Ball joint

The Cyberjets, like Hooligan here, were some of the earliest toys to make extensive use of ball joint construction. His knees, hips, elbows, shoulders and neck are all ball-jointed.

The ball joint is the polymer industry's gift to Transformers. It is simple in concept; a ball rotates in a socket, held in position by friction, and when used in a Transformer toy's limb or other flexible area it can allow a great range of motion, as long as parts don't get in the way, because it can both hinge on any axis and rotate.

Use in toys

Multiple ball-joints make for very bendy bits, like Quickstrike's cobra-parts here. (Also, knees, hips, elbow, shoulders, and neck once again.)

Ball joints may be made of many materials, but it was the use of strong yet tough plastics that allowed their economical application to toys: the ball and socket can each be cast in one piece, then snapped together. Early examples of ball-jointed limbs include Optimus Prime's combat deck Auto Launcher, Astrotrain, Whirl and the Deluxe Insecticons. Late Generation 2 started introducing more and more toys that made use of the joint style, and by the Beast Wars era it was a rare toy that didn't have at least one ball joint.

Takara designer Takio Ejima is credited for introducing ball joints as a standard feature of nearly all Transformers toys, as he had realized that they not only improved the toy's articulation, but also made it easier for a toy to conform to safety regulations—under stress, they simply pop off, allowing for easy reattachment, instead of a piece of plastic breaking into sharp shards.<ref name="henkei">Translated interview with TakaraTomy Henkei staff</ref>

Ball joints are extremely handy in customizing, as they allow for a toy to be easily disassembled and reassembled.

Weaknesses

Ball joints are cheap and flexible, but they are completely dependent on friction. Since friction depends on the force squeezing two parts together, and this force may not be increased arbitrarily without making the joints impossible to assemble, ball joints are hard to make with enough friction to support the heavy parts of a large toy. In these cases more elaborate mechanisms such as ratchets must be used.

Furthermore, if a ball joint wears or stretches even a little, it quickly becomes loose, and some plastics simply aren't tough enough to make a firm joint even when new. Knockoffs frequently have loose ball joints. Joints loosened in this way can sometimes be "repaired" by applying a thin layer of epoxy, glue, or clear nail polish to the ball and/or socket.

Another weakness that became more apparent with the Power Core Combiners series is that less flexible plastics molded into small parts such as the shoulder and hip joints of the Commander figures have a tendency to eventually break simply from the pressure of the ball pushing against the inside of the socket, especially if there are raised friction points inside the joint. The most common points of breakage in these cases are around the rectangular holes cut into the pieces to provide better malleability to the joint. As such, many of the mold designs used for the series simply crumble apart after a period of time.

Fiction

Sometimes ball joints become loose on older specimens.

Footnotes

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See also

• Ratchet (mechanism)
• Slide joint
• Swivel joint