Sunday, February 2, 2014

08 Joint Design Nº 449

A skull cap on a BJD is used for gaining access to the inside of the head for purposes of tensioning, changing eyes, stashing a small object, whatever. There is usually more than one way to do something. I have been thinking about how the skull cap is going to attach to the head. This is a part of joint design because there is a joint between the skull cap and the head. It may not be an articulated joint, but it is a joint nevertheless. The way I have it now is meant to be used with magnets. Velcro could be substituted for the magnets? Click on any image to enlarge it.

Here is an idea for using tabs. I sketched the tabs much larger than they would be if I actually made them. With tabs, the skull cap cannot move from side to side because of the tabs in the front and back. Nor can it move from front to back because of the tabs on each side. I would still have to stick the skull cap to the head somehow? It might stay in place with a wig that has an elastic liner? A piece of double-sided tape? That would not only hold the skull cap in place, but might help keep the wig on as well?

Using a loop which goes through a hole in the top of the head is the way that Martha Armstrong-Hand attached the head to the doll. However, I have not seen any of her designs with a skull cap. The loop is attached to an S-hook, swivel, or spring. This could also work by attaching the loop to something inside the head, maybe with a piece of small elastic?

Although I cannot remember where I saw this idea, it seems like it would also work. The hooks are flat and made of brass. The skull cap would have a screw on each side for the hooks to hook onto. The hooks would have a small screw to attach the hooks to the head. These would have to be low-profile so as not to get in the way of the wig.

I need to get the skull cap and the head in better alignment.

One other design thing that I have been thinking about as I am sanding is undercuts. In this sketch, the nostrils are shown as a place that undercuts can occur. The ears are another place. Around the eyes. Between fingers on the hands, and toes on the feet. Undercuts are especially important to think about when the plan is to make rigid plaster molds for slip casting. Also I keep in mind that the slip I am going to be pouring will have a total shrinkage of about five or six percent. That should loosen the casting up a wee bit, but not much. It will be better to avoid undercuts.

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