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The Wonders Of Nitinol
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Wisconsin, United States
Joined: April 18, 2005
KitMaker: 281 posts
Armorama: 201 posts
Posted: Sunday, August 12, 2007 - 03:54 AM UTC
Since I just placed a rather large order of the stuff for myself, due to my current supply running low, I thought I'd sing the praises of Nitinol. It's wire. Specifically, a nickel/titanium alloy developed by the Naval Ordnance Labs (hence the name Ni-Ti-NOL). It's best known as a "memory metal" that has a temperature induced phase change and it's most commonly used for making stents for patients with heart problems. It's inserted into an artery or vein in "compact" form and as it warms up (or is it cools?) it changes shape so that it does the job of keeping the appropriate blood vessel open.

However, its modeling purposes are less well known. This is where the "superelastic" form of the wire comes in. It too has a phase change, but you'll need to heat it up to the sort of temperature that causes plastic to evaporate to cause it to do so. In suitably thin form, it's the best thing in the world for aerials and other sundry antennae. The stuff does not kink. At all. You can wrap a length of it into a spring around a core, and when you release it, it returns to it's original completely straight form. Give a length of this to someone who likes using their handhold-making tool and watch them go insane.

After far too many experiences with music wire antennae that kink at the slightest provocation, I've switched to using this stuff almost exclusively where straight antennae are required. Note that it's not good for whip aerials since, well, you can't shape it.

It used to be pretty expensive stuff. My current supply, bought about four years ago, cost me several dollars for a 12" (30cm) length of 0.005" (0.25mm) wire. I figured this'd last quite a while. However, a recent scan of what I had to build revealed that somewhere along the line I'd bought at least half a dozen SP Designs kits of assorted command and control vehicles, any one of which has enough antennae to consume most of what I have left (yes, Pat, quite a few are BTR-80 variants with wheels). So it was off to www.smallparts.com to order some more - except their web site appears to be dead.

Never fear though - seems they now sell through Amazon, and if you're willing to drift a little in terms of the wire thickness you want, the stuff has become really cheap. The 0.005" stuff is still $1.50 for a foot, but by buying 3" lengths of 0.007" wire, the price drops to 50c a foot. So sometime in the next week I'll have enough Nitinol to last me roughly forever.

Now to buy more antenna bases - I've got to get a couple of dozen more Soviet ones, I reckon, and since I'm not entirely sure that Modelpoint still exists, maybe it's about time to order some of the Armo ones.