Using magnets for easy body part replacement - good idea or bad idea?

I made an armature with aluminum wire and epoxy putty, and had a thought to use small (1/16'') magnet discs on the character's ankles and wrists so that I could easily attach and remove the feet and hands. Is this a common or advisable practice as far as armatures are concerned? Are there better methods for going about this than using magnets? 

It seems to work like a charm, but I worry about the magnetism causing limbs to behave undesirably during animation, say if I need the character to bring his hands close together, or is standing tall with his feet close together.

On a related note it seemed like an idea worth exploring for attaching the character to a rig (magnet in the character's butt, and a magnet at the end of a rig arm). Thoughts?

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Bad idea is what I'm thinking.  You want all the body parts to be really strongly attached.  Especially the feet, since they are what holds the puppet up.   Magnets are sometimes used as tiedowns, instad of screws, but it takes a bigger, much more powerful magnet under the set than one you could fit in an ankle or wrist.

For detachable heads (so I can re-use the same bodies for different characters) I have a hole in the chest block for the neck wires, but instead of glueing them in, I have a screw coming in horizontally.  If it's a wood screw, I file the tip so it is flat.  Sometimes it is an aluminium chest block, with a thread tapped into the hole, and I use a machine screw.

For arms and legs, the usual way is to use the K&S square brass tubing, where one size fits neatly inside another.  Then you can have a screw going in through the side that locks the two tubes together.  I tend to avoid brass with my latex puppets, so I use round aluminium tubes instead.   Mostly my hands are not detachable, I glue the hand wires into the tube going half way, and the arm wires (which are heavier wire) into the other end to butt up in the middle.  

But for detachable hands I had the hand wires in the smaller tube, the arm wires part way in the bigger tube, then slid the small tube into the bigger one.  Then I pinched the two tubes with pliers into an oval, so they didn't rotate or slip out.  To remove the hands I would have to pinch them back the other way.  A small screw going right through would work for this too.  I don't think I ever took the hands off though, and I forgot which body it was!

You can see the head of the screw in the chest some of the time, in this armature making video.

https://www.youtube.com/watch?v=MbF6m3BeGUQ

Thanks for the advice, Nick!

I know the feet are meant to hold the puppet up, but I plan on using a rig almost 100% of the time and not really relying on gravity for the puppet's stance or stability. However, the idea of using aluminum tubes sounds very promising, and I'm familiar with the way hands from animationsupplies.net's armatures work with the square brass tubing - do you have any recommendations on measurements/brands for said aluminum tubing, say if I was to try looking for them at a hardware store? Is there any conceivable way to use such a system that doesn't require permanently glueing the hands in and allows for the ability to switch them out?

I can definitely deal with permanently secured hands and feet, I'm just exploring options with the armature I'm currently building before I start my next mold and silicone casting. Thanks again for any insight!

I used magnets as tie downs for my first animation and I wouldn't use them again. They don't hold the character totally still, and sometimes the magnetic grip on the puppet makes the puppet spin around. Due to the strength of the magnets when taking them off and putting them on the next foot they can make the stage bounce and move things. 

I find the aluminium tubing at hobby shops, right next to the K&S square brass tubing.  I have never seen it at a hardware store.  Don't know the brand. Sizes - big enough to fit the arm wires into the bigger one, I would usually have 4 or 5 strands of 1.5mm (1/16th") wire in the upper arm. You could take a short section of wire twisted together when you go to buy the tubing.  Or just buy several sizes like I do.  (A long way of saying I don't know what the sizes are.  But thinner than a pencil.)

I had one big dinosaur puppet that needed a rig to support the weight, but it still helped having the foot held down on the ground so it didn't skid around.  With a rig and no tiedowns you can put one finger on the foot to try and hold it in place as you move the puppet, but it can be difficult.  I run into trouble when a puppet is resting his hands on a bar and he's moving, it's almost impossible keeping the hand in one place unless I can put a pin through it or  loop of wire where it doesn't show.  So with a rig, something to locate the foot that is supposed to be taking the weight, even if it isn't actually bolted down, is a good idea.

I lucked out and found the K&S brand square brass at my hardware store. Wound up getting the exact same sizes that my animationsupplies.net armatures use. Score! For some reason they didn't seem to have it in aluminum - go figure.

You make a great point about the value of keeping the feet secure to the floor - I will take that advice to heart going forward. Thanks again, Nick!

StopmoNick said:

I find the aluminium tubing at hobby shops, right next to the K&S square brass tubing.  I have never seen it at a hardware store.  Don't know the brand. Sizes - big enough to fit the arm wires into the bigger one, I would usually have 4 or 5 strands of 1.5mm (1/16th") wire in the upper arm. You could take a short section of wire twisted together when you go to buy the tubing.  Or just buy several sizes like I do.  (A long way of saying I don't know what the sizes are.  But thinner than a pencil.)

I had one big dinosaur puppet that needed a rig to support the weight, but it still helped having the foot held down on the ground so it didn't skid around.  With a rig and no tiedowns you can put one finger on the foot to try and hold it in place as you move the puppet, but it can be difficult.  I run into trouble when a puppet is resting his hands on a bar and he's moving, it's almost impossible keeping the hand in one place unless I can put a pin through it or  loop of wire where it doesn't show.  So with a rig, something to locate the foot that is supposed to be taking the weight, even if it isn't actually bolted down, is a good idea.

I didn't see anything in this that explained why you want the feet and hands to be easily removed.  Why are you interested in this design?

Hands may need replacing because finger wires break, but the tubing solution Nick mentioned is pretty standard in the industry because it works well and is simple.

Unless the puppet is an ape not wearing shoes, feet won't have the same wire breakage problem hands do, so there are fewer reasons to replace them.  Assuming you want to quickly deal with breaking ankles, as Nick said tubing works well there, too.

Puppets need to be as stable as possible.  The more time you spend fighting a flimsy/flaky armature, the less time you spend animating the performance.  It will also limit the performance because the puppet won't be able to do some things it could with a slightly better armature.

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