK, OK, it’s advertisement! [}:)]

The Pro-Rail Wire is specially manufactured for modelling applications.
Its diameter is 125 µm (0,125 mm) ± 4%.
It is made from ternary Nitinol, containing some copper to improve its mechanical properties. It withstands a stress of 185 MPa or, more practically converted, a traction force of 2 N (approx; 200 g).
It has been treated to offer a very stable "2-ways" memory.
This means that its two lengths, respectively at cold and warm state, remain unchanged during its whole lifetime, even after several hundreds thousand cycles. It prevents a progressive untuning of your models as it often occurs with competitive wires.
Another exclusive advantage of the Pro-Rail Wire is that it requires a minimum pull-back force to return to its basic length when relaxing (a spring of a few grams or a rod put slightly out of form are enough). It allows you a much simpler design of your actuators.
These advantages are confirmed in the technical bulletins G12/2 (Oct 1997) and G22/1 (Nov 1998) of the MERG (Model Electronic Railway Group). http://www.merg.org.uk/

Certainly worth evaluation.[tup] [tdn]
Anyway, many thanks for your feed-back.

Regards,

Andre

[rolleiman]

If you want to see a SLICK way of using Memory wire (in HO) that can't be replicated with a Tortise,

http://www.rr-cirkits.com/uncoupler.html

I can't speak for how well it works, Yet.. I bought the components years ago but haven't done the project yet.. Memory wire Has been covered in MR in the past but not very much.. Anybody remember the Animation Notebook feature in MR??

Jeff

[nedthomas]

Menory wire is useful when a slow steady speed of motion is required. One application would be crossing gates. Switch machines would require a long piece of wire to get the travel neccessary and would take a lot of space under the layout.

[davidh48]

Does memory wire still adhere to the laws applied to pulleys/levers for mechanical advantage?

-D

[Anonymous]

Actuating a switch does need a little 5" memory wire and Jeff's example needs about 1" to actuate the uncoupler. So I think this is worth considering?
Anyway, many thanks to you Charles, Jeff and Ned for the useful tips.[:)]
Regards,

Andre

[davekelly]

Maybe I'm not remembering correctly, but didn't Model Railroader do an article about using memory wire for crossing gates?