Saturday, 20 October 2012

Armature research

There are many different ways to build an armature, where complexity is somewhat decided by how much is required of the puppet. At the most basic, a wire armature is a perfectly adequate solution. Two lengths of aluminium are twisted together to form a much stronger structure, which is used in pieces to form the body of the character. The limbs are typically separate, so the armature is fixed together where these multiple strands meet. Professional wire armatures may feature ‘junction plates’ as a means to connect the body together, but a blob of polymer epoxy putty (for example Milliput) will do the trick too- with the added benefit of being able to be shaped as needed.


‘By whatever methods are in your means, it is in your best interest as both a puppet-builder and an animator to prolong the life of your puppet as long as you possibly can. As you plan everything else, plan for eventual breakage of your puppet and balance this with how much animation you need to shoot.’
-Priebe, K. (Quote from pg. 77) (2011) ‘The Advanced Art of Stop-Motion Animation’

This statement is of critical importance, and one with which I wholeheartedly agree. From looking into methods for armature construction on a practical level, whereby the vast majority of armatures are created with twisted aluminium wire cemented in Sculpey (or alternative putty) blocks, the general consensus is that the wire is the first thing to break. Naturally, there is only so much stress and strain a material can take before its bonds weaken, even a malleable one such as aluminium. An armature almost entirely wire therefore poses the greatest risk.

It is possible to plan for such breakages by making a wire armature with detachable components, so if something breaks it can be easily replaced. Armatures are available with blocks at the hip and shoulders, where lengths of wire can be inserted and screwed into place. These blocks can even feature M3 screw holes as handy rigging points. This effect can be replicated fairly accurately on a budget for very little cost, by screwing your wire into terminal connector strips- a process I have documented with regards to my previous work.


In addition, it is possible to greatly increase the lifespan of a puppet by reinforcing the wires. As opposed to leaving the entire limb wires bare, it is a good idea to establish ‘bones’ (i.e. areas where the puppet should not be able to bend). Not only does this aid in creating a believable animation with realistic joints, but gluing brass K & S tubing (or aluminium tubing, as this is much easier to cut and offers almost identical practical results) over the wires provides strong areas to hold onto when moving the puppet. Heat sink tubing can be applied over the bendable sections to further increase its longevity.

A good method to strengthen a puppet is ‘coring’, whereby the solid parts which need not move are built to fill the shape of the puppet’s body from a material that will not deform through handling. Coring can be added with foam or putty over the aforementioned brass K & S or aluminium tubing.


Plastic ‘coring’ for the Were-rabbit puppet from Aardman’s ‘Wallace & Gromit: The Curse of the Were-Rabbit’

There is an issue however when it comes to the fabrication of foam latex build-up puppets, which by nature of their design and the methods through which to create them, may not be capable of being disassembled once complete. If the foam latex component of your puppet is something contained by a material boundary, such as a head or an arm which can be affixed to the puppet’s padded body through other temporary means such as screw connectors, there is no issue- but so many, dare I day the majority of foam latex puppets are whole, seamless creations with no visible joins. The entire puppet is one single, continuous material, and in these instances it is difficult, near impossible, to imagine a believable way of having each part separate.

As a result, it is all the more imperative that a complete foam latex build-up puppet has a professional, long-lasting armature. Everything needs to be reinforced, for there will not be a chance to alter the armature once the puppet has been built up over the top of it. Where possible, weak points must be established and replaced with a more permanent element.

It seems apt that, in creating a complete build-up foam latex puppet, its armature should consist not of wire but of solid rods, made poseable with ball and socket joints. Indeed, this is the form of most high-end armatures that can be bought online for a hefty price. Some elements however, such as the fingers, will likely need to feature wire. Don’t get me wrong- the aim is not to remove wire entirely from the equation, for it does have very useful properties and applications. This is more about limiting its inclusion to the bare essentials, for it can be temperamental.

Professional ball and socket armatures are the best option, offering durability and stability. They can withstand a great deal of use and are dependable- the most appropriate solution for a foam latex build-up puppet. They are however very expensive, ranging between £40 to over £100. A professional armature will usually come in kit form, for the buyer to assemble. Ball and socket joints are incredibly beneficial when it comes to animation, since each one can be manually ‘tuned’ (see ‘tuning an armature and the principle of resistance’ below) to pose different levels of resistance to movement.



The first planned element to my Gollum foam latex build-up puppet is to construct an armature that is more durable than a typical wire armature. It seems I have three options at this stage, my decision being forced by time constraints and cost:


1)     Buy a professional armature, to custom dimensions, for a high price.

        Pros: Highest quality, much faster than building from scratch, least likely to break
        Cons: Expensive, likely still requires advanced assembly

2)     Make my own ball and socket armature on a budget.

        Pros: Intermediate level armature, cheaper than full purchase, stronger than wire
        Cons: Difficult to source components, requiring of time and possibly additional   
        equipment

3)     Resort to a simple wire armature, and hope for the best

        Pros: Cheap, readily available, quick and easy to make
        Cons: Unpredictable durability, most likely to break whilst animating


Gollum is scrawny and has very thin limbs, which may go somewhat towards determining the size of the puppet. If I am able to either make or purchase a professional armature, which relies on steel ball and socket joints, then the size of those joints must be taken into consideration. If I can only obtain larger joints, the puppet will need to be larger to compensate.

(Note: John Wright Modelmaking is a leading supplier to industry professionals!)


It seems the smallest ball and socket joints I could buy utilise an M1.2 threaded rod with 3mm stainless steel balls. When screwed in place to form a joint, the dimensions are length 10mm x width 5 mm x depth 6mm. Bear in mind that on top of this, I would need to add foam padding and a rubber latex skin. Before I plan and sculpt the model, I need to be certain on what size the joints and rods will be, since these will need to fit comfortably inside, within the form of the latex ‘skin’ created from the sculpt.

Working to a student budget, it seems the most favourable option would be to construct a custom ball and socket armature myself. In addition to saving a lot of money, I will gain a much deeper understanding of the materials, techniques and processes used, which will help immensely with my research.

Nathan Flynn provides an excellent walkthrough of how he created ball and socket armatures for his stop-motion short ‘Opening Night’ on his blog, which I would highly recommend to any stop-motion enthusiast (as well as his brother Joshua’s blog, which is equally good.)



The same method can also be found documented here:


My original intention had been to follow this method, and to construct a ball and socket armature from the ground-up myself. My concern however is the time factor. With three weeks planned to fabricate my puppet, in addition to making the press mould, character bust and replacement mouths for my second micro project, I worry that I simply will not have the time to make a completely custom armature myself using this admittedly very advanced method.

Advice from my tutors and friends has been to buy my armature. Nevertheless, I wonder if there is a way to construct a professional ball and socket armature without having to employ these techniques? I have spent several days now looking into various processes, materials and components that can be bought individually. Could a cheaper alternative, such as hard plastic beads with a pre-drilled hole, be effective for a joint? It would be easy to widen the hole roughly 60% of the way through for steel rod to be inserted and glued into place. I would imagine that glue would indeed be strong enough, since the force applied to the joints will be horizontal and never to pull the rod from the ball.

According to several online sources, you can utilise the existing ball and socket joints from ‘helping hands’ (a.k.a. miniature vice grips), which can be acquired relatively cheaply then dismantled:



I have viewed some recently however and found the joints to be too large for my project. In addition, the metal rods attached to the balls are often short, and would need to be either lengthened by attaching another rod with solder, or replaced entirely.


On the other hand, Richard Svensson (over at loneanimator.blogspot.co.uk) uses homemade wire armatures comprising double aluminium wire cemented in Friendly Plastic, with wing nut tie-downs, for all of his build-up puppets. If I were to make a wire armature, with either aluminium or brass K & S tubing to strengthen the ‘bones’, the size consideration aforementioned would not be an issue.


Decided method



‘This brass ball-jointed armature falls in-between those two kinds of designs. It is meant for animators who want to move up to making metal-jointed armatures, but who aren't yet ready to purchase big machines that need to be bolted onto a workbench.’ (‘Sven’, 2006, online)

This method seems like the best chance I have at making my own ball and socket armature. Put bluntly, if I cannot create one this way, chances are I will be unable to (for this project, at least). My dad has experience soldering, and can teach me and provide assistance in this regard. The ability to use regular tools, and not desk-mounted workshop equipment, means that I should be able to construct my armature at home, enabling me to work beyond the constraints of university hours if need be to get the piece complete within my allotted timeframe. Furthermore, the affordability, availability and workability of brass components are far better than for the steel ones of the previous outlined methods. In fact, using pre-drilled beads (though brass in this instance) is similar to a method I suggested previously!

There are issues highlighted with using brass for armatures, in that it can be corrosive to many casting materials, including latex. Considering that I will be padding my armature completely in urethane foam however, such that none of the latex will be touching the brass, I have been informed by Ben Whitehouse (stopmotionben.blogspot.co.uk) that it should not be a problem- many thanks to him for the help and advice! 


I shall proceed to investigate this process further. Once I am confident that it is something I can achieve, and I can obtain all necessary parts and tools, I will create detailed plans for my armature taking account of the various sizes and dimensions given, to ensure correct proportionality for my Gollum puppet.


'Tuning' an armature and the principle of resistance



This is a link to a great article on joint tuning and resistance in stop-motion armature construction, providing some very useful tips and tricks. The information actually bridges the gap between armature theory and rigging theory.

Resistance in the context of stop-motion animation is all about the amounts which specific joints will allow movement. A stiffer joint will pose more resistance, and be harder to move. Conversely, a looser joint will pose less resistance and therefore be unable to support as much weight.

With the necessity to be secured whilst animating, stop-motion puppets are generally fixed from the feet i.e. attached to the ground to prevent them from falling over or moving between frames. The puppet’s resistance, therefore, must become looser the further from the feet you go. The legs must be the strongest point, with the most resistance, for they will be supporting almost the entire weight of the puppet. As you work your way upwards, you see that the weight each part needs to support reduces. Concurrently, so does their resistance.

The torso must support the arms and head. The shoulders need only be strong enough to support the puppet’s arms. The extremes of the puppet like the head and hands essentially need only to support themselves. It is important to take a considered approach to resistance, for it has direct effects on your ability to animate the puppet.

‘If your knee and your elbow are equally pliable, then when you try to bend the elbow, the knee will bend also (at least, more than you’d wish.)  When you move the wrist, you want as little as movement as possible from the elbow.  When you wish to bend the elbow, you should be able to do this with as little movement as possible from the shoulder.  And in both of these cases, you shouldn’t have any movement in the legs. I’m going to call this first concept the ‘basic principle of resistance.’

-Todd Elliott, ‘A 3D Animator’s Guide to Stop Motion’, online

‘Tuning’ is the process whereby each of the ball and socket joints of the armature are manually tightened/loosened to achieve the optimal resistances for animating. Naturally, this is something that is not possible with simple wire armatures, for the resistance therein comes from the wire itself, which is consistent throughout.



Resources:

  • Priebe, K. (Quotes from pg. 39, 77) (2011) ‘The Advanced Art of Stop-Motion Animation’, Boston, MA: Course Technology, a part of Cengage Learning.

1 comment:

  1. nice, thank for sharing the research, ive been thinking how i can get the university which focused on this subject

    ReplyDelete