Ball & Socket Armature - Hinge Joint

Hinge Joints

In today's post I'll continue discussing the construction of my Ball & Socket Stop Motion armature. I'll be showing how to make a different kind of joint called a Hinge Joint.
Hinge joints don't offer as much movement as Ball and socket joints, but they're perfect for creating elbow and knee articulation. Plus they're much simpler to make.

I'm making my hinge joints from steel bar. The materials and tools needed are similar to those used to make ball and socket joints. You can see/read about that in my previous post. LINK

I start by cutting 3equal lengths of steel bar. Above you can see the steel bars along with the M2 nuts and bolts that will be used to hold them together.

Next I marked a dot on the steel about 4mm from the end. This is where the hole will be drilled for the bolt. Before drilling I made a centre punch on the surface to guide the drill bit.

I stacked and clamped the 3 bars together and held them in a vice while drilling. I started with a M1.5 drill bit and then expanded the hole to M2.

This gave me 3 identical steel bars, all with an 2mm hole drilled in one end.

I used a M2 nut and bolt to tie all the bars together. I then rounded the corners (seen above in the picture on the right).  To do this I used a rotary tool and a reinforced cutting disk. (the same technique I used for making ball and socket plates in my last post.)

Next I loosened the bolts and rotated the middle bar so it was pointing in the opposite direction. I'm using K&S brass tubing to make my arms and legs so I cut the steel bar small enough to slot inside. This will be soldered together later.

I cut another small square of steel bar to go on the other end of the joint. This will be used to hold the two outer bars together and act as a tab to slot more K&S onto. I used a file to rough up the surfaces where each part will connected and applied soldering flux.

The rough surfaces help solder stick. Its also important to remove any dirt or grease to create a stronger join. I heated up the steel using my butane torch until the flux paste fizzed and then applied silver solder to the both side of the tab.

At this point I also soldered the nut onto the outer surface. This allows the joint to be loosened or tightened using just an Allen key. Above you can see the joint after being soldered.

The other end now needs to be cut smaller to allow it to slot onto the K&S. Also to give the joint a little more range of movement I marked where more steel can be removed. To do this I use the rotary tool and cutting disk.

Here is the joint after cutting. The change is only small but this allows the joint to bend into a smaller, acute angle. For example, If this joint was to be used as a elbow the character would now be able to touch their own shoulder. Or if this was a knee joint, the character could crouch down lower.

The final stage is to slot the joint into the K&S tubing and solder the join.

Wallah ! One hinge joint ready to be incorporated into a character armature. I will be using the one pictured above as a knee joint for my new 'Roy' (Mail Man) armature. I'm also using this kind of joint to make his elbows and toe joints. 'Elle's' knees and elbows will be made smaller with thinner steel bars.
The excess bolt will be cut shorter later. I usually leave them on until I'm done.

Thanks for reading.