Hello,

I was wondering if someone has tips on how to make knees/elbows hinges with rotation on the hips?( same system as Merrick Cheney )

What kind of steel do I have to use? to keep a smooth friction.

thx for all your answers

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For the very few ball and socket armatures I have made, I usually use a ball joint at the knee and elbow.  This allows a lot of forward and back rotation, and twisting is also possible.  In theory it should be a hinge joint, but I have done that a couple of times and found it too limiting.  

For the hip, a ball attached by a short rod to the hip block on each side, with step-block plates front and back.  This short video shows an armature I bought, and tested next to one of my wire armatures, and it has the same type of joint.  The knee is also a Step-Block ball joint, so it has only one ball, rather than a plate with a ball at each end, because I don't like those double joints.  They appear to be stainless steel of some sort (which makes the armature heavier than I like, that's why I never used it in a puppet - I thought it was aluminium when I bought it).  I mostly use aluminium for the plates, unless the puppet is very skinny and I need to keep the joint super compact, then I use hardened steel chain plates.  https://www.youtube.com/watch?v=uBNzH21XMWs

I googled and found these legs by Merick Cheney, which do use a hinge at the knee and have rotation built into the femur.  I can see the split in the block and the tension screw.  But sorry, I don't know what metal is used.  

Thx for the answer. I checked on the forum and I found "01 tool steel" which is use for knife making. If I machine this steel I think I ll need to heat it and dip into oil then bake in the oven to make it harder. Is it correct?

To answer to you Nick I think making hinges is more realistic to use on knees/elbows and it allows me to make it smaller than a ball and socket joint if I want a really thin puppet.

Hardening process is well above my level of expertise.  I mostly make wire armatures, and have got so used to animating with them I don't do any better with jointed armatures.  (Have made hundreds of wire armatures, compared to 3 or 4 jointed armatures.)  Good luck!

My two sense regarding O1 tool steel is that it's not ideal if you're not properly set up for heat treating and tempering it. You pay a premium with O1 tool steel, but if it's not able to reach its full potential then that premium is for not. The main benefit of tool steels over low carbon (like 1018) or stainless is the added wear resistance you get, but for basic armature components outside of long feature work or structurally demanding designs (larger OR smaller than usual) I don't think it makes a huge difference. That being said I do occasionally use O1 tool steel primarily for the rods of my ball stems (it's also easier to find in a wider variety of diameters for me), and would probably use it if I were to make ultra small joints but I usually don't have the need for something that can't be done with 1018 or 304 stainless.

Now, you're right on the basic process for heat treating O1 steel. It's heated to about 1500F (800C), ensuring even heat to avoid warping, then quenched in oil (commonly peanut or canola oil) that's been preheated to at least 125-150F (50-65C), and finally tempered immediately after (you don't want the part to cool below 125F-ish) in an oven at 400F (205C) for a minimum of 2 hours, and finally air cooled back down to ambient temperature. The main purpose of the tempering (baking) step is to actually reduce the overall hardness of the steel to reduce some of the internal stress and reduces the steel's brittleness. It's also very important to heat evenly and preheat everything as O1 can also be prone to quench cracking.

As far as specifics on machining hinge joints, if memory serves I believe Sven Bonnichsen in his blog on scarletstarstudios.com wrote about hinge joints (as well as loads of other useful machining write ups). I'll see if I can dig up his posts on it.


Alix LAINE said:

Thx for the answer. I checked on the forum and I found "01 tool steel" which is use for knife making. If I machine this steel I think I ll need to heat it and dip into oil then bake in the oven to make it harder. Is it correct?

To answer to you Nick I think making hinges is more realistic to use on knees/elbows and it allows me to make it smaller than a ball and socket joint if I want a really thin puppet.

EDIT: I found a couple of the blog posts I was thinking of:
http://www.scarletstarstudios.com/blog/archives/2010/03/armatures_m...

Another interesting post of Sven's is his post about the Coraline puppets and he gets into some more of the details about the armatures by Machinations and Merrick Cheney: http://www.scarletstarstudios.com/blog/archives/2009/02/coraline_pu...

Complex to fabricate the 'Merrick Cheney' (as you call it) ... actually some of these hinge joints style go as far back to Mighty Joe Young armatures and even the original King Kong.  Then later, Jim Danforth, Tom St Amand, & others used it with more refinement and miniaturization. 

These kinds of Hinge joints are complex in that that require higher exacting machining tolerances to avoid 'hinge slop'. I've attempted them but waaay too much work ... my time & life is limited ya know ... LOL ;)  High precision machining equipment makes it somewhat easier to construct, and computer aided machining helps with the precision and in producing quantity joints.

An alternative hinge joint style, is the the 'CLAMP HINGE Style joint. 'GreyGuy' (aka Jim Randall), does much of those kind of joints. He posts his work in progress projects at his facebook page. The 'clamp' hinge movement is very precise, and is somewhat forgiving in tolerances but you will still get a reasonably good working tight & smooth hinge movement, using the clamp style method.

I make a hinge using laminating parts. The metal is 510 bronze and I think 303 ss

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