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February 25, 2006

stopmo puppets: twisted vs. untwisted wire?

by sven at 12:41 am

I just wrote a long post over at stopmotionanimation.com that was more or less an essay in itself. It seemed worth re-posting here:

[Mike Brent wrote:] "To twist or not to twist? That is the question. Really it's a matter of personal preference."

I can't tell you how much I've been wanting to hear a vigorous discussion of twisted vs. untwisted wire, and about wire in general! Guess now's the time...

Here's what I understand so far:

(1) single strand vs. multiple strands

First off, there's a question of whether to use a single strand of wire or multiple strands. Most people favor using multiple strands -- the thinking being that if one of the strands breaks, the others will still work. The one exception seems to be among people who are using lead wire. The reason folks using lead wire tend work with single strands, I think, is because it's hard to find lead that's less than 1/4" diameter. (I've only been able to find lead wire in stores that carry fishing supplies, in the area where they sell lead sinkers.)

(2) twisting with a drill vs. twisting by hand

The main reason to twist multiple strands seems to be to hold them all together. At this point, there's a choice about whether to twist by hand, or twist the wire using a drill bit. Folks against using the drill bit seem most worried about accidentally nicking the wire in the process, which almost guarantees that the wire will break. It's also fairly easy to over-twist the wire using a drill, which may put extra strain on the strands. However, using a drill will give you a tight and even twist -- whereas hand-twisting can give you a very funky twist. In Susanna Oroyan's book, "Designing the Doll", it's suggested that uneven twists weaken an armature's strength (p.73).

This is a point where I'm hearing contradictory messages: some folks claim that uneven twisting strengthens, some claim that it weakens.

(3) stress between the strands

Some folks say that twisting strands inherently creates stress points between your wires. As I understand it, this is the main argument for using untwisted wire: no twists equals no stress between wires. Without twisting, though, you need another means to bind the strands together. Barge and silk thread are the only suggested solution I've encountered so far.

(4) when do multiple strands become a single wire?

The main rationale for using multiple strands is to have back-ups when one breaks... But if you twist the wires, do they start to act as a single wire? I've only had one break so far -- in a twisted-wire armature -- and it seemed like the wires all broke as one. I presume a wire armature usually breaks after it's been covered with foam, latex, clay, etc... Has anyone actually seen a puppet performing with just one of the multiple strands in a limb broken?

...Or am I misconceptualizing how this is supposed to work? Is the idea that twisted strands are stronger because they distribute the stress among each other -- so you'll never see just one strand broken; they'll break all together, but not as quickly as a single strand otherwise would?

(5) point of entry into the torso

Having multiple-strand limbs is supposed to distribute stress and protect against breakage. But with puppets that use epoxy putty torsos, the point where the arm enters the putty effectively turns the wire "rope" into just one strand. I think it's really note-worthy, then, what Nick does with some of his puppets: He uses a wood block, threads the wires through holes, and only twists them together afterwards. With the wires entering the torso at multiple points, you preserve the benefit of having multiple strands! (Nick's tutorials: http://www.picturetrail.com/gallery/view?p=999&gid=60051&uid=42706 )

(6) other strategies

I've read about a strategy where you twist together three types of wire: lead (for its lack of memory), steel (for strength), and aluminum (for a combination of these qualities). I've also seen someone mention actually braiding their wires together -- not just twisting them. Both of these strategies have been attributed to pros in the field -- but I haven't seen enough about either to really say anything else about them.

(7) accepting that wire armatures break

I'm probably thinking too hard about this... All wire armatures break. Maybe multi-strand untwisted aluminum that enters the torso at multiple points is the most durable -- and maybe not. When you build the puppet, though, you consider not just durability, but also ease of construction. Maybe you do a quick epoxy putty torso -- you accept some risk for the sake of convenience, having the wire all enter the shoulder at one point.

...Or, you could design your puppet the expectation that it's going to break -- having plug-in limbs that are attached into the torso with little socket set screws, limbs that can be replaced if needed. (See Juergan Kling's armatures for an example: http://www.animateclay.com/index.php?module=PayPalCart&cid=7 )

Hm. I seem to have written an essay...

I guess what I'm really curious to know, personally, is if anyone with an engineering background can actually say anything authoritative about the physics of wire...

Ever curious,
--Sven

posted by sven | February 25, 2006 12:41 AM | categories: stopmo