Stop Motion armatures: Hinge vs Ball & Socket Joint

We’d like to talk about the hinge joint used in stop motion armatures and compare them with the ball and socket joint type for armature knees.

Hinged knees

Hinged joints are moulded to each other in such a manner as to permit motion only in one plane. Think of it as your own knee or elbow, they only bend in one plane.

Ball and socket

A ball and socket joint are those in which the ball-shaped surface of one rounded piece fits into the cup-like depression of another piece. Think of it as your hip or shoulder, they move in a rounded way.

When to use each?

Both designs, hinged or ball and socket are a very good way to animate the bending of the leg at the knee but the animators in our studio prefer the feeling of the hinged design.

Hinged knees and elbows are one of the main features included in our stop motion armatures Ben, Lisa and Milo. We’ve chosen to bring this feature to you because it gives more natural and similar movements to a human.

To explain this we’ve built the lower body of our Ben Armature Kit with two different legs. One hinged and the other one made with a single ball and socket joint. The ball and socket joint design has an extra rotation on the Z-axis and a small sideways movement, which are blocked on the hinged design.

As you can see on the video below on the left both legs respond nicely, especially when the bending is straight but when the action has a bit of a sideways movement or you want a more open stand, the extra rotation on the ball and socket creates a non-natural posture, where the leg is not straight any more. This can be corrected frame by frame but is more work for the animator as shown on the video below on the right.

Straight up-down movement Sideways up-down movement

Undesired position with ball and socket joint

Also this extra rotation may cause non-natural postures that may lead to the re-shooting of the scene, which is something we should try to avoid.

With the ball and socket joint knee it’s more likely that you’ll need to rectify the rotation at every frame but with the hinged knee the issue is gone. Non-desired movements can lead to an awkward animation that can take longer to shoot or may even derive to re-shooting the scene.

Here at UPuno, we’ve developed high quality armatures, yet at a very competitive price, that include hinged knees and elbows. This way you don’t have to compromise on the armature, leading to a faster and easier animation process and lowering the costs at the end of your project.

UPuno Team

Update [25th May 2015]: We’ve released Tim Stop motion Armature Started Kit which has ball and socket knee and elbow joints at a very competitive price for those secondary characters of your project or if you’re on a budget.